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post #31 of 70 Old 05-15-2020, 01:17 PM
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You truly amaze me how quickly you have caught on to static pressure, air flow, pressure differentials. I assure there is a very small % of HVAC techs that understand it that well, especially the younger ones. Your mindset also amazes me, you are now looking at sensors repeatability accuracy and willing to pay more for more precision. You have made my Deans List this semester!

I'm glad to hear you called Dwyer, hopefully you found them as helpful as I did. I went back and read their statement on Covid 19, the amazing thing I took away was with those very low tolerance pressure differentials recommended they just said: "we got this" its what we do for a living.

I had not even tried to calculate how much air you would have to exhaust to equalize the theater. I believe you are on the right track but I'll go back and check my old NCI books and see if I can do a more accurate calculation. My original thinking was that it would just be a quick puff, obviously I was wrong. Maybe it would be better to go to 6" duct which will carry slightly more than 2X what a 4" will. The damper motor will likely be the same, so we aren't adding any more load to the control transformer. The other thing that came to mind was do we want to shut down the fresh air intake system while the barometric damper is open? It could easily be done with the sensors you are looking at with some minor wiring changes. If you are bringing in appox 55 CFM of air and you are only exhausting appox 50 CFM when will it equalize? Let me know if you want to explore this avenue and I'll sketch it out for you.

I know I've planted ideas that will cost you added money, and it's fun spending someone else's money I can't lie about that. I do believe I've given you some tips for saving some money too. One was ordering the Ultra Aire, if you do choose to order from Sylvane, call before you order and ask some technical questions, like I said they gave me a 10% discount just for calling. Another place you could save some money is on the DEH 3000. That controller is set up so you can enter some information about sq footage and other stuff and it calculates how much fresh air it guesses you need to bring in, it's based on the ASHRAE 62.whatever version. That's for people that just guess how much fresh air they need and not measure like you are doing. Don't get me wrong, I admire people that even see the need for fresh air and kudos for doing something. You aren't using that device to control anything but humidity. It's an intelligent device with most of the cost built into the algorithm for ventilation. All you need is an accurate dehu switch. I haven't researched but I'm sure Honeywell, Aprilaire, maybe even Dwyer make one for about 1/3 the cost and the same final effect for your application. Most humidity switches have a 5% deadband.

You made a comment about not wanting to go in the attic to change filters and I truly get it. Do NOT be negligent with replacing filters on the Ultra Aire or your fresh air intake filter. That's a very nice and well built machine, don't kill it from neglect.

I have truly enjoyed this collaboration, it's going to be a little sad once all the details are ironed out.
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post #32 of 70 Old 05-15-2020, 04:54 PM
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I've called in the big guns now. I reached out via email to Dave Richardson with NCI. Dave is an instructor and curriculum developer at NCI, a really great guy and lives in my area. I took a couple of his courses a few years ago.

I tried to explain the over pressure possibility and sought his guidance and recommendations. I'll share his response when he's able to get back to me.
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post #33 of 70 Old 05-15-2020, 11:14 PM - Thread Starter
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Your comments above are very kind. I'm a gearhead, what can I say. This all seems pretty straight forward to me and I've been enjoying the collaboration as well.

I was basing the 50 cfm exhaust rate for the Baro system from the Ultra-Aire manual that said the 70H would draw 50-55cfm of fresh air from a 6" duct Tee'd into the return duct. Then, for some inexplicable reason, I decided 4" would work fine. Nope! 50cfm through a 4" duct would result in a velocity well over 500 feet per minute. You were right to question the choice of a 4" duct!! 6" will have to do as I have found it difficult to find roof vent caps that will accept 8" ducts.

I would rather have the Baro system open for prolonged periods than short cycling. I will have the CO2 level displayed in the room so if I find I can't maintain my setpoint when I have a crowd in the room, I will know the system needs some augmentation. I can always add a boost fan and nearly double the baro pressure relief flow rate, if needed.

Here are the updated schematics:





I'm feeling really good about the evolution of the HVAC design! I really didn't expect it would go this well. Kudos to Bourbon County !! Your assistance has been way over the top!

I got the plans back from the architect today and spoke with my builder. Hopefully we can start demolition soon, or at least before the end of summer.

Mike
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post #34 of 70 Old 05-16-2020, 08:24 AM
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I think we're heading down a road that has very few footprints with this baro system. That's what I love, challenge accepted.

I was thinking that I could take your ideas for a passive system and add a little automation but still be passive with tighter controls. The more I think about it, I think your idea development is much more accurate. Logic dictates that to depressurize an area you must be pumping more air out than in. I also realize that with pressures that low, it likely would not even lift the backdraft damper on the roof cap. Let's develop your idea of putting an in line fan and going with 6" duct. This would also (in my thinking) require enabling the fresh air intake while the baro relief is active needed or not, have the baro fan set to move a little more air than the 50-55 CFM of the fresh air. There are also acoustical considerations to take regarding the cycle time. With that subwoofer system, you might be playing bass for Ft. Worth!


As far as the roof cap, I have learned painful and expensive lessons over the years do NOT use plastic or powder coat sheet metal they don't hold up in my area which is a milder climate than yours. Aluminum is the only choice, it has a very reflective surface that will reflect more solar gain than it absorbs. I used aluminum roof caps for bath fans on this house when we built it 22 years ago. When I had the roof replaced a couple of years ago, I reused them, they were still in pristine condition. I'm sure there are many on the market, here's one similar to what I'm talking about: https://www.solerpalau-usa.com/products/gv/rcxii.html they do tend to look commercial, but maybe a 6 inch won't be too obtrusive.

Another obstacle to overcome will be the amount of time it takes the damper to open, you don't want to deadhead or restrict the fan waiting on the damper to open fully. For my fresh air project, I chose Famco dampers, I wanted something with a switch to tell me when the damper was fully open. Remember my comment about assumptions and anticipations? There are add on end switches available for a lot of dampers that cost nearly as much as the damper itself. The Famco could be ordered with an intergal end switch. They seem to be made of a slightly heavier gauge sheet metal and have a really nice rubber air seal. https://www.famcomfg.com/product/mot...rmally-closed/

Adding the fan would require adding a relay to start it, needs to have a 24vac coil and contacts rated for the fairly low current draw of the fan. You would also need a manual speed control to slow it down, a 6" inline fan would likely move far too much air at full speed. This would not be something that requires frequent adjustment, once it's dialed in just leave it.

I have one of these fans: https://www.solerpalau-usa.com/produ...td-silent.html brand new in the box that I bought for a previously planned project that I ended up not doing. I am so vested in your project, I'll be glad to donate it to you. If you are interested you can contact me privately and I only ask send me a few bucks for shipping. I want to see it go to a good home. I believe I have a speed control and probably have a relay here that will work for this application with the same offer.

The wiring is starting to get a little more complex, but nothing we can't work out. I very highly recommend buying a junction box and putting a terminal strip in it. I'll try to find something suitable and send you a link. Devise a good wire labeling scheme and make all connections on the terminal strip, it can also house the fan relay. You can probably find one at a big box or maybe cheaper at an electrical wholesale house. By doing this, all of your wiring will be in one location and if you have to make changes during debugging it's all in front of you, as well as it looking professional. I'm going to have a label made for my control panel "FRESH AIR CO2MMANDER".' I probably have some modular terminal strips and some DIN rail that I'll also donate.

I want to hear Dave's thoughts on this before making final decisions. I contacted him via his work email and he might not even look at it until Monday. I do believe you have pulled me back from the brink and gotten this back on track.
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post #35 of 70 Old 05-16-2020, 03:02 PM - Thread Starter
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Quote:
Originally Posted by Bourbon County View Post
I think we're heading down a road that has very few footprints with this baro system. That's what I love, challenge accepted.

I was thinking that I could take your ideas for a passive system and add a little automation but still be passive with tighter controls. The more I think about it, I think your idea development is much more accurate. Logic dictates that to depressurize an area you must be pumping more air out than in. I also realize that with pressures that low, it likely would not even lift the backdraft damper on the roof cap. Let's develop your idea of putting an in line fan and going with 6" duct. This would also (in my thinking) require enabling the fresh air intake while the baro relief is active needed or not, have the baro fan set to move a little more air than the 50-55 CFM of the fresh air. There are also acoustical considerations to take regarding the cycle time. With that subwoofer system, you might be playing bass for Ft. Worth!
Rather than worry about a fan assist to overcome the resistance of a backdraft damper built into a roof vent cap, I would rather use an open vent cap without the backdraft damper. Given that the ducting is already protected by a motorized damper, I think the integral backdraft damper in the vent cap is superfluous and as you point out, probably detrimental to the function of the overall system. Furthermore, the inline fan option was only a contingency plan in the event the system could not maintain comfortable CO2 levels. For 98-99% of the time, I will be the only occupant. So for the majority of the use, the current system as designed should be more than adequate to maintain acceptable CO2 levels.

As far as the roof cap, I have learned painful and expensive lessons over the years do NOT use plastic or powder coat sheet metal they don't hold up in my area which is a milder climate than yours. Aluminum is the only choice, it has a very reflective surface that will reflect more solar gain than it absorbs. I used aluminum roof caps for bath fans on this house when we built it 22 years ago. When I had the roof replaced a couple of years ago, I reused them, they were still in pristine condition. I'm sure there are many on the market, here's one similar to what I'm talking about: https://www.solerpalau-usa.com/products/gv/rcxii.html they do tend to look commercial, but maybe a 6 inch won't be too obtrusive.
I had just finished specifying polypropylene vent caps after spending hours scouring the net for a good option when you wrote this. Argghhhh!

Another obstacle to overcome will be the amount of time it takes the damper to open, you don't want to deadhead or restrict the fan waiting on the damper to open fully. For my fresh air project, I chose Famco dampers, I wanted something with a switch to tell me when the damper was fully open. Remember my comment about assumptions and anticipations? There are add on end switches available for a lot of dampers that cost nearly as much as the damper itself. The Famco could be ordered with an intergal end switch. They seem to be made of a slightly heavier gauge sheet metal and have a really nice rubber air seal. https://www.famcomfg.com/product/mot...rmally-closed/
These cost about twice as much as the dampers I had planned, but again, it is not a huge amount in the pig picture, especially compared to the cost of Green Glue!
I could purchase the type with the end switch for the baro system and leave the end switch disconnected. It would be much easier and less hassle to have it available if I needed it later than to have to change out the damper after the attic is closed out.


Adding the fan would require adding a relay to start it, needs to have a 24vac coil and contacts rated for the fairly low current draw of the fan. You would also need a manual speed control to slow it down, a 6" inline fan would likely move far too much air at full speed. This would not be something that requires frequent adjustment, once it's dialed in just leave it.

I have one of these fans: https://www.solerpalau-usa.com/produ...td-silent.html brand new in the box that I bought for a previously planned project that I ended up not doing. I am so vested in your project, I'll be glad to donate it to you. If you are interested you can contact me privately and I only ask send me a few bucks for shipping. I want to see it go to a good home. I believe I have a speed control and probably have a relay here that will work for this application with the same offer.
That is a very generous offer! I'm not convinced yet there is a need for an auxiliary boost fan. For less than the cost of the fan, I could just increase the size of the baro damper and ducting to 8" and the flow problem is solved. I added a little table (below) to help with duct sizing.

The wiring is starting to get a little more complex, but nothing we can't work out. I very highly recommend buying a junction box and putting a terminal strip in it. I'll try to find something suitable and send you a link. Devise a good wire labeling scheme and make all connections on the terminal strip, it can also house the fan relay. You can probably find one at a big box or maybe cheaper at an electrical wholesale house. By doing this, all of your wiring will be in one location and if you have to make changes during debugging it's all in front of you, as well as it looking professional. I'm going to have a label made for my control panel "FRESH AIR CO2MMANDER".' I probably have some modular terminal strips and some DIN rail that I'll also donate.
I've been thinking about how to simplify installation and have toyed with the idea of a simple PCB layout, much like the early DIY Soundgroup crossover boards. I would then mount this in a medium sized project box with all the wiring protected by grommets where they enter the box from the sides. I have some leftover DIN rail and terminal blocks from another project as well (a PLC-based water well controller that supplies water for 3 separate homes), if I should choose to go down that route.

I want to hear Dave's thoughts on this before making final decisions. I contacted him via his work email and he might not even look at it until Monday. I do believe you have pulled me back from the brink and gotten this back on track.
Glad I can be the one to help, for a change!
Mike

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post #36 of 70 Old 05-17-2020, 10:59 AM
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The chart you referenced shows that a 6" round duct will carry 100 CFM @ 509 FPM velocity, and conversely you would need 509 FPM of velocity in a 6" round to deliver 100 CFMs of air. In your case with the only thing used to create air flow is the pressure differential, a very low pressure differential, you have to calculate the force on the air to create movement in the duct. I'm attaching a page from BAPI, they make instruments much like Dwyer only a little more high end and much more expensive. https://www.bapihvac.com/application...essure-sensor/. I did some rough calculations and using only a 0.07" WC pressure diff as a mover, a 6" duct would only pass 1.47 CFM at .626 FPM. Please double check my calculations, remember that duct cross area has to be converted to sq. ft.

I'm interested in how you calculated how many CFMs had to be exhausted to reduce the pressure if you would care to share.

The only thing that can cause the room to become over pressurized is the fresh air intake system, the only thing that will cause the fresh air system to run is rising CO2 levels, the only thing (in your case) that can raise CO2 levels is humans. I think it's a logical assumption that the room would only require depressurization while it's occupied or maybe for a short time after becoming unoccupied. If my calculations are even close, a naturally aspirated baro system would take an extremely long time to work. I'll try to do some research on how much CO2 humans exhale and how quickly it would quickly it would raise the level in a given space.

If a room could ever get to the internal pressure to lift a barometric damper, can you imagine the whoosh it would make? I believe this is something that someone thought was a good idea, and it was, but doesn't have a clue if it has ever worked or not, nor have they ever taken any pressure measurements.

Speaking of taking pressure measurements, start looking at a manometer. The old Dwyer Magnahelic has been a gold standard for decades but they are expensive, delicate, and must be in a level position to be accurate. There are a number of digital models like Fieldpiece, UEI you can probably pick up for around $100. Just make sure it's a 2 port and has a " WC scale. I'm not about to let you install a system this precise without testing and balancing which is really the fun part seeing your planning and execution come to fruition. Remember: if you don't measure, you're just guessing.
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post #37 of 70 Old 05-17-2020, 11:08 AM
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This is in no way a scam, nor am I just trying to sell you anything. When if found the S&P fan I told you about, I also found a KB Electronics model KBWC-115K manual speed control, a Fantech IR6 iris damper, and a pair of Fantech FC6 duct mounting clamps. I also have (somewhere) and Allen Bradley solid state contactor with a 24v activation as well as some Omron ice cube relays with 24vac coils. I bought all this stuff for a project that never nor will ever be done in my house. I was going to try to make a central dehumidifier switch between 2 different HVAC systems based on need. My new system is zoned on 1 system and works quite well.

If you are interested in any or all let's communicate privately.
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post #38 of 70 Old 05-17-2020, 04:39 PM - Thread Starter
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Originally Posted by Bourbon County View Post
The chart you referenced shows that a 6" round duct will carry 100 CFM @ 509 FPM velocity, and conversely you would need 509 FPM of velocity in a 6" round to deliver 100 CFMs of air. In your case with the only thing used to create air flow is the pressure differential, a very low pressure differential, you have to calculate the force on the air to create movement in the duct. I'm attaching a page from BAPI, they make instruments much like Dwyer only a little more high end and much more expensive. https://www.bapihvac.com/application...essure-sensor/. I did some rough calculations and using only a 0.07" WC pressure diff as a mover, a 6" duct would only pass 1.47 CFM at .626 FPM. Please double check my calculations, remember that duct cross area has to be converted to sq. ft.
The chart I made above did not assume any pressure differential, duct or fixture losses. It was just a simple table to show that for a given volume of air movement you would see a certain velocity in a duct of the given size.

As to your calculations, I believe the formula you linked is for calculating air speed using a pitot tube (total pressure probe). Delta p in that formula is the ram air pressure
from the air velocity minus the static pressure and does not represent the difference in static pressure between two points as in the baro pressure relief system we are discussing. I found a web calculator that calculates airflow through an orifice that would serve as a first approximation for airflow through a duct and have attached the results below. I used 0.1" wc as the delta p for the attached images. I then reran the calculation using the pressure loss through a 10' length of 8" duct and the the flow rate decreased less than 5cfm. The calculator came up with 75, 170 and 300cfm for 4", 6" and 8" ducts, respectively. Obviously with bends, dampers and vent caps, the flow rate will be significantly impacted.

I'm interested in how you calculated how many CFMs had to be exhausted to reduce the pressure if you would care to share.
You are a good teacher. You help me find my own errors by asking simple questions. I misapplied Boyles law in my original calculations and used gauge pressure differences rather than absolute pressure differences. when I use absolute pressure, I come up with such a minuscule difference I have a hard time believing the results. With my latest calcs, the room is completely depressurized to ambient outdoor pressure before the damper is even fully open. Just a little puff as you described several posts earlier. I have more research on my plate.

The only thing that can cause the room to become over pressurized is the fresh air intake system, the only thing that will cause the fresh air system to run is rising CO2 levels, the only thing (in your case) that can raise CO2 levels is humans. I think it's a logical assumption that the room would only require depressurization while it's occupied or maybe for a short time after becoming unoccupied. If my calculations are even close, a naturally aspirated baro system would take an extremely long time to work. I'll try to do some research on how much CO2 humans exhale and how quickly it would quickly it would raise the level in a given space.

If a room could ever get to the internal pressure to lift a barometric damper, can you imagine the whoosh it would make? I believe this is something that someone thought was a good idea, and it was, but doesn't have a clue if it has ever worked or not, nor have they ever taken any pressure measurements.

Speaking of taking pressure measurements, start looking at a manometer. The old Dwyer Magnahelic has been a gold standard for decades but they are expensive, delicate, and must be in a level position to be accurate. There are a number of digital models like Fieldpiece, UEI you can probably pick up for around $100. Just make sure it's a 2 port and has a " WC scale. I'm not about to let you install a system this precise without testing and balancing which is really the fun part seeing your planning and execution come to fruition. Remember: if you don't measure, you're just guessing.
I used to have a dozen of those Magnahelic gauges of various ranges (they were surplus from TI when they upgraded a semiconductor fab line). For the life of me I can't recall what I did with them.
With regards to your concern that I thought your generous offer for the fan and speed controller was a scam, nothing could be further from the truth. I apologize if I gave you that impression. I'm just trying to minimize the number of things that can fail over time. Every switch, sensor, damper, control and fan has a failure rate that ultimately impacts the overall reliability of the system. I'm a lazy guy and I hate doing maintenance, whether its replacing rotting wood on our deck, or replacing HVAC filters. So the fewer moving parts or dirty filters I have to maintain, the more time I have to enjoy life.

Speaking of which, it's time to take the jet ski for a ride!

Cheers!
Mike

ps. I tried a little more science (hopefully I did my math right this time...) using the ideal gas law to see how quickly the room pressure would increase when we open the fresh air damper. Assuming 50cfm of fresh air, we would see a pressure increase in the room of 0.18" wc in a minute. That's nearly double the designed maximum static pressure for the room! Based on this, I would expect the baro damper to start opening within 30 seconds of the fresh air damper opening.
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post #39 of 70 Old 05-18-2020, 02:48 PM
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I did hear back from Dave Richardson and he had some of the same observations as we did, some questions, some recommendations, and some simple, logical solutions.

He questioned the very need for a pressure relief system. His recommendation was to get a blower door test done. I realize you are going to construct this space as air tight as you can, but there are several opportunities for leaks. Remember, if it leaks air, it will leak sound. He recommended having a blower door test done too. BPI (Building Performance Institute) I'm sure has a number of certified raters in the Austin area, you might locate and contact one and check the cost for just a blower door test. My biggest area of concern is the ceiling. You show 2ea 8"x48" air diffusers (supply), 2ea 14"x14" returns, 6ea speakers of unknown size, and if the 25 lights you mention are recessed, that makes a total of 35 places that could potentially leak. There will be numerous wire/conduit penetrations for speakers, lights, sensors, etc which all represent a possible leak. Even the best craftsmen with the best intent can easily miss a place here and there. I would have the energy rater put his blower door in the doorway between the lobby and home theater. he will run the interior space down to 50pa which is 0.2" WC and take a thermal camera and look for leaks. Leaks will manifest under a negative pressure more so than a positive pressure. This would afford you the opportunity to caulk or putty any leaks they found. Even if you were to build it airtight, dimensional lumber will shrink over time, along with a number of things that can shift and move over time. The last few years of my career was doing reliability testing and we used ultrasonic test equipment made by UE Systems, they always taught that anything man made would leak at some point in time.

Secondly, test to see if you even need a relief system. I think there could be a measured and economical approach to this. First step, buy and install an indoor static probe like the Dwyer A-465 or A418N and an outdoor static sensor such as the A-420A which will set you back about $30. Run the tubing up to the area where you are going to install your project box and just crimp off the ends. Once everything is complete and sealed up, either jumper the fresh air intake or set the CO2 level very low, run the fresh air system for maybe an hour and hook up your manometer that you are either going to find or buy, and measure to see if you can actually over pressurize the room. Dave's number was 0.12" WC before over pressure was even an issue. If you can't over pressure the room, go enjoy a movie. If you can, go to next step.

If you have tested and proven that you can over pressure the room install a relief system. I realize it might be much easier to do during construction so go ahead and rough in the intake grille, damper and duct probably 6" or even 8" and just leave the damper closed. As Dave pointed out, that from an energy standpoint, it's not really a good idea to dump that air outdoors, you have paid to cool, dehumidify, and freshen that air already, There is nothing wrong with it, it's just more than you need. How about dumping it into the lobby? That area could be very slightly negative from the exhaust fans, and I'm sure that door isn't nearly as air tight as the one going into the theater and more likely to have some leakage. By not terminating that duct outdoors, it will improve the acoustics and save the $ for the exhaust hood. By the way, is that door to the exterior, or into your home? At that point order and install the Dwyer 1900 series pressure diff switch you sourced, Dave's number falls within the range of the sensor you specified. You can install it in your project box if there's room or near it, the tubing from the probes is already there. All of the wiring to integrate to is there and the complete install could be done quickly and easily.

If it proves out that you actually need the relief system or you decide to move forward with it there are some controls issues to consider. You don't want to be popping the relief damper after the fresh air runs for short period and set up a bouncing ball effect of short cycling both systems. This will probably have to be a bridge we burn when we get there. It will take some testing to do it accurately and effectively.

I'm working on a couple of ideas about monitoring these systems, economically of course. I think it would be valuable to see how often and how long each system operates for. I'll post later on once I do some research.

I don' know if this provides any clarity or just muddles it more. Dave is a very highly regarded in the HVAC and energy conservation fields.
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post #40 of 70 Old 05-18-2020, 04:27 PM - Thread Starter
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Are you guys suggesting my first ever dedicated theater is going to have air leaks!?! i CAN'T BELIEVE YOU WOULD EVEN THINK THAT! All my dampers will have perfect seals, all my caulking will have perfect seals with 100% bonds between wood and crumbly drywall. None of my lights will perforate the envelope. My first time ever built doors and frames will be square and straight and have perfect seals around the full perimeter. All of my HVAC penetrations and ducting will be absolutely airtight. Even my condensate drains will be capped and watertight!! Oh yee of little faith...
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Oh wait, wha happened? Am I awake or am I still daydreaming....
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Yah, somewhere in those suggestions is a sensible middle ground where I'm not spending too much time and money for equipment I won't need vs. saving myself a ton of work in a hot, cramped space later when it turns out some of it is actually needed. I think roof, eave and wall penetration are best made during construction rather than later. I love the idea of dumping the stale pressure relief air into the lobby. I'll have to give that some thought as there may not be much if any attic space where the roof line crosses the dividing wall between theater and lobby. The lobby will be built to the same standards of impermeability as the main theater, but it may have a few more penetrations. I'll have to give that some more thought, too. Hopefully it will still be pretty tight, but the proof will be in the test. I'll have to take a hard look at my damper selections as those have the potential for major air leaks. None of the lights or speakers will penetrate the inner envelope. If backer boxes are constructed to house any of the speakers, they will be constructed the same as the walls and fully caulked around the perimeter where the join the drywall. All wiring that penetrates the envelope will either be in conduit or will be in small through-holes that are fully caulked. But as you and Dennis Erskine state, its all in the details.....

I decided to have the blower door test done once the interior shell is complete, as much to satisfy my curiosity (and yours) as to find potential leaks that would degrade STC performance and thus my subsequent enjoyment. It might be worth doing once the exterior shell is complete as well to identify major air leaks and correct them before those areas become inaccessible. I'll have to shop around and see where prices are running if it makes sense to do multiple tests... I will have to carefully seal a lot of conduit for the test(s) and later remember to seal it again once the wiring is complete.

And yes, the exit door from the lobby empties out onto an upstairs loft in an open floor plan grand room.

Mike
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post #41 of 70 Old 05-18-2020, 06:10 PM
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I'm sorry I woke you from your daydream, but I thought you would be interested in Dave's opinions and suggestions.

I'm glad you have decided to get a blower door test done, I was actually going to suggest 2, but felt like I had my hand too deep in your piggy bank already. If you are going to contract out the shell construction, it might be a good idea to put a clause in the contract that it will be tested by 3rd party and must meet XXX leakage before you pay them. It will likely cost you a little more, but they will be much more cautious about their work. It would be a good idea to have the contractor there the day the blower door test is done and watch them skamper around with a caulking gun and see if they can reduce the leakage.

There are many places where the energy and acoustic realms converge, and there is a lot of snake oil out there for both. As I mentioned BPI is an organization that certifies energy raters. They are supposed to be for existing homes, RESNET is the organization that does the same for new residential construction. You'll find that most of these guys are totally anal about their code of standards and testing procedures and will tell you about them ad nasaum. Anything that they can't clearly identify is usually described as convection currents within the wall. Everblue, is a training institute that does a lot of prep training for the BPI and RESNET tests as well as Energy Vanguard. Sometimes there will be someone certified to do blower door testing working for an insulation company or even an HVAC contractor. I'll bet one of the training institutes has a database and can connect you with one living in your area. Another place to check would be if the Texas Community College system offers the training and see if they have a public database. By the way, they do have a ductblaster test to test for overall duct leakage. They use the same blower with some different attachments. If you don't measure it, you're just guessing.

As far as air sealing conduits, are you familiar with duct seal? Like the duct tape we have all learned to love, it's not designed to use on ductwork. It's a gray putty sold in the electrical sections of the big boxes for a couple $ per pound. It's perfect for sealing around wires at conduit terminations. It seems to stay pliable for all eternity and will not harm the wire insulation. No odor and doesn't stick to your fingers too much. Might want to go ahead and buy a 5 gallon bucket. Another thing to look at is the HVAC lineset penetrations, you will have 3 of those. I can't think of a brand off the top of my head, but I know there are several out there claiming to be airtight.

I'll let you return to your daydream now.
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The air you refer to as "stale" is not stale at all, it's cooled, dehumidified, and oxygen replenished. It's just a little excess that might be present in your theater, it's likely better than what's inside your house.

Out of curiousity, I've ordered a copy of Mr. Gervais' book, it's due Thursday. I'm sure his acoustic theories are "sound", but would like to see how some of his HVAC recommendations came to be. As far as the barometric damper; with your new understanding of static pressures and air movement do you think in a building built 30 years ago and probably very leaky as to today's standards, do you think it would ever open at 0.4" WC? It was a really good thought, but I wonder if it were ever tested. If they even called the building owner back to check, their opinion would probably be based purely on their comfort and no negative effects on the acoustics and if they even knew it was there probably didn't care. So it works great, at least that was the perception. Any further designs included the barometric damper since it worked so well, and 25 years down the road, they have included it in all designs since it has worked so well for decades.

The HVAC industry is loaded with old "rules of thumb", many of which have now been debunked. You saw yourself in the load calculation, that's probably the worst offender. This is part of the niche that NCI slipped into. All they concentrate on is air movement and teach how it can be accurately measured. I can tell you for a fact that load calcs work. My house is slightly >5K sq ft including finished part of the basement. I was originally talked into installing 8.5 tons of A/C. 3ea 2 ton units and 1ea 2.5 ton including a separate 2 ton for the basement. The equipment short cycled and humidity was running >60% indoors and I worked on the damned things for nearly 20 years. That's why I started researching and buying central dehumidifiers as well as seeking training. I searched for a year to find someone who would do an accurate load calculation. I had to do a little duct work and now have a grand total of 5 tons. There are 2ea 1.5 ton units, and a 2 ton 2 stage unit that is zoned with the basement being one zone on that unit. I'm still over sized simply because a 1.5 ton conventional unit is the smallest unit any manufacturer makes. I tested their efficiency using the NCI methods and all 3 units are performing >90%, the national average is around 60%. This is where the sizing delima comes in for contractors, they are scared to put in a smaller unit, and if the customer says it's not cooling properly, they recommend a larger one. A larger unit with duct sizing that was probably too small for the smaller unit. And so the problems keep on keeping on, energy usage increases even with newer higher SEER equipment and failure rates go up. NCI teaches to concentrate on duct sizing and air flow and save money on the equipment. As of last July all furnaces and air handlers manufactured had to be equipped with ECM motors which are constant torque. They will hide a multitude of sins in duct sizing and air distribution, but will take their toll eventually when the much more expensive blower motors have to be replaced. Oh yeah, my electric bills have gone down about 25%. I keep looking for time to do a spread sheet comparing KWH usage to cooling degree days for each month. I have data from before the replacement so I want to get a ratio of those 2 points of data to get a true understanding.

If you don't measure it, you're just guessing.
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post #43 of 70 Old 05-19-2020, 03:00 AM - Thread Starter
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Originally Posted by Bourbon County View Post
I'm sorry I woke you from your daydream, but I thought you would be interested in Dave's opinions and suggestions.
Yes, thank you for reaching out to him. You guys definitely have me reconsidering some of my assumptions, which is always a good thing!

I'm glad you have decided to get a blower door test done, I was actually going to suggest 2, but felt like I had my hand too deep in your piggy bank already. If you are going to contract out the shell construction, it might be a good idea to put a clause in the contract that it will be tested by 3rd party and must meet XXX leakage before you pay them. It will likely cost you a little more, but they will be much more cautious about their work. It would be a good idea to have the contractor there the day the blower door test is done and watch them skamper around with a caulking gun and see if they can reduce the leakage.
Excellent idea about putting the leakage performance spec in the contract! If it's not in the contract, it won't get done.
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....If you don't measure it, you're just guessing.

As far as air sealing conduits, are you familiar with duct seal? Yes, I have a brick of that stuff I labeled "C4" in the garage. I've used it to seal subwoofers where they mount in the enclosure. I plan to use it in lieu of the much more expensive putty pads to seal electrical boxes that are recessed rather than surface mounted. Like the duct tape we have all learned to love, it's not designed to use on ductwork. It's a gray putty sold in the electrical sections of the big boxes for a couple $ per pound. It's perfect for sealing around wires at conduit terminations. It seems to stay pliable for all eternity and will not harm the wire insulation. No odor and doesn't stick to your fingers too much. Might want to go ahead and buy a 5 gallon bucket. Another thing to look at is the HVAC lineset penetrations, you will have 3 of those. I can't think of a brand off the top of my head, but I know there are several out there claiming to be airtight. Yep, they'll be getting special attention as well.

I'll let you return to your daydream now.


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Originally Posted by Bourbon County View Post
The air you refer to as "stale" is not stale at all, it's cooled, dehumidified, and oxygen replenished. It's just a little excess that might be present in your theater, it's likely better than what's inside your house.
True dat. I need to change my nomenclature to reflect the reality of the situation and to influence my thinking to make better decisions about how to handle this "excess conditioned air". After all, perception is reality and our perceptions are colored by our biases.

Out of curiousity, I've ordered a copy of Mr. Gervais' book, it's due Thursday. I'm sure his acoustic theories are "sound", but would like to see how some of his HVAC recommendations came to be. As far as the barometric damper; with your new understanding of static pressures and air movement do you think in a building built 30 years ago and probably very leaky as to today's standards, do you think it would ever open at 0.4" WC? It was a really good thought, but I wonder if it were ever tested. If they even called the building owner back to check, their opinion would probably be based purely on their comfort and no negative effects on the acoustics and if they even knew it was there probably didn't care. So it works great, at least that was the perception. Any further designs included the barometric damper since it worked so well, and 25 years down the road, they have included it in all designs since it has worked so well for decades.
I had to chuckle. I'm beginning to think it was a marketing tool, as in "When we are done building this studio, it will be so airtight, you'll need a pressure relief valve to keep your ears from popping whenever the AC system kicks in!"

The HVAC industry is loaded with old "rules of thumb", many of which have now been debunked. You saw yourself in the load calculation, that's probably the worst offender.
....contractors, they are scared to put in a smaller unit, and if the customer says it's not cooling properly, they recommend a larger one. A larger unit with duct sizing that was probably too small for the smaller unit. And so the problems keep on keeping on, energy usage increases even with newer higher SEER equipment and failure rates go up. NCI teaches to concentrate on duct sizing and air flow and save money on the equipment. As of last July all furnaces and air handlers manufactured had to be equipped with ECM motors which are constant torque. They will hide a multitude of sins in duct sizing and air distribution, but will take their toll eventually when the much more expensive blower motors have to be replaced. Oh yeah, my electric bills have gone down about 25%. I keep looking for time to do a spread sheet comparing KWH usage to cooling degree days for each month. I have data from before the replacement so I want to get a ratio of those 2 points of data to get a true understanding.
Our electric bill decreased a similar amount after replacing our 20 year old, low SEER equipment with new Carrier variable speed indoor and outdoor units. Now we are adding an Ultra-Aire dehumidifier to cover those days when not much cooling is needed but the humidity is still quite high. This should also allow me to turn off "over cooling" for humidity management, which happens frequently given the dewpoint data I mentioned several posts earlier.
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post #44 of 70 Old 05-19-2020, 11:04 PM - Thread Starter
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So, I was thinking about my HVAC system (shocking, I know) and I thought I would revisit the size of the indoor unit for the main theater. We've already established that the cooling needs are rather modest (Load calc = 5130Btu + Lighting = 853Btu + Projector = 1273Btu) at around 7500Btu, but that the ventilation requirements are ~400cfm (6 room air recirculations per hour). I wanted a ducted air handler for the main theater for purposes of quiet efficient ducting as well as flexibility for incorporation of fresh air and filtration. To summarize, we need:

Cooling - 7500 Btu
Ventilation 400cfm

And here is a chart comparing several ducted air handlers that would be compatible with the system.


Originally I thought the 12,000 Btu KP12NA would be a good choice, but I was concerned about its cfm rating. I looked at the next larger size in the same line at 18,000Btu KP18NA and saw that not only did the larger unit have more than adequate airflow capacity, it was also 6dB quieter at the required system airflow. That's a big difference! Plus, the larger unit had enough cfm capacity to overcome restrictions from grilles and filters and still meet the target airflow. The downside is that this unit is substantially oversized for the cooling needs of the room; not good.

So I took one more look at Diamond System Builder and investigated the performance of the PEAD air handlers. These air handlers are a very different design than the traditional multi-position air handlers in the SVZ line, which is why I dismissed them from the outset. I'm thinking now that may have been premature. The 12,000Btu A12AA7 has more than adequate cooling capacity, and the target airflow falls in the middle of its airflow range. Furthermore, it is just as quiet as its larger cousins for the same airflow. The smaller size will cycle less frequently, which is more efficient and once the room is cooled, it should be able to switch to its low flow state for even more efficiency. Another benefit is a broader adjustment range of static pressures from 0.14-0.6" wg. The main disadvantage is the inlet and outlet duct sizes, which are fairly wide and thin. These will require careful diffuser design on the outlet to minimize turbulence while the inlet nozzle is much less critical.

How's my reasoning on this 2nd look at air handlers?

Mike
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post #45 of 70 Old 05-20-2020, 06:09 AM
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Wow, how your thinking has evolved. Kudos for being open minded about this progression.

I believe you're on the right track downsizing. I'll do some research on the Mitsubishi website before making any recommendations. I think your loadcalc probably came back a little high if anything. Air tightness and insulation are huge factors, and you've already made the wise decision to do blower door tests. You also stated that for much of the time there would be only 1 occupant which will make a pretty big difference in the load. Typically you don't design for the worst case because it so rarely happens and will cause you to be grossly over sized for the other 99% of the time.

Another factor to consider is the latent load (humidity). You have to study the manufacturers expanded cooling data on the condenser to see how it's appropriated. Most manufacturers designate 25-30% of their capacity for latent removal. By installing the Ultra Aire, the A/C will have close to 0 latent load. Normally you set the blower speed lower for better dehumidification, around 350 CFM/ton, and higher around 400 CFM/ton if humidity is not an issue. You can safely set yours higher since you aren't depending on the A/C to control humidity.

Once we work this out how about taking a look at the condenser? I'll have to look to see if they even build a 2 ton or 2.5 ton that will support 3 heads. That's where the real money savings will come in. I know that a 6K BTU is the smallest head they make, and that one in your lobby/snack area will have very little load, the one in your gear room could possibly be a 9K BTU. You could do a simulated loadcalc on that. enter the data for room size, this area only has 2 exterior walls, under appliances enter 2 or 3 electric ranges and just play around with the variables. I don't think you can ever get it up to 9K BTU.

Now I see you are looking for a circulation rate of 400 CFM, what is your target for db rating? With all of the duct liner and treatments you are planning I don't think you would ever hear any of the units you listed. Air flow is not an exact science and your actual flow rate could be a little different than listed performance. Even the NCI balancing standard is +/- 5%.

I've spent weeks spending your money, it feels good to try to save some now.
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I haven't had time to study the air handlers too much, but there are a couple more things I would like you to consider.

I don't know what material or color your roof will be. Black or dark gray or brown asphalt shingles absorb the most heat while white metal reflects the most solar gain. I realize that aesthetics play a major role and you will want the same roof as your house. Another unknown is are there mature shade trees to keep some of the sun off of your roof? The steeper the roof is, the bigger solar collector it becomes. When I mentioned air handlers/ducts in the attic in Florida i was hoping you would stumble across this: spray foamed attic. By spray foaming just the between the rafters and no attic venting to the outside, it becomes a semi-conditioned space. Even in your climate it should stay between 80-85 deg on the hottest days. This would make radical differences in duct design. You don't need that multi layered system you were talking about. Trying to move 400 CFM will be really easy, I can help you with duct design that will be efficient and very quiet. An additional benefit will be your comfort climbing up to change filters and clean condensate drains!

You are rightfully concerned about mechanicals wearing out. Any improvement you do to the envelope will be there forever and won't need any maintenance. I know there are some horror stories from the Houston area about spray foam. Don't know this to be the case there, but there a lot of hacks doing that work now. Since you have your plans why not talk to a reputable insulation contractor in your area about his recommendations, preferably someone who has been doing spray foam for a number of years and can offer some references. This contractor might possibly have a blower door and a trained operator. This is a local climate driven thing so a local would be by far your best bet.

I believe your theater ceiling is the weakest link from a thermal performance perspective with all of the things interrupting the insulation. I don't know if spray foam would have any effect on the SCT it will make a huge impact on the thermal performance.

Another good idea for the envelope regards the sheating for exterior walls. If you haven't already planned for it, installing either just a 1/2" or 3/4" layer of rigid form like polyiso will make an excellent thermal break. West facing unshaded brick walls act like a big solar collector in late afternoon/evening while the sun is near the horizon and fully shining on the wall. That wall will try to expel it's heat as temps drop some during the night, the thermal break helps prevent it from going in.

If you would like to read up on these subjects, look at Building Science Corp. their founder Joe Lstiburek (pronounced Stee-brick) is the godfater of energy conservation and probably the highest regarded expert in the field. It's also interesting to watch his videos shot at a conference, he's a little potty-mouth. Other good sources are Green Building Advisor, and Energy Vanguard.
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I haven't had time to study the air handlers too much, but there are a couple more things I would like you to consider.

I don't know what material or color your roof will be. Black or dark gray or brown asphalt shingles absorb the most heat while white metal reflects the most solar gain. Yah, aesthetics are driving this bus. We have tan asphalt shingles and dark brown cedar siding. I wish it were something friendlier from a thermal and maintenance perspective, but it is what it is...I realize that aesthetics play a major role and you will want the same roof as your house. Another unknown is are there mature shade trees to keep some of the sun off of your roof? The steeper the roof is, the bigger solar collector it becomes. I will get some shade on the walls, but the roof will probably never see shade. The pitch isn't too bad at 12:4. When I mentioned air handlers/ducts in the attic in Florida i was hoping you would stumble across this: spray foamed attic. By spray foaming just the between the rafters and no attic venting to the outside, it becomes a semi-conditioned space. Even in your climate it should stay between 80-85 deg on the hottest days. This would make radical differences in duct design. I've already had this conversation with my builder. I'm planning 2" closed cell spray foam inside the envelope on all the exterior walls and roof. I asked my builder about a radiant barrier and rigid iso foam on the outside but he was not too receptive. We'll have that conversation again before I sign off on his proposal. You don't need that multi layered system you were talking about. That was for sound isolation, not thermal insulation. I have very large grilles that penetrate 3 layers of drywall and the thin walls of the ducting will not contain the bass. I will be reviewing this aspect of the project with my acoustical consultant, Nyal Mellor. Trying to move 400 CFM will be really easy, I can help you with duct design that will be efficient and very quiet. An additional benefit will be your comfort climbing up to change filters and clean condensate drains! Likewise I need to design attic access that will not compromise my sound isolation.

You are rightfully concerned about mechanicals wearing out. Any improvement you do to the envelope will be there forever and won't need any maintenance. I know there are some horror stories from the Houston area about spray foam. Don't know this to be the case there, but there a lot of hacks doing that work now. Since you have your plans why not talk to a reputable insulation contractor in your area about his recommendations, preferably someone who has been doing spray foam for a number of years and can offer some references. This contractor might possibly have a blower door and a trained operator. This is a local climate driven thing so a local would be by far your best bet. Good to know!

I believe your theater ceiling is the weakest link from a thermal performance perspective with all of the things interrupting the insulation. I don't know if spray foam would have any effect on the SCT it will make a huge impact on the thermal performance. In general, rigid foam does not enhance sound isolation. That is why I have chosen to limit its depth to 2". I have read that that is enough to seal the surfaces and give you a reasonable amount of R-value for the depth of the foam. The rest of the depth will be filled with whatever insulation Nyal recommends.

Another good idea for the envelope regards the sheating for exterior walls. If you haven't already planned for it, installing either just a 1/2" or 3/4" layer of rigid form like polyiso will make an excellent thermal break. West facing unshaded brick walls act like a big solar collector in late afternoon/evening while the sun is near the horizon and fully shining on the wall. That wall will try to expel it's heat as temps drop some during the night, the thermal break helps prevent it from going in. Absolutely agree, our whole house has a West facing orientation to take advantage of the lake views. We have a 2-story west facing wall with nearly floor to ceiling windows! As I mentioned above, I want the rigid iso as well as a radiant barrier outside to keep as much heat outside as possible.

If you would like to read up on these subjects, look at Building Science Corp. their founder Joe Lstiburek (pronounced Stee-brick) is the godfater of energy conservation and probably the highest regarded expert in the field. It's also interesting to watch his videos shot at a conference, he's a little potty-mouth. Other good sources are Green Building Advisor, and Energy Vanguard. Thanks, I'll take a look. So far I've watched a number of videos by Matt Risinger who is a custom home builder here in Austin who uses a lot of leading edge building concepts. I think you'll like the video I linked.
Mike
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post #48 of 70 Old 05-21-2020, 11:00 AM
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Your tan roof is much more reflective than my black onyx. It really does look good with my house and I believe I have it ventilated right now. I've looked at those radiant blankets which are pretty much just bubble wrap with foil on both sides. I originally thought they were like a Ginsu knife or a Vegamatic, just a marketing scam. I did stumble across a report that the US Dept of Energy did and as it turns out it's really effective until it gets dirty. I too have a west facing house with a steep roof so I might just try this at some point.

Even with closed cell, I believe I would go ahead and get the rafter bays filled to the full 3.5", I'm assuming they are 2X4? Anything you can do to keep that attic temperature down will help in a number of ways. With their equipment already there, I can't see it costing much more at all, maybe just a little tip to the operator, maybe you have a spare case of cold beer sitting around.

Speaking of attic space, I don't know exactly how the roof over that area nor the rest of the house for that matter runs. If that space which is appox 25' X 25' is a separate roof and you are using 7.5" I-joists for ceiling joists, and the pitch is 4/12 do you realize that at the peak of the attic there will be <4' of headroom? If this is the case that will be a very tight install for the air handler and dehu even horizontal, even worse case for service.

I have another idea for your duct work: instead of using polyiso on the outside, what about Owens Corning 703? Believe it or not it is actually made to be industrial duct insulation. I'm sure you've read what a favorite it has become with the acoustics crowd. With the Linacoustic liner inside and 703 on the outside there can't be much sound leakage at all. Tape all of the joints with the foil tape with the peel off backing and smooth it out really good. The outer foil face can't hurt anything in the attic either. I believe it comes in 1", 2", and 4" thicknesses. I'm pretty sure you won't ever hear the air handler. While you're insulating, it's recommended insulating the suction line for the A/C running through attic space. It will only be 1/4" tubing so you might just look for some Armaflex to wrap the suction line along with the already insulated vapor line together.

As for the Ultra Aire, you do need to mount it on some vibration absorbers. The Mitsubishi compressor will be installed outside, whereas the Ultra Aire is a self contained unit. It's the compressor not the blower that vibrates. Look at your outdoor units and the rubber bushings everyone uses to mount the compressor on. If an air handler vibrates you've got some issues like blower wheel balance that need to be addressed. With vibration dampers size does matter. That unit weighs 70 pounds. Look for some that are rated at maybe 20-25 lbs. per and use one on all 4 corners. If you get a higher load rating they are more rigid and will tend to transmit the vibrations. When I installed mine, I just used some I had bought for some now forgotten project and they are a little stiff and I notice it a little bit. I'm the only one that notices it, but in this case, I'm the only one that matters. I'll see if I can find some that are suitable and link it to you, I'll also try to remember to make a pic and send you of mine to show the vibration dampers an how I piped the float switch/trap.

I'm in agreement with the SVZ -KP12NA air handler. I've done some looking at what is required to convert it to horizontal and you pretty much tear it apart down to the case, flip everything around and put it back together. It looks pretty labor intensive. Do you realize that it has a 1" filter built in? The thing I've been trying to research is a smaller condenser. I believe that a 2 ton 3 zone will work quite well if they even make one, but haven't quite caught on to following their website and nomenclature. The condenser is where you can save some $, both in the purchase and operating. No need to get crazy with SEER rating on this one with the insulation and duct system you have in this space. I believe a 6Kbtu head in the snack area since that's the smallest they make, and a 9Kbtu head in the gear closet, and the 12Kbtu air handler in the attic is more than you need. I do realize that on paper it's a 3Kbtu overload, but I don't forsee the one in the snack area ever running much at all. That area has conditioned areas on both sides and is super insulated too. Do their controllers on a zoned system allow you to prioritize zones? I don't know where you got the 400 CFM requirement, I suspect it's from Mr. Gervais again, and that works out to exactly 1 CFM per sq. ft., sounds like a rule of thumb to me. The mid setting on that air handler is 381/ton and I don't think your room will notice a <20 CFM difference. If you do find you need more, it is available. I remind you again it will only be at that speed when the thing is running wide open which will be a very small fraction of the time. Don't forget that you will get a little boost whenever the dehu or fresh air is running.

I didn't see the link to Matt Risinger's video show up. I am familiar with him and have watched his videos in the past though.

Is there a nice RV park anywhere near your house? I believe at this point, I'm more involved in the planning, (not the money), than anyone else other than you in this project.I might just tow my fifth wheel down and help you for a few weeks, provided it's in milder weather. By the way, I have truly enjoyed the process. I see so many people on this forum trying to hack a zone system into their home system which is a terrible idea. If your system isn't ducted and set up for zoning you can easily cause severe damage to probably the most expensive system in your home. The ones that do opt for mini-splits grossly oversize them thinking it will work better. I really appreciate your objective approach and hopefully you research my suggestions.
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WOW! I am floored by your generous offer! I would love to have someone with your knowledge and experience help me when I install this equipment. I will definitely be in touch once construction has begun on the outer shell. There are a half dozen RV parks within a 20' drive of our house, so hopefully you can find one that is acceptable (see attached map). Any of the parks in Hudson Bend are within 20' of our place.

My mention of the poly iso insulation and radiant barrier was for the outside of the house, underneath the siding. I'm not too worried about hearing the air handler (although I still want the quietest indoor unit that will perform the task). I'm worried about how much sound will escape from the room through the ducting into the attic. This is a major source of potential flanking sound and the attic will not be constructed to contain the sound as well as the rest of the theater. I will send a note to Nyal to see what he has to say with regards to acoustic isolation of the ducting and then we can revisit this topic. The 400cfm airflow for the main theater comes from the recommendation for 6 room air volume recirculations per hour, which in my case works out to be close to 400cfm. This number has been recommended by Dennis Erskine and others in this forum and seems to be gospel. I can't tell you what the underlying basis for this value is and whether it is derived from some ASHRAE chart or schedule.

Yes, I know there is not much room for equipment in the attic area. I plan to create a 3D model to make sure all the service items are accessible from the attic hatch without having to crawl over ducting. I plan to install everything in the attic before the framing for the ceiling is started for optimum access. All of the equipment will be hung from the rafters using isolation hangers such as these from Kinetics which come in a range of spring sizes:



Downsizing/Rightsizing

I have been thinking of ways to decrease the size of the indoor units and therefore the outside compressor, as well. The best way in my mind is to combine the Lobby and Rack Space cooling into one indoor unit of 9-12,000Btu (PEAD in drawing below). In doing so, I can reduce the condenser size by more than 30% (or I could use that capacity and put an indoor unit in the garage ).

One method I considered was to use a horizontal ducted unit that draws air from the rack space and blows it out into the lobby. Return air would be via vents in the rack space wall close to the floor to bring cooler air into the rack space. To avoid over-cooling the Lobby, I would use a wall mounted thermostat in the Lobby to regulate temperature. My concern with this approach is that I may not move enough air to the far end of the Lobby (18' 0") such that the area by the bathroom becomes too warm from lack of air circulation.
Edit - this drawing does not show the PEAD drawn to scale; it is much, much larger than in this drawing. So this is not a viable configuration. See the last drawing at the bottom of this post.




The second alternative I considered was to leave the Lobby wall unit in its original position and use basic fans controlled by either simple thermal switches or a proportional temperature controller for variable speed. The disadvantage is that this configuration requires additional fans and controls, partially negating the savings from eliminating one minisplit in the Rack Space. The advantage to this config is that there should be a more even temperature distribution, although there is a potential for the area by the racks and the theater door to be warmer than the rest of the room. It depends on how well the hot air from the Rack Space stays layered against the ceiling of the Lobby (see image below).





I'm not sure what's wrong with the youtube link. That particular video discussed Dr. Lstiburek's perfect wall concept.

Mike

Edit 5-25-20
After taking the time to draw my preferred configuration to scale, I now realize that it is impractical. Here is the scale drawing:

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post #50 of 70 Old 05-23-2020, 06:41 AM
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Thanks for the info on the RV parks, I'll do some research on that. Mine is 40' long and won't fit in a lot of parks. By the way, I pull it with an F-350 King Ranch edition; it don't get any more Texan than that.

I've been giving some more thought to the gear room also. I was at one time thinking of treating it like a server room or data center. I'm not sure what's under it, but maybe creating a slightly raised perforated false floor and making that space a supply plenum and pulling a good size return out of the ceiling would work. I think getting the warm air out is the key. Years ago IBM developed server room build standards if you think you could find that. Keep in mind that area as of now has no supplemental dehumidification. I don't think your gear will generate much latent load but an over sized mini head will short cycle and one of the downsides to short cycling is increased humidity. I don't think audio gear is nearly as humidity sensitive as a server, but they target humidity levels between 40-45% to help prevent static electricity. That's really low, especially in your area.

One of the PEAD units is an idea worth exploring. They aren't made to support very long duct runs but have a very low profile and fit into spaces nothing else will. I personally have aesthetic opposition to the mini split wall mount heads, but apparently people get used to them and accept them as the norm, and they are an option if nothing else will fit. If you watch any of the TV sows where people are looking at homes or condos in Hawaii or some banana republic, that's all you see. These locations typically have extremely high electricity rates.

I finally got Mr. Gervais' book yesterday and of course went straight to the HVAC and electrical chapters, hope to read the whole book this weekend. I understand now why he included the barometric damper in his design and was a good idea way back when. Barometric dampers were first designed many many years ago to use in the venting system for naturally aspirated gas, oil, and coal fired furnaces. The idea was to keep the draft positive as to the outdoor barometric pressure, if it became negative it could result in carbon monoxide spilling back into and building up in the home. There is no way of ever knowing how many people died from carbon monoxide poisioning because of those being improperly adjusted. I believe everything now has to have a draft induction fan for combustion. Remember that all residential air handlers manufactured since July, 2019 have to have ECM (variable speed) motors? The older models with PSC blower motors would start with a noticable blast of air that could easily be picked up in a recording studio. All of the ECM blowers that I've seen have a settable speed ramp up on a cooling call. They do keep the options within a range that will prevent the coil from freezing. Not only are the motors more efficient, this lets the coil get really cold during that time of lower air flow. The downside is that the supply air will be extremely cold when it gets to full speed, I personally like that. His diagram shows the barometric damper in the supply trunk ahead of any registers so I'm sure depending on how it was (mis)adjusted could open every cycle. This would also help eliminate over sizing since most of the cold air would be blown into the atmosphere. This could also potentially be a condensate making machine. I see he is from CT, obviously a heating dominated climate, this would only be worse in that climate. The carbon footprint on one of his studios must look like Sasquatch walked through! I't worked well for all these years...........

I think many of his electrical theories are wrong too, and some of his recommendations are actually code violations. When you start planning that, we need to talk some more. When he starts talking about humming from ground loops, keep in mind that he designs recording studios, not home theaters. The difference is that input devices like microphones and guitar pick ups are much more sensitive to that than amplifiers. He talks about isolated ground receptacles which in reading this forum are widely misapplied and misunderstood. In fact, in a residential application wired with type NM cable (romex) or non metallic conduit it will create a code violation. I saw where in one case they looked for a month for the source of a ground loop issue and finally cut out a section of I'm assuming was copper water pipe and replacing it with non metallic pipe because it was at a higher impedance than the other grounding electrode. This is a code violation, at least now, you must have 2 grounding electrodes and an underground water piping system is one of the most preferred electrodes.

I don't know what music you like but if it's your thing this is well worth some DVR space. If you get AXS TV on your satellite or cable they are running a concert called "The Last Waltz" off and on the entire holiday weekend. This was the last concert for "The Band" and was recorded on Thanksgiving night 1978, you have to factor that in for the audio and video quality. They had almost everyone who was anyone in 1978 as guests; Ringo, Clapton, Bob Dylan, Van Morrison, Joni Mitchell, Muddy Waters, and on and on. I recorded it and plan to give it a proper listen in my meager theater tonight.
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post #51 of 70 Old 05-23-2020, 04:08 PM - Thread Starter
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I'm not sure I need to go full-on server room standards for my simple AV closet. The main consideration is the ability to ramp up airflow/cooling as demand increases when I really challenge the system. The PEAD air handlers are actually designed for longer duct runs than traditional ducted minisplits with a static pressure rating as high as 0.6"wc. In the application for the Rack Space, I'm envisioning no ducting, so this point is moot, however, for the main theater, it becomes relevant. In that application, however, the ducting and grilles are substantially oversized, so static pressure losses should be minimal.

Short cycling, on the other hand, is a real concern for the Rack Space and even in the lobby. The Lobby will rarely have occupants, so moisture loads should be easily handled so long as the unit isn't short cycling. By combining the heat load of the Rack Space with the minimal heat and humidity demands of the Lobby, I think results in a better overall design. Mitsubishi makes a 9,000Btu (PEAD-A09AA7) that should be about right for the two areas. Although it is undersized to handle sustained peak amplifier loads, such a situation would be exceedingly rare. When such an event does occur, merely exchanging the Rack Space air volume with the Lobby air will remove the heat load and the larger air volume of the Lobby will act as a buffer preventing rapid temperature surges when sustained high heat loads from the amplifiers do occur. For the majority of its life, the minisplit will be running at minimum capacity. Even at its lowest fan setting, the minisplit is performing a complete air exchange in the Rack Space every 35 seconds, so heat build up shouldn't be a problem.

We'll have a chance to discuss star grounding and isolated ground electrical outlets in a future thread. I've spent a lot of hours researching that topic as well, thanks to Mr Gervais. As to musical preferences, I'm more of a progressive trance/deep house techno kind of guy. As I tell my kids, somebody has to be the oldest guy at the rave!

Mike
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post #52 of 70 Old 05-24-2020, 04:02 PM
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I failed to get back on the bus at the last stop. So you are planning a PEAD 9K btu in the rack space and another one in the lobby area? Or are you saying that a single PEAD 9K btu will be used to serve both areas? I don't understand how you are planning a ducted air handler and no ducting either.
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WTF! Where did my drawings go?!? I need to edit my posts above and add my drawings back in. I'm not sure what happened.

I'm now considering a single 9k for both areas. It will have less than 3' of ducting, so it hardly counts, however, it will pass through 2 filter grilles and possibly a rack cooling plenum, so there will be some static pressure loss. I'll build a return plenum to house a filter grille (#1) up high in the Rack Space and a short exit duct to mount a linear bar grille that directs conditioned air into the Lobby. I haven't drawn it out in detail yet, so I don't know if I can make it a straight shot or if I will have to introduce a 90° bend in one of the short ducts. I can place a 2nd filter grille (#2) in the wall between the Lobby and the Rack Space close to the floor for the return air from the Lobby that acts as supply air for the Rack Space to complete the circuit.

In summary, the conditioned air will exit close to the ceiling and blow into the Lobby from the ducted mini mounted in the Rack Space area. The cooler, denser air will mix with the air in the Lobby and then flow through the floor level filter grille (#2) back into the Rack Space, possibly into a plenum that supplies the racks from below. The warm air will rise in the Rack Space and be drawn into the return side filter grille (#1) for the PEAD-9K. Rinse and repeat. I'll put a drawing together tomorrow and append it to this post.


Mike

Edit 5-25-20
See the post below for the updated configuration. The PEAD was just too big to fit in the Rack Space!

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post #54 of 70 Old 05-24-2020, 06:54 PM
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Sounds good. Are you planning on a 2 ton condenser now?
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post #55 of 70 Old 05-25-2020, 10:19 AM
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After all the evolution your system has undergone in the past few weeks, I'm really interested in what it's done to your budget. I'm not asking you to post your budget or expenses, that's none of my business, but if you have a % or $ difference I would like to see that. I know I've saved you a ton on your A/C......by ton I mean 12K BTUs HaHa.

I think that what you have planned now will be efficient, precise, and comfortable. It will deliver all you need without going to excess on anything.

One question I do have is where is your fresh air intake going? Can you get it in the soffit or gable end wall or will it have to be through the roof?
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post #56 of 70 Old 05-25-2020, 10:38 PM - Thread Starter
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Here is the latest configuration for the Lobby and Rack Space. These areas will share a single 9,000Btu minisplit positioned over the bathroom door to facilitate circulation in the Lobby in conjunction with a boost fan in the Rack Space. Warm air in the Rack Space will be drawn through a fan positioned above the racks and exit through a 9x24" linear bar grille placed near the ceiling and will be directed toward the minisplit over the bathroom door. The conditioned air from the minisplit will be directed outward and downward toward the Rack Space. Cool air for the Rack Space will be drawn through a 12x24" filter grille into a plenum beneath each rack. The equipment in the racks will be supplied with the cool air from the plenum and exhaust the warm air out the top of the racks to be recirculated by the boost fan. The boost fan will have a temperature sensor based linear fan speed controller to minimize noise during low demand operations but will have the ability to ramp up the fan speed as needed.




Rack Space false wall with racks and grilles visible from Lobby.

With regards to the fresh air inlet, the gable wall facing North makes the most sense. The West wall/roof is above where I have my smoker and the east wall/roof is above the driveway and trash cans. That leaves the gable wall a few feet below the eaves (in case some smoke gets trapped directly under the eaves) as the least smelly place to get fresh air.

Just looking at the cost of the R410A AC hardware, not counting ducts, dampers or sensors/controllers and using acwholesalers.com pricing gives the following - Original system config: 36kBtu condenser with 3 indoor units of 6k, 12k and 18k Btu is $6077. The current system with a 24kBtu condenser, and 2 indoor units of 9k and 12k Btu plus boost fan hardware is ~$4617, a savings of ~$1460. Alternatively, I've saved enough to put an indoor unit in the garage...

Mike

Edit 5-26-20 Drawings updated and attached, AGAIN! This is really getting frustrating. I click Save Changes and review the post and everything looks fine, only to find out the next day that my images have disappeared. I'm so aggravated that this has become the norm for some reason.....

Edit 5-27-20 I recalculated the new system cost with the 12kBtu indoor air handler. The right sized system has saved me nearly 25% over my originally planned system and should have lower energy costs as well! Thanks @Bourbon County !
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post #57 of 70 Old 05-26-2020, 06:30 AM
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For some reason your drawing did not attach. I'm really interested in this variable speed booster fan, sounds like a good solution. Please attach the make and model on that fan.

I'm glad you can use a gable wall for fresh air intake, that keeps all the ducting in the attic space and eliminates a roof penetration. Are you going to have to have a plumbing vent roof penetration?

I wouldn't be too concerned about using a 2 ton condenser. Remember that inside the main room even at full occupancy you are still about 40% over sized even using the smallest air handler they offer. It's difficult to estimate the actual load in the rack space, the heat generation will not be constant but whatever heat it does generate has no where to go in that small space and in such an airtight and super insulated space. Where are you locating the thermostat for that unit? I am assuming that the head in your garage is just for use while you are working in there, not to maintain a constant temperature? If you are more comfortable with a 2.5 ton it won't be a problem. Like I have said before the variable speed equipment will hide a multitude of sins in unit sizing.

Do you have the Ultra Aire installed in your house yet? I actually 2 dehumidifiers in mine because of the way the zoning is set up. I had a Honeywell DR120 installed a few years ago. At that time that unit was a relabeled Ultra Aire 120H painted a different color, and cost quite a bit less than the Ultra Aire. Since then Honeywell has moved their dehumidifier manufacturing to China. That's the reason when I replaced the other one a couple of months ago I went with the Ultra Aire. Both of these have been working overtime the past week or so. I'm sure you will notice a big difference in comfort once you get it in.

Let's get started on the electrical. I have some ideas and recommendations to do the isolated ground system correctly,code legal, and I think economically.
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post #58 of 70 Old 05-26-2020, 12:43 PM - Thread Starter
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Quote:
Originally Posted by Bourbon County View Post
For some reason your drawing did not attach. I'm really interested in this variable speed booster fan, sounds like a good solution. Please attach the make and model on that fan. Here is a link for the temperature controller and here is a link to the boost fan.

I'm glad you can use a gable wall for fresh air intake, that keeps all the ducting in the attic space and eliminates a roof penetration. Are you going to have to have a plumbing vent roof penetration? Yes, at least one and possibly two roof penetrations; one for the bathroom adjacent to the theater and then there is a washer and another bathroom below the Lobby which will need venting. I don't know enough about plumbing or how the current vents are plumbed to know what the final vent stack configuration will look like.

I wouldn't be too concerned about using a 2 ton condenser. Remember that inside the main room even at full occupancy you are still about 40% over sized even using the smallest air handler they offer. It's difficult to estimate the actual load in the rack space, the heat generation will not be constant but whatever heat it does generate has no where to go in that small space and in such an airtight and super insulated space. Where are you locating the thermostat for that unit? The thermostat will probably occupy 1RU and the temperature sensor will be mounted above the racks, probably adjacent to the inlet grille for the boost fan. I haven't decided what amplifiers yet, so I don't know if they vent back-to-front or vice versa. I would prefer front-to-back or side-to-back because then I could contain the heat inside the racks and could draw directly off the top after enclosing the racks. I am assuming that the head in your garage is just for use while you are working in there, not to maintain a constant temperature? Yah, the garage door is uninsulated so I would go broke trying to maintain that space at a constant temp. In all honesty, I would probably use it more for heating than cooling whereas in the summer, I'm more concerned about dehumidification than sub 80° temps. I'm still undecided. It will be easy enough to add a 3rd unit at a later date, so I may just postpone that expense for awhile (on the other hand, to do it later I would have to evacuate the system again and recharge it, which would add substantial cost...) If you are more comfortable with a 2.5 ton it won't be a problem. Like I have said before the variable speed equipment will hide a multitude of sins in unit sizing.

Do you have the Ultra Aire installed in your house yet? It goes in this coming Monday. I'm thinking I will set the Ultra-Aire internal humidistat to 45% and set the 5Ton Carrier unit to 50% I actually 2 dehumidifiers in mine because of the way the zoning is set up. I had a Honeywell DR120 installed a few years ago. At that time that unit was a relabeled Ultra Aire 120H painted a different color, and cost quite a bit less than the Ultra Aire. Since then Honeywell has moved their dehumidifier manufacturing to China. That's the reason when I replaced the other one a couple of months ago I went with the Ultra Aire. Both of these have been working overtime the past week or so. I'm sure you will notice a big difference in comfort once you get it in.

Let's get started on the electrical. I have some ideas and recommendations to do the isolated ground system correctly,code legal, and I think economically.
LOL, you are like a kid in a candy store! The dust hasn't even settled on this design and you are already moving on!! I love it!

Mike
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post #59 of 70 Old 05-26-2020, 02:45 PM - Thread Starter
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Addendum
It's not clear in the description unless you read the whole thing, but the temp controller above will start the fan at 50% power and ramp up to 100% as the temp climbs to 10° above the set point. As the temp cools, the speed will slow in a linear fashion back to 50% at set point and then remain on until the temp drops 3° below the set point. The set point is not adjustable, but you can choose between 80°, 90° or 100° and the alarm is fixed at 115°.

This is the controller I meant to link to.....
It has the programmable setpoints and ramp rates I'm after and offers much greater flexibility. It also has a programmable relay and alarm and includes a 12v trigger output as well. You can also use a remote temp sensor for convenient display mounting. "Yeah, that's what I'm talkin' about!"

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post #60 of 70 Old 05-26-2020, 07:06 PM
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You should be able to tie the vent for the washer below, the sink, and the toilet into one 3" going through the roof. Plumbing codes differ between states, but in Kentucky you basically just build a vent manifold in the attic that ties all the vents together and you penetrate the roof with one either 3" or 4" depending on number of fixtures on system. It really helps the looks of the roof since you can take the vent out on the backside of the house. One recommendation: use a lead boot on the plumbing vent where it penetrates the roof. Probably the only downside to putting spray foam under the roof is that it is water imperemable and when you have a leak it's really hard to find and will likely so some damage before you see any sign of it. Lead is not allowed in the water system, but can be used in this application. I don't think there is a rubber compound made that will stand up to the uv light for any length of time. The only enemy the lead has is squirrels, they like to chew on it. It will outlast the next 3 roofs going on that structure.

I like the fan/controller you chose. The fan looks very much like a Soler and Palau.

Is the internal sensor your Ultra Aire the only control it will have? You might want to experiment with that setup some. Most dehumidistats have a 5% span so you might want to set the Carrier a little higher. The Ultra Aire can remove the humidity much more efficiently and quickly than the A/C.
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