The Plains Theater - Page 17

Wow, just kinda went thru this entire thread, very nice. I'll attempt to stop by and keep up, as it was an enjoyable read.

My take on securing wires/cables etc (after decades of being around such things); In my experience, it all depends on if you're going to have access. If you have access to the area, bundle away however you wish. But if you don't have access, I would not secure them tightly. Any number of things could happen, and it's always beneficial to have the capability to utilize one cable as a pull wire for another pull. Again, that's my take,...YMMV.

Anyway, my 2 cents, and after a good read to this point, it's the least I could do.


Best of luck

Yeah, looking at those pics, I don't know what I was looking at. My advice was just big picture-overview type stuff. Please don't let it bother you, merely keep it in mind.

Your pics are great and your lot, place, wow, just the ideal combo of elements. Congrats on getting in, ....... what an exciting time I'm sure.

I'm going to peruse back thru the thread, I'm interested in the audio/acoustics aspects of the HT, so going to re-read a bit.


Again,
Good luck

....a little white noise outside from the exhaust side might be a good thing, it could help cover up any sound leakage from your theater into other rooms

Over on the Black Cat theater thread thread we had some challenges with a 6 inch version of that fan. Even with the fan connected to the theater with 15 ft of TRUE acoustical duct the transition of the 6 inch duct into Linacoustic lined box which opened into the theater was too noisy due to the velocity of the air and other pipe to box transitional noise effects. We ended up transitioning the 6 to an 8 inch duct and dumping into a refrigerator sized serpentine box on the supply side. And a coffin sized box on the return.

Hey JPA - I was just catching up on your thread and saw a couple of my own comments that jumped out at me as unclear so I thought I would set the record straight.

First, regarding the above interaction. Typically speaking a single 8 inch pipe handles 200 CFM and a six inch pipe handles 100 CFM, so it stands to reason that with the loss at the split and other air resistance that each of the two 6 inch pipes would rate slightly less than 100 CFM. In a professional design it would be more typical to split the 8" duct with a piece referred to in the industry as a "T on Taper" with the 6" pipe coming off the T and a 5" pipe (yes, five) coming off the tapered end. So in the example it would be called an 8-5-6 T on Taper. This will maintain the same CFM in both pipes, despite the pressure drop from the 6" coming off the 8" pipe first. That is for the CFM. Now, as far as the FPM (feet per minute) face velocity, this depends exclusively on your input CFM to be calculated properly. Normally, an HVAC guy will target 400 to 450 FPM face velocity....but this is home theater where the upper end target is somewhere around 250 FPM according to the Illuminati of this forum and other industry professionals. I ONLY use linear slot diffusers for the supply registers. Nailor has a handy calculator based on duct size, CFM input, etc. where you can precisely calculate the expected face velocity. However, given 100 CFM as the max throughput for a 6" rigid pipe, most applications will call for a 24" 2 slot diffuser. This will yield acoustic performance under NC-20 (Noise Coefficient less than 20db) which is the maximum acoustic noise threshold with the mechanicals running fully on. The return side is far less complex and simply involves some sort of muffler or dead vent system for the intake to sequester or suppress the light draw of the return ducting system. As I said before, 8" return is sufficient for two 6" (or one 6" and one 5") supplies, but I like to go up to a 10" due to the increased frictional resistance of the dead vent to maintain equivalent draw. If you really wish to dial it in, a damper can be used inside the 10" return pipe to slightly close off any return flow and put the entire HVAC for that room in near perfect supply / return balance. I don't know what I was thinking when I wrote the above, but it was careless and I wanted to correct my misstatement.

Second, regarding this interaction. Dennis is right, zoning systems are well-defined and relatively easy to set up through establishing zone priorities. But what I was getting at was I did not see any accommodation in your plans to add motorized dampers to truly zone out the supply lines to the theater when they are providing heat to the rest of the house. I was essentially throwing a little thought-provoking challenge to your HVAC design about throwing in some "normally open" dampers because you are cooling most of the time, but have the system close them completely whenever any other zones call for heat so the theater does not get the heat. The ducted split system naturally sidesteps all of these issues and provides you with a dedicated system for your theater where you have independent control of heating and cooling for the room and all the noisy bits are located away from the room near an outside wall. Certainly the easiest and most effective, but also the more costly option.

So please forgive my brain fart on these two points above....I promise I'll do better in the future!!

Now, let me harass you a second about clipping those ends off the cable ties....LOL!

Awesome post!

Can you add a variable speed controller to the fan? That could allow you to tweak the return flow while making things a bit quieter. I'm guessing you won't need 400CFM the majority of the time if you only have a couple people in the room.
Will your fan be accessible for maintenance?

A variable speed controller for ceiling fans will work. At Lowes for ~$20 Run at 1/2 speed

This sounds like a good option, maybe run at slow setting all the time and thermostatically get actuated to full power? 

Wow - a lot of posts since last night.... a few thoughts regarding the full conversation above since my last post:

• My CFM statistics were based on rigid duct. Even when insulated, rigid is not ideal for home theaters for soundproofing reasons. However, given your limited amount of airflow you have to preserve the function of the system first and foremost, followed by the soundproofing. As flex lines offer much higher air friction resistance, a good rule of thumb is to upsize the flex 2 inches vs. the rigid. For example, if you have 6" rigid, you should use 8" flex. If you use 8" rigid, you should use 10" flex, etc. to preserve the same air handling capacity.
• Regarding adding a 10" damper to the return air duct to balance the system....You don't want to overpressure a room with too much supply or too little return. Likewise you don't want to oversupply and under-return. You need everything to be in very close balance to work properly. If you had relatively sparse supply and a very strong return, the system will create its own "micro climate" between the supplies and the return because the negative pressure caused by the return will not allow for all the conditioned supply to mix with the room air before it is returned. Think of this as no different than water. If you had an aquarium with two tubes supplying red-tinted water and an oversized pump pulling water from the tank at a higher rate than it is being replenished.....I think it would be easy to imagine how a current would form in the aquarium where most of the "new" red dyed water would be headed straight for the pump intake and there would be diminished mixing of the red dyed water with the other water in the tank. Sometimes it is easier to visualize thermal transfer when you put it in these terms and use these example scenarios. So the lesson to learn here is - everything in perfect balance. That being said, the variable control will work to help put the system in balance, but where it gets complicated with these in-line systems NOT tied to the HVAC is how they know when to come on and off....and even further how do they know what to do when supply dampers to the theater may be closed as not to allow heat to be supplied when it is called for upstairs. Similarly, the HVAC system may not be running at all and causing the same negative pressure situation. By running the theater's supply AND return off the main HVAC system, a damper is used to balance the amount of return with the amount of supply and, when motorized, both supply and return can be programmed to close when heating is called for on the first floor or any other zone. I realize you are limited in your options and your system design by the limitation of your new HVAC system. There are ways to add zone controllers to existing equipment that can be independently set up and programmed, but it begins to cost more money to modify and make an existing system work than it is to cut bait and purchase a ducted split system so 100% of the theater conditioning is on its own dedicated zone. Hopefully this point is clear.
• I don't recall what posts, but I do remember when your house was being constructed discussing getting the right "brains" in your HVAC system so the basement could be zoned separately. If you don't have the correct control board that will allow for separate zones PLUS the pressure balance ducting and everything else needed, then your HVAC tech is right - it is difficult if not near impossible to add at this point. Although expensive, another alternative would be to purchase a two-zone dedicated system specifically for the basement. This would give you the ultimate in comfort and flexibility for your basement and your theater.
• HVAC runs on 24v signals, all AV trigger equipment runs on 12v or less. So triggering power to the in-line fan from the AV equipment is very easy. Triggering the in-line fan from any HVAC feedback is doable, but not as straightforward. Integrating the two in an either/or scenario with some sort of logic behind it is difficult and something I have personally never seen or heard of. I don't mean to shoot down your idea, but I would caution you against using the power of the Panasonic in-line far for just the PJ hush box and AVR. It is simply too powerful for those small areas. And while it will certainly pull out the heat, the greatly accelerated amount of air pulling from these areas will have your equipment filled with dust in no time. The only way to use this fan would be to carefully balance the size/length/type of the duct and the amount of CFM through this duct via damper. Of course this still doesn't solve the negative pressure issue created if ONLY the in-line fan is running and you are not receiving any supply into a highly sealed room.

I know your head may be ready to explode from the information above, but you begin to see why I am not a fan (pun intended) of one fan handling all chores....and having that fan be off the HVAC system actually supplying the room. To me, the way to go is a ducted split system dedicated for the theater, but outside of this option here is some practical advice and clarity to how I would proceed with making your existing equipment "work" as best as possible.

• Allow your projector to breathe in free space at its mounted position in the room. If you MUST (or really want) to put the projector in an appropriately sized hush box, purchase a Cool Cube from Active Thermal Management to ventilate the heat from your projector hush box to outside the room. http://www.activethermal.com/page33.html The Cool Cube can either be triggered to come on when your projector comes on, or it also has a built-in thermostatic control with variable speed fan which works extremely well to keep things at 85 degrees and less.
• For your AV closet, buy either the Active Thermal Management System 1 with the in-line fan: http://www.activethermal.com/system%201.html OR buy a 80CFM Panasonic Quiet fan and a Honeywell 120v digital thermostatic control. I personally like the Panasonic / Honeywell combination because it is significantly cheaper and works extremely well. Panasonic Fan: http://www.amazon.com/Panasonic-FV-08VQ5-WhisperCeiling-Ceiling-Mounted/dp/B003TJAGPS
• If you need more supply to your home theater, use in-line duct booster fans to draw more CFM into the theater supply lines. Install normally open dampers in the supply lines since most of your air conditioning will be cooling. Install a normally open motorized damper in the return air duct. Purchase a controller that will interface with your existing HVAC system and CLOSE the two supply and one return dampers if your primary HVAC system calls for heat. Purchase a variable fan control and match the total CFM of return with your Panasonic in-line fan to the total CFM of supply coming in to the room. Talk with your HVAC tech on ways to integrate this now-variable speed fan to come on ONLY when the dampers are open and ONLY when the HVAC system is running. Don't forget the controller will also need to turn off the in-line duct booster fans in the supply lines if the dampers close.

That ducted split system is looking better by the minute, right? Good luck!

Wow great writeup TMcG.

One option for inline fan control is a smart thermostat. I use the HAI thermostats that connect to my PC where I run home automation software. Another lower tech option might be a pressure sensing switch:

http://www.combustiondepot.com/store/cart.php?m=product_list&c=124

Hey J_P_A,

 

After playing with the fan do you think its too many cfm for just a projector hush box and equipment rack or would you step back to like the 240cfm?

 

Thanks,

 

Nicholas

Still finalizing designs?

I'm still shocked at her passing.

Your models look great, but I have a hard time understanding what your issues are and the proposals to work around. Couldn't you just put a dedicated AHU in one of the rooms next to your theater? That seems a lot simpler than trying to tap into the existing system and run lines all over the place. That way it would be self contained and you wouldn't necessarily have to use the same HVAC contractor as your house or risk impact to your main system. You could look into getting a low noise dedicated unit and run a metal soffit around the room to maxamize your cross sectional area. Maybe bring the soffit further out into the room, in exchange for shallow hegiht? Have you asked the HVAC guys that did your house what they think would be best?

Hi JPA,

Id be concerned that if they were close to each other the flow would "short circuit" and just loop back onto itself and not mix with the room. Especially due to the high velocity......

Nicholas

Oops, yeah i see now, thought they were supply and return side by side.  Ignore me.  :)