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post #1 of 93 Old 08-13-2013, 05:02 AM - Thread Starter
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After what seems like months of research and planning of a workable HVAC design for my theater and equipment room, I feel only marginally better than when I had started! I've had several (5+) local HVAC contractors over and was surprised to find that none of them had any experience with this type of thing. It seems these guys think only in terms of heating and cooling. Most did not understand my desire (or the importance) to develop a plan to quietly deal with air exchange. I ultimately lost confidence in them and started to design a system myself based on best practices and common tricks found here.

Just this week I managed to find a local Mechanical Engineer who I had over to discuss the plan I had been working on. I hired him to review the plan and to suggest any modifications based on his calculations. While he's doing this I figured I'd share the plan here. Any comments or suggestions would be greatly appreciated.


Some Facts
  • I'm in Central Ontario (-25c to -30c in the winter months to 30c in the summer months)
  • Theater is in the basement and is 22' x 14' x 7.5' and will be sealed up rather tight (DD, Acoustic Caulk etc)
  • Seating for 6, though 90% of the time, just myself and my wife
  • Equipment housed in an adjacent room.
  • Existing furnace (single stage, single zone) seems to work well (no heating or cooling complaints in the house)


The Plan

I'm trying to develop an HVAC plan that works without breaking the bank. What I've come up with is the following:

  • Two six inch supplies in the front ceiling. Flex duct would be run from the main trunk inside of "joist mufflers" to a pair of diffusers.
  • One six inch "return" built in rear soffit. Rather than tie into the existing cold air return, an inline Panasonic Whisper series exhaust fan would be used to pull air out of the room (and from the PJ box) and dump it into an adjacent space where it would then get picked up by the existing cold air return.
  • One six inch "return" built above the rack in the equipment room. This time a Fantech FR-150 fan would be placed under the basement staircase and would be used to pull air out of the equipment room and dump it into another part of the basement.
  • A ductless split would be roughed in to provide additional cooling. I would likely purchase a Mr. Slim unit with the Low Ambient Temperature Kit in the spring.




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post #2 of 93 Old 08-13-2013, 06:34 AM
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This seems reasonable. Keep in mind that your powered return needs to be able to remove as much air as your supplies provide. Rule of thumb for a 6" flex supply is about 75 cfm. You'll be looking at 150 cfm for two, so that puts you looking at the 240 cfm whisperline. Those things move a lot of air, and they don't like cheap speed controllers. Morph1c and I both have them, and we both discovered that because they move so much air they generate a lot of wind noise. You'll probably need to step that 6" up to an 8", and plan on a large lined plenum to deal with the noise.

Are you planning to turn on the HVAC blower whenever you're in the roomt? If that basement stays cool year round, you may be able to move enough air from adjacent rooms to keep the theater cool. You can take a look at Morph1c's thread for a well documented approach to this. If you're going to try to keep it cool just by exchanging air with other rooms, you may need to consider stepping up to the next size exhaust fan, but then you have to deal with noise again. That said, I like that you've built in an option for direct cooling, but it certainly can't hurt to see if the room will be cool without any help.

The issue I do see is heating in the winter. With no zoning, how will you keep the heat out of the room when the rest of the house calls for heat?

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post #3 of 93 Old 08-13-2013, 06:58 AM
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Quote:
Originally Posted by J_P_A View Post

This seems reasonable. Keep in mind that your powered return needs to be able to remove as much air as your supplies provide. Rule of thumb for a 6" flex supply is about 75 cfm. You'll be looking at 150 cfm for two, so that puts you looking at the 240 cfm whisperline. Those things move a lot of air, and they don't like cheap speed controllers. Morph1c and I both have them, and we both discovered that because they move so much air they generate a lot of wind noise. You'll probably need to step that 6" up to an 8", and plan on a large lined plenum to deal with the noise.

Are you planning to turn on the HVAC blower whenever you're in the roomt? If that basement stays cool year round, you may be able to move enough air from adjacent rooms to keep the theater cool. You can take a look at Morph1c's thread for a well documented approach to this. If you're going to try to keep it cool just by exchanging air with other rooms, you may need to consider stepping up to the next size exhaust fan, but then you have to deal with noise again. That said, I like that you've built in an option for direct cooling, but it certainly can't hurt to see if the room will be cool without any help.

The issue I do see is heating in the winter. With no zoning, how will you keep the heat out of the room when the rest of the house calls for heat?

Couldn't he manually close the air vents? I know that isn't perfect but it should remove 90% of the warm air flow into the room.
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post #4 of 93 Old 08-13-2013, 07:13 AM
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Originally Posted by djkest View Post

Couldn't he manually close the air vents? I know that isn't perfect but it should remove 90% of the warm air flow into the room.

That would certainly eliminate a lot of the warm air, but I think even a little will be a problem. That said, most of the registers I've used tend to whistle when closed. Maybe I don't have good quality registers, though.

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post #5 of 93 Old 08-13-2013, 07:14 AM - Thread Starter
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Originally Posted by J_P_A View Post

This seems reasonable. Keep in mind that your powered return needs to be able to remove as much air as your supplies provide. Rule of thumb for a 6" flex supply is about 75 cfm. You'll be looking at 150 cfm for two, so that puts you looking at the 240 cfm whisperline. Those things move a lot of air, and they don't like cheap speed controllers. Morph1c and I both have them, and we both discovered that because they move so much air they generate a lot of wind noise. You'll probably need to step that 6" up to an 8", and plan on a large lined plenum to deal with the noise.

Are you planning to turn on the HVAC blower whenever you're in the roomt? If that basement stays cool year round, you may be able to move enough air from adjacent rooms to keep the theater cool. You can take a look at Morph1c's thread for a well documented approach to this. If you're going to try to keep it cool just by exchanging air with other rooms, you may need to consider stepping up to the next size exhaust fan, but then you have to deal with noise again. That said, I like that you've built in an option for direct cooling, but it certainly can't hurt to see if the room will be cool without any help.

The issue I do see is heating in the winter. With no zoning, how will you keep the heat out of the room when the rest of the house calls for heat?


I was hoping you'd chime in J_P_A so thanks! Here are some comments and some answers to your questions.

  • I'm dealing with 12" o/c joists framed with 2x10's. That means I'm limited to 6" insulated flex frown.gif
  • Yes, I was planning on the 240 cfm whisperline - which would exhaust the room and the PJ Box (both via the rear soffit). Perhaps I can move from 6" to 8" when the duct leaves the ceiling joist and enters the rear soffit.
  • Yes, this plan requires the furnace fan to be set to "ON" while we're using the theater

I didn't want to complicate my initial post too much but yes, I need to deal with heating in the winter. The best solution I've come up with is to install 2 motorized dampers on the 6" supplies and install inline duct stats along with a tstat in the theater. The idea would be that when the theater is at the desired temp and the heating cycle starts for the rest of the house, the duct stats would measure the temp of the incoming air and if above a set threshold they would close until the temp of the air passing through dropped back down. I'm not sure what equipment/models would be required, but I'd like to hear if you have any suggestions.

With this type of setup, would I need to have the Panasonic fan turn off while the supplies are blocked? If so, I can't think about how this would be accomplished.

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post #6 of 93 Old 08-13-2013, 07:19 AM
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Originally Posted by memmo View Post

I was hoping you'd chime in J_P_A so thanks! Here are some comments and some answers to your questions.

  • I'm dealing with 12" o/c joists framed with 2x10's. That means I'm limited to 6" insulated flex frown.gif
  • Yes, I was planning on the 240 cfm whisperline - which would exhaust the room and the PJ Box (both via the rear soffit). Perhaps I can move from 6" to 8" when the duct leaves the ceiling joist and enters the rear soffit.
  • Yes, this plan requires the furnace fan to be set to "ON" while we're using the theater

I didn't want to complicate my initial post too much but yes, I need to deal with heating in the winter. The best solution I've come up with is to install 2 motorized dampers on the 6" supplies and install inline duct stats along with a tstat in the theater. The idea would be that when the theater is at the desired temp and the heating cycle starts for the rest of the house, the duct stats would measure the temp of the incoming air and if above a set threshold they would close until the temp of the air passing through dropped back down. I'm not sure what equipment/models would be required, but I'd like to hear if you have any suggestions.

With this type of setup, would I need to have the Panasonic fan turn off while the supplies are blocked? If so, I can't think about how this would be accomplished.

In my thread I got many suggestions for my HVAC issues. Most people told me I should tie my theater in with a return. Like hooked into the actual return air from the furnace.

Also, if you can only do 6" ducts for a return, I think you should do 2 of them.
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post #7 of 93 Old 08-13-2013, 07:32 AM - Thread Starter
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In my thread I got many suggestions for my HVAC issues. Most people told me I should tie my theater in with a return. Like hooked into the actual return air from the furnace.

Also, if you can only do 6" ducts for a return, I think you should do 2 of them.

I'd love to use the existing return system but I have two problems...

  1. Literally all but one joist space in the rear half of the theater (which run left to right) are used up. They either contain supply ducts for upstairs rooms, 4" hrv return ducts from upstairs bathrooms or plumbing.
  2. It's incredibly noisy!

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post #8 of 93 Old 08-13-2013, 07:48 AM
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Excellent choice in using automated dampers. Here's a couple 24 V dampers (here and here). I've used the second one most recently, but only because it came in a kit I needed. You'd likely need to pick up a 24 V transformer as well to power them.

As far as controlling it, now you're getting into an area where you almost need a zone controller. If you just wanted to close them when the heat came on, I think that would be fairly simple. But trying to control them only when a certain temp is exceeded AND heat is being called for is a little more difficult. You could do it with a few relays, but that would be a bit of Rube Goldberg approach. I wonder if iRule has some options for controlling dampers and the like?

I would probably turn off the fan when the supply dampers are closed. That would be easy enough to do with a relay in box (RIB). Here's a post in my thread where I used some RIBs to turn my fan "ON" when my equipment is on. If you wanted to do the same thing, you could add one more relay and have it turn on with your equipment, and back off when a damper closed. Again, I think there are probably more elegant ways to do this with a control system. It might be worth checking into iRule to see what it can do for HVAC controls. Otherwise, if you just want to use some relays, we can probably make that work, too.

What size soffit will you have?

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post #9 of 93 Old 08-13-2013, 11:02 AM
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Would something like this help you?:

http://www.theactivent.com/
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post #10 of 93 Old 08-13-2013, 11:18 AM - Thread Starter
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Would something like this help you?:

http://www.theactivent.com/

Woah. That seems perfect in theory. Could it really work though? Hrmm.

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post #11 of 93 Old 08-13-2013, 11:25 AM
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I also concluded that an air exchange system would be most suitable to achieve the goals of ventilating the room and not spreading theater noise (i.e. soundtracks) to the rest of the house -- most notably the kitchen right above.

 

In my original design, I had a 6" flex duct supply and a 6" flex duct return, both with Fantech in-line fans.  But I got spooked by peoples' warnings about how much heat the equipment and people in" the room needed to be accounted for.  So the one modification I made was to put a "Y" connector about 35' from the supply vent in the theater which is connected to some hard metal duct in the room next to the theater.  I figured that by this point in the duct, all the sound that would be a problem would be diffused enough to not be an issue.  And certainly the little bit of duct noise coming into the system would be diffused as well by the time it got around to the vent 35' away.  

 

But the fact that I do have to heat my house in the winter necessitated some sort of damper be put in there so that heat is not injected into the the theater when the furnace is on.  I used a manual damper which is accessed in the ceiling behind my AV rack it its little AV closet.  This damper will only have to be accessed twice a year when the season changes from heating to cooling or vice versa.

 

The results of this "engineering" will be borne out in a couple of weeks when the electricity gets hooked up and I start up the recirculating fans.


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post #12 of 93 Old 08-13-2013, 11:29 AM - Thread Starter
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Another form member was kind enough to draw out this diagram for me in the spring. Does this make sense to anyone?

His description was:

"If room is calling for cooling but the duct temp goes above 82F the zone dampers will close do the spring return. Once the furnace cools down the dampers will power open. If the room wants heat, the duct stat will be bypassed."


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post #13 of 93 Old 08-13-2013, 11:33 AM
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Manual damper might be a good option as well. In this part of the country it might not be ideal because we go from heating to cooling sometimes in the same day. But if you live in an area where that's not a problem, sometimes the simplest solution is the best smile.gif

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post #14 of 93 Old 08-13-2013, 11:37 AM - Thread Starter
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Manual damper might be a good option as well. In this part of the country it might not be ideal because we go from heating to cooling sometimes in the same day. But if you live in an area where that's not a problem, sometimes the simplest solution is the best smile.gif

Unless I misunderstand something, a manual damper will not work for me as I rely on the supplies to bring in fresh air. The supplies are ideally open all the time (with furnace fan set to "on") and only close when the theater is already warm enough and the upstairs t-stat calls for heat for the rest of the house. I don't want to be jumping up and down in the middle of a movie to open dampers smile.gif

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post #15 of 93 Old 08-13-2013, 11:52 AM
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Unless I misunderstand something, a manual damper will not work for me as I rely on the supplies to bring in fresh air. The supplies are ideally open all the time (with furnace fan set to "on") and only close when the theater is already warm enough and the upstairs t-stat calls for heat for the rest of the house. I don't want to be jumping up and down in the middle of a movie to open dampers smile.gif

Well they also do sell electronic dampers, which can be open and closed remotely and can integrate with a remote programmable thermostat control unit. I think this was something BIG and I looked into originally when planning out my HVAC system but never really looked into it much beyond some initial research.
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post #16 of 93 Old 08-13-2013, 11:55 AM
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Maybe I mis-read or mis-understood your plan and my situation may be different enough from yours to not be applicable because of your latitude, but my basement is completely subterranean and pretty much is almost perfect temperature-wise all year round.  Humidity is an issue in the summer time, though.  Since you mentioned in-line fans, I assumed that you were planning a pure air-exchange system with the ductless split being the "suspenders" in your belt-and-suspenders strategy.  I also just planned on a pure air exchange system but my "suspenders" is the "Y" into the hard metal duct of the HVAC system the supplies the rest of the house.  Again, this depends on the rest of the basement (or wherever you are planning to exchange air with) being suitably conditioned already.


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post #17 of 93 Old 08-13-2013, 01:04 PM
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Unless I misunderstand something, a manual damper will not work for me as I rely on the supplies to bring in fresh air. The supplies are ideally open all the time (with furnace fan set to "on") and only close when the theater is already warm enough and the upstairs t-stat calls for heat for the rest of the house. I don't want to be jumping up and down in the middle of a movie to open dampers smile.gif

I thought about that after I replied, but couldn't get back to update it.

The diagram you have above looks to be a good solution. It would certainly do what you're asking. I'd have to double check the connections that are shown, but whoever did that seems to know enough about HVAC to have those labeled correctly. You even have the part numbers you need. To add the fan, you just need to wire in another relay from the T-stat to turn the fan on/off.

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post #18 of 93 Old 08-13-2013, 01:14 PM - Thread Starter
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I thought about that after I replied, but couldn't get back to update it.

The diagram you have above looks to be a good solution. It would certainly do what you're asking. I'd have to double check the connections that are shown, but whoever did that seems to know enough about HVAC to have those labeled correctly. You even have the part numbers you need. To add the fan, you just need to wire in another relay from the T-stat to turn the fan on/off.

I suppose the question becomes, is that setup any better than a simple 2 zone controller, a couple of inexpensive motorized dampers + a cheap t-stat for the theater? it probably costs more.

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post #19 of 93 Old 08-13-2013, 01:23 PM
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The setup above doesn't actually turn on the AC or the heat. The T-stat just controls whether or not the dampers are opened or closed. You are depending on the air in the rest of the house to be cool enough or warm enough to keep the theater comfortable.

Compare that to a zoned system where it will either turn on the heat or turn on the AC depending on what the theater needs, and not affect the rest of the house.

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post #20 of 93 Old 08-13-2013, 01:31 PM - Thread Starter
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Well, in the setup that I imagine, its not a "real" two zone system. Basically I'd have a zone controller and 2 motorized dampers for the supplies into the theater. All I would be able to do is control whether the dampers are open/closed with the help of a t-stat in the theater. Without major re-jigging to the ducts, I wouldn't be able to heat or cool ONLY the theater space for instance.

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post #21 of 93 Old 08-13-2013, 01:37 PM
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Here's a slightly revised version of the above scheme with the relay added for the fan. This would turn the fan on anytime the dampers are open.



It sounds like you're asking for the same functionality from either setup, in which case I would think using the T-stat and relay would be cheaper. In either case you will have the same dampers and T-stat, so that cost is a wash. The relay I have shown costs $16 which is much cheaper than a zone controller.

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post #22 of 93 Old 08-13-2013, 01:41 PM
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And what happens when the basement is getting heated by the HVAC and the theater is already too warm? I guess you'll just have to plan for that and use the theater to heat the rest of the basement.
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post #23 of 93 Old 08-13-2013, 01:47 PM
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And what happens when the basement is getting heated by the HVAC and the theater is already too warm? I guess you'll just have to plan for that and use the theater to heat the rest of the basement.

I think this will be a problem with any passive system (or pseudo-passive in this case). I was operating under the assumption that since the house has a single zone, the basement isn't actively heated (T-stat on the first floor?). However, even if the furnace has to "warm things up" to 68 degrees, that's still reasonably cool air to use in the theater once the furnace shuts back off. The problem being if you have a long heat cycle, those dampers will stay closed until the furnace is done with its thing, and the whole time the temp in the theater is getting higher and higher.

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post #24 of 93 Old 08-13-2013, 01:55 PM - Thread Starter
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So if I understand correctly, this is the "duct stat" he recommended:

http://www.pexsupply.com/Johnson-Controls-A419GBF-1C-Single-Stage-Digital-Temperature-Control-24v-SPDT

The little unit would be mounted somewhere outside the theater (probably in my unfinished storage room and the remote sensor would be placed inside the duct. The dampers would be closed if the air moving thru the ducts was warmer than what was set as the threshold on the unit. Seems to make sense. How does the in-room t-stat play into things though I wonder? I'm missing a piece of the puzzle smile.gif

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post #25 of 93 Old 08-13-2013, 02:09 PM
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You are correct about the in-duct t-stat. The in-room T-stat is responsible for deciding whether you actually want the dampers open when the furnace is supplying heat.

The logic is something like this.

The room is HOT (above the cool setpoint) - The t-stat calls for cool. IF the duct stat says the air inside is cool, it lets the dampers open.
The room is COLD( below the warm setpoint) - The t-stat calls for warm air, and this bypasses the duct stat and opens the dampers to allow air into the room.

If you never expect to need heat in the room, you could eliminate that part altogether, and just use the duct stat. You would essentially turn the AC blower on at the main T-stat in the house, and the duct stat would decide if the air is too warm to be used in the theater or not.

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This sounds like a perfect solution. And its pretty inexpensive smile.gif

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post #27 of 93 Old 08-13-2013, 02:21 PM
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Which one?

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The duct-stat option with two motorized dampers, the t-stat in the theater and the relay to control the exhaust fan in conjunction.

So I need:

1 x Johnson Controls A419GBF-1C Duct stat ($58)
1 x T-stat for theater (any recommendations?)
2 x 6" motorized dampers - it was suggested to use these 3 wire versions as they are more reliable. ($95 each)
1 x RIB2401B relay ($16)

So for about $300 bucks I can make this happen smile.gif

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post #29 of 93 Old 08-13-2013, 02:53 PM
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Why not have the return from the theater direct to the HVAC system (though a dead vent if so desired).

You can add the whisperline fan on an intermittant timer or occupancy sensor to move the stale air out into the adjoining room. If the HVAC is not on in the theater the makeup air would be furnished from the HVAC return. Otherwise the whisperline would be creating a negative pressure in the theater, as the damper furnishing the supply duct would be closed.

Install a zoned system.

Wire an ice cube relay at the zone controller such that if the theater thermostat calls for cooling, it interrupts the call for heating from the other zone. ie connect the NC terminals of the relay to the W (heat) terminal on the house thermostat and the furnace. When the theater thermostat calls for cool, the call for heat on the first floor is interrupted and the damper to the first floor closes so no cool air is pumped to the rest of the house.

If the rest of the house is calling for cooling, it would receive cooling, as we are only interrupting the call for heat.

Basically it's priority cooling for the theater. There are probably fancy controllers out there that will allow you to do the same thing, but at a much higher price point.

As noted, 240cfm through 6" is not going to be quiet.

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Looks good! Sadly, I don't have a recommendation on the thermostat. I think the important part is it needs to be able to switch between heating and cooling automagically. Outside of that, anything will do.

BTW, if you have the space to pull one 8" line off of the supply, you would save yourself a damper. I'm not sure how your ductwork is laid out, but if you can bring the 8" off the supply, put on the damper, and then split off with two 6" lines, you'd have the same result with one less damper to deal with.

Edit. Just saw Mr. Tim's post. When in doubt, I defer to Mr. Tim smile.gif

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