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post #1 of 43 Old 03-13-2013, 12:48 AM - Thread Starter
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My room is 17' x 11'. Was thinking of putting a ductless minisplit in there to heat and cool separate from the rest of the house so I don't have to turn the whole house up or down, not to mention running up to the thermostat on the main level. I looked in to zoning and it's beyond my budget. I checked out some videos online and the minisplit noise isn't too bad(definitely won't be able to hear it while watching a movie) Would having the minisplit and a deadvent design per Ted's diagram for a return work in this air tight HT? Thank you.


Also, I guess i'm missing a step. I've been reading about people using dead vents for their return and supply to exchange air. But how do you control the temperature of the room?

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post #2 of 43 Old 03-13-2013, 05:14 AM
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You control the temp of the air in the exchange source usually the rest of the baement. You also pray that you guesstimated the correct volume of air exchange to keep up with the heat load in the theater. If you wanted you could install a line voltage thermostat to control the fans in the dead vent system. But even if the temp is OK you may want some fresh air.
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post #3 of 43 Old 03-13-2013, 07:05 AM
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Maybe I'm misunderstanding what you're asking, but if you put a ductless minisplit in the room, I don't think you would have to have a deadvent. The minisplit will handle cooling the air in the room. However, as BIG said, you might want to have a deadvent supply and a deadvent return that is ducted to another part of the basement for fresh air exchange.

I think the setup you are getting mixed up here is where deadvents are used the exchange air from other parts of the house to cool the room without a minisplit. In that case, you have to make sure you get sufficient air movement between the cool space and your theater to keep the theater cool when it's full of people and whatever heat generating equipment you have. Not as easy as it sounds. Again, you assume that the rest of the house is a comfortable temperature (or even cool) and using that air sets the temperature in your room. Again, a thermostatically controlled fan can also be used as BIG pointed out if you are fortunate enough to have air cool enough to make the theater uncomfortably cool (I can't remember a thread where that's happened, though).

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post #4 of 43 Old 03-13-2013, 07:33 AM
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Quote:
Originally Posted by mijotter View Post

My room is 17' x 11'. Was thinking of putting a ductless minisplit in there to heat and cool separate from the rest of the house so I don't have to turn the whole house up or down, not to mention running up to the thermostat on the main level. I looked in to zoning and it's beyond my budget. I checked out some videos online and the minisplit noise isn't too bad(definitely won't be able to hear it while watching a movie) Would having the minisplit and a deadvent design per Ted's diagram for a return work in this air tight HT? Thank you.


Also, I guess i'm missing a step. I've been reading about people using dead vents for their return and supply to exchange air. But how do you control the temperature of the room?

Have you actually gotten an HVAC installer to give you an estimate for adding zone control or are you basing costs on retail hardware pricing? A quick internet search shows the typical minisplits appears to run around $1000 + installation (not a DIY job). When we had our HVAC systems replaced a few years ago, adding zone control for the theater room was about an $800-1000 upcharge, depending on the quote. Obviously, price may vary with the difficulty of the install and my installer may have absorbed some of the zone cost into the overall system replacement cost.

With our zone setup, only clue that the HVAC is running in the theater is if you happen to feel the air flow or hear the relay in the 'stat click...no noise from the vents themselves. :-) You probably want to check out minisplits in operation first hand before you decide if they're quiet enough for you...a video recording tells you nothing about actual volume levels. Speaking of anecdotal evidence, we rented a mountain cabin a couple of years ago that had minisplits throughout...while quieter than a typical window A/C, they were still considerably louder than even my old Infocus X1 projector...certainly louder than I would find acceptable in my theater room and loud enough that we had to ride the TV's volume control as the A/C cycled on/off. Noise will vary by brand and model, though, so maybe this house just had bad examples of the breed. YMMV and caveat emptor. :-)

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post #5 of 43 Old 03-13-2013, 09:39 AM
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I am planning a ducted mini-split, with the air handler mounted in the attic outside the theater sound envelope. We don't normally air condition homes here, so the theatre will be the only room in the house with A/C. Thus we will have "wooly worm" ducts to to and from the theatre, with the obligatory 4" x 36" Nailor-type bar diffusors for supply and return. This setup also facilitates fresh air exchange. One of the challenges I am working on is that the mini-splits typically come with integrated remote controls, which is a complication when you want to integrate it with your remote controls (iRule, in my case). Still trying to figure out if I can substitute a conventional automation-friendly thermostat.
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post #6 of 43 Old 03-13-2013, 12:20 PM
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Originally Posted by riverwolf View Post

A quick internet search shows the typical minisplits appears to run around $1000 + installation (not a DIY job).

I disagree with the above DIY assertion.

A mini-split is quite simple to install. The only part most would probably not be able to perform is connecting the refrigerant line since it has to be evacuated and potentially topped off, but that's roughly a $100-200 service call for an HVAC tech. The model you appear to have had experience with must have been very old or inexpensive. Current models are very quiet.

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post #7 of 43 Old 03-13-2013, 12:59 PM
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Originally Posted by rms8 View Post

I disagree with the above DIY assertion.

A mini-split is quite simple to install. The only part most would probably not be able to perform is connecting the refrigerant line since it has to be evacuated and potentially topped off, but that's roughly a $100-200 service call for an HVAC tech. The model you appear to have had experience with must have been very old or inexpensive. Current models are very quiet.

Agreed that running the linesets shouldn't be much harder than pulling cable. As you mention, the refrigerant charge was the main "installation" I was referring to. However, there's also the electrical connections to be considered...while possible to DIY, I"m sure most would rather let a contractor add the necessary dedicated circuits. So figure another couple $100s for electrical. Don't forget to pull your permits, at least in my jurisdiction, for the electrical and HVAC work, so you're probably looking at minimum $500 on top of the purchase price of the hardware.

One also needs to look at the limitations for lineset lengths for the particular minisplit they're considering. You might find you can't place the outdoor unit in an aesthetically acceptable location.

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post #8 of 43 Old 03-13-2013, 01:52 PM
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I just had a quote for a Mitsubishi minisplit. Our local power company offers a $750 rebate, but even then, the installed price was over $3700...
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post #9 of 43 Old 03-13-2013, 02:21 PM - Thread Starter
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Well I'm looking at a very small one. Only need one for the 200sqf room.

The other side of my basement is 100% un insulated utility room. While it never gets frigid on that side in the winter, it certainly is not warm comfortable air.(my wife gets cold easy) I just don't see that being realistic and plus if I have 6 people in this room and need to cool just that room down quickly, I don't see how a deadvent supply is going to do a good job at that. So I'm thinking using the minisplit for warm/cold air according to the rooms needs and the deadvent return to have proper air flow and fresh air.

Another question would be how to control the fan motor inside the return deadvent. Would the termostat you suggested BIG work for this. As far as kicking on when I need it to?

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post #10 of 43 Old 03-13-2013, 06:59 PM
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Are you planning to add a supply?

You have several options for how to control the fan. You can put in a line voltage thermostat as BIG suggested, the other easy options that I see would use a relay to turn on the fan whenever some other component in your theater turns on such as the AVR or PJ. That way you are circulating air whenever the theater is in use. You might be able to setup a relay to turn on a fan when the minisplit turns on, but I would think that would be getting more complicated.

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post #11 of 43 Old 03-13-2013, 07:03 PM - Thread Starter
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Do I really need a supply with the minisplit providing the air hot or cold? Is there a way to have the dead vent fan NOT run for the entire movie or is that recommended. Seems a bit overkill. Perhaps in intervals.

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post #12 of 43 Old 03-13-2013, 07:26 PM
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I may be wrong, but I don't think a ductless minisplit brings in any fresh air. So the return wouldn't have anywhere to pull fresh air in without another deadvent just for that purpose. I don't have any experience with minisplits, so I'm just going on the pictures that I've seen.

It's recommended to have four to six fresh air exchanges per hour. If you decide to meet that, then you can run a slow fan the whole time, or a fast fan for short intervals. It doesn't matter. Just however you want to get there. Keep in mind that you'll want to minimize the noise, and faster fans tend to be louder.

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post #13 of 43 Old 03-13-2013, 07:38 PM - Thread Starter
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Those minisplits work kind of like a central air unit. They use air from the outside and heat or cool it and send it in to the room. That's all a CA unit does and furnace right? I may be wroung pretty noob in HVAC.

The four to six exchanges is good to know. Let's say I watch a 3 hour long movie. How long should the fan be on, on slow?

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post #14 of 43 Old 03-13-2013, 07:51 PM
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A central air unit doesn't move air from outside to inside. It only cools the air inside the house. The unit on the outside expels the heat removed from the air inside the house.

You have to calculate the volume of your room. Let's say 200 s.f. with 8' walls. That's 1,600 cubic feet (c.f.). You need to move that a minimum of 4 times per hour (4 times/ 60 minutes). That works out to 107 cfm (1600 c.f. * 4 times / 60 minutes). Now, you can either get a small fan connected to a small duct that operates around 110 cfm which will likely be loud, or you can get a larger fan connected to a larger duct that moves the same amount of air at a lower velocity. The Panasonic whisper line fans are pretty popular here because they are quiet. If you turn your fan off for half that time, then it will need to run at 2 times the capacity to make up for the time it's off.

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post #15 of 43 Old 03-13-2013, 07:57 PM - Thread Starter
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Oooooo! So how is the other side of the basement going to have fresh air then? Where is this fresh air initially coming from? In the summer with the CA on and no windows open obviously, the house doesn't get stuffy or anything. How is that different than one small room? Sorry just trying to understand the mechanics of this whole monster.

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post #16 of 43 Old 03-13-2013, 08:06 PM
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The standard that the four to six exchanges comes from is intended to provide "fresh" air exchanges as you've pointed out. I don't think most homes meet this criteria, but there is a larger volume of air to dilute the "stale" air. Opening and closing exterior doors as well as all the vents in the bathrooms and the kitchen vent provide some air exchanges. if your house is older and/or has fiberglass insulation, then you also get a lot of exchange through leaks in your building envelope. Newer houses, and particularly homes with spray foam insulation have little to no leakage, so they rely solely on the air exchange mechanisms mentioned above unless they have an ERV of some variety.

At any rate, the idea is four to six people in a small room will get stuffy pretty quickly. Compared to that, the air in the rest of your home is "fresh." I don't think it really meets the intent of the standard, but it's an oft quoted value, and it's seemed to provide good results for a lot of people on this forum. As an example, you can checkout The Black Cat Theater where Morph1c used dead vents to keep his room cool. He documented quite well the amount of air he's moving as well as testing his room with several heat sources to see if his approach was viable. It's a good resource for anyone looking for cheap alternatives to HVAC.

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post #17 of 43 Old 03-13-2013, 08:14 PM - Thread Starter
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Ok so would it be an idea to maybe put the minisplit on the other side of the basement? That way it's one less thing that creates noise and is not on the wall in the theater room. What it all comes down to is i'm looking for the most economical way to have my HT on it's own heating/cooling in case I need to raise the temp or cool the room without raising and cooling the rest of the house. I still fail to see how using the other end of my basement as supply and return will give me any of these options without some sort of device in one of the rooms cooling or heating it to where I want.

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post #18 of 43 Old 03-13-2013, 08:21 PM
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I've seen this mentioned before, but I can't think of a thread off hand that has done this. The primary advantage is to limit the noise in the room, and, as you said, eliminate the wall clutter. The down side is you have to add a powered supply and return into your room. A ducted minisplit might be just as economical. I really have no idea.

A quiet minisplit will work in the room. You may not even need the fresh air. It just depends on how many people will be in there and how tightly your room is built.

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post #19 of 43 Old 03-13-2013, 08:38 PM - Thread Starter
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Gosh, so since the minisplit just cools/heats the air already in there, and the return will be dumping the air out. I would almost NEED a supply of some kind huh? Ugh I don't like more holes in my wall and I cannot do a soffit because of ceiling height issues.

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post #20 of 43 Old 03-13-2013, 08:51 PM
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Well, you could round up all the neighborhood dogs, preferably some big ones (think great danes or mastiffs) and lock yourself in your theater for three hours. If you haven't decided you need the extra ventilation by then, well, you're probably good to go without it biggrin.gif

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post #21 of 43 Old 03-13-2013, 09:12 PM - Thread Starter
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lol won't need it since i'd probably be a corpse. How much do those Panny fans you mentioned cost?

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post #22 of 43 Old 03-14-2013, 02:06 AM - Thread Starter
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I was wondering if an ERV would work.

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post #23 of 43 Old 03-14-2013, 05:22 AM
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yes just make sure it is quiet, Panasonic makes some "whisper" series units designed for in-ceiling mounting in one room, Not sure how quiet they are. This one looks pretty quiet in the low speed mode.

http://www.iaqsource.com/product.php?p=panasonic-whispercomfort-spot-erv-fv-04ve1_panasonic_fv-04ve1&product=171090&utm_source=google&utm_medium=Product_Search&utm_campaign=google_base&gclid=CNfoycWY_LUCFQKrPAodaiwACg
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post #24 of 43 Old 03-14-2013, 04:56 PM - Thread Starter
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Thanks for the link Big. So i just spent the last hour talking to my wife about everything we talked about last night J. She thinks getting a minisplit is an unnecessary expense. The room is already hooked up to the furnace with 2 supplies and 1 return. The room gets warm or cold quickly and i'm thinking will hold that temp fairly easily with it being so well insulated. She was thinking running the deadvent return and just have one supply that is hooked to the furnace and control the temp/airflow through the vent inself whether opening it all the way or closing it slightly. Was thinking of maybe putting a relay on the deadvent fan to always kick on when the furnace does, that way it's not constantly sucking air out of the room even if the supply isn't on.

I have a fairly modest budget and am still saving for a nice panasonic projector so multi zoning is out of the question, and those minisplits are a littler higher than I would like.

Does this seem like it would work? I'd say 80% of the time it'll just be her and I down there. Any critiques or tips would be most helpful thanks.

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post #25 of 43 Old 03-14-2013, 06:02 PM
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Not to make things more confusing, but here are my experiences.

I installed a mini-split in my theater room. Installed the electrical, wall unit, outdoor condensing unit and copper lineset myself. I had a buddy come over and pull a vacuum on the lineset and then I released the refrigerant charge. Pretty simple depending on how comfortable you are with that type of work. I spent about $800 when all was said and done, but I had a good source for the split system, I isntalled the unit myself, and had a buddy evacuate the refrigerant lines.

A few comments I have on my system now that it has been operational (and used a few times).
-If it is just me and the wife watching a movie, the split system is not used. The heat does not build up enough with just the two of us.
-When I have 4 or more people in the room, its very nice to have. Put it on low and it cools the space perfectly (and it quiet).
-I do not have supply or return vents installed in my room for fresh air. It does not seem to get stuffy in there at all.
-I installed ductwork in the soffit area in case I wanted to install them at a later date. I do not feel it is necessary.
-My house does not have any true "fresh" air coming into the house, infiltration or an open window are the only ways fresh air is introduced. I personally think the ERV is unnecessary.
-For purely aesthetic reasons, if I were to build my room over again, I would install a ducted mini-split. Mainly because a nice painted linear diffuser would look better than the white wall mounted unit.
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post #26 of 43 Old 03-15-2013, 08:26 PM
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Quote:
Originally Posted by mijotter View Post

Thanks for the link Big. So i just spent the last hour talking to my wife about everything we talked about last night J. She thinks getting a minisplit is an unnecessary expense. The room is already hooked up to the furnace with 2 supplies and 1 return. The room gets warm or cold quickly and i'm thinking will hold that temp fairly easily with it being so well insulated. She was thinking running the deadvent return and just have one supply that is hooked to the furnace and control the temp/airflow through the vent inself whether opening it all the way or closing it slightly. Was thinking of maybe putting a relay on the deadvent fan to always kick on when the furnace does, that way it's not constantly sucking air out of the room even if the supply isn't on.

I have a fairly modest budget and am still saving for a nice panasonic projector so multi zoning is out of the question, and those minisplits are a littler higher than I would like.

Does this seem like it would work? I'd say 80% of the time it'll just be her and I down there. Any critiques or tips would be most helpful thanks.

When you say the room is hooked up to the furnace with 2 supplies and 1 return... is that in addition to another return on the floor? The answer leads to 2 possibilities:

1) If you essentially have 2 parallel loops - supply & return for the theater, and supply & return for the rest of the floor... you're in pretty good shape. I would be inclined to just see how it goes. Air the furnace pulls in from the room will mix with the air pulled from the other return and you'll get "fresh" air, same as dead vent. Zoning a system like that should be relatively inexpensive. When you check prices, explain that you already have dedicated supply & return ducts run to the room and are just looking to make it a separate zone. I don't see a dead vent really buying you anything. A mini-split would be overkill.

2) If the only return for the floor happens to be in the theater room, then things are more complicated. That would mean the 2 supplies in your theater plus all the other supplies on the floor were intended to return through the theater room. In that case, at a minimum you'll want to put in a 1 way passive dead vent that will allow the other rooms to pass their air into the theater so it can be returned properly. If you don't, and your theater is sealed, you'll starve the furnace of return air. In turn it won't be able to supply as much. When you're cooling and have less than the designed airflow there is actually risk of the condensation removed from the air freezing on the coils. The ice blocks more air further compounding the airflow problem. It creates a vicious cycle, performance plummets, and there is risk of damaging the equipment (or having the unit shut itself down to prevent damage). So put a dead vent in and see how it goes. In this case, though, zoning is not as easy because they would have to run additional ducts (to create 2 parallel loops). Depending on your house layout it could range from more expensive to cost prohibitive. A minisplit could help if you placed it opposite the return, but that conditioned air would still make it back to the furnace return. Not a big deal unless the mini-split is trying to cool the room while furnace is set to heat (it would just be really inefficient).

For my room I considered putting a mini-split in a dead vent. That way I could control the temperature of the air coming into the room and control it locally. I decided against all the complication and just went with a conventional forced air heat pump with 2 loops - 1 for theater, 1 for the rest of the basement. I also have an ERV which I agree isn't necessary, but a nice to have in new houses that are tightly sealed. I'm going to see how it goes. My 2nd floor is zoned with the master suite on it's own zone. If I need to put the theater on its own zone, I will, but the HVAC contractor thought it was overkill.

Edit: not saying those are the only 2 possibilities. For example, you might have 1 furnace for the entire house. But I don't feel like going through every possible permutation, so just assumed the 2 most likely cases.

 

 

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post #27 of 43 Old 03-16-2013, 12:55 PM - Thread Starter
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Oh man Rabident you sure threw a monkey wrench in here lol. But that's good I hadn't thought about that. I didn't think was another return in the basement(as it's a smaller basement, just the theater room side and utility/storage room side) I went down and looked again and nope. The only return right now for the whole basement is in the theater room. Which is weird because when I bought the house it was finished off and separate from the other side of the basement for many many years. I took a couple pictures of the return trunks where, it looked like to me, a return used to be in the return trunk and wondering if they the sheet metal cover can be removed and a return put in; maybe it's not not sure.



I was going to dead vent the return for the theater and leave the supply from the furnace as is(just with flex duct) and see how it handles equipment and people in the room. Then If i need to take other measures, I can at that point. I figured regardless i'm going to need that hole in the wall for the supply in whatever setup I choose whether the supply is from the furnace or a dead vent.

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post #28 of 43 Old 03-16-2013, 01:15 PM
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The theater already has a supply and return in it? I'm really confused now.

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post #29 of 43 Old 03-16-2013, 01:19 PM - Thread Starter
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Yes I has 1 return and 2 supplies directly connect to the furnace. The other side of the basement has 2 supplies but no return.

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post #30 of 43 Old 03-16-2013, 01:34 PM
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If I was in your situation, I would look into DIYing a separate zone for the theater if I didn't want to pay someone to do it for me.

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