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I am getting ready to do my dead vents and wanted to discuss the safety of this type of arrangement. The room will be sealed tight as a drum with the exception of the dead vent 6" supply in and 6" return out. I will have a fan on both the ins and the outs. I was thinking of just hooking the fan outlet up to a light switch in the theater room so I could turn it off and on. That got me thinking though, what if the kids use the theater why I'm gone and don't turn on the fans at all. Will the fact that the dead vent is technically always open both in and out be enough to not let the oxygen levels drop too far? Or should I figure out how to trigger the outlet from the receiver or projector being turned on? Not sure how that is done.

What do you all think? Maybe the room is big enough it wouldn't matter, (14x22) but wanted some opinions.
 

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A single six inch supply sounds small for a dead vent which by design are very inefficient method of cooling and heating because it exchanges air that is only slightly different than what is in the theater. Unlike air coming from a furnace or an AC unit.
 

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A single six inch supply sounds small for a dead vent which by design are very inefficient method of cooling and heating because it exchanges air that is only slightly different than what is in the theater. Unlike air coming from a furnace or an AC unit.
Thanks Big. I was actually planning on two 6" supplies. One on each side of the room in the soffit just behind the beam. The return would then be on the rear wall. Can I just use my single supply fan and use a "y" connector to attach two flex ducts? or would I have to have two fans. I could also bring the supplys off the main HVAC trunk since there was one originally in this room and then use the deadvent just for the return. I couldn't control this room separately, but the air would be cooler. Our basement stays really chilly anyways. What do you think?

 

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sounds better if you are tapping the main supply duct. the volume of air will be dictated by the size of the take off before the Y. If the area is accessible you could add a damper to offer some control. I did a dead vent return on a project because of layout issues and it worked fine. keep the fan as far away from the theater as possible. There should be a regular return in contiguous space somewhere.
 

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Discussion Starter #5
sounds better if you are tapping the main supply duct. the volume of air will be dictated by the size of the take off before the Y. If the area is accessible you could add a damper to offer some control. I did a dead vent return on a project because of layout issues and it worked fine. keep the fan as far away from the theater as possible. There should be a regular return in contiguous space somewhere.
Thanks. Thats what I will do then. I'll take the supply off the trunk and deadvent for the return. There is a main basement return right outside the storage room door. I was going to add a dummy vent above the storage room door leading out to the main rec room where the return is to allow air to flow better even if the storage door is closed. If I am coming off the main trunk should I just tap the two supplies separately? As I mentioned there was only one in the room originally, but I know our unit is sized for our total square footage counting this room.
 

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Another data point for you...

In my build, I have two supplies:
1) 6" duct off the HVAC trunk
2) 6" dead vent with inline fan

1) This is the primary cooling and heating source. Works fine when up to 3 people are in the theater. Used a joist muffler with flex duct to absorb sound to avoid sound escaping into the HVAC and seeping up to our main floor. Works great. Cannot hear any sound from the ducts in the room immediately above the theater.

2) Provides auxilliary cooling. Used when room feels warm or stuffy. The fan is outside the room in a box under the adjacent stairs. The box has 2 layers of 5/8" drywall with GG between. Cannot hear the fan at all even though it is less than 2 feet from the theater.

The room has one return which is powered by an inline fan. I haven't sealed the room yet with Zero door seals, but the return has been used as frequently as the powered supply. Unfortunately, I had to put the return fan in the room. It is sealed up very tight so I don't hear it unless it is on full power. If pressure built up in the room, air could flow through when the fan is off. Similar to #1 above, used a joist muffler to absorb sound before dumping the return air in the rec room. Works fantastic.

Take the time to do the calculations to determine how much air flow you need and how large your ducts and vents should be to keep the room comfortable without introducing unwanted noise - unless you already have?
 

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I am getting ready to do my dead vents and wanted to discuss the safety of this type of arrangement. The room will be sealed tight as a drum with the exception of the dead vent 6" supply in and 6" return out. I will have a fan on both the ins and the outs. I was thinking of just hooking the fan outlet up to a light switch in the theater room so I could turn it off and on. That got me thinking though, what if the kids use the theater why I'm gone and don't turn on the fans at all. Will the fact that the dead vent is technically always open both in and out be enough to not let the oxygen levels drop too far? Or should I figure out how to trigger the outlet from the receiver or projector being turned on? Not sure how that is done.

What do you all think? Maybe the room is big enough it wouldn't matter, (14x22) but wanted some opinions.
A thread May-2014 had exact same discussion as you on Oxygen levels....a quick search on "oxygen" in posts it came up - since I posted there it was in my memory, check out the title
http://www.avsforum.com/forum/19-de...ruction/1530833-my-theater-going-kill-us.html

Ok, aside from bleeding from the ears, my wife is worried that we will all suffocate and die while watching a Lord of the Rings marathon.

We are decoupling, and the room will be pretty much sealed up. We will be using a ventless system to cool the room, but do not have vents to move air in/out of the room. She is worried that if the 4 of us are in the room for a long period of time that we will all die. I have no idea if her concerns are valid, or what, so I thought I'd ask the people who would know better.

On a side note. One of the walls is next to the stairs coming into the basement. I was thinking that the space under the stairs could be used for a dead vent system to bring air in/out without taking away space in the theater. Wasn't sure if that had been done, or made any sense.
So regarding Oxygen levels I think you have zero worries....
From data source;
http://health.howstuffworks.com/human-body/systems/respiratory/question98.htm
The average adult at rest inhales and exhales something like 7 or 8 liters (about one-fourth of a cubic foot) of air per minute. That totals something like 11,000 liters of air (388 cubic feet) in a day.

You can calculate from there.

My home theater is about 2400 cu ft, that's good for 6 people for a whole day if perfectly sealed.

Via Mikes brain/thumb interface, LLAP
Now;
for cooling load do not underestimate the heating your gear will do, especially if you have 1-2 amps for subwoofers like I do.
Even with the fan mod to slow down the fan noise, they still are making same thermal heat load into your room.
Further, the fans push out thru the front, and if you reverse those fans you will have early thermal failure....
I measured my EP2500 front fan area at 98 deg f and the iNuke6000 at 103 deg f, that hot air is blowing into your room unless you restrict it via a front glass and then have some ventilation method for your AV rack gear (AVR, sub amps, anything that generates heat really).

 

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Discussion Starter #9
A thread May-2014 had exact same discussion as you on Oxygen levels....a quick search on "oxygen" in posts it came up - since I posted there it was in my memory, check out the title
http://www.avsforum.com/forum/19-de...ruction/1530833-my-theater-going-kill-us.html

So regarding Oxygen levels I think you have zero worries....


Now;
for cooling load do not underestimate the heating your gear will do, especially if you have 1-2 amps for subwoofers like I do.
Even with the fan mod to slow down the fan noise, they still are making same thermal heat load into your room.
Further, the fans push out thru the front, and if you reverse those fans you will have early thermal failure....
I measured my EP2500 front fan area at 98 deg f and the iNuke6000 at 103 deg f, that hot air is blowing into your room unless you restrict it via a front glass and then have some ventilation method for your AV rack gear (AVR, sub amps, anything that generates heat really).

Thanks. As for heat load really the only equipment in the room is the projector, so its mainly bodies. Three kids and 2 adults usually. All other equipment is located in a closet outside the sealed theater. I am thinking of doing the two 6" supplies and increasing the return to 8" through the dead vent. I have an 8 inch fan now to give a try.
 
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