Cold Air Return


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Old 11-27-05, 01:25 PM
Fridge
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Cold Air Return

I am finishing my basement and have a wall that goes right in front of my furnace/AC by 12 inches. I was wanting to put in a cold air return right in the return trunk using a 6" starter collar, then a pipe and then a grate. However, if I have been reading it appears that a cold air return has to be a least 10' from the furnace. Can you please let me know if I can tap directly into the main return trunk (next to the forced air return) or if I have to have my return some here else and not in the main part of the furnace. Also, if you can not tap into the main cold return can you please let me know the reasoning.

Thanks.
 
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Old 11-27-05, 04:02 PM
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You can tap into it as long the wall/door breaks the two room apart.. Also have a fresh air supply in the utlity room itself..

Only down fall you will have if you do this, you are going to get the air rush sound, and also may be hearing the blower itself running.
 
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Old 11-27-05, 04:11 PM
Fridge
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Jay,

Thanks. Yes, there will be a wall between the cold air return and the furnace. The cold air return is in the room that is different than the furnance. However, am a little concerned by your fresh air comment you made. My furnace is in a room/ storage area. There is going to be two doors into this room. What kind of fresh air are you referring to here.

Also, what kind of rush are you referring to in your statement. Do you think that it will just be loud. Already can hear the blower so figure that is just something can have to live with.

Think I should do a cold air return another way but this is by far the easiest.
 
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Old 11-27-05, 04:28 PM
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You should have a pipe come into the room itself to make up the air that is drawn out of the room.. The furnace, water heater, dryer, maybe exhaust fan will pull the air out of the room itself, and that air has to be made up some how.

How old is your home?
 
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Old 11-27-05, 04:34 PM
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The home is 11 years old. I have no other air lines that I am aware of that comes in to this room. If I were to put an opening in the wall say 20' away in the drywall, say using an air grate in the opening, that I cut from one room into this storage closet would that be sufficient. The air then would be coming in from the other side of the wall in the storage closet. Also, there will be a slight air gap under the doors that air can go through that could help.
 
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Old 11-27-05, 07:53 PM
MechEng
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Return

Yes, you will get more furnace noise. One way to minimize that is to install the return with one or two elbows. Although flex duct is lousy, in such a short run you might use it as the insulation will help buffer the noise. Make sure it isn't pinched at all. Depending on how nice of a space it is, you can build a little enclosure around it to hide it.

Typically you want the return away from the furnace so you aren't getting "warm" air back into the furnace, which will affect its performance. As this is a separate room, you should be fine.
 
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Old 11-27-05, 08:28 PM
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11 years old?? I am surpise that you don't have it.. However, there are homes that the fresh air is tied right into the return ductwork..

If you don't have either, I would suggest putting a fresh air in.

What are your equipment in that room? Sealed 90% furnace?
 
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Old 11-28-05, 07:00 AM
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Unsure if I have cold return then I guess. Maybe it is in through the duct work. Anyway you can tell? The equipment in that room is a gas furnace and a gas water heater.

I like the ideas of the elbows. However, unsure if I have the room available to do this with the bends and all. Was thinking of coming with a 6" or 8" starter collar straight accross. I was thinking this would be sufficient. The flex pipe is a thought but everything I read says to stay away from those things.
 
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Old 11-28-05, 08:55 AM
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As for fresh air, do you have an extra hood along the side of the home.. Most looks like a dryer vent. but no flapper.. just screen to keep stuff out.

If it was tied into your return, you will see a duct going out to the side wall, and some are wrapped in insulation.

Where are you from? Is your furnace a 90% system with PVC?


You may use flex if the run is short.. I just don't like them on long runs. Flex may help dampen the sound and air rush sound.
 
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Old 11-28-05, 09:53 AM
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I do not have that cold air return on my house. It is not a 90% furnace with the PVC as you suggest. I would think the combustion is coming from the air around the system
 
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Old 11-28-05, 09:58 AM
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That's odd. I always thought that with a gas furnace you needed a fresh air intake located beside the furnace.

Maybe because it is not considered a high efficiency furnace.
 
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Old 11-28-05, 11:59 AM
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A 11 years old home are some what tight.. so My advise is bring fresh air into the room from outside..

The air that is lost up the flue has to be made up.. Lot of time windows start getting drafty...

Bring a pipe into the room, and goose neck it up "U" to help slow down the cold winter air.
 
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Old 11-28-05, 12:57 PM
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Thanks for the advice. Still unsure about he fresh air being needed. My house is not that air tight so do not think it is a big issue. However, is not that a big of deal to add one if needed. What size pipe is recommended?

Jeff
 
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Old 11-28-05, 01:02 PM
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I would suggest the 5-4".. I put 4" in mine.
 
 

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