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Old 03-09-2013, 06:07 PM   #1
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air return and register size


If I wanted to add a register and and cold air return to a room does anyone know of a good way to determine the size that should be used?

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Old 03-10-2013, 07:52 PM   #2
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air return and register size


that questions is best answered with a little bit of science and a little bit of experience. The science is found with a manual j calculation for the room. man j takes into account the size if the room, the size of doors and windows, the wall and insulation type and the north, south,east, west orientation of the room. You will also need to know the size of your current system in btu's and its current static pressure. You will have to also design the placement of the supply and return in relationshiop to each other, as well as to the throw of air and the air movement within the room and the relationship of where you are trying to keep comfortable.

the experience on the other hand is all about how to "run" the duct within the limits of the homes construction, as well as the craftsmanship of the install.

so, start by checking out manual j, static pressure, your hvac equipment, where the duct could run in the wall or ceiling or crawl space, what materials you would use to run the ducts etc.... so, bottom line is that it can be done, by guess, by science or by a pro... all of which are your call...

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Old 03-10-2013, 07:56 PM   #3
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air return and register size


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that questions is best answered with a little bit of science and a little bit of experience. The science is found with a manual j calculation for the room. man j takes into account the size if the room, the size of doors and windows, the wall and insulation type and the north, south,east, west orientation of the room. You will also need to know the size of your current system in btu's and its current static pressure. You will have to also design the placement of the supply and return in relationshiop to each other, as well as to the throw of air and the air movement within the room and the relationship of where you are trying to keep comfortable.

the experience on the other hand is all about how to "run" the duct within the limits of the homes construction, as well as the craftsmanship of the install.

so, start by checking out manual j, static pressure, your hvac equipment, where the duct could run in the wall or ceiling or crawl space, what materials you would use to run the ducts etc.... so, bottom line is that it can be done, by guess, by science or by a pro... all of which are your call...
for a 10 by 10 room can you just give me a typical register and cold air return size?
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Old 03-10-2013, 08:24 PM   #4
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air return and register size


What kind of typical room is it. Where is it, east, west, north, south exposure, ceiling height, how many windows, any doors to the outside.
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Old 03-10-2013, 09:41 PM   #5
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air return and register size


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for a 10 by 10 room can you just give me a typical register and cold air return size?
since this room doesn't have direct heat now, is it really cold in there, or just somewhat, or not much cold ? most likely a 6" duct would be recomended, and overkill. just guessing, a 4" and no return would be fine. as long as there is space below the door for air to return to the rest of the house.
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Old 03-11-2013, 07:34 AM   #6
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since this room doesn't have direct heat now, is it really cold in there, or just somewhat, or not much cold ? most likely a 6" duct would be recomended, and overkill. just guessing, a 4" and no return would be fine. as long as there is space below the door for air to return to the rest of the house.
no air return? Don't you need same amount of air return as air supply?
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Old 03-11-2013, 07:35 AM   #7
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air return and register size


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What kind of typical room is it. Where is it, east, west, north, south exposure, ceiling height, how many windows, any doors to the outside.
2 windows. 7 Foot ceiling height, one interior door.
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Old 03-11-2013, 11:55 AM   #8
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air return and register size


6" diameter is "standard". One of each seperated by enough distance so the air doesn't come in one and get sucked right back into the other.

Put a damper in the supply run so that you can adjust the amount of air/heat being delivered.

Is this answer exact? No. Guaranteed to be the correct answer? No. Without knowing the exact heat loss of the room and the capacity of your existing system and where and how you'll be connecting to it it's a generic answer from generic information.
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Old 03-11-2013, 03:41 PM   #9
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air return and register size


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2 windows. 7 Foot ceiling height, one interior door.
Orientation.
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Old 03-11-2013, 06:31 PM   #10
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air return and register size


trial and error

try 6 inch flex supply and 8 inch return flex.

install damper at the beginning of the supply duct if you have too much flow

get a kids toy pinwheel it should spin in the airflow from the supply duct 4 feet into room
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Old 03-11-2013, 10:17 PM   #11
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air return and register size


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no air return? Don't you need same amount of air return as air supply?
yes, you do. but the returns in the other rooms will cover that. that is, unless this room you want to heat, is basicly air sealed. and i doubt it is. how high off the floor is the door ?

i have 1 return for the whole house living area. 1 floor house. gas bill isn't high, and house is plenty warm.
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Old 03-12-2013, 07:56 PM   #12
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air return and register size


Too mucgh return is possible but not easy to do.If the windows are newer and you have some onsulation in the walls a 10x6 register and a 14x6 return grille will warm up that room nicely. You would want a 6 inch supply run and a 7" return run.
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Old 03-12-2013, 09:05 PM   #13
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air return and register size


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Too mucgh return is possible but not easy to do.If the windows are newer and you have some onsulation in the walls a 10x6 register and a 14x6 return grille will warm up that room nicely. You would want a 6 inch supply run and a 7" return run.
How do you incorporate panning into the return? That is what I get confused by? You mean a 7" round duct? How would a 14x6 and a 10x6 fit in 2x4 wall?

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