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Rick52768 12-02-2009 10:16 PM

Adding a return vent/room pass through
The master bedroom closet which is 5x15 has a supply vent in the ceiling, but no return vent. If you leave the closet door open the hvac system keeps it a nice temp as the rest of the rooms. If not, cold in winter and hot in the summer. Keeping the door open all the time is not an option. So I was wanting to add pass through grill so the cold or hot air can return and be conditioned by the heat pump.

The question is how big should the vent be? Where is the best location, high or low? Since the bathroom is the room where the vent will exit, is installing the vent above the shower (2-3 feet above) a bad idea? Thanks for any help you can be.

beenthere 12-03-2009 03:56 AM

Thats not a good idea. Transfer grille into the bathroom can cause troubles. Such as mold problems. Blowing odors into the house, when the system is running. Since the bathroom doesn't have a return.

Just under cut your closet door, and let it return into the room the closet serves.

Rick52768 12-03-2009 10:22 PM

Sorry I left out some info. The master closet door leads to the master bath, so the vent would do the same work as opening the door, without the door getting in the way. Then the bathroom empties to the bedroom and right outside the bedroom is the main return for the second floor rooms. The bathroom and bedroom doors are almost always open.

So back to the original question, high or low on the vent and what size. The door is cut for the carpet in the closet, but the gap cannot get the job done. So something between the gap under the door and the door itself in size for the added vent will work. Thanks

beenthere 12-04-2009 04:14 AM

High or low makes little to no difference.

But. If there is a wall to the hall, I'd put the grille there instead.

Rick52768 12-04-2009 07:47 AM

Thanks. The hall is not a good option as it would really put thr vent closer to the first floor return (vaulted ceilings). A have two units, one for each floor. So into the bathroom is my best option. Does it matter how small or big the vent is in size?

beenthere 12-04-2009 10:07 AM

Needs to be able to let the same amount of air out that the supply puts in.

As far as it being close to the first floor return if installed in the hallway. That doesn't matter.
It would have no effect on either system.

tpolk 12-04-2009 10:15 AM

is this a first or second floor prob? if second can you access return in attic or if first a return from under floor

Rick52768 12-04-2009 12:13 PM

Well, I could access the return from the attic, but that would be a bite. Edge of roof line, lots of blown-in insulation and I am not sure it would be the best idea. Both units have only one main return in a hallway for each unit. So adding a true return in just one room may add in new problems. Should the "return" pass through vent for closet be the same size as the supply vent for the closet? Thanks

beenthere 12-04-2009 03:24 PM

50% larger, since you'll have 2 grilles for the air to go through.

Presuming they didn't install a 4 X 12 in a closet.

Rick52768 12-04-2009 08:52 PM

It is a 8"x12" vent. I guess you are saying that the grilles will hurt airflow and
therefore the size of the returning air vent needs to be twice as big. I did not expect that. Am I correct on what you meant? Thanks

beenthere 12-05-2009 05:52 AM

Yes you are.

Since it sounds like you have a sidewall register. Go with a 8X14.
An 8X14 return grille will have almost if not 50% more free area, then a 8X12 sidewall supply will(presuming the supply has adjustable louvers).

8 X 12 = 96 X .6 = 57.6
8 X 14 = 112 X .8 = 89.6

Rick52768 12-05-2009 02:39 PM

You have really helped me out been there. I am glad that you included the math as there is no telling what I would have figured out. Just in case it matters I have adjustable ceiling registers as the air handler is in the attic. Thanks again.

beenthere 12-05-2009 03:36 PM

They would be about 60% free area then.
So the 8X14's are fine.

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