mobilehomerepair.com

recent purchase doublewide. 1100 ft sq Northeast US location.
heating systems is forced hot air by oil.

seperate air conditioning system outside house. (believe it is called a split sytem),
that utilizes the heating ducts to disperse cold air.

my question is that there is one large return duct ( 14x14) in the living room.

is that the return for the AC, and if it is, should it be closed off in winter to max heating?

furnace has seperate small intake vent in door to obtain air flow.

Thanks in advance for any direction you can give me.

Hi & welcome. I am not well versed in the heating area, but I am sure someone will be along to give you a much better answer.

Greg

Sounds like you have a typical "Package System" which is outside and has the blower/coils all in a big metal box looking thing. There should be Dampers already installed that will prevent hot air during heat use from going out the return duct and being wasted. And there should be another one that prevents cold air during ac from being blown up into the furnace and being wasted or worse cause condensation inside the furnace which is no good. As long as the dampers are working like they should you should be good!

I have cut a piece of styrofoam to fit in the a/c return (yes, that's what it is) and then put a sheet of plastic under the grate to block it off in the winter. It does stop the cold air from coming in.

The main reason cold air comes into the home through the ac air return box is the air conditioner supply side damper most likely failed. It is supposed to close after the air conditioner's blower shuts down. Since the hinge is these things is usually just a piece of duct tape, it probably dried out, fell apart and no longer allows the damper to close properly to keep heat from flowing through your air conditioner. Not too big of a problem as long as the air conditioner ducting is in good shape meaning no holes and securely attached to the boots at the home and unit. Doing what you have done already helps prevent most of the lost heat but you may want to open up the skirting during a heating cycle to see how "warm" it is under your home. If you feel a fair amount of heat hitting you in the face there's probably a duct problem.

Well I can tell you that in my setup, there is no damper on the a/c return air, it just drops down from the floor and out into the package unit, so there is a direct path for the cold air to enter. Maybe there should be, but it hasn't had one since it was installed 24 years ago.

Yeah, there should be a damper in there. You can fab your own or do what 1987Commodore has done to his return. If it's your supply also then I would see what you can fab to fit. Usually they come off the package unit in Flex Duct something like 14" maybe.

thanks for all the great replies.

It has helped me greatly.

Please close this issue.

NO there is NO damper in the return air ducting. It is in the supply air box that is attached to the main duct of the home. That is where the air conditioner supply duct attaches to provide the cool air into the home. Think of this air supply/damper assembly as the interface between the air conditioner flex duct and the main ductwork in the belly of the home. The damper is in that box.

Yeah, now that makes sense now. The system would be pretty much sealed. So as long as the supply damper in the bottom of the indoor unit wasn't leaking you shouldn't be getting draft out of there. Unless the flex or outdoor section is letting air pass in through it which I could see for a older unit.