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LaCentra
Outside air directly into return air plenum

I am assisting a friend on some basic maintenance on their furnace. I noticed they have a duct from the outside that is attached directly to the return air plenum. I assume it was supposed to put fresh air into the house. I have seen this before but with a heat exchange on a super insulated house. This is not a super insulated house and no heat exchanger is used. Would we be better off to remove this source of outside air to the return air plenum?

JLMCDANIEL
Re: Outside air directly into return air plenum

I take it this is an old house probably built by some well to do people. Fresh air is considered healthy, and the well to do who didn't have to worry about the cost of heating often installed such a set up. Closing off the outside air should significantly lower heating costs. You will need to substitute and inside vent to replace the outside one sealed off.
Jack

canuk
Re: Outside air directly into return air plenum

Ummm ..... I think if I were you .... a call into your local building department would be in order.

Around here it's a code requirement for a fresh air source to be supplied to the furnace. Either with a duct supplying air fom outside run into return plenum .... like being described by the original poster .... or by using a Heat Recovery Ventilator.

The idea is for make up air being supplied to the home.

JEWEATHER
Re: Outside air directly into return air plenum

On my house here in Houston, I have the same thing. There is a 4" duct that runs from outside directly into the return air plenum. It comes in just before the filter. The house is new, and all the houses in the area have this. With as tight as they are making houses these days, I can understand the need.

LaCentra
Re: Outside air directly into return air plenum

Thank you for the feedback.:)

bsum1
Re: Outside air directly into return air plenum

Same thing here on our furnace a fresh air intake is needed.

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