Thread: Missing gas flue from the furnace

Is this proper combustion air inlet ?

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Originally Posted by Terry Choi

Hello brothers,

Is this proper combustion air inlet ?

"Brothers"?

Terry,

Depends on whether or not there is adequate combustion air provided to the room/closet which houses the furnace.

Originally Posted by Terry Choi

Is this proper combustion air inlet ?

Yes it is.

Nope.BTW, see those rings?Combustion air Inlets protected from blockage/obstructions. This includes openiings in surfaces, ledges where idiots store junk.

From the title, I'd say 'no'. The flue is the exhaust pipe. You are referring to the intake pipe or lacktherof. Generally not required by most mfrs. as long as you need the combustion air requirements but..............its still very stupid to do it this way for a number of reasons. First of all, you are depressurizing the CAZ, which in turn could backdraft an atmospherically vented appliance in the house. It could also cause infiltration of more cold air which makes the thermostat call for heat more often.

Of course, an open top allows small items to fall into the combustion chamber. If the CAZ goes negative from other reasons such as leaky ducts, this provides a convenient route for CO spillage back into the room. At the very least, it should rise 2-3 feet to a broad radius elbow with an approved inlet screen.

Best practices is always two pipe it from the outdoors. This may be an energy code issue in your area so check with your AHJ.

Originally Posted by Bob Harper

From the title, I'd say 'no'. The flue is the exhaust pipe. You are referring to the intake pipe or lacktherof. Generally not required by most mfrs. as long as you need the combustion air requirements but..............its still very stupid to do it this way for a number of reasons. First of all, you are depressurizing the CAZ, which in turn could backdraft an atmospherically vented appliance in the house. It could also cause infiltration of more cold air which makes the thermostat call for heat more often.

Of course, an open top allows small items to fall into the combustion chamber. If the CAZ goes negative from other reasons such as leaky ducts, this provides a convenient route for CO spillage back into the room. At the very least, it should rise 2-3 feet to a broad radius elbow with an approved inlet screen.

Best practices is always two pipe it from the outdoors. This may be an energy code issue in your area so check with your AHJ.

Well stated and thoughtfully explained Bob H.

I would further add that taking the combustion air from a space subject to indoor pollutants further risks HE deterioration.