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jkennedy99 · Mar 1, 2009, 11:46 AM

A year ago I had my old furnace (a York) replaced with a lennox 95% efficient furnace. The exhaust from the new furnace exits the side of the house, and the furnace heats up the house fine. However, I also see some exhaust coming out from the old exhaust on top of the house. Should I still have exhaust coming out from the old exhaust on top of the house? I'm not sure why anything would be coming out of there.

I plan to call the company that installed the new furnace Monday to ask, but they've been less than helpful in the past on another issue I had.

This is a G61 lennox gas furnace.

Thanks,
Joe

KC13 · Mar 1, 2009, 01:18 PM

Perhaps the "old exhaust" you refer to is a b-vent that still serves your water heater... is it metal or plastic?

KISS · Mar 1, 2009, 01:46 PM

When the furnace was installed, the chimney should have been lined unless the water heater is a direct vent model. This is essentially a small tube for the water heater vent to go up. It's not allowed to use the chimney by itself.

At that time usually a vent cap on the chimney is added if there wasn't one before.

jkennedy99 · Mar 2, 2009, 02:48 PM

KC13, it makes sense that it's for the water heater, and the vent I'm referring to is metal. However, I see exhaust coming out of this pipe when the furance is running, but the exhaust stops immediately when I turn off the furance. I've tested this a couple of times.

KeepItSimpleStupid, the vent exit is not coming out of the chimney (located on one side of my house) it's actually closer to the center of the house. Is there a way to test to make sure the exhaust is due to the water heater? Should I just crank up the heat on the water heater, shut off the furnace and see if anything comes out of the vent?

BTW, both the water heater and furnace are gas.

Thanks,
Joe

KC13 · Mar 2, 2009, 02:55 PM

Are you sure the new unit is exhausting through the sidewall of your home? Perhaps the installer put a combustion air intake on the side and ran the exhaust up the existing b-vent chase... if so, this would be less than ideal, as draft problems could arise during windy periods due to the pressure differential between the two locations. What, if anything, is connected to or passing through the old vent?

jkennedy99 · Mar 2, 2009, 03:39 PM

KC13, there is definitely air being sucked in and exhaust coming out of the PVC pipes running out of the side of the house, as the furance is running.
I'm scared of exactly what you commented on, the installer has somehow allowed exhaust/ or heat to exit through the roof vent.
As far as what connected to that vent terminating on the roof, I don't know. Can you give some guidance into figuring that out? I can take a picture of the set-up in the basement (furance and water heater are in the same area), if that would help.

KC13 · Mar 2, 2009, 04:54 PM

Good idea, post some pics.

KISS · Mar 2, 2009, 05:04 PM

"smoke bomb" tests are the standard to check for ventilation, but you'll need a way to force a draft. If you have the water heater with the fan, this may not be a problem.