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I recently had two 50K BTU gas furnaces installed in my duplex. A chimney liner (5″) was run in the chimney flue designated for the furnaces only. Living here in the midwest, a problem in the form of condensation began to be a problem. The liner ran a good 35-40′ up the inside wall chimney. Condensation began to flood the first furnace which is joined inline with the second furnace.The contractor after some convincing decided to powervent the the two furnaces jointly. Seemed to be OK for a few weeks, but now I’m noticing a white build up on the joints of the vent pipe (4″ x 26ga.). It seems to me that condensation is still a problem! Your thoughts on this matter would be greatly appreciated.
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David,
"The contractor after some convincing decided to powervent the the two furnaces jointly"
I'd say you need someone else: IMHO, any heating contractor who needs convincing to correct a flue problem needs to be shown to the door.
"now I'm noticing a white build up on the joints of the vent pipe"
That is almost certainly a condensation problem and needs to be corrected ASAP.
It is unusual in my experience as a home inspector in NW Ohio to see condensation problems with the set up you're describing, so something must be screwed up: an obstructed flue or improper configuration are the 1st two possibilities which spring to mind.
In finding a new heating contractor, try to find a contractor who has been trained as a Carbon Monoxide Analyst. In my experience, they are more likely going to be able to spot the problem(s) and come up with a fix (although there are some other HVAC folks who are also very good on this stuff.)
Please don't let this slide: if there are condenstion problems, there may well be carbon monoxide problems, as well.
*I will call him this week. I have a CO detector in the bedroom and will keep an eye on it. What do you mean when you speak of an improper configuration?
*An improper configuration could be several things, including (but not limited to): improperly pitched; too much horizontal for the amount of vertical; wrong flue size for furnace output.A CO detector is a great idea: I recommend the type that has an LED digital readout: they are more sensitive than the type that merely sounds an alarm.