HE Furnace supply/exhaust vent - NOISE

[jeff1975]

We recently moved into a brand new home which included a Bryant 92% high efficiency furnace. The 2 PVC supply/exhaust pipes are connected to a common cylindrical PVC pipe and vented out the side of my house. I have heard clicking/popping sounds from the area where the 2 PVC pipes meet at the elbow to vent out through the 1 cylindrical vent. This noise occurs at 10-20 second intervals and travels through the duct work where a noticeable "bumping" noise can be heard in the bedrooms located on the opposite side of the home. (approx 50' away). It also appears to occur only during the combustion phase.

I have contacted the installer and he "has never heard of such a noise..." He's scheduled to come "listen for the noise" next week, but it sounds like he thinks we're out to lunch.

Other forums on other sites discussed heating/cooling expansion noise, and possibly a malfunctioning flap located in the PVC elbow.

Would anyone here have any idea as to what is happening and, hopefully, some solutions to the problem? Any advice would be greatly appreciated. Thank you.

[paul52446m]

That does sound interesting. The first thing would do is look at that concentric fitting real close. It sounds to me like it is trapping water in this fitting. When the inducer come on it pushing the water up to a point and then the water weight get heavy enough so it runs back
and drains a little and then it starts building up again and starts all over again. I don't like those concentric fitting, if you don't get them in right they will not drain right. Later Paul

[jeff1975]

Thanks Paul, one thing I didn't mention is the noise gets worse when it's colder outside. Where we live the temperature routinely drops to -15F at night and +15F during the day. This popping noise is more prevalent at night which lead me to think it was the heating/cooling expansion inside that PVC coupler. (warm furnace exhaust in the middle surrounded by -15F air!), but this is the normal setup where we live so you'd think it wouldn't be an issue.

I'll pass on your thoughts to our installer.

Thanks again.

[jeff1975]

Another thing, when looking at our supply/exhaust pipe and concentric fitting, it appears to slope down towards the furnace. Should it slope towards the outside so proper drainage occurs?

[paul52446m]

Another thing, when looking at our supply/exhaust pipe and concentric fitting, it appears to slope down towards the furnace. Should it slope towards the outside so proper drainage occurs?

It is suppose to slope back toward the furnace and the 2" off the side should be down far enough. better than 45 degrees so it let all the water drain out,
I still think your are getting water in there, maybe even making ice.
Plastic pipe does not expand very much to make a noise. Later paul

[Chris8888]

I know this is an old thread but I am experiencing the exact same problems with a new HE Lennox furnace. I was wondering if you had any resolution? Any help would be appreciated.

[Finster]

I am having the same issue. I just bought an older manufactured home, that the heat/ac is run by a Trane heatpump....and have the same noises inside the ducts. They are extremely irirtating in the middle of the night. IT's not in all the ducts, the master BR duct is the loudest. Are the ducts under the house?
Like Jeff's situation from an earlier thread, it's cold here..and the noises occur when the heat goes off..like it's expanding. They look to be made of a soft metal. HELP!?

[HayZee518]

the problems might be inside the ductwork where turning vanes are installed at the elbows. These are tin flaps mounted at an angle inside to direct the flow of air around the elbows. they could be vibrating when the fan comes on. short change of direction elbows are a no-no when it comes to forced hot air. long sweeping elbows are better. but they use the shorter ones to conserve space.
the joints use an S cleat to keep the ductwork flat, 1/2 inch drives keep the whole joint together. there are holes at the extreme corners which should be covered with duct tape.

[Finster]

Thanks Hayzee..I thought I replied to this, bu don't see it posted, so forgive me if I duplicate it! I didn't know there were flaps inside, but that might explain the fluttering sort of noise I hear in addition to the pings. I was worried there were mice in there. It is worse now as it's below freezing here, and the heat is constantly running.
Do you know where I could find a diagram, or pictures of what the inside of ductwork looks like, and how they work, to give me a better understanding? Rookie first home owner