Question:
> In the past couple weeks, I’ve noticed a bang/pop noise coming from the vents > in our forced hot-air heating system (gas furnace, also has central air, but
The commonest cause is a single rigid metal panel that is slightly dished (not perfectly flat), so that when heated it expands enough to move in the opposite direction. The only cure is to identify which panel does this, and either attempt to give it a millimetre more space, or else to deform it permanently so that no amount of heat pops it in the other dierction. — | Donald Phillipson, 4180 Boundary Road, Carlsbad Springs, | | Ontario, Canada, K0A 1K0, tel. 613 822 0734 |
Response:
>>open). The bang/pop sounds and the faster frequency when the heat is on >makes me think it’s metal expansion/contraction, but I have no idea where it >could be. It could be that bad damper, but I’d think it would make a louder >Brian >It’s most likely metal expansion and contraction. And it’s most >likely happening everywhere there is a metal HVAC duct.
Exactly so and is probably because the contractor didn’t put plastic or rubber between the metal ducts and all their support hangers, etc. It is a stick-and-slip type of motion, hence the intermittency of it. If you can get at the ducting, try inserting a piece of plastic sheet between the hangers and the ducts. Anything to help them slide freely as they expand and contract.
Response:
This noise is fairly normal in a hot-air system with metal ductwork. The metal ducts expand when heated and hence slide in their mounts and squeeze tighter together at the joints. This creates various creaking, popping, and banging sounds. You could also get some noise from dampers opening and closing, of course. I suspect the best advice would be to learn to live with it. I find the noise of a heating system on a frosty night to be a real sleep inducer. Don’t know what would have shorted the transformer. Simply pressing on ductwork shouldn’t have caused a problem. – Hide quoted text — Show quoted text – >In the past couple weeks, I’ve noticed a bang/pop noise coming from the vents >in our forced hot-air heating system (gas furnace, also has central air, but >I don’t recall this noise occurring during the summer – maybe it did, but we >didn’t need the AC at night at all, so I wouldn’t have noticed even if it >did). It’s a fairly faint noise, that occurs only when the furnace is on and >for about 20 minutes after the furnace goes off, with an intermittent >frequency – every 20-60 seconds when the furnace is on, every 60-300 seconds >when off (the fan goes on and off with the heat, not a continuous fan). We >have a 2-zone system with dampers (although the guy who installed our furnace >a year ago said the downstairs damper is rusted/rotted away and is stuck >open). The bang/pop sounds and the faster frequency when the heat is on >makes me think it’s metal expansion/contraction, but I have no idea where it >could be. It could be that bad damper, but I’d think it would make a louder >noise, like metal flapping in the wind. (I went down to the furnace last >Sunday and tried pushing on the duct going to the upstairs zone, but that >caused the furnace to shut off (!) – Monday the installer/service guy said >the transformer was fried and replaced it. Since then it’s hands-off the >furnace for me!. The wiring around the furnace is sort of messy, so it’s >possible that I did short something when pushing the duct. But the bang/pop >was even before the transformer problem.) >Any ideas? One vent is right by my head in bed, so the noise has been waking >me up a couple times this week, then it’s like Chinese water torture waiting >for the next bang/pop while trying to fall back asleep. I could close off >that vent, but that would cut heat to the bedroom by 1/2. (Moving the bed is >not a good solution.)
Dan Hicks Hey!! My advice is free — take it for what it’s worth! http://www.millcomm.com/~danhicks
Response:
>. > Don’t know what would have shorted the transformer. Simply pressing on > ductwork shouldn’t have caused a problem.
FWIW, since he put in the new transformer, the furnace seems to be better at . detecting flame on the 1st try. Last winter I remember about 1/3 of the time I could hear the gas valve open once, and then a minute later open again and then the fan and heat would start. (It’s an Amana furnace, w/ HSI.) Since I’m not contemplating ripping up floors and drywall to find and fix the offending duct, I guess I’ll learn to live w/ it. tnx-R.
Response:
It’s most likely metal expansion and contraction. And it’s most likely happening everywhere there is a metal HVAC duct. >open). The bang/pop sounds and the faster frequency when the heat is on >makes me think it’s metal expansion/contraction, but I have no idea where it >could be. It could be that bad damper, but I’d think it would make a louder
– Return address munged to prevent SPAM… SOHO DataComm wiring, FAQ’s, etc: http://www.geocities.com/researchtriangle/3300
Response:
In the past couple weeks, I’ve noticed a bang/pop noise coming from the vents in our forced hot-air heating system (gas furnace, also has central air, but I don’t recall this noise occurring during the summer – maybe it did, but we didn’t need the AC at night at all, so I wouldn’t have noticed even if it did). It’s a fairly faint noise, that occurs only when the furnace is on and for about 20 minutes after the furnace goes off, with an intermittent frequency – every 20-60 seconds when the furnace is on, every 60-300 seconds when off (the fan goes on and off with the heat, not a continuous fan). We have a 2-zone system with dampers (although the guy who installed our furnace a year ago said the downstairs damper is rusted/rotted away and is stuck open). The bang/pop sounds and the faster frequency when the heat is on makes me think it’s metal expansion/contraction, but I have no idea where it could be. It could be that bad damper, but I’d think it would make a louder noise, like metal flapping in the wind. (I went down to the furnace last Sunday and tried pushing on the duct going to the upstairs zone, but that caused the furnace to shut off (!) – Monday the installer/service guy said the transformer was fried and replaced it. Since then it’s hands-off the furnace for me!. The wiring around the furnace is sort of messy, so it’s possible that I did short something when pushing the duct. But the bang/pop was even before the transformer problem.) Any ideas? One vent is right by my head in bed, so the noise has been waking me up a couple times this week, then it’s like Chinese water torture waiting for the next bang/pop while trying to fall back asleep. I could close off that vent, but that would cut heat to the bedroom by 1/2. (Moving the bed is not a good solution.) Thanks -R.
If you like this post and would like to receive updates from this blog, please subscribe our feed.