Big "POP" sound from Furnace - Canadian TV, Computing and Home Theatre Forums

deltafin · 2008-12-04, 07:37 PM

I have a new furnace (installed in October 2008- Lennox G61V-2 stage). The issue is that when I increase the temperature say from 21C to 23C, the T-stat shows that it switches to 1st+2nd Stage. After about 2 minutes, I hear a loud POP from the furnace and then nothing else. the temperature rises ok but I am dumpfounded by this sound like somebody bashed the furnce with a big log. All those HVAC gurus, anything you can recognize ??
Thanks for your feedback

dabell · 2008-12-04, 08:35 PM

I'm not an HVAC guy, but I had the same issue - a friend who used to be in HVAC knew right away. For me it was when the fan came on the main duct would pop in from the initial vacuum created. The solution was to screw a 1x2 across the duct, 3 screws - sides and middle.

wgauci · 2008-12-04, 08:57 PM

I'm not too familliar with that particular model but "dabell" sounds like he's right. Chances are that when you go over to hi fire (2nd stage) your blower motor is probably increasing in speed and the increased air flow is causing a section of your ductwork to bow in or out depending on where it is on the supply or return ductwork.

Check along your ductwork and see if there's any spots that easily flex in or out when you press on it, that's probably the problem area. There's a couple different things you could do to stop this.

The only other thing that might cause a poping sound would be delayed ignition but on a new HE furnace it's very unlikely.

Bent · 2008-12-04, 09:28 PM

It could be air pressure related causing the duct to "pop", but more likely it's thermal expansion of the duct/plenum.

deltafin · 2008-12-05, 08:06 AM

Thanks guys for the suggestions. I will take a closer look this weekend and report back.

2008-12-04, 07:37 PM	#1
deltafin Join Date: Nov 2005 Location: Waterloo On Posts: 39	Big "POP" sound from Furnace I have a new furnace (installed in October 2008- Lennox G61V-2 stage). The issue is that when I increase the temperature say from 21C to 23C, the T-stat shows that it switches to 1st+2nd Stage. After about 2 minutes, I hear a loud POP from the furnace and then nothing else. the temperature rises ok but I am dumpfounded by this sound like somebody bashed the furnce with a big log. All those HVAC gurus, anything you can recognize ?? Thanks for your feedback __________________ Deltafin

2008-12-04, 08:57 PM	#3
wgauci Join Date: Apr 2008 Location: Windsor ON Cogeco Posts: 1,072	I'm not too familliar with that particular model but "dabell" sounds like he's right. Chances are that when you go over to hi fire (2nd stage) your blower motor is probably increasing in speed and the increased air flow is causing a section of your ductwork to bow in or out depending on where it is on the supply or return ductwork. Check along your ductwork and see if there's any spots that easily flex in or out when you press on it, that's probably the problem area. There's a couple different things you could do to stop this. The only other thing that might cause a poping sound would be delayed ignition but on a new HE furnace it's very unlikely. __________________ Aquos LC42D64U Yamaha HTR6080 Emotiva XPA-5 Polk CSiA6 RTiA7's RTiA1's Velodyne DLS4000R Mot. 6416 III PS3 Harmony One

2008-12-04, 09:28 PM	#4
Bent Veteran Join Date: Dec 2001 Location: MB Posts: 1,788	It could be air pressure related causing the duct to "pop", but more likely it's thermal expansion of the duct/plenum. __________________ I'm a sleep expert.

2008-12-05, 08:06 AM	#5
deltafin Join Date: Nov 2005 Location: Waterloo On Posts: 39	Thanks guys for the suggestions. I will take a closer look this weekend and report back. __________________ Deltafin

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2008-12-04, 08:35 PM	#2
dabell Join Date: Nov 2005 Location: Sooke,BC Posts: 622	I'm not an HVAC guy, but I had the same issue - a friend who used to be in HVAC knew right away. For me it was when the fan came on the main duct would pop in from the initial vacuum created. The solution was to screw a 1x2 across the duct, 3 screws - sides and middle.