load explosion when new furnace ignites

Ken Sorenson · 03-22-2011, 07:31 PM

We have had a new EVEREST EXTREME COMFORT furnace installed 01/20/11. Since it has been installed it has a banging every time it ignites. I was told...that is the way it is ! MODEL GHM950904CX
SERIAL # 1003413560
There is someting not correct for this to happen !

Thanks in Advance !

Ken

hardwareman · 03-22-2011, 09:36 PM

you should move this over to the HVAC section, but it sounds to me like the plenum is probably expanding when the fan kicks on causing a banging noise. Not normal and is fixable

kenmac · 03-22-2011, 10:43 PM

Either sheet metal duct work popping or something isn't lined up correctly .Ie, burners, ignitor or both..

Like hardwareman said............. It Ain't normal

P. Boots &Sons · 07-20-2011, 07:10 PM

If you still have the banging on ignition, check for a restriction in the exhaust piping. Long lengths should be increased from 2" to 3". Some installers make the mistake of putting the intake screen on the exhaust also. A quick check to see if you have an exhaust restriction; shut the furnace off, remove the door covering the gas valve and burners, turn the furnace on. This eliminates any back pressure. If it ignites smoothly, you have a restriction.

hvac122 · 07-20-2011, 09:02 PM

Quote:

Originally Posted by P. Boots &Sons

If you still have the banging on ignition, check for a restriction in the exhaust piping. Long lengths should be increased from 2" to 3". Some installers make the mistake of putting the intake screen on the exhaust also. A quick check to see if you have an exhaust restriction; shut the furnace off, remove the door covering the gas valve and burners, turn the furnace on. This eliminates any back pressure. If it ignites smoothly, you have a restriction.

The pressure switch would not let it come on with backpressure.

First you need to find out if the bang happens on ignition or when the fan comes on. Then we can narrow down what's going on.

P. Boots &Sons · 07-20-2011, 09:34 PM

Yes a pressure switch will let this happen, the pressure switch will snap open then closed during the mini explosion during combustion. After ignition the unit usually runs fine until shut down. I have seen this several times. Actually saw one chatter on and off for 15 seconds until the exhaust flow smoothed itself out. Try it.