macx351
Dec 1, 2010, 01:42 PM
On a Luxaire nat'l gas furnace with inducer fan & outside air intake, I've been struggling with occasional failure to light for several years. Worst when it got colder outside. Nobody could figure it out. I thought I'd post this in case it could help
some one else with gas furnace lighting problems that are difficult to diagnose.
During troubleshooting I found the gas valve was getting voltage at the right time and clicking and allowing gas into the burners. The igniter would glow, and the intake air and exhaust were open and clear as were all the pressure switch and drain tube hoses. The pressure switches and ignitor control were working properly (no LED codes on the control and proper voltage through the switches).
About 10 years ago we quit installing new oem igniters because they would burn out every couple years. We got a universal
Norton brand locally (Luxaire dealer had left the area) that fit and no more burned out igniters, but began having occasional failure to light. By then most parts had been replaced (draft fan, limit switch, gas valve, ignition control, etc)
and everything checked out. At that point the furnace was 10 years old.
Doing more research this morning when it turned about 20 degrees colder and it refused to light again, I found out about
the new silicon nitride igniters and found one locally. I also pulled the pilot tube (correct description?) with the numerous small holes in it that feeds gas past the igniter out from the burner air intake box and checked to make sure all the holes were open as by viewing it with a mirror I saw where one of the original style ignitors had come in contact with the tube and left a couple very small melted spots of igniter material on it. No holes were blocked, but I pushed a small sharp pick into each one just to make sure they were all fully open.
The ignitor in the furnace that we had replaced the original style with had a small perforated sleeve around the igniter element. I don't know if this was partly blocking the gas flow out of the pilot tube or not, but with the new non-sleeved round silicon nitride igniter it lights quicker - almost instantaneously when the gas valve clicks - and it no longer rumbles while it's lighting but lights very smoothly. And it has worked flawlessly through a number of trials. Best $50 I ever spent on this furnace! The link shows information on that type of igniter, although is not the exact one I found locally and installed.
http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=HSI1096048A&Category_Code=p-hot
some one else with gas furnace lighting problems that are difficult to diagnose.
During troubleshooting I found the gas valve was getting voltage at the right time and clicking and allowing gas into the burners. The igniter would glow, and the intake air and exhaust were open and clear as were all the pressure switch and drain tube hoses. The pressure switches and ignitor control were working properly (no LED codes on the control and proper voltage through the switches).
About 10 years ago we quit installing new oem igniters because they would burn out every couple years. We got a universal
Norton brand locally (Luxaire dealer had left the area) that fit and no more burned out igniters, but began having occasional failure to light. By then most parts had been replaced (draft fan, limit switch, gas valve, ignition control, etc)
and everything checked out. At that point the furnace was 10 years old.
Doing more research this morning when it turned about 20 degrees colder and it refused to light again, I found out about
the new silicon nitride igniters and found one locally. I also pulled the pilot tube (correct description?) with the numerous small holes in it that feeds gas past the igniter out from the burner air intake box and checked to make sure all the holes were open as by viewing it with a mirror I saw where one of the original style ignitors had come in contact with the tube and left a couple very small melted spots of igniter material on it. No holes were blocked, but I pushed a small sharp pick into each one just to make sure they were all fully open.
The ignitor in the furnace that we had replaced the original style with had a small perforated sleeve around the igniter element. I don't know if this was partly blocking the gas flow out of the pilot tube or not, but with the new non-sleeved round silicon nitride igniter it lights quicker - almost instantaneously when the gas valve clicks - and it no longer rumbles while it's lighting but lights very smoothly. And it has worked flawlessly through a number of trials. Best $50 I ever spent on this furnace! The link shows information on that type of igniter, although is not the exact one I found locally and installed.
http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=HSI1096048A&Category_Code=p-hot