Burners Light When Box Is Open - DIY Chatroom

SpeedyMick · 10-16-2009, 07:00 PM

I've been having some problems with my furnace. I have an Armstrong Air SX90 with a Honeywell Smart Valve. When the furnace kicks on, the blower starts. After about 30 seconds the ignitor or the pressure valve clicks and the pilot lights. However, the pilot only stays on for a minute or less before shutting off.

I had someone come over and look at it. He said the electricals and mechanicals looked fine. He blew on the hoses to make sure everything was clear and they're fine. He thought the problem might be with the flue, thinking something might be stuck inside. I shined a light down the flue and it's completely clear.

He was able to get the burners to light when he took off the cover on the box with the burners.

Does anybody have any idea why the burners would light when the cover is open as opposed to when the cover is on?

Thanks!

yuri · 10-16-2009, 07:49 PM

Less draft across the burners. Your intake may be partly plugged which causes more velocity of air thru the burner box and causes the gas to lift off the burners and not light properly. Or you got a cracked heat exchanger and air is entering the chamber and interfering with the draft. Had that on a Heil. May need a Pro to check that. Not a DIY job that I can describe.

Plumber101 · 10-16-2009, 07:50 PM

Very possible you have a cracked heat exchanger

SpeedyMick · 10-16-2009, 08:23 PM

Can a heat exchanger be replaced or am I looking at a new furnace situation here?

yuri · 10-16-2009, 08:34 PM

There could be other problems like dirty burners, incorrect gas pressure (Smart Valves are notorious/problematic). I would get a Armstrong tech in to check the whole unit. Most furnaces have a 20 yr heat ex warranty, are available but the labor to install one is $600-$1000 or more depending on area.

SpeedyMick · 10-16-2009, 08:38 PM

Thanks!