Brr....furnace won't light

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Old 01-01-11, 07:32 PM
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Brr....furnace won't light

Hi. First up: apologies if this appears twice. I sseem to have lost what I wrote up, but it might have posted.

I have a 5 year old American Standard Freedom 80 Comfort R furnace, original to the house. Controller is a White Rogers Intell-Ignition.
It is installed in the attic, horizontally, and runs on propane. It is 2 stage but the installer only hooked up the first stage. I haven't bothered to rewire the thermostat as I think the unit is way bigger than it needs to be and it works fine (when it works) the way it is. It is 62KBTU stage 1 and 97KBTU stage 2.

I replaced the ignitor about a year ago; it seems to be fine.

It worked fine, then was intermittent for a week or so and now won't light. The ignitor glows, the gas valve opens and the gas ignites, but only in the first burner tube; the flame does not advance to the other 5 tubes. Within 1 or 2 seconds the system shuts down. The flame sensor doesn't have a chance to see the flame as the system shuts down before the flame moves down to it. I tested it by hitting it with a propane torch and it gave the 5 blink 'flame when I didn't think there should be one' error. And yes, right after I did that I thought about how stupid it was.
No error codes except for a 2 flash lockout code after it tries to light a few times.
Thanks in advance for your help
 
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Old 01-01-11, 07:55 PM
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One more thing: thinking it might be a gas flow issue I tried hooking up a 5 gallon propane tank through a different regulator: same symptoms.

Thanks again!
 
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Old 01-01-11, 08:05 PM
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The burner tubes may be dirty and dusty. Have you cleaned them? I had a situation where the first two tubes would light but it took awhile fore the other four to ignite. The tubes had cobwebs, dust, and god knows what in them an on them. Cleaning took care of it.

Second thing the gas valve can be bad. Propane test with a manometer at the test port. Should be 10" water column. If not replace gas valve.

Mike NJ
 
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Old 01-01-11, 08:35 PM
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Aha!

The burners were fairly clean (I brushed them a bit) but your comment on the valve made me think: perhaps something in the gas clogged it up as that would account for the intermittent operation before the full out failure.
So I did a bit of percussive maintenance (smacked the valve a couple of times) and it fired up. Might have been some crud in the valve, perhaps blocking an orifice that limited the gas flow.

Many thanks, Mike!!!
 
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Old 01-01-11, 08:40 PM
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Hmm.... Sounds like a quick fix. Selenoid on gas valve not opening all the way. Gas valve? Voltage issue??


Good luck and let us know.

Mike NJ
 
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Old 01-02-11, 01:25 AM
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Ummmm. It's unlikely the problem is the gas valve.


Dirty burners ---- 90% likely the problem.

Poor gas pressure 8%

Plugged orifice or gas valve --- 2%


If you are having very cold weather, the propane in your tank may not be able to evaporate fast enough to provide gas to operate the furnace properly. That can cause poor gas pressure which can interfere with the burners lighting.
 
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