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Posted by Dan Kohlman on December 1, 2006, 12:57 pm
gofish@gonefishin.net wrote:
>
> >Greetings:
> >
> >I am hoping someone can offer me some assistance here. I have a
> >customer that has a standing pilot Trane furnace. Some time ago it
> >started failing to light the last burner once the heat exchanger was
> >hot. The flame will come within about an 1 1/2 inches of the burner on
> >the spreader. Of course, after a short period there will be a small
> >explosion and the burner may light. This only happens when the
> >exchanger is hot, it will work normally when it is cold, and don't
> >happen all the time.
> >
> >I replaced the burner assbly, gas valve, adjusted the manifold pressure
> >above 3.5" and below, I adjusted the air up and down and yet the
> >problem still presists. I think I could solve the problem by moving the
> >pilot to the center or restricting the air flowing to the burner, but I
> >don't want to modify the furnace. I am more interested in finding the
> >solution. I'm sure it is something simple that I am overlooking. One
> >thing I haven't done yet was check the reaction time or flow
> >differences between the Honeywell gas valves and WR that normally comes
> >with the furnace.
> >
> >If anyone can help me I will greatly appreciated it and so will my
> >customer.
> >
> >Thanks in advance
>
>
> prior to replacement, was the gas valve in the furnace the original
> oem valve?
>
> you've inspected the flue & vent for any obstructions?
>
> Is there adequate combustion and makeup air?
>
> Orifaces not plugged or partially restricted?
>
> you've did a complete & thorough inspection of the hx for cracks etc?
>
> years ago I had to replace a 400,000 btu valve, only to find out the
> largest available then was 350,000. Same problem, not enuf gas to
> reach the last few burners. 5/16 brass plugs on the outer burners
> solved that problem. Over firing is not recommended.....
Hi:
Yes the valve was the orginal WR. I have checked the flue and we have
plenty of combustion air. I also cleaned out the manifold and orfices
but
nothing of consequence there. There are no indications of a cracked HX.
What your saying about the valve is my last thought. I have replaced
many
of the WR valves with the Honeywell and they all worked fine. To be on
the
safe side I even replaced the Honeywell valve with another just in case
there
was a problem in the valve, yet still the problem persists.
Unfortunately I can't
plug the outer burner, that is causing the problem since it is only a
100K
furnace. If you think of anything else I will greatly appreciate it.
Thanks again
Dan
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