gas heater problem / infrequent ignition


  #1  
Old 02-09-03, 07:38 AM
Jackjeb
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gas heater problem / infrequent ignition

RE: intermittent ignition problem
Rheem Deluxe Drum 90Plus [11/92 installation date]
model UGED-10ERAJS
105000 btu / natural gas / 120v blower

Problem: on infrequent schedule [several week interval] ignitor sequence willnot properly cycle.

Blower goes on as called for by thermostat.

Ignitor goes on [approx 25 seconds prior to gas].

Gas valve opens, Gas ignites, stays lit approx 5 seconds.

Blower pitch sound changes / gas goes out, ignitor goes out.

Cycle repeats in approx 30 seconds.

After 'rest' period of approx 1hr +, unit reverts to normal operation & remains in seemingly regular cycle operation for several weeks until next round of symptons.

What is causing this infrequent problem?
 
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Old 02-09-03, 08:13 AM
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could be a flue problem

what type of pipe, how long, what size and is the water heater hooked into it? the pressure switch may be dropping out, the noise pitch change you hear could be the increased load on the inducer motor, as there is more load after ignition. just a few ideas
 
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Old 02-09-03, 08:17 AM
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Talking ooops!

i see it is a 90% furnace, ditch the flue idea. i would look at the inducer motor, especially if the pitch is changing. be sure the flue outlet is unobstructed.
 
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Old 02-09-03, 10:48 AM
Jackjeb
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Information that came with furnace indicates unit will do 5 retries on burner sequence before 'lockout' occurs. Turning unit off via thermostat or emergency switch for 10 seconds reprograms.

This morning I stopped unit after approx 10 retries. Would that indicated the integrated furnace control [IFC] is in error?
 
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Old 02-09-03, 11:05 AM
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hard to say,

have a pro check out the draft with a manometer, it will tell if the pressure switch is dropping out or the inducer fan
 
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Old 02-09-03, 11:15 AM
Jackjeb
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Roger that. Will report back with solution when found. Thanks for insights....

JackJeb
 
 

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