Intermittent Heat - York Diamond 90

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Old 02-19-15, 07:06 AM
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Intermittent Heat - York Diamond 90

Am new to forum and am not an HVAC guy. Had the HVAC guy out for 3 hours this past Saturday, and he was not able to resolve. He gave me some homework, which I've done. York model number on propane furnace is P3URD12N07501A. Apologies if any of my terminology is confusing.

This or a very similar trouble is described by many other posts on the forum. Problem: From power up, inducer blower motor runs, igniter heats up, and burners usually ignite on the first, second, or third try. On a good day, furnace will come up to set point and will continue to operate well for a few hours. On a bad day, it will not ignite and will lockout without producing heat. Error code shown on White Rodgers 50A50-241 controller may be 3, 6, or 8. In all cases, burner box pressure switch opens to lockout furnace.

I have cleaned out everything associated with condensation inside the furnace, in the condensate pump, and in the drain line. Have replaced the flame sensor and igniter. Have swapped the controller with a known good one. Have checked incoming and outgoing 2" PVC lines for blockages. Have opened the burner box and condensate pressure switch tubing connections and verified that diaphragms are intact and that both open and close electrically. Have checked gas pressure both before and after furnace gas valve. Have cleaned burners, removed some small leaf pieces from burner box and from opening to heat exchanger.

Before I throw any more parts at this thing, does anyone have ideas? Is there a way to test the inducer blower other than verifying that it does run? Is there any real likelihood that the pressure switch tolerance has changed or that it has otherwise failed?

Thanks,

Bruce
 
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Old 02-19-15, 08:54 AM
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Do you have this TS info? Pages 37-39 may be of some help.
http://johnsonsupply.com/york2001/PUB/N4u.pdf
Geo
 
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Old 02-19-15, 09:26 AM
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Thanks for reply. Your link matches the diagnostic information I've found. I do not have a York service manual that shows this specific York model number.

I am suspecting the inducer blower, mainly because there is not much left. It's labeled as a Fasco Swirlwind, but has no part number. Would these typically stop pulling enough air to clear the heat exchanger to cause intermittent ignition? Or would they just stop turning? This one turns, but don't have anyway of gauging whether it's moving air like it should.
 
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Old 02-19-15, 09:30 AM
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You would have to put a manometer on the inducer to see what the pressure is.
 
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Old 02-19-15, 03:38 PM
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It would just stop unless the blower wheel was somehow restricted.
Geo
 
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Old 02-20-15, 04:59 AM
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Yesterday afternoon, inducer motor started making a jingling sound that I probably wrongly assumed to be bearing noise. I ordered a replacement that will arrive today. Since I've got 2 furnaces that run same part, think it will serve as a spare.

Have been running without errors since late yesterday. I believe that burner box pressure switch was opening as a result of condensation backing up into the inducer housing. The short sort of s-shaped hose from the inducer housing drain into the condensate trap appeared to be installed backwards (slightly uphill to tank). When I pulled it, a good bit of water drained from housing. Turned hose end-for-end and shortened it by 1/2". The jingling sound stopped immediately, and I've had no errors since. Not ready to celebrate just yet, but think problem is resolved. Will confirm later if so. Thanks for replies.
 
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Old 02-20-15, 03:14 PM
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That could be it,causing a slight restriction.
Keep us posted
Geo
 
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