Payne Plus 90 - Inducer Blower Hot?

[Alley Oop]

This 20 year old Plus 90 with a Chromotherm III stat is tripping the aux-resetable limit switch on the main blower housing after a few minutes. I reset the aux limit switch, set the thermostat, and supplied AC, I got a normal ignition cycle, and maybe 5 minutes of heat before the thing shut down again. The only thing I could find is the combustion draft inducer blower motor heating up, as in hot to touch the case. That motor is thermal protected/limited to 40 degrees C (104 F) ambient. The inducer blower motor did screech on cold start-up, so I drilled a very small hole in the end bushing cap and lubricated the bushing, first with a PTFE spray, then ATF oil. I got it through a 2 degree cycle of maybe 10 minutes to auto shut down after that, but that motor was too warm again for my liking. I probably need to get at the bushing on the blower end of the shaft and lubricate that if I'm going to use it, but may need to jerk it and ohm the windings. There is maybe 1/8 or more shaft end play.
The blower control card is good, ICM replacement, same condition with original type card (spare I cleaned the relay contacts on after replacement), inducer card is good too.

There was a recent windstorm with power outages, and the unit went cold and the blower stuck on shortly after the power came on. It worked normally until then. I came home and it was blowing cold air.

Ideas? Other conditions which might cause the inducer blower motor to overheat, like exchanger restrictions or ___? Can that alone trip the aux limit switch, or is it some other condition? Barking up the wrong tree? I'm basically flying blind and furnace illiterate, but know a bit about machines and electricity. Calling someone in is not an option right now.

Thanks,

Alley Oop

[HayZee518]

one eighth end play is too much. more than likely internally there are fiber washers which have worn through. A motor needs some end play to seek its magnetic center when running, using oil lite bronze sleeve bearings. but too much slop puts a load on the windings causing as you found out -- heat -- go to grainger or baldor motors and get an exact replacement. There are several hvac sites that you can look into too! ball bearing motors don't have this end play problem as the bearings lock the rotor in position.

[Alley Oop]

Thanks kindly, Hayzee. I will look into those manufacturers for the replacement. That is a pretty high RPM little motor. Yea, I had the same impression on the end play, and that motor really shows signs of heat, but is that enough heat to trip the aux limit on the main blower housing in the next compartment up, or is there some configuration between the inducer card and the main control card which would signal that aux limit switch either from the inducer motor heat or excessive current draw? If I could be sure that is what tripped the aux switch I could bypass that until I get a replacement in. That one is a Magnetek. Once I heard it screech on startup, I realized I had heard it doing that for a while, only not close up. The screech is gone now, but I will have to jerk the the inducer blower to get at the other end bushing, so I may as well replace it.

I wonder if that wasn't what ate the relays on the old control card I replaced.

Thanks,

Alley Oop

[bobbyj57]

I am currently in the midst of the exact smae problem, here is a question for you. Are there any strange smells in the house not gas but a lite exhaust smell or scorhed water? I have torn my furnace apart as the smell was getting worse and found in my 20 year old Payne Plus 90m that the lower heat exchanger has rusted through. Thus causing much for the exhaust fan work to be directed to pulling exhaust fumes (carbon minoxide) to pulled from the exchanger and not directed tot he exhaust of the fumes thus over heating the burn chamber tripping the relay. Now heres the proble, cant seem to find a replacement lowere exchanger.

Good luck hope that this is not your issue, but check to make sure as the heat exchanger collects condensation and rests through.

[bobbyj57]

Next time I'll run a quick spell check before posting.

Sorry

[HayZee518]

I found the following site for you guys - the guy with the heat exchanger burned out - a new one costs over $650. No: Z10-90 PLUS-06PW.
Site is: http://www.expertappliance.com/partfinder.php

[Alley Oop]

I don't think mine is rusted out, bobbyj, and I don't have the smell issues, but I understand the secondary on these can get plugged with algae and condensate. Is yours upflow, downflow, or horizontal? I haven't had mine apart, but the clear line to the pump is pretty clean, and I'm hoping I won't have to tear into the exchangers. If you have that problem, I would vacuum clean your primary for soot while you're in there, and run some ammonia or alcohol through the line to clean that. Just don't cut your plastic exhaust line.

Have you been through any control cards? Mine ate one in the first five years while it was still under warranty, then another one last winter, which I tore apart and filed the relay contacts, putting it back in service. I still have it for a test card, but replaced it in November with an ICM generic.

The inducer blower motor bushing is absorbing some of that lubricant now, and I used the furnace for a 2 degree cycle this morning to take the chill off, then bumped it another degree and it held, so I figure the that motor overheating was tripping the aux reset. I left it off and burned wood today, but I'll probably let it run a little longer tomorrow morning and see what happens.

Thanks for the parts source, Hayzee. If this thing doesn't complain I'll probably wait until summer.

Alley Oop