Help with Carrier 58CLR oil fired hot air furnace weirdness

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Old 01-28-19, 09:38 AM
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Help with Carrier 58CLR oil fired hot air furnace weirdness

I have a 10 year old Carrier 58CLR oil fired hot air furnace. Starting the end of last week it started behaving strangely. We'll have the thermostat call for heat and the furnace will start normally (Burner pre-purge, ignition, burn beyond flame sensor shutdown/lockout). Shortly after the burner starts the fan to circulate the air across the plenum/heat exchanger starts. I know that under normal operation when the thermostat stops calling for heat the burner will shut down, but the circulating blower will continue for a few minutes to cool the plenum/heat exchanger down. The weirdness is that now the blower stays running for much longer. I thought it was controlled by a timer, but now I'm wondering if there is a plenum temperature sensor that is going bad and reporting a higher plenum temperature causing the fan to stay on.

I've also found that at this point if the thermostat calls for heat again while the air circulator is still running the burner doesn't turn on. I know the burner could be in lockout if the flame blew out, however when I hard reset the furnace (turning off the main power and back on) the burner ignites normally, I've also cleaned the flame sensor to make sure that it is working, and if I turn on the furnace without fuel turned on the system shuts down because there is no flame, so that appears to be working properly.

My only hypothesis is if there IS a temperature sensor it is causing the system to think there is a hot plenum so keep the blower blowing and don't bother turning on the burner.

Does anyone know if there is a temperature/limit sensor on the Carrier 58CLR low-boy furnace, and where it might be or how to access/test/change it? I haven't been able to find a service manual for it, and the installation manual I found doesn't specifically address this point.

Or if I'm completely barking up the wrong tree I'm willing to be told so and any suggestions for where I should be looking would be gratefully accepted.

Thanks,

Metalmangler
 
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Old 01-28-19, 11:33 AM
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Welcome to the forums.

I'm not an oil specialist. Flame sensor ?? Do you mean the cad cell/fire eye ?
That looks like it uses a timer circuit on the control board to control the blower. If the blower is running when it shouldn't be.... it could be caused by a tripped or open high heat limit sensor.

You need to locate the control board and post the part number.
There should be a wiring diagram on the service door. That would be handy too.
How-to-insert-pictures

There is very little online service on this unit. Possibly due to its age.
 
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Old 01-28-19, 01:00 PM
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Pete - Yes, the flame sensor is a photocell attached to the Riello Primary Controller box.

I'll get a picture of the Carrier control board when I get home this evening and post it to the thread.

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Old 01-28-19, 02:59 PM
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If you can post pics it would help. Your burner and cad cell are working normally so I wouldn't worry about that.

Your cad cells only job is to shut the furnace off if it doesn't see light in a certain time, whatever time limit is on the control you have. They vary but mostly 45 sec.

It sounds like your fan/limit switch or sensor is getting stuck. If you let the blower continuously run when this happens until the air becomes cool that's a pretty safe bet. If that happens instead of shutting off the switch see if your stat is satisfied. If so turn it up to see if burner comes on by itself.

There may be nothing wrong with the burner since your stat controls that, just a stuck fan switch or whatever controls it.

Pages 3 & 5 has info about your blower. Sounds like it's a timer that comes on at 60 sec.

https://www.manualslib.com/manual/25...ma.html#manual
 
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Old 01-28-19, 07:07 PM
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Spott - Thanks for the link. While that one is a slightly different model (58CMR), I was able to find my model (589CLR) at the same site: https://www.manualslib.com/manual/47...?page=3#manual. This is great since it does provide a general diagram showing basic locations of things such as a High Limit Switch!

I'd found a document which also seems to cover my furnace (https://dms.hvacpartners.com/docs/10.../58CLR-2SI.pdf) and while it has some more detailed technical information it didn't even show where the high limit switch might be located.

I took pictures of the furnace control board but since it's still in place (I'm not ready to yank it yet if I don't need to) the wires tend to obscure things. I found one that may be a match, depending on what numbers you go by. I did find a board which is a VERY close match (see below the links for the differences in the numbers on the sides of the boards)

https://rdt.prod.repairclinic.com/Pa...99G004/2760066
Board Front: https://www.rcappliancepartsimages.c...4-01643774.jpg

Board Back: https://www.rcappliancepartsimages.c...4-01643779.jpg

I'm also attaching two pics of my board showing various numbers: R99G004, 1158-110, 0749 on one edge, and 1158-83-121A on the other edge. The board on the website has R99G004, 1158-110, 1330 on the one edge and 1158-83-122A on the other edge. So this may be a compatible replacement board if I need it.

I'll see if I can't figure out how to access the high limit switch and see if I can get a part number off it to figure out how to test it. I've noticed that the DIP switches are in the position to have the blower on for only

I did some more testing this evening and here's what I experienced:

Turn thermostat up to call for heat. Burner kicked on, and shortly after (I didn't time it but based on the wiring diagram it should be about 1 minute after the burner started and that seems about right) the blower started.

I let the system run for a while then turned the thermostat down, heard the burner turn off and started a timer. Based on the diagram (also attached) the blower should have shut off after 5 minutes but after 6 minutes the blower was still on. If the thermostat calls for heat again the burner starts normally. This is slightly different from some times in the past where the burner would not start (didn't even appear to be trying to start, no oil pump, no electrodes arcing to ignite, etc).

MM
 
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