Rheem 90 Plus intermittent operation


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Old 02-15-14, 01:03 PM
J
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Rheem 90 Plus intermittent operation

Thanks for being here everyone! I read a previous post on a similar problem, but am stuck right now with slightly different symptoms. Maybe someone can point me in the right direction for further troubleshooting my furnace

Name: Rheem Classic 90Plus
Fuel propane gas
Age: approx 5 years
Model Number: RGRB 07EMAES

Symptom: Completely intermittent operation for the last two weeks. Sometimes it will shutoff immediately Ė no flame sensor light, but other times the sensor light blinks amber and the furnace works, sometimes it is steady. Last night it was out cold for about 4 hours, then suddenly was working perfect (solid yellow) by itself. Right now it's working but with a blinking amber light.

What I've done so far: Cleaned flame sensor with Emory cloth. Also swapped flame sensor with equivalent sensor from the furnace next door (this is a duplex and the model is exactly the same. ) Problem stayed with furnace, in other words, my flame sensor worked fine next door, and hers didnít work on mine.

Also have checked pressure hoses (were clear) and condensation drain hoses (clear). There is a small crack in the plastic T PVC pipe that leads from the induction blower motor to the main exhaust pipe. This appears to be the source of some water that leaks into the bottom of the furnace. Most condensate is probably going down to the sump pump as designed, plus sump pump is working fine.

The only thing I can think of is there's something more clogging one of the pipes, and that condensate is draining too slowly for the rest of the process to be ok. Because eventually it drains enough the furnace can start? I donít know how to test for clogs above and beyond the hoses. and would a clog translate to a no flame sensor condition?

The tech from the boiler company said it was 95% bad flame sensor, but since I ruled that out, can anyone suggest other ways to troubleshoot what might be going on? He said that if it wasnít the flame sensor, he would have to get on the phone with Rheem and do other tests, such on voltages etc. Sure would be nice to not have that new support call, since he knows about as much as what might be wrong as I do. But I donít think I can call Rheem directly.

Again, sometimes it works perfectly, other times with a blinking yellow flame sensor light, and every so often no sensor and no operation.

Thanks for any and all advice!
John and Nancy

PS, the first tech (we had two diff ones) said that our problem was that the exhaust pipe was angled back towards the furnace (about a 20 foot semi horizontal run), which means that condensate and other water would go back to the furnace an carry dirt back to clog things up. The second said, no, it has to be that way by design, otherwise you would have ice buildup on the end that would block exhaust and shut things down. Is there a right answer, or is a matter of opinion?
 
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Old 02-15-14, 04:54 PM
J
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Another clue? I unplugged the hoses to see if they were precipitating condensation, and i ran it for more than 4 or 5 minutes (with heat working), but nothing came out. when i stopped it, a whole bunch of water did come out of one (the one attache to the back of the unit, not the exhaust pipe. would this be normal, as in the pressure from the exhaust fan keeps the water up in the system until you stop?

otherwise, i did notice the sump pump kick after it was running by itself for a while, fan running, so maybe the condensate flow is normal?
 
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Old 02-15-14, 11:47 PM
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Welcome to the forums.

It may not be the flame sensor rod but it sounds like a problem in its path. If the light doesn't stay yellow then the signal is not correct and reliable. Check for ground issues on the burners and control board. Remove and reinstall screws so that they are tight. Make sure flame rod is solidly IN the flame.

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This is from page 56 in the following manual for your furnace.
Rheem documents rgrb-installation-instructions.pdf
 
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Old 03-09-14, 10:58 AM
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I'm having the same problem with ignition; years ago, I blew compressed air in the lines, and she came back on. But today, I don't have any compressed air, but I have checked all my electrical connections including the IFC board and resets. I am wondering if I could have jarred something loose when re-installing the air handler door. I replaced the old filter with a new ("high dust" disposable type) at the intake. My next step is the service technician. Any ideas about if I have jared a bimetal ignition of sorts internally? I'm not sure about the igniter on the system?
 
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Old 03-09-14, 11:02 PM
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Welcome to the forums.

You didn't leave me much to work with. Do you have the same exact furnace that the OP had in this thread ?
Does your control board have an LED on it ? What code is it blinking ?
 
 

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