Rheem doesnít like to run in cold weather

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Old 11-11-17, 11:41 AM
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Rheem doesnít like to run in cold weather

Hi folks- our Rheem runs great in warm weather but when cold it requires a long wait before it will fire up again. It will start and run just fine in cold weather as long as it hadnít ran an hour or less before that. It seems like something needs time to drain. The colder it is the longer it has to wait before re-firing. It will blink 3 times and try to start up 4 times then go in lockout. Does that make any sense? The Rheem is located in the attic is a natural gas furnace. It had a short ~10 ft 2 inch exhaust. When the sun is out hitting the roof and warming the attic it would run fine. You could stop it and restart it and it will work fine. But when temperature in the attic gets down to 50 or 40, it just wonít start up until about an hour or more after it ran last. It will run fine, can run for 30 minutes or an hour but if the thermostat calls for heat soon after reaching temperature it will just short cycle. To me it seems like something needs time to drain, not sure if the condensate line or the water forming in exhaust? Would water in exhaust cause it to short cycle or does this sound like water in condensate or something else causing the short cycle? Thanks for all your help.
 
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Old 11-11-17, 12:33 PM
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On most Rheem furnaces a three flash code is a high limit open. That could mean the furnace is overheating. The fault code definitions are on the back of the blower door.

You need to post the model number which can be found behind the burner service cover on the sidewall near the burner.

A condensing furnace in a cold attic is not usually ideal depending on where you live.
 
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Old 11-11-17, 02:37 PM
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Thanks, let me get back to you on the model and error code. Iím with you- I inherited this furnace with the house and have to make do.
 
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Old 11-12-17, 04:49 PM
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Hello again, It is a RGTC-06EMAES. I’m going to try to attach a video showing the lights after 4 unsuccessful attempts. I think it just flashes once now that I look closer at it. I let the furnace run fine for 30 minutes, then once it stopped I immediately turned the temperature up on the thermostat and went up to take the video. About 20 minutes after I took the video (after resetting the power) the furnace ran fine. It just won’t run directly after it just ran, and that length of time increases as it gets colder. Once it’s 45-50 degrees up there you have to wait an hour before it calls for heat again or else it will do this. I turned off the power this time and disconnected the rubber hoses that lead condensation out of the burners and exhaust and neither “was plugged” or had excessive amount of water. I don’t think the trap is slow to drain or anything. Maybe the condensate is slow to flow out of the burners? I don’t really know exactly how that water works it's way to that rubber hose - I get the exhaust side and there is plenty of slope and just a short run on that aspect. I just don’t understand why it needs such a “rest period” between heating runs when it gets cold.

Here is a link to the video:
https://spaces.hightail.com/space/0LebtK1ePl
 
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Old 11-12-17, 05:56 PM
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Two green LED's .... one power and one fault.
One amber LED for flame sensing status.

The LED's and their meaning should be on the back of the blower door.

Your amber LED is flashing which signifies a weak flame signal. You will need to remove the flame sensor rod and clean it with a scotchbrite pad. Needs to be shiny and bright.

This manual covers your furnace. As you look thru you'll see parts layout pictures. Part # 10 is the flame sensor and will be near the burner as the rod sits in the flame.

manuals/installation/RHEEMRGRM.pdf
 
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Old 11-13-17, 05:12 PM
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Thanks for the tip, I cleaned the flame sensor and so-far so-good. It's been mid 60's up in the attic today so the real test should be when it gets colder. Will let you know - thanks!
 
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Old 11-13-17, 07:33 PM
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After you cleaned the sensor rod that yellow LED should have stayed locked on.... not flashing. If that is the case..... you should be good.
 
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Old 11-14-17, 06:14 AM
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Thanks again, you're right. The yellow light stays solid now when the gas furnace is burning. Last night there were no issues even as the attic temperature dropped. While cleaning that sensor seems to have fixed it this time, is that a part that needs to be replaced occasionally, or is just doing a cleaning of it once a year OK?
 
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Old 11-14-17, 09:32 AM
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It is just a metal rod. Cleaning it once a year is ok.
 
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