trane condensing gas furnace blinking 3 flashing lights

Problems related to residential installations.

trane condensing gas furnace blinking 3 flashing lights

Postby benzene123 » Tue Jan 24, 2017 9:30 am

My furnace has been blinking 3 flashing lights. The furnace will cycle couple of times and it will start sometimes. When it is working, it would sometimes stop eventhough the desired temperature has not been reached. There is gurgling water noise at the exhaust flue pipe. There is two drain ports, one that connects to the exhaust fan which seems to be dry and the one that is connected to what appears to the internal housing which is a little damp but no water pouring out. Both the air intake flue pipe and exhaust flue pipe exits through the roof but the air intake flue pipe has a opening next to the furnace. One of the HVAC technician said that the furnace flue might be blocked but offer no solution to fix it. The other said that the flue pipe is installed incorrectly since the exhaust motor is connected to 2 elbows back to back right at where it exits the furnace (makes a 180 degree turn) thus attributing to the water noise/blockage. The furnace is also not leveled but is tilted toward the back of the furnace which might cause the condensate to collect at the back of the furnace. His solution is to replace the entire furnace and connect new flue pipes. Both said the drain is not blocked but I'm seeing water leaks around he furnace. Any ideas on how to fix it so the furnace works consistently? It seems that the situation is getting worse and worse. Thanks for your help and advise.
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- trane condensing gas furnace blinking 3 flashing lights

Postby Freon » Tue Jan 24, 2017 8:06 pm

What is the make and model number of the furnace? On the furnace should be a list telling you what problem the 3 flashing lights signify. Please tell us the indicated problem and then we can try and help.
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- trane condensing gas furnace blinking 3 flashing lights

Postby benzene123 » Tue Jan 24, 2017 10:56 pm

It's a Trane XR90. I don't know the model number. The 3 blinking light on Trane furnaces indicates a pressure switch problem but the technicians can "trick" the pressure switch such that the furnace runs. What is your take on the double 90 degree elbow design as well as backsloped furnace causing condensate to not drain properly? The fact that sometimes the furnace shuts down before the desired temperature is reach, does that indicated a heat exchanger problem?
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- trane condensing gas furnace blinking 3 flashing lights

Postby Freon » Thu Jan 26, 2017 10:47 am

If your furnace has been working for several years, then the double 90 and back-slope should not be an issue. If they were, you'd have had these problems day 1.

The furnace shutting off could be due to the inducer pressure not being within specs due to the buildup of condensation while the furnace is running. Again if this is a new issue and not a problem since installation you know where to look for answers, the draft inducer assembly.

I would first check all hoses involved with the inducer assembly. Look for cracks, clogs or pinched places. Any of these can affect the pressure at the pressure switch.

Next I would disassemble, if possible, and clean the 2 condensate drain pipes. Again clogs, especially in any P trap, will affect performance and resulting pressure achieved by the inducer.

Next see if you can remove the inducer blower wheel and inspect it for debris like dust and other matter that could affect performance. Wiggle the motor shaft looking for excessive movenemt side to side, top to bottom indicating possible bearing problems.

Finally the pressure sensor itself could be defective. I would save replacing that to the very end. If you can remove it and inspect it, do so.

Unless your house has settled since the furnace was installed, the pipe pitch has not change. Since the furnace was working fine for years before now (I assume), the pitch should not be an issue.
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