Strange problem with a natural gas Trane 2-stage furnace, XL80.

Hi everyone,

When the thermostat calls for heat the furnace flame turns on, 45 seconds later the fan motor starts. About 2 1/2 minutes later the furnace flame turns off and at that very moment the fan motor turns off. The fan should run for 140 seconds after flame shut down as set on the Integrated Furnace Control circuit board. This problem only occurs roughly once every 20 heat cycles. This problem can occur in the morning, afternoon or evening. The 20 heat cycles works properly and the fan will turn off 140 seconds after flame shut down.

The setback thermostat drops the temperature by 2 degrees at 10:00pm and back to normal at 8:00am (7 days a week).

Is the problem originating in thermostat or the Integrated Furnace Control circuit board?

Would appreciate any input.

Location:
Ontario Canada near New York state border.

Below is the list of HVAC equipment and settings.

Thanks everyone.



Installed new on July 2006.

(1) Trane furnace 2-stage XL80, model TUD080R936K
Original Integrated Furnace Control circuit board, model White-Rogers CNT03077 REV. I, (50M61-495) - (Heating Fan Off -140 seconds / Cooling Fan Off - 0 seconds)
(2) Trane A/C 1-stage 80XL, model 4TTR4024A1000AA
(3) Trane thermostat 3H / 2C, model TCONT803AS32DA (I confirmed this is a Honeywell VisionPRO 8000 Touch screen Programmable Thermostat)
(4) Honeywell C7089 Outdoor Sensor

Thermostat settings:
0160 Schedule Options (4) 7-day programmable
0170 System Type Selection (9) 2 heat / 1 cool multistage conventional
0180 Fan Control in Heating (0) gas or oil furnace equipment controls fan in heating (factory setting)
0220 Cycles per hour (cph) for 1st Stage Compressor (3) cph recommended for compressors (factory setting)
0240 Cycles per hour (cph) for 1st Stage Conventional Heat (4)
0250 Cycles per hour (cph) for 2nd Stage Heat (Aux Heat for 2H/1C Heat Pumps) (4)
0300 Changeover (0) manual changeover (factory setting)
0320 Temperature Indication Scale (0) fahrenheit temperature display (factory setting)
0340 Remote Temperature Sensor (Outdoor or Indoor) (1) outdoor temperature sensor for display only
0380 Indoor Dehumidification Control (0) No indoor dehumidification control
0530 Adaptive Intelligent Recovery (0) Conventional Recovery (system starts recovery at programmed time)
0540 Number of Periods (4) four periods available (Wake, Leave, Return and Sleep)
0680 Temperature Control in Heat (2) Standard temperature control in heating (factory setting)
0700 Temperature Display Offset 0 °F (0 °C) (no difference in displayed temperature and actual room temperature)

 

Are you getting any fault code on the board?

Kinda going off track, you know if W1 and W2 is wired up by itself at furnace and t-stat?

Does it start up again or do you have to reset it? (Power off)

It's may be the board.



I'd suggest to set this to 3.

Why not use the smart recovery? (I also noticed you don't have a much of set back temps)

 

Thanks for your response Jay,

Are you getting any fault code on the board?
>>No fault code.

Kinda going off track, you know if W1 and W2 is wired up by itself at furnace and t-stat?
>>W1 and W2 have separate wires going back to the thermostat (not jumpered together at furnace).

Does it start up again or do you have to reset it? (Power off)
>>No intervention or power off/on is required on my part. When the thermostat calls for heat again later, it works normally (acts if the last heat cycle was normal). (problem never happens twice in a row).

It's may be the board.
>>I’m going to order a new Integrated Furnace Control circuit board to have as a spare, (White-Rodgers 50M61-843). Just in case the problem gets worst. As it stands now there’s no impact home comfort.

I'd suggest to set this to 3.
>>I’m going to change it to 3

Why not use the smart recovery? (I also noticed you don't have a much of set back temps)
>>I will also change 0530. I did have a different schedule at one time, retired early due to economic conditions. Bit of a waste having a simple schedule on a powerful thermostat.

 

Not sure how old the furnace is, but board may be under warranity.. Otherwise, not a bad ideal to have one sitting aside when it does act up on you in the dead of winter.

 

I brought a brand new Trane 3-stages furnace 95XC. The furnace is frequently locked (soft lock) after consecutive failed attempts to turn on flame. This happened several times a day [ERR 22]. Technicians came and checked but could not detect what went wrong with the furnace. Accidentally, the issue was fixed when I switched ISU# 530 from 1 (Adaptive Intelligent Recovery) to 0 (Conventional Recovery). Perhaps you should try to see if it helps.