Trane Weathertron 900 XE wierd issue

[trader_Mike]

The compressor on my trane Weathertron 900 XE heat pump was replaced recently with the correct model and now is experiencing a wierd problem.

While troubleshooting the earlier problem, the HVAC consultant made a number of wiring changes near the control board on the outside unit, replaced both run and start caps and eventually determined that the compressor was defective.

The heatpump compressor and compressor fan start correctly from the inside thermostat but the compressor fan will stop running after 45-50 minutes. Subsequent to that the compressor will overheat and shutdown due to thermal overload. Once the heatpump cools down it does not restart automatically but will restart if the outside fuse is removed and reseated whereupon the compressor fan will again run 45-50 minutes before stopping while the compressor is running and the cycle continues.

To resolve this condition, The HVAC consultant has replaced the compressor fan, thinking it was undergoing a heat related shutdown as well as checked discharge and return pressures and temps which are all normal. Replaced the filters inside the house, checked the air handler and just about everything else.


I am not a HVAC guy but I think the issue is related to the wiring work that was done during the earlier diagnostic tests and that the heat pump is running a defrost cycle during normal AC operation. As In uderstand it, during cold winters when the heatpump is in heater mode, the fan will cycle off every 45-50 minutes to allow the compressor heat to melt accumulated ice to prevent ice buildup.

Is there a way to test this or even better is there a way to determine if the wiring is correct as my options are to buy a new control board.

any help appreciated,

trader_Mike

[Brian_UK]

Is the unit running in cooling or heating mode when this problem occurs?

It does sound suspicious though.

[trader_Mike]

good question, I checked last night and the unit has exactly the same behavior when it is in heat or cool mode.

I dont see how its possible for the unit to be wired correctly and have this problem. The more I research it the more I am of the opinion that its not wired correctly or in some defrost test mode, if thats even possible.


trader_Mike

[jhd1234]

probably repaired by now- if the capacitor were miswired, the motor would overheat faster than 45 to 50 minutes. Miswiring or bad capacitor are possible but my money is on worn motor bearings.

[trader_Mike]

Is the unit running in cooling or heating mode when this problem occurs?

It does sound suspicious though.

Its been a long time coming but the issue was resolved and we can close the X files on this one.

Briefly,
The original 7.5uF fan cap was replaced some time ago with a 10uF cap and that caused the fan to overheat. When the fan overheated, it stopped turning (thermal overload) and the Compressor overheated. It just so happened that the symptom looked like it was being caused by the heat pump entering defrost mode. Putting the correct fan cap in resolved the fan overheating issue.

Again thanks

Mike

[Brian_UK]

Thanks for the update Mike and glad to hear that the problem has been resolved.