I have a trane xl 1100 heat pump split system the outside fan shuts off for no reason all readings are good I have tried 3 different motors with blades that were the right size but still runs about 20 minutes than shuts off, the compressor keeps humming I have had 2 techs look at it but have no idea please help

Kenneth

Trace the wiring down and see what is turning off the fan. Usually the fan and compressor are on the same contactor. Did you replace the capacitor with a new one specifically for the new motors you replaced? It is possible the fan motor is going out on the internal overload if it is heating up. It is a possibility that you have the incorrect RPM and horse power motor installed causing this situation. I have seen that before after the first motor replacement. NO one took the time to make sure the motor Exactly matched what was the original specs. Also it is possible the motor is running in reverse or the wrong direction/degree of pitch blade is installed. Check the original factory specs and then see what you have installed.

I have done all the above it makes no sense why the fan keeps shutting off

Could be the defrost control board going bad.

I wired straight to the contactor and went around the board any more suggestions I would appreciate it
Kenneth

Curious... is the fan running in the right direction? Also have your outdoor coils been cleaned latly?

Yes to both questions I have tried everything any more suggestions I would deeply appreciate it
Thanks
Kenneth

I wired straight to the contactor and went around the board any more suggestions I would appreciate it
Kenneth

If you wired the motor direct it should never shut off under normal conditions unless it is going off on the internal overload. Many items can cause this and I believe you addressed some of them but I will list a few.

Dirty coil causing the fan to have a hard time moving the air causing the motor to go off on overload. If you have two sections of this coil like a coil in a coil setup most people never separate them to really get them clean. If you have this setup do not attempt to clean them until you repost with the answer since you can really make a mess of things when trying to separate the coils enough to clean them correctly. Usually to find this out you have to remove the top and see how many coils deep the unit is. Most professional service people will also miss this on there cleaning because it is a big pain in the A$$.

Some condensing units require a higher service factor motor than others. Higher service factor means it will perform at higher temps and loads than standard motors among other things.

The condenser fan blade is critical in all applacations wrong pitch/rotation will also play a big part in motor overload problems.

The wrong capacitor for the motor can cause it to loose HP or gain HP at the risk of overload. Make sure if the motor/capacitor has been replaced that the old capacitor is out of the circuit. I have seen where a old dual capacitor(compressor and fan) has actually been left in the circuit and just the wires used for the new motor. You end up with two capacitors working for the condenser fan motor and that is not good and causes similar problems.

If you have access to a Amprobe get the fan motor started with the cabinet put together or make sure the access door is leaning on the unit. Then take a reading and match it to the draw specs on the tag on the unit. The motor draw/amps should be very close to those posted on the unit.

Check the voltage at the unit when the unit is running. Many times when a unit is running the voltage supply will drop from loose connections that could be in the indoor box all the way to the outside unit. I have seen voltage drop from 240 to 210 volts on a few units in my time. The drop will not trip a breaker but it will place a hardship on the fan motor and compressor.

Give these ideas a shot and let us know what you find.

ALSO post the specs of the motor you are using in the unit. RPM and HP are my main concerns but just post the entire label including part number off the motor.

I have to agree with hvac1000. Need to know more about the motor.
Also when you changed motors did you use the same blade or change blades too? Changing blades could alter pitch and air flow causing it to not run correctly.

Thanks everyone for the help I put a smaller capacitor in for the fan and so far the problem is fixed again thanks to all that helped me
Kenneth

Yep the wrong size cap can cause problems.