New Condenser Fan Motor(s) trips on OT

[lafittejdubb]

I have an 20Ton 16 year old AAON unit that keeps tripping the 1st condenser fan motor (left side-when facing unit). The 2 motors are rated at 3/4HP, 1075 RPM, 2.5A, 460v. 10uf/370v Run Cap. <--(what the motor is rated for)
1.) My condenser coils are clean and clear of blockages.
2.) OAT is 100 degrees and dry. Condenser coils face North and has a 30-45 degree downward pitch toward the tar/gravel roof.
3.) I have 472v, 2.2A, motor is moving at 1000+ rpm's and balanced. I'm not getting any voltage or amperage lows/highs. It's steady power from a 2p/ 30amp new contactor feeding both fans. I have new 14ga wiring running to the problematic motor.
4.) Run cap tests at 9.8 mfd. (within tolerance)
5.) Discharge pressure on both circuits is 245-270 psi. Suction pressure is 65-75psi both ckts. 16 degrees SC, 8-14SH
6.) Replaced the motor and capacitor 3 times and blade twice, however will trip on overtemp in about 1 hour if both stages are calling.
7.) I have three more units that are the same 20T AAON and have the same motors, but without any problems.


Desparate Ideas:
* The unit is three phase, but my motors are wired for single phase. I thought about changing the motors out to three phase motors and wiring directly, but none of the other units need this. Don't think it would solve the problem anyway.
* Thought about putting something down on the roof underneath the condenser coils to reflect the heat so it's not drawing air from the superheated roof. However, strong wind would likely blow it up and block the coils.

Anyone else ever experienced this? Would be grateful for any intelligent thought!!

[Thomasg]

Not sure but i read in another thread not sure if its your model number or not where guys were having trouble with aaon condenser motors. They were saying they had to go up to a 1hp motor. If i find thread ill send you link.

[tlb]

I did have same problem on smaller york package units.Voltage,cap,amp draw all good but would cut on internal.These were generic motors that we had put on to replace the OEM.We had to upsize from 1/4 to 1/3 or we got the OEM and no more problems.

[GoColts]

You have to use OEM with AAON units. Whats the pitch supposed to be on your fan blades? Swap motors from the unit thats working and see what happens. It might be worth a try. tlb we just had and issue with a York and a non OEM motor salesmen did not listen to the tech sold an after market CFM we had 5 call backs ( 1.5 hours away) before someone steped up and call tech support and they were told to put an OEM motor in. :cheers:

[Little NATE]

I have learned to that when you match factory motors to generic you match by amperage not horsepower if your new motors not rated at a higher amperage step up a size !

[XcelTech]

Just a shot in the dark but I would say your converter is having issues.

[darkbeekeeper]

I ran into this on a set of aaon units before the ambient temp rating on the new motor i picked up at a local parts house was lower than the oem motor they worked fine in a few of the units but the ones that had a good load on them would go out on thermal or just cook them after ordered the oem from aaon worked fine. all my amp, voltage were fine just the non oems could not handle the air temp and cooked them hope this helps

[ryan1088]

You have to use OEM with AAON units. Whats the pitch supposed to be on your fan blades? Swap motors from the unit thats working and see what happens. It might be worth a try. tlb we just had and issue with a York and a non OEM motor salesmen did not listen to the tech sold an after market CFM we had 5 call backs ( 1.5 hours away) before someone steped up and call tech support and they were told to put an OEM motor in. :cheers:

X2

Oem motor will make all your problems go away!

[Texas-Tech]

You say the coils are clean but are they suffering any deterioration to the aluminum? Ours here are all coming apart and when that happens they have a hard time pulling air through them. Those condensers are pretty thick, can put a lot of strain on the motors especially if they're not the right motors.

[lafittejdubb]

Thanks for the tips on OEM motors. I'm going to go with that and I'll repost my results.

[chillerout1]

also notice on oem motor for aaon is an open motor like you would use for indoor blower for better cooling of motor most replacements from parts house are either not vented or a few vents on bottom

[Pion]

I have learned to that when you match factory motors to generic you match by amperage not horsepower if your new motors not rated at a higher amperage step up a size !
I have found also that amperage is the true gauge to use when replacing a motor.

[ascj]

I have learned to that when you match factory motors to generic you match by amperage not horsepower if your new motors not rated at a higher amperage step up a size !

I would agree with this stated....if your strictly talking single phase ac motors.

This statement doesn't hold true for 3 phase ac motors.

[lafittejdubb]

For anyone still interested, replaced the motors with OEM and that has fixed my problem. Thanks everyone for all of your inputs!!

[james mo]

I'll bet they draw slightly over fla stamped on the side of the motor. Most of the Aaon condenser fan motors I see run well into the service factor.

[lafittejdubb]

Yea, they did! FLA was 2.0 however i was pulling 2.2. I noticed the motor was also considerably larger (depth) than the A/M's. I figured it must be more run windings. Also, I noticed it was open-type motor (ahu motor) but with a rain guard that doubles as a ventilator for the motor windings. (Fixed Centrifugal fan blades)

What a bunch of BS!!