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.
* 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!!