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HVAC School - For Techs, By Techs


Jun 25, 2024

In this short episode, Bryan talks about wiring in condenser fan motors, including aftermarket motor considerations and the different wire configurations.

When condensing fan motors fail, we need to know what to use to replace them. We often use PSC motors, though in cases when we replace a motor with an ECM, we still need to match the horsepower despite the increased flexibility. The motors we typically keep on our truck are 1/3 or 1/6 HP motors. 

Frame size (diameter) and depth also come into play; you may encounter a 42-frame motor or a 48-frame motor. You can't replace an 825 RPM motor with a 1075 RPM one because the poles are different (6-pole vs. 8-pole). Single-phase 208/230v will be the most common motors in residential systems, and the phase and voltage must match. You should also know how to reverse a motor if it is reversible. The bearing type will have some tradeoffs; ball bearings last longer but are louder than sleeve bearings. 

3-wire and 4-wire condensing fan motors are essentially the same; the white wire and brown-and-white wire are essentially the same, as there is a jumper inside the motor. You can connect a 4-wire condenser to both sides of the capacitor; in any case, follow the wiring diagram.

When mounting a motor, make sure the wires are strapped properly. Then, remember to unplug the correct weep ports (opposite side of the shaft) to allow condensate to drain out.

 

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