3-Wire and 4-Wire Condensing Fan Motor Connection

Diagram courtesy of Emerson

New techs have a common question of how to wire a condensing fan motor for 3 vs. 4 wires. Jesse Grandbois submitted this tech tip to help make it simple. Thanks, Jesse!


This tech tip is a quick one on the difference between wiring universal condenser fan motors and why brown + white is the same wire as white. This one seems to confuse even experienced technicians, but it's actually very simple once you see it. Now, keep in mind that wire colors ACTUALLY MEAN NOTHING, but the colors tend to be consistent on service replacement motors. As always, refer to the wiring diagram on the particular motor you are using.

I'll provide a diagram and explain the wires below.

Here's the 3-wire method:

  • White wire from the condenser fan motor to one side of power on the contactor (T1) and jumped to one side of the fan capacitor. This is AC power and not a dual capacitor, so the terminal side does not matter.
  • Black wire from the condenser fan motor to the other side of power on the contactor (T2).
  • Brown wire from the condenser fan motor to the other side of the capacitor opposite the jumper wire.
  • Cap off brown + white (unused).

Now, for your 4-wire method:

  • White wire from the condenser fan motor to one side of power on the contactor (T1).
  • Black wire from the condenser fan motor to the other side of power on the contactor (T2).
  • Brown wire from the condenser fan motor to the capacitor. Again, this is AC power and not a dual capacitor, so the terminal side does not matter.
  • Brown + white wire to the other side of the capacitor.

As you can see, the only difference is that there is no jumper from the contactor to the capacitor. That is because the brown + white and the white is the same wire. They're joined inside the motor. The brown wire with the white stripe is only there for convenience.

If you want to prove that the white and brown w/ white stripe are the same, take an ohmmeter and test between the two. You will find that it either reads zero or very low ohms, proving that they are directly connected within the motor.

 

—Jesse Grandbois

P.S. – If you would like to understand 3 or 4-wire connections within the entire process of replacing a condenser fan, please check out this article.

Related Tech Tips

Sensors, Measurements, and Physics
As HVAC/R Technicians, we use tools and instruments to take measurements every day. In fact, 90% of our job could not be done efficiently without some kind of measurement.  “How do we measure?” “With what instruments?” “How accurate are these measurements?” These are all questions a thoughtful technician should ask before spending money on a […]
Read more
What is Compressor Volumetric Efficiency?
Simply stated, a compressor’s volumetric efficiency (VE) is its ability to pump the most pounds of refrigerant over time. The compressor’s function is right in the name: it compresses vapor refrigerant. After compression, the gas moves to the condenser via the discharge line. From there, the refrigeration cycle continues. However, some of the refrigerant vapor […]
Read more
5 Things to Consider When Maintaining a Commercial Package Unit
If you are primarily a residential technician working on equipment under 5 tons, there are many similarities between the systems you are used to and 5-20 ton rooftop units common to the light commercial market. There are MANY additional things to consider on larger equipment, and here are just a few. Wash Fresh Air Filters […]
Read more

7 responses to “3-Wire and 4-Wire Condensing Fan Motor Connection”

  1. Usually choose the 4 wire method and have always trained guys that way. Is there a difference in operation between methods? It’s always been my understanding that it doesn’t make a difference. I teach the four wire method because it is impossible to get confused.

      • Yes, my comment was for the 3 wire & what I was saying was instead of jumping from the starter/contactor you can also jump common direct from the cap.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from