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

Building Automation Basics for the HVAC Tech w/ Phil Zito (Podcast)
In this episode Phil from Building automation monthly comes on and talks building automation and demystifies some of how it works. If you have an iPhone subscribe to the podcast HERE and if you have an Android phone subscribe HERE
Read more
Uncommon Start and Run
I walked into my first real job interview in the HVAC trade. The manager was a guy named Ernie, and he walked me out to the warehouse. Quick warning: guys named Ernie are tough. Don't mess with a dude named Ernie. He walked up to a box, snatched a pen out of his shirt pocket, […]
Read more
UV Lights
A quick note about UV lights: they work like sunlight in that they prevent and kill many types of bacteria and fungi when exposed to the light on surfaces. They do not generally do a great job of killing spores suspended in the air stream. UV lights are great at killing yucky stuff on surfaces […]
Read more

8 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