PF Choke for ECM Motors


As you are probably aware, the most vulnerable part of an ECM motor is the control module.  With energy requirements becoming tighter and tighter, ECM motors are becoming the standard rather than the occasional motor of choice. Early on, it was found that the most common failure of an ECM motor was the control module.  Back in October of 2006, we started to add what is called a “choke coil” to all furnaces with 3/4 and 1 HP ECM motors. The addition of the choke coil has greatly reduced repeat motor module failures. 

So, what is a PF choke coil?

PF (Power Factor) is a fraction of power actually used by electrical equipment compared to the total apparent power supplied, usually expressed as a percentage. A power factor indicates how far the electrical equipment causes the electric current delivered at the site to be out of phase with the voltage. The ‘PF Choke’ is used to reduce this ’Out of Phase’ or , in other words ‘Choke’ the Power Factor coming into ECM Module preventing the burn out of its electronics.  

As I mentioned earlier, we have had these on all of our furnaces with the larger HP ECM motors since 10/06 but there are probably a lot of furnaces out there before this was initiated that do not have the PF Choke Coil.

If you have a site that has had ECM module failures with either the 3/4 or 1 HP ECM motors, then you might want to consider installing a PF Choke Coil  on that unit to help prevent future failures.  The replacement Power Factor, PF, Chokes for 1600 CFM Units with 0.75 HP ECM Motors: 11 Amps;is our part number S1-024 35605 000. For 2000 CFM Units With 1.00 HP ECM Motors: 12 Amps;the part number is S1-024 35604 000 

It is not normally necessary for 120 VAC 1200 CFM units with 0.50 HP ECM Motors or any 240 VAC applications to need a choke. However, The following kit can be added to help resolve all problem applications.  That kit number is S1-324 35604 000.

Keep in mind that this is not a “cure-all” for power surges or other power problems, but this will help alleviate repeated module failures if there is not a Choke Kit already installed on the furnace.

One last thing, these kits will work with ANY manufacturer’s ECM motor that may be experiencing failures.

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About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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One Response to PF Choke for ECM Motors

  1. Oliver Lewis says:

    Thanks for taking the time to post this, I recently came across an ECM motor that wouldn’t start and when I moved the wire on the choke it came on, I first thought the choke was a transformer until I looked at the wiring diagram and it said it was a power choke. I learned from you what a choke actually does. The only problem is that it is pretty expensive to replace so I’ll have to look around.

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