[RFI] Motors/controllers and something to think about

Roger (K8RI) k8ri at rogerhalstead.com
Wed Aug 15 22:30:49 PDT 2012

The issue has dealt with specific makes and models with and without RFI, 
but as PWM is by its nature an RFI generator we need to stop and think 
about how companies (any company) acquires the motors and speed controllers.

It's already been mentioned that one company was using PWM speed control 
on a motor that ran at a constant speed.

Do each of these companies use the same controller on the same model?
Do they build the controller, or do they contract out the motor and 
controller, or do they, like many stores contract out parts on a 
periodic basis so that this year company A builds the controller for 
company B's motors while next year company C builds the controllers. IE 
can you, or can you not depend on the same motor and controller 
combination for a specific model furnace/air conditioner?

Perhaps when purchasing a system we should contract it out and stipulate 
that the system generate no RFI.  I've had companies that would do it 
for a complete GEO Thermal installation and some that refused. IE you 
install it and if it works as the contract stipulates I'll pay you, 
otherwise fix it or take it out.  Turns out our old system is so 
efficient that it'd take nearly 50 years (47 point something) to reach 
the payback at current rates. With the average system life of 25 years 
or less ... we kept the old system.  OTOH with the extreme spring and 
summer temps we've had this year it would have been quite a bit less, 
but still not enough.

You might have to pay a bit more, but as long as the final price is 
within reason it would be worth it and there would be no haggling about 
whether their system created RFI or not.


Roger (K8RI)

More information about the RFI mailing list