Topband: Furnace RFI

[Tim Shoppa]

Some good news/bad news intermingled below :-)

At my house we had two modern air handlers and heat pumps put in about 5
years ago.

They were high-efficiency rated and had Genteq ECM motors. Note that I call
them ECM motors, not DC motors - they have power electronics that take
regular 60Hz AC and electronically commute with semiconductors to make a
variable frequency 3-phase drive. Almost certainly they do go through DC
along the way.

The good news, is that I never noticed any RFI from the ECM motors.
Possibly because of good wiring practices in the units (they always route
AC wiring around in pairs so there is no large loop. I think some
after-market ECM blower installations made poorer choices about AC wire
routing.)

The bad news, is that the ECM motors in my units died early. They have very
poor reliability. In both cases they were under warranty. If you have to
replace an ECM blower motor outside warranty you are looking at $300 for a
used/rebuilt unit and closer to $1000 for a brand new factory module.

The good news is that these ECM blower motors die early so often that they
will almost die in warranty.

Tim N3QE

On Thu, Oct 3, 2019 at 5:42 PM lmlangenfeld <lmlangenfeld at tds.net> wrote:

> We are in the market for a new high-efficiency furnace, and I note that
> many (if not most) of the current models use variable-speed DC blower
> motors.  I am concerned about the potential for RFI from the speed
> controllers, and wonder if any list members have any recommendations or
> recent experience (good or bad) with such units.Tnx es 73,Mark --
> WA9ETWSent from my U.S. Cellular® Smartphone
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