"Jake" wrote in message
news:xB85h.54$xD.43@trndny08...
Interesting discussion, folks....

As a controls engineer and High-Voltage electrician.... as well as delving
into HVAC control of late... here's my observations...

These manufacturers will always take the cheapest route possible and damn
the consequences. This is particularly true in power and control systems.

A whole lot of manufacturers are moving toward PWM drives on their blowers
in particular. Many solutions are an 'on-board' frequency chopper that is
integral with the blower's motor.

These choppers are cheaply built and cheaply engineered. I suppose they
thought RFI and EMI would be insignificant due to the control being
mounted on the motor... but they're noisy as hell.

Suggestions: Replace the power cables with a shielded, VFD rated cable.
Belden makes a wide variety... I think they're called the VFD classic
line. Pay close attention the unit and cable grounding. Check to be
certain your house ground and neutral connections are only tied together
at the service entrance panel of your home.

My 2 cents...

Jake

As Jake said.... with the addition of....
Make sure that you have proper earth grounds for your power, and the HAM
rigs/shack. That will go a long way towards eliminating RFI. Make sure that
all the bonding screws in the furnace are clean and tight, make sure that
the furnace has a proper ground also.
When I put the shack together, I drove a seperate 8ft copper ground rod, and
silver brazed #6 solid copper to it, then silver brazed the wire to the
copper ground buss on the back of the bench. All equipment grounded.....no
problem.

de n6ojn