Topband: Furnace RFI

[ed_richardson at shaw.ca]

Mark

 

We installed a top of the line Lennox heating and AC unit 3 years ago. The
PWM motors were a big concern of mine based on reports I had read about
online. Lennox makes an RFI kit that they will provide if requested. There
was no charge for the kit consisting of 2 toroids and an AC line filter.

 

I had the contractor order the kit when they ordered the furnace. On
installation day I asked the technician for the literature that came with
the RFI kit before they left.  I went and scanned the HF bands shortly after
they left and was disappointed to find a number of spurious signals at
discrete frequencies across the 20m - 10m bands.  These signals ranged from
S3-S7. I Couldn't find anything at 6m or above and my noise floor is so high
on 160-80 that I couldn't hear or see anything new.

 

After reviewing the literature that came with the RFI kit, I opened up the
furnace and discovered the technician hadn't installed the items correctly.
I could have fixed them but decided to call the contractor back to avoid any
warranty claim issues.  Once re-installed, the noise level dropped down to
an S1-2 worst case on 17 and 15m.

 

Not being satisfied, I went ahead and added some external 2.4" cores on all
external wires coming and going from the furnace. The end result is a very
usable spectrum with just a small handful of s0 level spurs across 17m.

 

I have been very happy with the furnace and AC units themselves. I just wish
these companies would spend the extra $10 and take care of RFI/EMI right at
the source during design and production.

 

Good luck with your search!

 

Ed VE4EAR