Radio interference caused by refrigerators containing the Danfoss BD
brush-less compressors is not only bothersome on boats with these
refrigerators but they also affect other boats radios in the same
anchorage. Refrigeration system manufacturers over the last fifteen
years have asked Danfoss for a solution. The feedback relayed back to
the consumer is, next generation of electrical module will include
noise suppression built in. After several model changes the noise
problem is still being reported. From the small number of complaints I
see it makes me believe that all boats are not experiencing the noise,
and one of the many recommended fixes might have worked.
Here are a few of the suggestion offered by electronics people in the
past:
1. Suggestion, determine if it is transmitted by air why not try
grounding the transmitter, the unit and the copper tubing. The
refrigeration system is not grounded. Run a separate ground wire
from the compressor to the base plate and then back to the battery.
2. Shield the power wires
3. Twist the power wires
4. Shorten the wires
5. Use a filter
6. Installed ferrites on positive and negative power leads at the
refrigerator and at the radio(s)
7. Installed a stereo noise filter on the power leads to the
refrigerator
8. Some time back it was recommended to try a filter from Marine
Technology in Signal Hill CA.
9. Refrigerator should not be connected to a buss both wires must go
direct to the battery
10. Wrap power wires for refrigerator through a toroid core
11. Try a ground shield screen over the controller module
12. To use a separate battery for the radios.

Danfoss is going to offer two new electronic modules for the newer BD
35 and BD 50 compressors. One of the new units is similar to
Frigoboats SSC that provides automatic compressor speed control. Code
numbers of these units are 101N0300 and 101N0301. The second new
module is reported to have shielding to eliminate radio interference.

I would like to survey owners of boats that have, or have had and
corrected, radio noise caused by onboard refrigeration. For a good
survey its important to list which radio is affected by refrigerator
noise-; VHF, AM/FM, SSB or Ham radio.
If you previously had a problem with noise and no longer have it, how
was it corrected?
Some manufacturers refrigerators may not cause this problem, so it is
important to know what manufacturers system you have when responding
to the survey.

If you post your answer or Email a response I will see that you get
the survey results. Since the manufacturing industry has not
identified the problem and solution for the after sales customer,
maybe we can.

Richard Kollmann

http://www.kollmann-marine.com