For over thirty years and dozen different models of the Danfoss electronic control modules failures are common. Danfoss was not responsible for the installation
application in boats but they did give us clues about future failures by indicating the following bad practices:
1. To voiding refrigerator
power wiring through multiple connections to battery
a. Thirty years ago it was pointed out that the pulsation of actual current in this circuit needs the battery’s mass compasatance to dampen out feed back in two pole brushless motor
b. Today the newer variable speed BD compressor modules are still exposed to dirty power from trenchant voltages generated by other parts
of boats wiring when connected through secondary circuit breaker buss or multiple ground connections.
2. Installing a voltage only trouble LED source terminals on earlier modules and an expanded LED code system on newer models only a few system manufacturers install the one dollar LED on their new systems.
a. The flashing LED single
code on older 4 pin modules also produced a electronic beep sound only indicated starting voltage was out of an expectable range.
b. New model three pin compressors trouble LED codes now identify five common troubles once understood can detect other problems narrowing down the hours and cost of troubleshooting.
3. Danfoss assumed those responsible for printed instructions and actual installation
information of refrigeration
would follow the marine
ABYC recommended standards although they may not cover all the unique characteristics of each boats wiring.
a. Choosing the correct gage s ize and length for one of these Danfoss BD powered refrigeration
systems is important. Stranded rather than solid tin plated wire will produce a better quality of current over time.
b. If you compare the different system manufacturers wire sizes and even Danfoss recommendations for a Danfoss BD powered refrigerator’ correct wiring sizing are different for the same size compressor.
c. Too small or too short of refrigerator
power wiring allows voltage dropping volts that if duration time is short can not be detected with a volt meter but the control module’s sensitive boot up test circuit will and prevent compressor from running.
d. The biggest error in defining refrigeration wire sizes is in total length in distance of power wiring. The total length of this wire is the complete trip from battery positive to module and the round trip back to battery ground terminal.
e. The basic Danfoss designed system speciation sheets
defines system fuse protection old four pin connectors were fused at 10 amps with fuse mounted on module which meant power wire size was protect from overheating
by a source fuse or breaker near battery.
Newer variable speed compressors do not have fuse protection at module so they must rely on a circuit breaker or preferred fuse near battery. Many compressor start up problems begin at the fuse holders or because of poor quality circuit breakers, fuse holders, switches, and wire terminals. If you want reliable Danfoss powered refrigeration stay away from low cost hardware
. I found one boat manufacturer using panel switches costing only 70 cents each. Inexpensive circuit breaker contacts are not designed to be operated frequently as on and off switches. Even quality OFF-ON circuit breaker switch contact points used on aircraft are service
hours limited. Because voltage and amperages are the major cause of compressor not starting it is a good idea to carry a circuit breaker with alligator clip jumper wires to bypass possible trouble area as a test