Danfoss Designed Control Modules for BD35 and BD50 compressors.

[Richard Kollmann]

I attribute most all of the Danfoss electronic control modules failures are due to poor system application or dirty electrical power supplied to modules. When improper installation application of this compressor causes compressor temperatures and output pressures to exceed normal operating conditions this will over stress the Danfoss control module circuits. The Danfoss BD compressor’s design does not use the conventional safety devices such as high temperature switches or refrigerant pressure cutoff switches, instead it relies on module monitoring of amperage and voltage to prevent compressor from running and exceeding its design limits established by Danfoss.

Having spent the last thirty years in south Florida known as the boating and lightening strike capital of the world where there are three hundred miles of waterway with boats at the docks offer a great test ground for mobile refrigeration. The live aboard boats up to 46 ft most all have 12 volt refrigeration powered by Danfoss BD compressors. Small boats with refrigeration units sometimes use Swing vibrating AC/DC compressors. Because of the moist tropical weather year round many of the thousand of docked boats here keep their Direct Current 12/24 volt refrigerators powered all the time from shore power. Both of my boats had icebox conversion units powered by Danfoss BD compressors that ran most of my 25 years there. It did not take much more than two years to find out that these DC compressors averaging 5 amps when running will cause even a smart battery charger, that keeps battery at full charge, will not remain at float charge rate when compressor starts to run. The end result of using a battery charger or even a smart charger I found battery life was cut in half. To avoid over stressing batteries some boaters use a timer to power charger on and off. I added a sacrificial 12 volt battery and a separate 10 amp charger for both my 12 volt refrigerators when connected to shore power.

The earlier Danfoss BD 2, BD2.5 and BD3 were all fixed speed two field coil brushless motor compressors where the design demanded direct current from the battery. Some one claimed that one field coil was charged the other sent current back to the battery as a reason for Danfoss battery on line requirement so these units must be powered direct from battery.

The newer variable speed Danfoss BD compressors with a different three field coil electronic pulse excitation motor and control module could be operated without the battery on line if you then purchased a separate power supply converter 115 to 24 volts the compressor could be operated on either AC or DC. The BD 35 and BD50 were both capable of running on 12 or 24 volts. WAECO mobile Solutions developed a external AC to DC converter for the BD35 and a larger one for the BD50. Adler Barbour engineer reported problems with this unit. Several companies now use different AC to DC power supply units on Danfoss BD compressors in small cabinet refrigerators.

Any boater that spend much time with boat connected to shore power or has an AC power unit on board should purchase the Danfoss 101N0500 module that comes with a built in AC/DC converter that handles 85 Volts AC to 265 Volts AC in 50 or 60 cycles.
Think of the dollars saved when this $30 additional module cost can extend the life of your house battery bank. This 101N0500 module was introduced in 2005 as an improvement module for BD35 and BD50 compressors only.

I recognize that not everyone will share my preference for Danfross products but after testing 70 to 100 of the Danfoss control modules per year I feel I have enough information to form my opinions on why some modules fail while others last for ever.

If you disagree with my technical positions on refrigeration do it professionally. Please avoid hateful insult mail or change your name and IP address, then I can ignore you.