Author Topic: Short Danfoss Engineered Module Service Life  (Read 555 times)


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Short Danfoss Engineered Module Service Life
« on: December 28, 2018, 07:11:55 pm »

Short Module Serviceable Life can be caused by how refrigerator was installed.

Danfoss has always experienced problems with electronic control modules on BD compressors. After ten to fifteen different Danfoss module models still randomly failures occur with no warning. If we exclude lightening strikes and corrosion due to water module failures seem to be caused by voltage spikes or heat.

Voltage spikes at module are not always visible with a meter and can be present on any boat. Unstable voltage is why the module must receive power direct from battery buss using correct size wiring, fuses, circuit breaker and switches that allow no voltage drop. When compressor is correctly wired to battery buss battery will absorb voltage surges like a very large electrical capacitor reducing module electronics failures. When refrigerator is powered from a branch circuit breaker panel any item in that panel can cause a damaging voltage spike when that item is powered up or powered down. Any relay when power is turned off sends a voltage spike back towards the source. Windless, power wench, generator start relays and even cabin light relays can damage refrigerator control modules if refrigerator is wired through a circuit breaker panel instead of main buss.

Module overheating maybe the primary reason for so many electronic control module failures. Through the years Danfoss has designed static air heat sinks on modules to conduct and radiate heat away from transistors and other components inside module. Module heat increases as compressor load (amperage) increases. Danfosss installation application data sheets have always assumed system designers and installers would insure compressor design power amperage limits were not exceeded. What you will find in the marine industry is the elimination of module and compressor cooling air along with higher than design compressor heat loads. Only Danfosss AEO modules have built in module cooling fans. Danfosss variable speed specifications for BD50 require an additional fan for cooling control module if compressor is to be operated at maximum capacity (3500 rpm). All of the following conditions can cause module overheat failures; High condenser cooling temperatures, Repeated attempts to start do to an overloaded compressor, First box temperature pull down in a hot climate, System ambient temperatures above 105 degrees F, and too large or poorly designed holding plate evaporator coils. Failure to maintain good cool flow of condenser air, a normal maintenance item, should not be overlooked as cause of module failure.