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Old 26-05-2016, 08:49   #1
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Danfoss compressor operating temp

Have two Indel Danfoss compresors running separate similiar size reefers. If I check the temperatures in the middle of the tops of the compressors I get temps of 108 F and 134 F. Which is the temp that is the correct one. Both cool the reefers, but I think one is probably more efficient.

Anyone know what the spec might be.

Used to know the correct temps at the inlet and outlet of the plates, but those have long since vanished into the abyss.
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Old 26-05-2016, 09:41   #2
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Re: Danfoss compressor operating temp

I am not an expert but recent successin with a Danfoss 35 fridge repair gives me the burning desire to offer an opinion. Perhaps I'll learn something. The difference may be due to slight variation in amount of Freon. The correct amount, according to sages, and it may vary with season, is simply just enough to make the whole evaporator plate frost over, but little or none of the return Freon line. I am guessing the one with slightly larger Freon charge will have a cooler compressor but will not be more efficient.
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Old 26-05-2016, 09:45   #3
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Re: Danfoss compressor operating temp

I have recently replaced a blocked evaporator on a keel cooled frigoboat BD50 system. I also installed a receiver dryer. Why they arent fitted as standard is one of lifes great mysteries.

We have an equivalent system in our freezer.

Richard Kollman indicates the compressors run hot and apparently that is not an issue. Unfortunately he does not define hot in terms of temp.

These systems are very sensitive to charge. In fact you often need to adjust the charge when moving from hot to cold regions.

I would guess that refrigerant charge might explain your temp diff without more info.

Placing a hp gauge on might validate this assumption.

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Old 01-06-2016, 05:57   #4
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Re: Danfoss compressor operating temp

Danfoss compressor temperatures.

Most small hermetically sealed compressors are protected from heat damage by a thermo switch that stops compressor when it is exposed to excessive heat. Larger compressors use high refrigerant pressure switches to prevent heat and high pressure damage to a system. Danfoss 12/24 volt compressors rely on abnormal high amperage generated by high liquid pressure to prevent compressor and its oil from damaging heat.

All refrigeration compressor companies application engineers provide operating limits and approved refrigerants for each compressor. By reviewing Danfoss application performance specification sheets it is easy to see operating limit conditions based on amperage, ambient standard day temperatures and a condenser hot gas temperature based on 55 C ( 131F ). Hot gas vapor/liquid leaving condenser temperatures on BD compressor systems for best performance will range from 105 Psi to 115 Psi with a condenser air cooling medium temperature of 70 to 90 degrees F. These application sheets set out process boundaries for watts of current, amperage, and Btu output. If any one of the manufacturerís performance limits is exceeded overall performance may be compromised as well as systemís extended reliability. Danfoss makes no mention of condenser cooling mediums other than convection air flow cooling condenser, compressor and electronic control module.

Operating temperature of a Danfoss BD compressor is controlled mainly by sub cooled refrigerant vapor returning from evaporator. Additional compressor cooling is provided by convection air flow directed across compressorís thick steel mass in warm climates. It is not unusual for compressorís thick dome to reach 130 degrees F for short duration of 1 to 3 hours even when properly serviced with correct amount of refrigerant. There does not seem to be any quantifying data on returning gas vapor temperature needed to cool theses small BD compressors but 40 to 60 degrees F return gas vapor is desirable. In tropical climate temperatures I find 60 to 80 degrees F returning gas as a norm. Demands on compressor to remove heat from large boxes or for cooling low temperature freezers will reduce sub cooling of return gas vapor temperatures.

Most pleasure boat refrigerators powered by Danfoss BD compressors are air cooled and with the proper application design and installed correctly can provide 20 to 30 years of service life. Contamination of refrigerants and extended operation of compressor at high temperatures are the only reasons I have found for Danfoss BD compressor failures.
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