FYI: New Danfoss BD35/50 Control Module

[a64pilot]

Secop In their literature says their compressor is not cooled by return refrigerant but by oil.
However I can’t find a max temp allowed, I would think that would be a spec.

[OzePete]

Originally Posted by a64pilot

Secop In their literature says their compressor is not cooled by return refrigerant but by oil.
However I can’t find a max temp allowed, I would think that would be a spec.

That is not correct. Oil in the compressor plays a very minor role in cooling the compressor.

Like Missourisailor said earlier, the compressor is mostly cooled by refrigerant gas passing through. The cool but heat laden return gas (suction) enters the compressor cavity (like air into a 2 stroke petrol motor) and collects heat from the motor windings etc. This now hotter gas is pumped out of the compressor, carrying this heat along with heat collected from the evaporator, into the condenser where it is absorbed into the air or water.
As much as approx 20% of the heat the condenser disposes of, is heat from the compressor itself.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

[Richard Kollmann]

[QUOTE=missourisailor;2647388]

Originally Posted by a64pilot

... the condenser fan may help cool the compressor even if it is blowing heated air from the condenser, or maybe a compressor isn’t cooled by air very well, it’s not like it has cooling fins.
QUOTE]

The returning refrigerant plays a larger part in compressor cooling than air circulation. Hence, one of the reasons the return lines (low pressure lines) are insulated on almost every other system made...except marine refrigeration!

You are correct the general excepted rule for hermetically sealed electrical refrigeration compressors is, compressor cooling relies on sub cooled returning refrigerant and its flow. The job shop that designs and builds pleasure boat refrigeration is responsible for degree of compressor cooling. The recognized standard for returned cooling gas temperature is 60 degrees F although normal temperatures are slightly warmer than this.

These small compressors used in mobile marine refrigeration are each exposed to a number of temperature and installation applications where poor compressor cooling over time can destroy a complete system. The Italian refrigeration companies that use the Danfoss DB compressor use a small fan with heat sink attached to compressor for additional cooling. Adler Barbour, Isothern Nova Cold, Seafrost and others rely on condenser fan air to remove the mass metal heat of compressor. AC compressors ¼ HP and larger are available with an oil cooler coil inside compressor to assist in compressor heat removal.

It is the water cooled Danfoss BD compressor systems that are most likely to fail do to extended operation with compressor temperatures over 130 degree F. These are not mechanical failures they result from piston head gasket heat damage or oil heat contamination.

For those that say oil cools compressor, What do they say cools the oil? The maybe one drop of oil per minute returning with refrigerant gas vapor is not going to dispose of much heat.

[john61ct]

It apparently was Secop making that false claim, not a member here.

[Flyingriki]

My old C-200 Cold Machine has the two control panels (?). The secondary one, shown at left, is giving me fits. Have to wiggle it and push on the components to get it to work and now has stopped altogether.
Have been advised to remove it and wire direct to the base panel at the right below but that appears to eliminate the power fuse and some resistors in the thermostat lines. Any advice on this process?
Does this new controller described above replace them both or the first one or the secondary one or.....??
Thanks!!

[senormechanico]

I would bet you have bad solder connections on the circuit board.
It's not rocket science to resolder them, but get someone who is good at it.
NO accidental solder bridges where they don't belong or you could kill it dead.

[Richard Kollmann]

Originally Posted by Flyingriki

My old C-200 Cold Machine has the two control panels (?). The secondary one, shown at left, is giving me fits. Have to wiggle it and push on the components to get it to work and now has stopped altogether.
Have been advised to remove it and wire direct to the base panel at the right below but that appears to eliminate the power fuse and some resistors in the thermostat lines. Any advice on this process?
Does this new controller described above replace them both or the first one or the secondary one or.....??
Thanks!!

Klyingriki, From time to time we find design flaws in Pleasure boat refrigeration and attempt to notify the manufacture. Adler Barbour added an unnecessary circuit board to the CU model cold machines. There are three failures occurring with this printed circuit board; crack on copper ground, 15 amp fuse mounting and telephone thermostat jack. See TECH TIP #1 on my forum for information on by passing this circuit board and a picture of a failed board. If a replacement board is ordered it must be a improved structurally.


I represent no favored refrigeration company or job shop that assemblies Ice box conversion refrigeration. No one should infer I am referring to their product unless I mention the product by name.

[a64pilot]

Originally Posted by OzePete

That is not correct. Oil in the compressor plays a very minor role in cooling the compressor.

Like Missourisailor said earlier, the compressor is mostly cooled by refrigerant gas passing through. The cool but heat laden return gas (suction) enters the compressor cavity (like air into a 2 stroke petrol motor) and collects heat from the motor windings etc. This now hotter gas is pumped out of the compressor, carrying this heat along with heat collected from the evaporator, into the condenser where it is absorbed into the air or water.
As much as approx 20% of the heat the condenser disposes of, is heat from the compressor itself.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems

I understand how compressors are normally cooled, yet this is from Danfoss / Secop. How do you explain this?
Click on picture to expand it, read the explanation of why the outside of the compressor is hot.

[john61ct]

Seems like a different oil system than the few drops in the coolant Richard was talking about?

[Richard Kollmann]

Originally Posted by a64pilot

I understand how compressors are normally cooled, yet this is from Danfoss / Secop. How do you explain this?Attachment 171415
Click on picture to expand it, read the explanation of why the outside of the compressor is hot.

The facts about a refrigeration system that differ from conventional systems are generally found on manufactures web site or in the installation and maintenance manual. There are links to this manual. Has anyone seen this manual?

[Richard Kollmann]

For someone who does not like Danfoss/Secop compressors because they are made in Chaina he spend time keeping the compressor he uses a secret.

If you are really interested in what true experts say about this type compressor cooling
https://www.achrnews.com/articles/10...ressor-cooling

[john61ct]

I did not detect any dislike of Danfoss in that line of questioning, and the "true experts" dig is childish at best.

I would personally like to know if their advertised internally circulating cooling-oil is a thing or not.

And if that issue makes a difference compared to the other three to four (?) major compressor brands out there.

Yes I agree it "would be nice" for every maker to be fully transparent about their design and components' sourcing, but I think it's their right to choose what to reveal or not as they see fit.

I was under the impression the only non-Chinese ones left were Italian owned by Webasto?

[a64pilot]

I think the ones Cool Blue usually use are Spanish?
On edit, this is Cubigel I think in Barcelona
https://www.huayicompressor.es
There are I think several Chinese clones, the little icemakers and dorm fridges for example.

[a64pilot]

Seems odd Secop is either distributing false information, which is illogical, if they were hiding something, just keep quiet.
Their statement that they are a DC driven compressor, BD means battery driven by the way, and now they say the compressor is not cooled by return refrigerant, but by oil.
Meaning as I see it that the oil carries the heat to the case, where it’s cooled by air.

So either Secop is deliberately distributing false information, or they are a different animal so to speak, a different way to skin the cat.

[a64pilot]

Originally Posted by john61ct

I would personally like to know if their advertised internally circulating cooling-oil is a thing or not.
?

According to Richard’s link, it is. At least his link speaks to air cooled and the Secop verbiage said the oil carried the heat to the case, meaning in my opinion air cooled, oil is the medium by which the heat is transmitted to the case.