Correct amount of refrigerant in a capillary tube boat refrigerator system

[Richard Kollmann]

Originally Posted by David B

From our perspective (freezer repair - new compressor and nitrogen flush to get the oil out of the capillary), it was a matter of filling while keeping an eye on the gauges, then monitoring freezer temp.
This went on for 36 hours before it seemed right (and we saw -18C in the freezer).
Bit of a 'test and see' situation when performance and current draw are important.

What brand of refrigerator do you have as oil blockage of cap tube is unusual?

[David B]

Originally Posted by Richard Kollmann

What brand of refrigerator do you have as oil blockage of cap tube is unusual?

Vitrifrigo (if my memory recalls the spelling correctly - we are on travel ban in Australia, the boat is in virus free Montenegro …).
They are the standard installation for Beneteau - at least the ones built in France anyway.

It had been running poorly for at least a couple of weeks. I think that's what did it.

[wannacat]

More than likely it was moisture in the system or a small piece of something that blocked the capillary tube. Oil will not block the cap tube. Oil is entrained with the refrigerant in small amounts and moves threw all refrigerant systems.

[Richard Kollmann]

Because of the very small cap tube orifice sizes on small 12 volt systems oil blockage does occur. We normally find oil exposed to extender periods of high compressor temperatures in warm climates thickens blocking flow. One system manufacturer has recommended changing compressor oil but this is almost impossible unless condensing unit can be turned upside down and line disconnected. Air cooled units like this one rarely experience oil viscosity thickening as compressor receives external supplemental cooling from condenser fan.

Solid material cap tube blockages on orifices of 29 thousands of an inch are not likely to be removed.

Small amounts of moisture in cap tube are easy to confirm as they will freeze and thaw repeatedly resulting in a cold evaporator with condensation on it and no frost.

[David B]

Originally Posted by Richard Kollmann

Because of the very small cap tube orifice sizes on small 12 volt systems oil blockage does occur. We normally find oil exposed to extender periods of high compressor temperatures in warm climates thickens blocking flow. One system manufacturer has recommended changing compressor oil but this is almost impossible unless condensing unit can be turned upside down and line disconnected. Air cooled units like this one rarely experience oil viscosity thickening as compressor receives external supplemental cooling from condenser fan.

Solid material cap tube blockages on orifices of 29 thousands of an inch are not likely to be removed.

Small amounts of moisture in cap tube are easy to confirm as they will freeze and thaw repeatedly resulting in a cold evaporator with condensation on it and no frost.

Agree Richard.

Yes, the oil to some extent moves through the lines, but as you describe, is I think the situation we had. It was generally above 30C, and the compressor was running 90% of the time (we were on anchor for ten days - away from any service). With the compressor being 8 years old, I suspect the reeds were not as good as they could be, and the situation just escalated. Remember too, this is a freezer, not a fridge.

When (after replacing the compressor, and the results were still not good) the lines were flushed, quite an amount of oil was purged through - oil that the compressor running for 48 hours could not deal with.

As to cooling of the compressor, when I get back to the boat, I am looking at improving airflow. Currently, just a small fan blowing through the condenser (onto the legs of the poor person in the galley - on a hot day it is quite uncomfortable), and in so doing, drawing air over the compressor first.

Need to look at new fan (or pair of fans) to increase airflow, and not blow the hot air straight into the galley. Ducting and an inline fan is already purchased ready to deal with that part, and get it out to the ventilated lazarette area.

Inline keel cooling (with the condenser fan switchable for when on the hard) is on the wish list.

[RaymondR]

Hi David B,

The folks at Ozefridge use what I think is a clever solution to the air/water cooled conundrum.

They have their condensing heat exchangers as conventional fin and tube devices with two sets of tubes adjacent to each other. One is the normal refrigerant vapor/liquid cooling tube and the second for cooling water. You have the choice of which you use.

[David B]

Originally Posted by RaymondR

Hi David B,

The folks at Ozefridge use what I think is a clever solution to the air/water cooled conundrum.

They have their condensing heat exchangers as conventional fin and tube devices with two sets of tubes adjacent to each other. One is the normal refrigerant vapor/liquid cooling tube and the second for cooling water. You have the choice of which you use.

OK, that's one way too, and you could tap into the air-conditioning cooling supply for the water feed.
What a friend has done is installed modules on the hull that take the refrigerant in series from the condenser. If the boat is in the water then they work as intended. If the boat is out of the water, the condenser (now with fan running) works as originally intended.

Only concern for me is how hot they would get bolted to the hull out of the water - may well affect the sealant of even the FRP.