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Old 15-01-2025, 00:57   #1
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OK to lag dripping evaperator pipe on Fridge?

I have a "Cold Machine" that (now) works OK. However it leaks condensation from the compressor compartment, that is outside the main fridge. The gas coming out of the freezer is cold, so it builds up ice on the outside, and then that melts when the compressor switches off.


The gas pipe has the very thin liquid pipe attached to it. Nice design as it cools the liquid before entering the freezer.


I am thinking to lag the gas pipe (Wrap insulation around it) to avoid the condensation. This will put cold gas into the (hot) compressor.



Any reason not to do this? Might make it slightly more efficient.





(A previous fixed problem was wires too thin. The voltage would drop, cycling the compressor after a while. Took a little while to understand as compressor did go on.)
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Old 20-01-2025, 13:54   #2
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Re: OK to lag dripping evaperator pipe on Fridge?

Quote:
Originally Posted by aberglas View Post
The gas coming out of the freezer is cold, so it builds up ice on the outside, and then that melts when the compressor switches off.
The gas pipe has the very thin liquid pipe attached to it. Nice design as it cools the liquid before entering the freezer.
I am thinking to lag the gas pipe (Wrap insulation around it) to avoid the condensation. This will put cold gas into the (hot) compressor.
Any reason not to do this? Might make it slightly more efficient.
"Generally," speaking, (lots of variables,) the return line from the evaporator should only frost-up for a few inches from where it exits the evaporator.
If it frosts-up much more than that it may be an indication of a slight overcharge.
As those units use a cap tube and have no receiver, they're quite sensitive to charge levels, they have no way to regulate flow/slow down refrigerant flow as the evaporator reduces its temperature.
The "very thin liquid pipe" is the cap tube, and having it soldered to, or as some units do, run inside the suction line does add efficiency by means of two main reasons.
1, It "sub cools" the liquid to a lower temp than when it left the condenser.
2, The heat that the cap tube gives up into the return gas helps to keep the frosting down on the return line by raising its temp slightly.
A by-product is that by getting the return line up above frosting temp the pressure goes up a little which helps the return of the oil, a certain amount of which is always circulating along with the refrigerant.
But it's all a delicate balance on those little systems.
Putting insulation on the suction/return line is a common practice as much of the cooling of the compressor is achieved by cold return gas.
However, we don't want to see any frost-up at or too near where that line enters the compressor when it's running, that can "dump" liquid refrigerant into the compressor, and that's a big no-no.
Edit: I would add that the earlier 12VDC units were of the "constant speed" variety, but the newer units vary the refrigerant flow by using multiple speeds by means of the control module in conjunction with the thermostat, this reduces the tendency to "frost back" when the demand for refrigerant is lower.
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Old 20-01-2025, 18:35   #3
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Re: OK to lag dripping evaperator pipe on Fridge?

Thank you. I do think that the frosting is due to an overcharge. It was re gassed buy a gas monkey in Fiji.

I will slowly and carefully let out a little bit of the gas until the frosting becomes more manageable. Upon reflection I think lagging it might be a very bad idea as it may enable the liquid to get into the compressor.

I am just going to let out a small amount of gas, run the fridge for a bit look at the frosting then let out a little bit more gas. I'm thinking just a couple of seconds at a time.

As a footnote, i dropped the cap of the filling point into the bowls of the boat never to be seen again and certainly not with my endoscope.
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