Quote:
Originally Posted by aberglas
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.
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"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.