Level V Member
Join Date: Jan 2017
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Pick up a book and read, your ideas about a/c are hilariously funny, and no insult intended. Like this...........
'I know for residential ac you use the temp scale of the high side vs actual temp of the liquid side to the temp rating of the unit.'
The high side and the liquid side are the SAME THING, and WTF does your last 6 words there mean? NOTHING, goofy. Residential gets charged close to the very same way a car does BTDT.
The high side can run from 150 psi all the way to 300+ and you still be getting 40-50 psi on the lowside, why you CANNOT set the levels correctly like that. Your low will still be around the same, it CANNOT tell you anything doing that other than when things are major messed up. Using lowside only to set cooling on a good working system is a joke and how you got to where you are now........................LOST.
The HIGH side is what you temperature match to, NOT the lowside as it is pretty much worthless there, the pressure will be close to the same since it is the low and pressure to temp varies less there.
If you have two expansion valves then BOTH ends should be getting the same cooling. A stuck open valve lowers cooling as the pressure differential across it is lower, cooling occurs because of pressure drop not flow. One stuck open then messes the other up since the overall pressure drops even on the other one, but it depends on how much compressor capacity you have.
I say again......................the ONLY real rock-solid-works-every-time way is to use both gauges to measure both sides at same time, the relation of what one does as compared to the other tells you much.
If you have not bled every single time you add refrigerant then by now you probably have air and by extension water in the system and half your trouble can come from that. What eventually happens to all a/c DIYers.