Every small compressor I've seen in the back of a fridge or A/C or dehumidifier, etc has 3 copper pipes coming out. I can make sense out of 2 of them: hot out to condenser coils, cold in from evaporator coils (or 1 to suck, 1 to blow). But what is the third one for? It's usually crimped closed.
Google's happy to tell me how refrigeration works, but not what the third pipe is for.
Red
Think about how the factory introduced the refrigerant charge based on what you are looking at.
It's called a compressor "process tube" and it's used in the manufacturing process to charge the sealed system with refrigerant, since most small hermetic systems don't have any service valves for access. It can also be opened up in the field for maintenance and then re-pinched. Or, it can have fittings soldered or brazed to it to make for easier for future access.
The third pipe is called a "process stub", as I've heard it. When they make the fridge, etc. They hook a vacuum pump onto the process stub, and evacuate the air. Then, they fill with a charge weight of refrigerant, and oil. The process stub is pinched off, and brazed shut. If nothing is leaking, the refrigerator, or window / wall AC is good to go for many years. There is a special tool called a "pinch off tool" which is used for this.
Damn that makes sense. I am about to replace my compressor and was wondering how I was going to get a vacuum pump on it. I will just use that as my service port then to vacuum it and then charge. If I am not supposed to do it yell so I know.
Is the pinched pipe the same as the suction pipe
some walkin freezers have a hot gas bypass valve that is usually called a head pressure control. hot gas is bypassed into the compressor to warm it when it is very cold outside. this is the reason for the third port in some cases.
I guess yes
'Seems as though folks here MIGHT see my little question. So I'll post. I was looking for an answer to a supremely simple question. I bought a new Whirlpool frig here in Mexico--and I live in a small town. This is April, 2022. So all I got was someone dropping off the frig. In the back, on the side of the compressor marked "SUCTION," there's a short, 5" piece of copper tubing sticking out, with some blue tape and/or blue plastic covering over the end of it. DOES THAT COME OFF OR STAY ON?!? (The blue tape stuff.) I've read the Owner's Manual. 'Says nothing about this particular item. I ask because inside the frig there's LOTS of blue tape holding things in place, and it all come off--naturally. Since the town is SO small, I just don't want to screw this up. Hence the question to folks who know. Thanks!!!
Sounds like that's where they charged it at the factory and is there so that in the rare case that it needs to be charged in the future, the service guy can sweat on a service port. Doesn't matter what you do with the tape.
Blue tape is from the factory to keep stuff from moving and falling off inside the box, the blue tape can be taken off because after the frig is delivered it serves no purpose
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