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.
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.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.