Ninja tips: AC systems Options

[technicalninja]

This thread is my base AC thread for suggestions, questions, whatever...

I run
https://granburyautoac.com/

I specialize in automotive heat and air conditioning systems.

I've been doing AC work since 1983 and have seen all of the changes, good and bad, that have occurred over the last 40 years.

I'm keeping the first post short as they always show up at the top of each page and if long, they clutter up the thread...

[technicalninja]

3rd tip...

Oil balancing is very important!

A modern AC system uses approximately 4 ounces of oil per LB of refrigerant.

Putting too much oil in degrades system efficiency. It coats the inside of the tubing and the heat exchangers and can seriously degrade system heat transfer.

The oil DOES NOT stay in the compressor. It runs around the system with the refrigerant and the liquid refrigerant mixes completely with the oil. When the liquid goes through the phase change from liquid to gas it releases the oil as fine droplets and this oil mist is how the compressor oils.

Ever been in front of a fan with a water mister on it?
This is how the compressor oils...

The ONLY thing that needs the oil is the compressor.
Modern compressors have multiple ways they try to keep the oil in the compressors.
IMO none of them work. I expect 33% of the system oil in the compressor and the other 66% will be in the system, mostly in the evaporator as this is the main area the phase change occurs in.

Most of those expensive refrigerant cans have 3 ounces of oil in them. If you've had an explosive decompression of the system, you might lose 3 ounces. Ripping a hose off is an example of explosive decompression. This vents the entire system charge in a second, you get a BIG bang and a pretty impressive cloud for just a moment.

If you haven't violently vented your system, you NEVER need the amount of oil in one of the fancy cans and putting 3 ounces of oil in a system that needed none is "shooting yourself in the foot."

A slow leak does not vent much of the oil out of the system. You might only need a 1/4 ounce of oil. Experience is what makes me able to determine how much oil to put back in. It's usually a very minor amount...

I have a Hybrid capable machine and it did not have an oil injection system.
At first I was pissed, My 5K machine could not inject oil!
I far prefer it that way now.
I use a 60CC cow injection hypodermic srynge to dispense oil into the high side of the system (ONLY!) during vacuum operations. Work like a charm and was dirt cheap.

Robinair and others make an actual oil injector to allow injection of oil into a charges system. I originally wanted one but after getting used to the cow needle I'm fine with out one.