new to HVAC work

[taiwanluthiers]

Hi

I'm in Taiwan (just so you know) so the laws and such are different here. For example I can still easily and cheaply obtain R22 and no license are required to buy them either.

Anyways I have a mini split, 8000btu, non inverter AC. Compressor failed (locked rotor) 2 weeks ago. I purchased a replacement from Taobao (30 dollars plus shipping), and replaced it. That system uses R22 so the compressor is matched to that. Anyways I went a little unconventional because I don't have any oxy acetylene torch so I paid someone (5 dollars) to braze a copper tube to the inlet and outlet, then I used flare couplings to join them inside the condenser unit. No nitrogen purge (I did some tests brazing using butane and turns out there's no oxidation without nitrogen purge with the small, 6mm and 10mm diameter tubing involved).

I'm getting a MAPP gas torch so I can braze stuff myself as butane torch I have can't get it hot enough if there is anything interfering with heat transfer (such as compressor outlets).

New compressor has much better performance than the old one before it failed. The old compressor was causing the AC to underperform by quite a bit, meaning I was paying too much for electricity. New compressor is making the room VERY cold and it would come to temperature in 1/4 the time than before. I guess compressor loses performance over time (or the compressor was bad when I bought the system second hand). I'm actually moving in a month but it's the middle of freaking summer and I NEED the system working (the AC belongs to me so the landlord won't pay to fix it).

Anyways I have a question... why are we using such difficult oils with the newer refrigerant (like 410a) that seems to cause a ton of problem, like reacting with moisture to form acids, needing completely immaculate procedure and all that? Like for example R22 uses mineral oil for lubricant and you don't even have to nitrogen purge when brazing because the mineral oil doesn't affect the oxide scales, and mineral oil also does not react with moisture, but R410a somehow requires POE that strips oxide (which is why you need nitrogen purge) AND it reacts with even a tiny amount of moisture to form acids, killing compressor, etc.

So is newer and newer refrigerants like R32, 410a, etc. just making it harder for DIYers to fix their system?

R22 system works well enough, and I realize that they are a bit ozone depleting but it seems like we're just wasting more carbon emission manufacturing new systems, throwing away old systems (because newer ones are more "efficient) that's perfectly good "just because"? It seems like a R22 system with a good, full performance compressor will work just as well as a new system using R32 anyhow... Why do we need to use such finicky oils like POE with R410? Why can't we use oils that won't react with moisture?

By the way I asked a HVAC tech nearby (he was installing a rather large system, works for Daikin) if they do any nitrogen purge when brazing refrigeration lines, he said he only do it for ACR systems because no flare fitting exists for large diameter pipes that they use... not sure what ACR is though. My guess is you get little to no oxide buildup when brazing smaller diameter pipes?

Sorry for all the questions...

[tenletters]

- not sure what ACR is though
-- air conditioning and refrigeration

- Why do we need to use such finicky oils like POE with R410? Why can't we use oils that won't react with moisture?
-- mineral oil doesn't provide enough lubrication, so we have to use poe. downside is at higher pressures poe scrubs the walls of the copper bring back all that oxidation to screens, reacts to things in the system like rust inhibiters from certain manufacturers also plugging up txvs, and reacts to moisture creating acid which causes coil leaks on evaporators, condensers and kills compressors.

- why are we using such difficult oils with the newer refrigerant (like 410a) that seems to cause a ton of problem, like reacting with moisture to form acids
-- vacuum the system and braze with nitrogen and there's no issues

[Porcupinepuffer]

As far as I know, the only reason we nitrogen purge when brazing is to keep oxygen out of the inside of the tubing since it creates oxides that gives the flaky contaminants inside the tubing that eventually gets washed down the piping to clog up txv's and/or orifices. When we braze correctly with nitrogen flowing through the tubing, the inside remains completely clean after the braze is done. It has nothing to do with the oils. We still need to do it on brand new system that have never been exposed to any of the oils.

[tenletters]

It has nothing to do with the oils.

It has everything to do with the oils. POE oil will scrub the walls of the copper. It's more of an abrasive oil than mineral oil in r22. There's virtually no scrubbing effect with a mineral oil.

[Porcupinepuffer]

It has nothing to do with the oils.

It has everything to do with the oils. POE oil will scrub the walls of the copper. It's more of an abrasive oil than mineral oil in r22. There's virtually no scrubbing effect with a mineral oil.

It has everything to do with keeping the inside of the system clean of oxides that can, and will eventually move their way through the system and plug up smaller components. You just have to look at the oxides the wrong way and they will travel down the tubing without needing any kind of scrubbing, Regardless of what oil is being used. You're implying we can braze without nitrogen when mineral oil is used and the oxides created inside are fine.

[tenletters]

It's very unlikely to pug up anything up in an r22 system because the carbon sticks to the walls of the copper. That's why you hear oldies say, "I've been doing this 30 years and never used nitrogen." It only became a problem when we switched to 410a, increased the pressures and oil.

Edit: I've already said this, but here's a link anyway
https://hvacrschool.com/how-and-why-to-flow-nitrogen-while-brazing/

Why Old-Timers Say it Doesn't Matter

Many techs who have done this work for a long time haven't flowed nitrogen EVER and have gotten away with it because of mineral oil. Older CFC and HCFC refrigerants used mineral oil rather than POE/PVE or PAG oils that we see today, which have higher solvent properties that "scrub" the oxide from the walls and deposit it into driers and screens. Techs in the grocery industry know that when a system is converted from mineral or AB oil over to POE, it is very common for this cupric scale to clog screens pretty quickly after the changeover. The point here is that mineral oil was forgiving on small amounts of cupric oxide on the tubing walls, but POE isn't.