Confused about fittings: AN, Compression, Flare, etc...?

[dolorm]

Hi, am assembling the parts for my air supply system and despite many hours of scouring the internet, I am confused.

The plumbing solution has me stumped. Between which tubing and fittings to use, and the mixing of metals corrosion problem have me on the ropes. Advice much appreciated.

Design of system and component pics below.

The compressor currently has a 1/2" OD aluminum tubing with brass compression fittings, and ferrous metal compression nuts from the compressor head to the check valve.

The fin & tube cooler have -8AN brass inlets (37 Degree Flares). It is made out of copper tubing, aluminum fins, and a ferrous (mild steel probably) metal structural members.

My plan was to buy aluminum tubing since it is much cheaper than copper, but I read never mix the metals as the aluminum will corrode fast. OK, so then I look at spending the extra money on copper, but then I see a couple things:

1. the copper I saw at the store was not 1/2" OD, it was ID.
2. I look online and find 1/2" OD copper does exist, but then I see the 8AN fittings are aluminum and have 37 degree flare so it requires me to buy another flaring tool, the cheap flaring tool has very poor reviews, so the cheapest out is a $130 rigid 37 degree flaring tool for a few flares.
3. So, I think, well, they used compression, so why not me too. However, I see the AN fittings show the only two options for tubing is stainless and aluminum.

I also start to ask, how did Kobalt mix ferrous, aluminum, and brass if it is rapid corrosion? How did the highly reviewed fin and tube manufacturer mix the trhee metals?

Dazed and confused. Does anyone have advice on how to plumb this system?

Thank you.

PS. I know the romex wiring is improper. Was a pinch fix when building our house. When I install the air system, I will wire properly.

-Mike

 

[The Cobbler]

The dissimilar metals is much less of a concern with air than when carrying water , almost non existent

 

[dolorm]

The dissimilar metals is much less of a concern with air than when carrying water , almost non existent

Wow. Thank you! Seems to jive with what I am seeing. Kobalt had no problem with aluminum tubing, brass ring, and ferrous nut. But I allowed all the internet voices make me lose rationality. I have the science of a ten year old compressor with this and no problem.

Thank you for bringing me back to rationality.

 

[dolorm]

So, I think I will go with the aluminum tubing and compression fittings with appropriate adapters.

 

[The Cobbler]

I think you have a solid plan now

 

[RTM]

The do make dielectric fittings for joining metals that don't play nice together, but I have not had to use them for over 25 years, so the memory is beyond foggy.

 

[Beerhippie]

There is water in your system, and it's acidic--your condensate. But only before the air dryer (hopefully). Dielectric fittings only work if the two dissimilar metals are entirely electrically isolated from each other (meaning no connection to ground or anything grounded) and galvanic corrosion is different for acidic solutions vs. alkaline solutions.

That said, air coolers for compressors are usually aluminum and before the air dryer, as the refrigerated air dryer would have to be huge to handle the load otherwise. My I-R rotary has been working flawlessly for a decade or so now set up that way.

Just watch--it'll spring a leak tomorrow now that I stated that.