[AC_Hacker]

Originally Posted by AirConditioner

Why is that? The one I was looking at on ebay was rated at 725 PSI with 1/2" NPT female threads. I was hoping I could assemble the whole thing with threaded and flare fittings so that I don't have to braze anything. I know compression fittings aren't good for A/C work, but what's wrong with normal threads?

My thinking on my first system was exactly the same as yours. But I realized along the way that I would need to join copper tubing. I had all the equipment and supplies, propane torch, flux, solder, etc. Even though I had heard that brazing should be used I decided tried soldering since I was only doing an experimental system. My initial failures convinced me that using plumbing solder on the copper tubing which was subject to severe temperature cycling and constant vibration was absolutely not going to work.

So I bit the bullet and bought a small MAPPS gas brazing torch and a bottle of MAPPS gas and a small amount of Sil-Fos® 5 (I hate to use brand names, but this stuff is awesome), and if your tubing is nice and clean, you will not need flux. The equipment looks very much like a propane torch, but it will get to the temperature you need. I even tried to use a propane torch and failed to get the tubing hot enough.

Here is some advice from the Homemade Heat Pump Manifesto thread

HERE

Here is some information regarding brazing:

HERE

I tried avoiding brazing to the BPHX also and wanted to use threaded connectors but the system it slowly leaked refrigerant and oil.

When you braze copper tubing to Brazed Plate heat exchangers, you are "joining dissimilar metals" so you will need to use silver brazing flux, as discussed in the Homemade Heat Pump Manifesto thread..

HERE

When you braze, you will need a purging gas, like dry nitrogen or argon, etc. I used propane, which worked just fine, but I would not ever recommend that anyone do anything as dangerous and foolish.

Brazing is not very difficult, and the tools and supplies are not so expensive. Having that simple skill opens up a large range of possibilities.

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Also, I think you are on the right track in regard to your choice of BPHX. Don't get deflected by too many options.

Sincerely,

-AC_Hacker