This is a response to a question that originally appeared on the R-290 thread, but I thought it would be good to post it here...
Quote:
Originally Posted by Geo NR Gee
We are preparing to use the R290 (22a) in an outdoor ASHP soon, I need to figure out the amount to install.
According to the Enviro-Safe instructions: Each ounce of Enviro-Safe 22a Refrigerant is equivalent to 2.5 ounces of R22. That would mean a system that normally holds 200 oz. should now be evacuated and filled with ____oz.?
This should be a simple math question. I think that you take 200 oz. divide 2.5 = 80 oz.
According to the folks at Enviro-Safe, I should also check the pressure from the manufacturer and match it to that.
Next is to research the proper method of removing the old R22......
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Wow, 200 oz of R-22 is 12.5 pounds... that's a lot of r-22.
Your conversion from R-22 to R-290 or Enviro-safe is correct, but it's still 5 pounds of hydrocarbon refrigerant, so play it safe.
Regarding pressure, I found that when I used R-290, the pressures required to get good performance were actually much less than the pressures called out for R-22.
For instance, when the R-22 pressures were:
- Hi side = 400 psi
- Lo side = 250 psi
I was getting good performance from R-290 at:
- Hi side = 200 psi
- Lo side = 125 psi
...sometimes even lower.
I started with the same pressure for R-290 as were called out for R-22 and when I ran my compressor, I didn't see any evidence of the miracle of refrigeration taking place... in face I was completely crest fallen and was sure that I was a complete failure until I reduced the pressure way down.
The unit had a very slow leak and ran my compressor through several days with the vacuum gauges attached and got to see the range at which the setup would work... it was very interesting.
I also did some efficiency tests over that range, and that was even more interesting.
Another thing, when I was hacking my unit I changed out both HXs, and the overall system volume was significantly changed, so I couldn't rely on weight of refrigerant... I had to go by pressure and performance.
-AC_Hacker