[AC_Hacker]

Welcome,Fred_Fredowski to the conversation...

I downloaded the Goodman PDF you mentioned. I'm not quite sure which part has the information you are referring to, however.

Originally Posted by Fred_Fredowski

I think the high side pressures compare pretty well. The GSH14 operates at about 190-220 psig with about a 100 degree warm air temp. This seems to match your data of 210 psig for 100 degree water.

There is a bit more difference with the low side pressures. It appears from the data that your unit stabilizes at about 40 psig with a 48 degree loop temp, and for propane this pressure corresponds to an evaporating temperature of about 20 degrees. For the Goodman unit, at a 47 degree outdoor air temp the pressure is about 60 psig, which corresponds to an R22 evaporating temperature close to 35 degrees. It looks like the Goodman heat pump works with about 15 degrees lower lift. This might be worth looking into as it has a big effect on COP.

Well, first off I am very interested in improving COP, that's pretty much why I'm involved in this project. I'm interested in any approach that will improve COP.

Now, I do recall reading on one of the 'CPU phase-change chilling blogs' that the charge pressure level for R-290 should be lower than for R-22. It's been a while since I read it, but I seem to recall it was because R-290 has a lower density than R-22. I think the first time I charged the system up, I overcharged it and it never even made frost until I reduced the charge pressure level to be a good bit below that specified for R-22.

Originally Posted by Fred_Fredowski

Have you measured the dT in the water going through each heat exchanger? I thought that you mentioned that the sump pump was pumping about 2 gpm through the earth loop, so with a 5000 BTU/hr compressor I would expect about 5 degrees of dT across the low side heat exchanger. Is this what you see?

I just ran the system for about 40 minutes and I used a non-contact IR thermometer and measured off of the HX water and refrigerant fittings here's what I got (bear in mind that the system was changing all the while I was measuring it):

Low-Side HX

Water In = 56F
Water Out = 52F

Low-Side HX

Refrigerant in = 23F
Refrigerant out = 59F

High-Side HX

Water In = 95F
Water Out = 99F

High-Side HX

Refrigerant in = 123F
Refrigerant out = 93F

(* more comments to come, gotta break for a bit... *)

Regards,

-AC_Hacker