Along the way, I did conclude that 1/4 tube would be better than 3/8 for the condenser. With it buried under silicone caulk and great stuff, I do not intend to replace it.
Anyway, here's the last data I took before installing. I started the test in the morning so all the temps are stable. With it on the bench, I can insert a thermometer into the top water outlet & get good water temps which I use for calculating COP. The overall COP is calculated over the whole cycle. The column with incremental COP is from one data read to the next, so not real accurate, but interesting how it improves as the pressures come up and then declines as the hot water temp comes up and the bucket water temp drops.
After installing and filling the tank, I set the various water shut-off valves so there was no flow thru the tank and brought it up to temp using the resistance heater then let it alone for a day to measure watts just to maintain at temperature. Then repeated using the heat pump. It took 389 watt hrs per day with resistance heater and 285 watts per day with HP. So in that comparison COP is 1.36. In those cases it is maintaining water temp between about 98 & 103. I believe the COP will be better for heating cold water which is now coming in at 50F.
When I installed it, I added a liquid filter that you can see just behind the high pressure gauge in the photo in my last post. It took 3 oz of charge more than without the filter and the performance changed, I think for the better. I guess a little more pressure drop, Just thought that was interesting. Here's some data after installing. The water temp is from a thermocouple pasted to the outside of the tank next to the thermostat, it's not accurate enough to use for COP calculation.
After running for 2 months now it seems to have lost a little charge. The low pressure tends to run at 60 and the high is a little lower too and the watts never get over 290. I think it is better at this lower charge.