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Nowty - does your GSHP have a cap tube or TXV as its metering device?

My Kensa GSHP has a 9kW compressor which always seems to draw 9kW. When the input temp is higher, I just get a higher output temperature, so I suppose a better COP. I can see this as the thermal store temp at the top gets to a higher temp before the (much lower down) temp sensor turns off the pump. My GSHP runs off a 36 panel roof array as the 'ground loop' so the temps are quite variable.

The Kensa has a TXV and I suspect your heat pump uses a capillary tube.

I don't have a metering device.

Don't think jon is referring to a Heat Meter he is referring to the method of controlling the flow of the refrigerant into the evaporator.

cap tube and TXV refer to either Capilliary tube or Thermal Expansion Valve. As I understand it they effectively control the flow of the refrigerant through the evaporator.

A capillary tube - coil of small bore copper tube - the flow is "controlled" or dictated by the temperature and pressure - cheap and effective but has a slow response.

Thermal Expansion Valve - more complicated and expensive but quicker responding, so in theory could make the pump more efficient?

I don't know, I thought it was controlled electronically as there are some wires going to it but that might be a sensor.

Picture of it.

Ah yes, you are correct - it is an electronic expansion valve. Like this: https://www.bosta.com/en-gb/electronic- ... er=7028152

Looking again at your table, I guess the system is regulating things to maintain a fixed heat output. My Kensa which has an essentially mechanical expansion valve is just outputting what it can with fixed pump load and so fixed power draw.

nowty wrote: ↑Fri Jun 24, 2022 6:45 pm
Playtime was about to start.


But playtime was halted because I need a 1/4 male to 5/16 female adapter for my vacuum hoses to fit the charging port on the outdoor unit.

I presume you used any old pump and not an r32 pump as you were only after the precharge vacuum?

Andy wrote: ↑Fri Jan 13, 2023 1:11 pm I presume you used any old pump and not an r32 pump as you were only after the precharge vacuum?

Yes, if I understand you rightly, the pump is NOT for pumping in any refrigerant gas. Its a vacuum pump and Its ONLY used for vacuuming down the lines and indoor unit before sealing off and opening the gas valve on the outdoor unit which releases the precharged gas into the vacuumed down lines and indoor unit. The outdoor units have enough precharged gas in them for up to 6 metres of line. It comes with a 4 meter line as standard. If you need more than a 6 metre line, then you have to add more gas which is more technical and you probably need to get someone in to do it because its hard (or impossible) to buy the gas without the FGAS licence.

I believe the only difference is the calibration on the gauges for superheat and subcool. Many aren’t calibrated to R32, but you can read off the PSI and convert manually or just use the R410A scale which is very close to R32.

In any case you don’t need to bother too much with any of that for this kind of install.

Stinsy wrote: ↑Fri Jan 13, 2023 4:19 pm I believe the only difference is the calibration on the gauges for superheat and subcool. Many aren’t calibrated to R32, but you can read off the PSI and convert manually or just use the R410A scale which is very close to R32.

In any case you don’t need to bother too much with any of that for this kind of install.

Yep the gauges can be used for diagnostic purposes but that's an advanced thing that is not required for the install. You only need the vacuum gauge to make sure the lines + indoor unit gets to a good vacuum and holds it.

Thanks so any of the pumps are suitable in that case though I might need an adapter as you mentioned. Cheers