Quote Originally Posted by NoNickName
No, it is not a matter of flash gas... suppose the liquid refrigerant is 40°C in summer, and it is 20°C in winter.
What would you think the temperature after evaporation would be in the two cases?

It would be lower in the second case, that would results in lower evaporation pressure and lower suction pressure, and lower compressor performance.
Haven't read thoroughly the whole thread:
Liquid 40°C in summer and 20°C in winter will give a lower evaporationg temperature in winter conditions at the same condensing pressure??
It will increase the net effect on the evaporator a lot because teh enthaply of the liquid has increased seriously.
The COP of the compressor will increase with +/-25 to 30% and you're talking about a lower performance?

The power factor of a motor varies
according to its load. The higher the percentage of
the rated load, the higher the power factor
This is true but it may not be exagerated to much.
What is then the advantage of the digital scroll?
And form the unloader valves on larger machines and so many small semi-hermetic machines?

The net effect you gain by increasing the suction pressure by unloading is by far much higher then the negative effects of increase of the power factor.

We measured this some 15 years ago on a open 8CC compressor of DWM/Copeland and there was as far as I can remember almost no measurable difference.

And you pay - at least in Belgium - only the power you consume for smalelr applications, not the apparent power.
Line current will be a little bit higher but that's all. So if power factor rises, you could say, who cares!?

I agree on the conclusions, and on the fact that higher subcooling does not equates in better overall performance
I'm almost sure this is a wrong statement. Will try to simulate this the next days.