orifice

Yeah... but only the size of the pistons.... 2 1/2 ton, I would expect to see a .065 piston for a 10 seer and .095 for 12 SEER with an expansion valve.

No, I don't think that's the problem. If your heat pump isn't working, there is something wrong. But a 2% size diff of orifice isn't enough to make it "not work".

The heat part works great it doesn't cool 100% and everything else is the same.

2% throughput?

What are you saying here?

Good question.

Why not bullshit a little. It's fun!

OK, here we go:

Neglecting CR (compression ratio), 2% size increase equals 4% flow increase.

Pressure drop is depenant on CR vs orifice flow rate.

With constant load and air temps, CR drops slightly with increased orifice size, slightly offsetting the flow rate change, but not by much. And a 4% increase is twice the percentage increase of a 2% increase, but it's still only 2% more increase than the smaller orifice.

So I would just remove the orifice and pinch off the liquid line until it's throttled enough for good superheat. :-)

And since flow rate per ton is a constant formula, [200(Hd-Hs)/(Hc-He)], just just use any old refrigerant with enough enthalpy and latent heat per pound that won't strain the motor, and adjust the charge and amount of pinchoff on the line. Maybe try experimenting with capacitor sizes. And for heaven's sake, don't waste money on new ones!