How well do heat pumps work?

[DFord]

I've never seen a combined start/run capacitor. Start capacitors are round bakelite plastic while run capacitors are in metal cans. The start capacitors are only in the circuit for a split second. There should be some sort of device (used to be called a start relay but these days may be a solid state device called a PTC/PTCR or Positive Temperature Coefficient Resistor device) to take it out of the circuit - technically when the compressor nears full speed. The run capacitors stay in the circuit all the time and make the motors they're used on (PSC - Permanent Split Capacitor) more efficient and thus draw fewer amps. PSC motors have very little starting torque and that's why the start kit (capacitor and relay) are used.

With a start kit, the compressor should be able to restart without any delay. Without one, it would need to rest and allow the refrigerant pressures to equalize for at least 3 minutes before restarting.

[BobJones]

Interesting! Thanks for the info - it's good 'grounder' for me as I did not know how it really works. I was inferring that maybe it was two caps in one from what I was reading in the manual but I didn't get to make it up to the roof today

Would I be correct in assuming the caps go out of spec over time and that I will be able to see it by measuring them, or do they just up and fail?

[DFord]

Bob, Capacitors don't wear out. If you were to open one up, you'd find what looks like tin foil separated by wax paper wrapped like a roll of toilet paper. A voltage surge can pop a hole between the layers of foil causing a failure or (especially the start cap) can overheat if it's in the circuit too long and the "wax" melt blowing out the top. Run capacitors often puff up the top when they fail. If the readings you get when testing yours (with no wires attached) are close to the label, they should work.

[Mr_D]

Have had heat pumps on and off for 40 yrs now. In mild climates they work well and can save money on your heating bill. You do need to make some adjustments though as the output doesn't feel warm like a gas furnace.