compressor

creger.robert

Copeland scroll compressor

have 240 feeding compressor

contactor pulls in

capacitor is good

compressor does not even try to start

megged out compressor all checked fine

any thoughts?

HVACNUT

I don't believe you test that compressor with the meter set to Mega ohms. Set it to auto range. The readings between Start and Run should be the approximate sum of the other two readings. Have you checked each to Ground?

creger.robert

yes and everything checks out

mattmia2

And it all should be under 50 ohms. Usually under 20 ohms but it depends on how it is wound.

mattmia2

What is the voltage at the compressor terminals? Could be a bad connection somewhere.

Does it hum?

ratio

Amp draw on the compressor R, S, & C when the contactor draws in? Resistance between R & C and between S & C?

pecmsg

what’s the starting amps?

What’s the run cap uf reading and rating?

Factory start parts installed?

EBEBRATT-Ed

As others mentioned you need an amprobe on it to see if it is trying to start.

If you have power to it and the contactor closes and the capacitor is good and the windings check out and the overload is closed its either going to start or burn.

Check terminals at the compressor and check for voltage drop across each leg (top to bottom) of the contactor.

Chances are the contactor is pulling in but the contacts are burned or not closing.

creger.robert

i measure 240 on outlet of contactor

130 volts across capacitor

40uf

no humming at all

mattmia2

what do you measure on the terminals of the compressor?

pecmsg

amp draw?

109A_5

Sounds like something has failed open, or the overload device has failed. I too would be curious about the winding resistance and the current draw.

ratio

Resistance of the windings is different than megging the windings.

Winding resistance is taken with a multimeter (or ohmmeter) set to resistance/ohms/Ω (if not autoranging then generally the lowest range). Should be less than 40 Ω between the run terminal ("R") and common ("C"). It will be different between start ("S") and common, but I can never remember if it's a little higher or a little lower. The measurement between R & S is ≈ the sum of the measurement between R & C and S & C.

'Megging' a compressor is measuring the resistance of the insulation of the motor. It's taken with a megohmmeter between any one compressor terminal (doesn't matter which) and ground. With a cold compressor, it may be as low as 20 MΩ but may creep up as you measure. A regular multimeter isn't a good choice for this measurement. While it can tell you if the windings are good and shorted, it can't tell you if there's a weak spot that's getting ready to blow through.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1863634#Comment_1863634

Agreed.

A Megger is used for testing leakage not coming out windings. Does the compressor have a plug on the side and did you check it?

creger.robert

Thanks for all the insight I know the difference between a megger and multimeter I am just checking all the bases-unit does not try to start no amps-I will investigate-There is a plug on compressor I removed and ran wires to compressor diirect still nothing

ratio

Sorry, I added that for anyone else who might find this later on.

In any case, if you have voltage to the terminals and continuity between the terminals, you will have current flow. Ohm's Law isn't like a traffic law, easily broken—it will happen.

I think what most people are saying is that something isn't adding up. Double check your assumptions. Verify your instruments. Recheck your measurements using different instruments and methods..

creger.robert

Thank you I agree definitely not adding up-I will recheck everything -thanks appreciate it!

mattmia2

so i'll ask a 2nd? 3rd time? what voltage do you have on the compressor terminals?

pecmsg

https://forum.heatinghelp.com/discussion/comment/1863826#Comment_1863826

and amperage?

creger.robert

I am heading back this afternoon to verify voltages

ratio

The amps will tell you more than the voltage; that is, amps without volts will tell you more than volts without amps.