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knkreb
21-04-2008, 12:36 PM
Good morning everyone!

Well, I'm getting ready to replace the compressor in my heat pump at home. According to the Copeland Performance Sheets, it's drawing too much current.
So, I'm thinking to myself, must be something wrong inside.

ZR34K1PFV (obsolete compressor)

It's drawn too much current from day one, and checked everything out, it's okay. Ohm value from winding to winding, capacitor okay. It does not over heat, or anything. So, I just purchased a clamp on watt meter. Verified it's wattage, and the wattage is dead on as compared to the performance sheet for the conditions is operating. I'm having a little problem understanding just why.

Conditions: 60 psig suction 162 psig discharge. 60hz
Volts 240v

Wattage on Run winding to line: 1.15KW
Wattage on Common to line: 1.98 kw
Wattage on Start winding to capacitor: .90kw

Performance sheet said (at closest condition) 1960 watts. Why the difference between Run and Common?

Here's the other kicker: Amp draw 12 amps. Performance sheet is 9.5 under those conditions.

?????

SteinarN
21-04-2008, 01:11 PM
The correct place to measure amps and wattage is the commons line only. The run winding and start winding line amps is out of phase with each other. Therefore the sum of amps and wattage in those two lines is higher than your actual total wattage.

How du you calculate the wattage?

knkreb
21-04-2008, 01:25 PM
Thanks for the clarification about out of phase, I was wondering what part that might play in all of this.

As far as wattage measurement, I didn't calculate it. It was what was measured by the clamp on/watt meter. This meter uses the leads to measure the voltage, and uses the clamp to determine wattage at the same time. So this isn't a hand calculated value. It's a true RMS meter too, if it makes much difference. I tested it on my electric water heater first to see how accurate it was with a resistive load, and proved quite accurate. Now with an inductive load, this is the first thing that I've measured.

nike123
21-04-2008, 01:25 PM
What instrument you use for current measurements.
Do you have another instrument to confirm that measurement.

SteinarN
21-04-2008, 01:31 PM
The most important is the wattage. The amps will vary with variations in the voltage at otherwise same running conditions. I supose the compressor is for 60Hz and not for 50Hz. Are you sure your performance sheet is for that exact compressor with that exact motor? I know Copeland has had different motors in some of their kompressors. If the amps is the only thing deviating from your performance sheet I would not replace the compressor. Frankly I doubt it is anything wrong with it.

SteinarN
22-04-2008, 12:23 PM
ZR34K1PFV (obsolete compressor)

60hz Volts 240v

Here's the other kicker: Amp draw 12 amps. Performance sheet is 9.5 under those conditions.?????

Todays 1-phase compressors (motorcode PFJ) is rated for 265V at 60Hz. If the voltage is under 265V, then the amperage will increase. If your compressor also is rated for 265V, then the reason for higher amperage than on the performance sheet is your lower voltage. The allowed voltage is however plus or minus 10% from the nameplate voltage.

hendry
18-05-2008, 04:56 AM
Hi knkreb,

i will normally check the below & i suggest you can consider.

1] measure voltage upstream & downstream;
2] check power factor;
3] clamp each cable for amperage;
4] mega testing the motor coil;

when i check/measure above, i have better pictures of what i faced.

may it helps.

Hendry, on wesak day holiday.