3 Phase compressor

[yoda22]

hello everybody,

i have a IMI marstaire unit,a CUE 100 condenser. The unit keeps tripping its contactor overload.

I've taken its readings and on the three phases its pulling,

red= 6.1
yellow= 6.0
blue= 5.2

The overload is set to 10amps.

I noticed on the compressor start up the amps go up to 14.9amps for a milli second, is this normal for a three phase compressor to go that high on start up??

[chemi-cool]

The deferences between the 3 phases are too big, thats the compressor way of saying good bye.

But, a 10 amp OL should not trip. I would change it first and follow its behaviour.

Starting currant of this compressor [3 HP?] is about 70 amps but your amp meter doesn't have the "peak" function.

And of course, let us know your progress.

[yoda22]

Thanks Chemi-Cool. I've already ordered another overload,fitting it on Monday, see how it goes.

[stevo]

Thanks Chemi-Cool. I've already ordered another overload,fitting it on Monday, see how it goes.

Hi, I would recommend you also change the contactor, as one of the legs may have a bad connection !

[philstead]

g,day all.
i assume you are taking the current draw of the compressor only. check the insulation resistance of the compressor ,and look for hot joints ( high resistance joints ) on the 3 supply (line and load)and contactor. then test the contactor and o/load.

[Grizzly]

hello everybody,

i have a IMI marstaire unit,a CUE 100 condenser. The unit keeps tripping its contactor overload.

I've taken its readings and on the three phases its pulling,

red= 6.1
yellow= 6.0
blue= 5.2

The overload is set to 10amps.

I noticed on the compressor start up the amps go up to 14.9amps for a milli second, is this normal for a three phase compressor to go that high on start up??

Yoda.
All the Guys before have given good advise.
I will add that according to the Marstair Site the current drawn for a MCU 100 (Can't find CUE 100) is
Start Current LRA 51A.
Nominal Current FLA 7.2A

So in answer to part of your question 14.9A Would not seem excessive.
That's assumeing the data I am using is relevant to your model?
Having said that you would expect a surge on initial start-up.
good luck Steve.

[monkey spanners]

It would be worth checking the voltages on the phases as well and swaping the wires around to see if the low current follows the swaped wires or stays on the blue phase.

contactor in-swap to-contactor out
red -swap to-yellow
yellow -swap to-blue
blue -swap to-red

In effect you have just rotated the phases so the compressor should still run the same way.

Jon