Loss of Phase Current

[cubecool]

Hello, I have a Trane Chiller rtaa 216.

It was running fine till about a 1/2 year ago.
Now it's tripping on:Loss of Phase Current.
I checked the compressorwindings with a ohmmeter,the current transformers and the cables.
I also checked the contacters.

Can anyone give a hint on what to do next?

[Gary]

Check and tighten wiring connections. A poor connection will overheat, so an IR thermometer can be very useful for this.

[Grizzly]

Hi Cubecool.
Gary's advise is sound.
What is happening is there is no current being sensed on one or more of the current transformer inputs.
So I would check the obvious, if you have not already done so.
That there is a phase supply to each of the run contactors.
Just in case a line fuse has not blown?
Secondly with the power off do you get continuity across the contactor terminals. Are there any signs of the overheating Gary mentions.

Thirdly if voltages are OK then check out your CT coils.
From what you describe something has failed, you just need to identify what.
Good Luck Grizzly

[CV_Geardrive]

Hi Cubecool,
Some units have double HP switches.
Check external and internal reset of HP switch.
You can also place a jumper (for test purpose) to HP switch to check if the compressor starts or not.
You can also check or replace all auxiliary contacts of compressors contactors and you can check if the contactors coils are OK.
If not, please let us know following:
1. Is part winding or Y-D?
2. If part winding has a 0,5 seconds timer or not?
3. Year of manufacturing.
Regards,
CV

[cubecool]

Thanks guys,

I checked the contacts of both the main contactors and
replaced the starpoint contactor.
I also checked the voltage to the contactors.

Could there be something wrong in the controllboard?

I wiil check your remarks as soon as I get to the chiller.

[binti]

Only a stab in the dark, ( not familiar with model #)
Is it a screw or a scroll? does it have a phase rotation /failure module? could there be a problem with that?

Just thinking out loud.

[NoNickName]

I think you could have a voltage unbalance that causes one phase to draw more current. Check and report back to us accordingly.

[serviceman]

a very common problem on these machines is that the auxiliary contacts do not confirm the start of the compressor and this is read by the module and phase loss

[goshen]

Hi i have had to replace the control board ,it has the current inputs and might of blown a diode,
i wouldnt change this board unless you narrow it down to that,check your ct's
and check your inputs on the card.
good luck