Chiller tripping main breaker

[engineer973]

Our chiller is blowing 1000AMP breaker when running at 90%. The breaker has a trip range dial on it and it is set at max. When it runs @ 85% its fine and it has been like that for years. Anyone have any idea why this is happening, it runs at about 600 amps under heavy loads.at 85%.

[enart9591]

Check the actual current draw at the breaker with the chiller at full load. You may also want to have the breaker scanned with an infrared camera to check for hot spots.

A machine that is only drawing 600 amp on a 1000 amp breaker tells me that something is up with the breaker, not the chiller.

[Shophound]

Offhand I'd say check your condenser pressure. What kind of chiller do you have?

How warm or cool are you running your condenser water inlet temperature? Tubes punched recently?

Does you chiller have a demand limit set on it? And has it never run past 85% until recently? If so I'd look into where the extra demand is coming from.

[acjourneyman]

Breaker problem, condensor prssures etc will never have the effect of blowing the main breaker.It will run a 15# head all day long if breaker is fine.

[acxpert2]

You could have a loose lug somewhere that is causing the breaker to generate heat and trip. I had a similar problem once that traced all the way back to the building connection at the transformer on the utility side. Or it could simply be a bad breaker.

[captinsano]

maybe it is just hot and tired I know I am!
Just thought you might likes some humor ,it might need a few beers.

[fixerup]

Breaker may be getting too hot. Loose connections or high ambient.

[maustin]

Just had that happen here. It was the thermal trip unit in the breaker itself. On some equipment you can replace the trip unit and leave the breaker in place.

[madhat]

Check the last condensor fan motor that comes on. Had a condensor motor, that had a running ground. It would trip the breaker after it ran that motor, tripped the chiller main, but didn't touch the fan motor fuses.