A/C Tripping Main

[dheaston]

A/C unit is tripping the 1600 amp main. A/C unit is feed with 480 volt, on a 35 amp 3 phase breaker, subpanel feed with 250 amp 3 phase breaker, in a distribution panel protected by an 800 amp main, distribution panel is feed with a 400 amp 3 phase breaker at the main 1600 amp switchgear. Fault makes all the back to the 1600 amp main and trips.
Would you say?
Thank you

 

[Little Bill]

@dheaston
Could you please change your profile to add your occupation?

 

[dkidd]

A/C unit is tripping the 1600 amp main. A/C unit is feed with 480 volt, on a 35 amp 3 phase breaker, subpanel feed with 250 amp 3 phase breaker, in a distribution panel protected by an 800 amp main, distribution panel is feed with a 400 amp 3 phase breaker at the main 1600 amp switchgear. Fault makes all the back to the 1600 amp main and trips.
Would you say?
Thank you

Check for a ground fault setting on the main.

 

[winnie]

Check for a ground fault setting on the main.

This is my first thought when a failure on a small branch circuit trips a main several levels up.

-Jonathan

 

[Little Bill]

@dheaston
Thank you for updating your profile!

 

[hillbilly1]

Pretty common occurrence with the ground fault settings. Usually it is a bad second stage compressor during the summer, or a faulted heating element in the winter.

 

[ATSman]

I agree with all comments.
OP can you send us a clear pic of the front of the main breaker?

 

[Jraef]

It's a fair bet that if a single A/C unit is causing a 1600A Main breaker to trip, it's the result of there not having being a "coordination study" performed. Unfortunately unless there is one specified and performed, 90%+ of people never change the factory default settings on breakers. The factory default settings for GF are often ridiculously low, probably as a "CYA" for the breaker mfr.

 

[ATSman]

It's a fair bet that if a single A/C unit is causing a 1600A Main breaker to trip, it's the result of there not having being a "coordination study" performed. Unfortunately unless there is one specified and performed, 90%+ of people never change the factory default settings on breakers. The factory default settings for GF are often ridiculously low, probably as a "CYA" for the breaker mfr.

Or, what we find a lot is if Acceptance/ Commissioning tests are performed by a testing company, they often turn the current setting down to minimum to limit the size of the test set they need for current pickup. Then forget to turn it up before they leave. This is also the case with breaker OC and instantaneous trip unit settings.