A ground fault occurred in my plant and the ground fault indicator on the main switchboard popped out causing the main to trip> It worked as it should have but the question I have is it went through 3 breakers to get to that fault indicator so it shut down the whole plant. The problem was a compressor in a roof top unit went bad. How come the breaker in the unit or the 3 pole 60A in the panel or the main breaker for the panel located on the switchboard did not trip? Any ideas would be helpful. Thanks
Gound Fault
- Thread starter eric d
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: Gound Fault
The simple answer is that they were not ?coordinated.? ?Fault Coordination? takes a specific effort in the process of designing a facility. It is possible to set up conditions such that the breaker nearest to any fault will trip first, and such that the breakers upstream stay closed. This way, the fault does not de-energize any more equipment than is necessary to clear the fault. This is a design issue, not an NEC issue. You need to seek professional advice, if you want this not to happen again.
The simple answer is that they were not ?coordinated.? ?Fault Coordination? takes a specific effort in the process of designing a facility. It is possible to set up conditions such that the breaker nearest to any fault will trip first, and such that the breakers upstream stay closed. This way, the fault does not de-energize any more equipment than is necessary to clear the fault. This is a design issue, not an NEC issue. You need to seek professional advice, if you want this not to happen again.
Re: Gound Fault
Eric, What is the groundfault pickup setting of the main breaker set at? A 60a breaker without a ground fault will commonly have a instantaneous short circuit pickup 600a or more which may not coordinate with the main ground fault. Unless there is a reason to set the main groundfault pickup at a lower setting it can be set to the highest setting. If that doesn't do it then somebody has to spend some extra buck in adding groundfault on downsteam devices which somebody didn't think about or want to do when the system was specified.
Eric, What is the groundfault pickup setting of the main breaker set at? A 60a breaker without a ground fault will commonly have a instantaneous short circuit pickup 600a or more which may not coordinate with the main ground fault. Unless there is a reason to set the main groundfault pickup at a lower setting it can be set to the highest setting. If that doesn't do it then somebody has to spend some extra buck in adding groundfault on downsteam devices which somebody didn't think about or want to do when the system was specified.
- Status