Parallel Generator Breakers

Status
Not open for further replies.
N

Natfuelbilll

Senior Member
I have three generators each with a 200A breaker at the generator.

These three generators tap into a common buss at the generators.

The buss is connected with 600A cable to a 600A main circuit breaker at an MCC.

Questiin: do the generator breakers provide short circuit protection for the feeder?

Is there a way to coordinate three breakers to open on one fault?

There is no utility.
 
Natfuelbilll said:
I have three generators each with a 200A breaker at the generator.

These three generators tap into a common buss at the generators.

The buss is connected with 600A cable to a 600A main circuit breaker at an MCC.

Questiin: do the generator breakers provide short circuit protection for the feeder?
Click to expand...
They should, with the sum of their ratings equal to feeder ampacity.

Is there a way to coordinate three breakers to open on one fault?
Click to expand...
Not my area, so I'll leave this one to the more experienced...
 
In simpler terms.

Is overcurrent protection for a feeder, that is tied from a main generator buss, provided by the overcurrent protection of the generators? The circuit breakers are factory assembled in parallel and listed as a unit per 240.8. The load end of the feeder is tied to a MCC through a main circuit breaker.

445.19 allows multiple generators to parallel when feeding a switchboard.
 
If you have a three pole circuit breaker as a single mechanical assembly, it can be (and usually is) constructed with a common trip mechanism.
If you have three separate CBs they will usually be independent trip, but as soon as one of the trips from overload the other two will immediately see a 50% jump in current and will trip too.
If there is a real need for more positive coordination you can use a single trip unit to drive a shunt trip on each of the breakers or can use auxiliary contacts on each breaker to shunt trip the others.

Sent from my XT1080 using Tapatalk
 
Natfuelbilll said:
In simpler terms.

Is overcurrent protection for a feeder, that is tied from a main generator buss, provided by the overcurrent protection of the generators? The circuit breakers are factory assembled in parallel and listed as a unit per 240.8. The load end of the feeder is tied to a MCC through a main circuit breaker.

445.19 allows multiple generators to parallel when feeding a switchboard.
Click to expand...
The Code is a bit lacking on parallel power production source requirements IMO. If you have 3 parallel sources, each with 200A ocpd feeding common busbar/wire conductors with an ampacity of 600A, I'd say it is protected... but I don't know of any Code which absolutely says it is.
 
A similar project has 3 400A breakers feeding a 1200A main breaker in a MCC.

This main needs ground fault protection - right?

Thank you
 
Status
Not open for further replies.
Top