PV Source Breaker and Breaker Coordination

[who]

I have a PV panel with a 100A main and a 100A branch breaker, but the 100A branch breaker is going to a PV inverter. In most cases, the 100A main and a 100A branch breaker won't coordinate with one another, but in the case of a PV source, does it need to if the breaker is not actually a LOAD and is connected to the PV source?

I've been looking through the code and haven't been able to find anything and the Photovoltaic section in the CEC doesn't explicitly say anything about the PV source. Has anyone come across this?

 

[jaggedben]

I think if coordination is required then it is still required because a fault on the PV output circuit will still be fed primarily from the grid source. Likely the current contributed from the PV source is not significant enough to make a difference. But the larger the PV system, and the higher the stakes if coordination fails, the more due diligence should be done.

 

[jaggedben]

To the extent 690 and 705 don't modify requirements in earlier chapters (they don't), then those requirements remain applicable.

 

[ggunn]

I think if coordination is required then it is still required because a fault on the PV output circuit will still be fed primarily from the grid source. Likely the current contributed from the PV source is not significant enough to make a difference. But the larger the PV system, and the higher the stakes if coordination fails, the more due diligence should be done.

What do you mean by "coordination"?

 

[who]

What do you mean by "coordination"?

Selective coordination of the circuit breakers.

 

[ggunn]

Selective coordination of the circuit breakers.

I got that, but what does it mean?

 

[ron]

I have a PV panel with a 100A main and a 100A branch breaker, but the 100A branch breaker is going to a PV inverter. In most cases, the 100A main and a 100A branch breaker won't coordinate with one another, but in the case of a PV source, does it need to if the breaker is not actually a LOAD and is connected to the PV source?

I've been looking through the code and haven't been able to find anything and the Photovoltaic section in the CEC doesn't explicitly say anything about the PV source. Has anyone come across this?

I don't think the NEC requires selective coordination (or any type of OCPD coordination for that matter) for PV feeders / circuits.

 

[don_resqcapt19]

I got that, but what does it mean?

It means that the OCPD closest to the fault opens without causing upstream OCPDs to open. For example, in a selectively coordinated system, a fault on a branch circuit will only cause the branch circuit OCPD to open.
With smaller breakers on a system having a reasonable amount of fault current, this is difficult to do as the instantaneous trip ranges of breakers 200 amps and smaller typically overlap. All breakers will see the same amount of fault current and often more than one breaker will open.

 

[jaggedben]

I don't think the NEC requires selective coordination (or any type of OCPD coordination for that matter) for PV feeders / circuits.

Unless it's swept up by the new 240.11, I guess.

 

[don_resqcapt19]

Unless it's swept up by the new 240.11, I guess.

That only applies where other code sections require selective coordination. It does not apply generally throughout the code.

 

[ggunn]

It means that the OCPD closest to the fault opens without causing upstream OCPDs to open. For example, in a selectively coordinated system, a fault on a branch circuit will only cause the branch circuit OCPD to open.
With smaller breakers on a system having a reasonable amount of fault current, this is difficult to do as the instantaneous trip ranges of breakers 200 amps and smaller typically overlap. All breakers will see the same amount of fault current and often more than one breaker will open.

I have never been asked to consider this in any of my PV system designs.

 

[electrofelon]

That only applies where other code sections require selective coordination. It does not apply generally throughout the code.

When is selective coordination NEC required?

 

[ron]

When is selective coordination NEC required?

The NEC requires selective coordination for overcurrent protective devices in systems related to life safety, including emergency systems (NEC 700.28), legally required standby systems (NEC 701.18), and essential electrical systems in healthcare facilities (NEC 517.26). Also multiple elevators fed from the same source.