PV power disconnect type and location

[kingpb]

Does a properly labeled emergency off pushbutton that shunt trips the PV combiner panel mains suffice for disconnecting the PV system for a commercial build?

 

[ggunn]

Does a properly labeled emergency off pushbutton that shunt trips the PV combiner panel mains suffice for disconnecting the PV system for a commercial build?

What code cycle are you in? If you are operating under the 2020 NEC, then no, you have to have rapid shutdown at the PV modules. You have to get the maximum DC voltage down to 80V or less between any two conductors within the array boundary within 30 seconds of RSD initiation.

 

[Carultch]

Does a properly labeled emergency off pushbutton that shunt trips the PV combiner panel mains suffice for disconnecting the PV system for a commercial build?

Who is the intended user of the disconnect, and what is its application? Many utilities require an open blade disconnect, so that they can open the enclosure door and see that the blades are disconnected. Is this for rapid shutdown, or for the utility, or both? It is common that the utility disconnect doubles as the point of rapid shutdown initiation.

If you are operating under the 2020 NEC, then no, you have to have rapid shutdown at the PV modules.

Most module-level rapid shutdown methods with which I'm familiar, can initiate the shutdown as a result of either shutting off the power to the inverter(s) as is the case microinverters or the SolarEdge system, or by shutting off the power to the device that controls the module-level devices (Tigo RSS or Tigo CCA/TAP).

 

[jaggedben]

Does a properly labeled emergency off pushbutton that shunt trips the PV combiner panel mains suffice for disconnecting the PV system for a commercial build?

Suffice for what? There are various different requirements for disconnecting means in the NEC, and then the utility will probably have some on top of those.

 

[ggunn]

Most module-level rapid shutdown methods with which I'm familiar, can initiate the shutdown as a result of either shutting off the power to the inverter(s) as is the case microinverters or the SolarEdge system, or by shutting off the power to the device that controls the module-level devices (Tigo RSS or Tigo CCA/TAP)

From the context of the question I assumed that he was asking about conventional strings connected to a string inverter through a DC combiner with contactors deactuated by a pushbutton switch at ground level, not module level rapid shutdown. That would work for earlier code cycles but not for the 2020 NEC and possibly not for the 2017 NEC, either.

 

[ggunn]

From the context of the question I assumed that he was asking about conventional strings connected to a string inverter through a DC combiner with contactors deactuated by a pushbutton switch at ground level, not module level rapid shutdown. That would work for earlier code cycles but not for the 2020 NEC and possibly not for the 2017 NEC, either.

For rapid shutdown.

 

[jaggedben]

I took his question to be mainly about whether a shut trip breaker may be used as the main disconnecting means for a PV system. As far as I know there's no prohibition on that in the NEC. Of course the main disconnecting means for the PV system may or may not also serve as the rapid shutdown initiation device, depending on the rapid shutdown technology used. In fact, if the main disconnect initiates rapid shutdown but is inside the building, and the pushbutton to initiate the shunt trip is outside the building, then that could be a great way to meet the rapid shutdown requirement economically. However, I hasten to add that the utility might have a requirement for an exterior visible-break disconnect, in which case the shut-trip breaker would probably be pointless. So we'd have to know the utility requirements as well.

It also seems possible that he was asking about other disconnecting requirements for the PV system, not the main disconnect, since the question is quite vague and general.