Emphase M215 Micro 240v grid-tied switched neutral

[Gategator37]

I was currently working on a project where the PV installer used a 3 pole 60 amp safety switch to disconnect the AC before it was backfed onto the MDP Buss with a 60 amp 2 pole breaker. My question is: The installer switched the neutral (ac side) along with the (2) ungrounded circuits within this 60 amp disconnect... Does this meet code? I can't figure out why the neutral would be switched... Any help would be greatly appreciated.

 

[jaggedben]

Can't find a specific code reference right now but I'm pretty sure this is a code violation. There is certainly no reason to do it.

 

[don_resqcapt19]

I don't know why the grounded conductor was switched, but it is not a code violation. 404.2(B) Exception

 

[Gategator37]

Thanks for the information. Since they are simul. disconnecting all ungrounded and grounded conductors at the same safety switch the exemption allows it.

Thanks again.

 

[DanS26]

690.13 All Conductors. Means shall be provided to disconnect all current-carrying conductors of a photovoltaic power source from all other conductors in a building or other structure. Where a circuit grounding conductor is not designed to be automatically interrupted as part of a ground fault protection system required by 690.5, a switch or circuit breaker used as a disconnecting means shall not have a pole in the grounded conductor.

"shall not have a pole in the grounded conductor" means do not switch the neutral.

 

[DanS26]

In the US and Canada it is required that a dc to ac grid tied inverter does not bond the neutral and ground in the inverter even though the inverter is considered an electrical source. Thus a grid tied inverter such as Enphase micro inverters are not classified as "separately derived systems" The reason for not bonding the neutral and ground in the inverter is that with a bonding there it would allow two paths for current to travel to the first service disconnect. Dual return paths is a code violation for various reasons not the least being safety.

Since the Enphase inverters are NOT "separately derived systems" then in all cases without exception the neutral is NOT to be switched. Here's why.......in a situation where you open the ac switch (thus opening the neutral) all the Enphase inverters are now isolated electrically. A fault between hot and neutral will go unnoticed. Thus the risk of electric shock is raised. That is the reason that the NEC does not want the neutral to be switched. It is a safety issue and a violation of the code.

Grounds do nothing at all to mitigate the risk of personal electrical shock from a fault between hot and neutral. With the neutral open, the over current devices will not trip and worse they may not trip when anyone is in the current path.

 

[jaggedben]

Since the Enphase inverters are NOT "separately derived systems" then in all cases without exception the neutral is NOT to be switched. Here's why.......in a situation where you open the ac switch (thus opening the neutral) all the Enphase inverters are now isolated electrically. A fault between hot and neutral will go unnoticed. Thus the risk of electric shock is raised. That is the reason that the NEC does not want the neutral to be switched. It is a safety issue and a violation of the code.

I agree that neutrals should not be switched, but your logic is a bit lacking. If an ungrounded conductor is opened at a switch, then any fault beyond that switch will go 'unnoticed' by the overcurrent protection whether or not the grounded conductor is also opened.

 

[DanS26]

I agree that neutrals should not be switched, but your logic is a bit lacking. If an ungrounded conductor is opened at a switch, then any fault beyond that switch will go 'unnoticed' by the overcurrent protection whether or not the grounded conductor is also opened.

Agree. The OCPD's are also isolated. Thanks for pointing that out. Dan