I'm reviewing a drawing package where the supplier is switching the 120v control power grounded conductor. I'm trying to find a NFPA reference as to why I don't want them to do that. I feel like I found it before in the NFPA 79, but can't located the paragraph...

Thanks.

I don't believe there is an NFPA 79 prohibition against neutral switching.

Is it switching only on the neutral? Or is it switching both the hot and neutral?

There is nothing at all wrong with switching both hot and neutral, in fact its common. Motor overloads are usually mounted on the neutral side of a coil. There might be a reason for switching the neutral, however convention is to switch on the hot side. I couldn't say whether there was a valid reason to switch the neutral without knowing more about the circuit and its function.

One thing you should not do when switching grounded current carrying conductors is use a white wire between actuator and swi tch, because when the switch is open its not a grounded couductor - only the unbroken wire is to be identified as neutral.

Any neutral switched system must be designed so that if a short circuit to ground occurs between the actuator and the switch unintended operaion won't occur - a short will operate the actuator and won't blow a fuse/breaker.

I found the following in NFPA 70 Section 404.2
(B) Grounded Conductors. Switches or circuit breakers shall not disconnect the grounded conductor of a circuit.

Exception: A switch or circuit breaker shall be permitted to disconnect a grounded circuit conductor where all circuit conductors are disconnected simultaneously, or where the device is arranged so that the grounded conductor cannot be disconnected until all the ungrounded conductors of the circuit have been disconnected.


Is that what you were looking for?