Photocells question.

[Strife]

I just realized something the other day.
A 240V photocell has a black for one hot leg, a red for the switch leg and a white for the other hot leg. Been wiring photocells for a while now, but I was just thinking the other day: one leg will stay on all the times and backfeed all the way back. I could swear for some reason the code doesn't allow to have only one leg switch, but rather both legs had to be switched in a 240V single phase. (not talking about 120V or 277 where there's a neutral who doesn't need to be switched)

 

[hurk27]

I just realized something the other day.
A 240V photocell has a black for one hot leg, a red for the switch leg and a white for the other hot leg. Been wiring photocells for a while now, but I was just thinking the other day: one leg will stay on all the times and backfeed all the way back. I could swear for some reason the code doesn't allow to have only one leg switch, but rather both legs had to be switched in a 240V single phase. (not talking about 120V or 277 where there's a neutral who doesn't need to be switched)

A photo cell is a control, and the NEC treats controls and disconnects/OCPD's differently.

Disconnects and OCPD's are required to disconnect all ungrounded conductors, controls are not.

 

[jeremysterling]

I just realized something the other day.
A 240V photocell has a black for one hot leg, a red for the switch leg and a white for the other hot leg. Been wiring photocells for a while now, but I was just thinking the other day: one leg will stay on all the times and backfeed all the way back. I could swear for some reason the code doesn't allow to have only one leg switch, but rather both legs had to be switched in a 240V single phase. (not talking about 120V or 277 where there's a neutral who doesn't need to be switched)

Both legs shall be disconnected at the light circuit's required disconnect.

The control of the photocell only turns the light on and off, and does not feature safety disconnecting means. This is legal.

This is similar to some air-conditioning contactors that have only a single pole, hence, they have 240V across them when open (like your photocell.)