240volt lighting ckt (single pole switch)

[Dsg319]

At the current job I am at we have one outside lighting ckt powered by single phase 240volt. No photocell or relay/contacts involved... just a regular single pole switch rated 120-277.

Is this done very often to just open the one “leg” of the 240 to turn the circuit off?

I know in my head it will function normally (at least I think). But just wondering if this is typically done or is it kind of an oddball.

 

[don_resqcapt19]

The use of a a switch that has a marked "off" position for that application is not permitted by 404.20(B).

 

[drcampbell]

Unless the 240 volts is derived from a 240Y416 circuit and the unswitched leg is grounded. (speaking of oddballs ... )

 

[electrofelon]

Also IIRC HID lights require both poles be switched. Not sure what the reasoning is for that.

 

[Todd0x1]

Also IIRC HID lights require both poles be switched. Not sure what the reasoning is for that.

charge in the capacitor?

 

[Dsg319]

Thanks!

 

[rnatalie]

Haven't seen many 240 lighting circuits, but in commercial buildings, 277 is quite common. My old office building had a 277 panel with nothing but the fluorescent lights in it.

Amusingly, the emergency lights came from the 120/208 panel, so it was quite possible something could take out the lights and not energize the emergency lights. Some idiot had also relabeled the breaker that solely fed the emergency lights backward (I guess to his thinking when you opened the breaker off the lights came on, so it should be it should be so labeled).

 

[hbiss]

Unless the 240 volts is derived from a 240Y416 circuit and the unswitched leg is grounded. (speaking of oddballs ... )

The use of a a switch that has a marked "off" position for that application is not permitted by 404.20(B).

Is this done very often to just open the one “leg” of the 240 to turn the circuit off?

Think about it. Just opening one leg of a 120/240 circuit will still allow there to be 120 volts from the unswitched side to ground or neutral. Sure, it will turn the lights off but will present a safety hazard for anybody who turns the switch off, assumes the power is off and attempts to work on the lights or wiring.

Use a 2 pole single throw switch that will disconnect both sides of the line.

-Hal

 

[Bluegrass Boy]

What about 2P 2T Maintained switch.
See Fig 3 .
There are momentary and maintained switches. I have installed the momentary before, but ours controlled a contactor for multiple light circuits in a warehouse setting.

 

[electrofelon]

Think about it. Just opening one leg of a 120/240 circuit will still allow there to be 120 volts from the unswitched side to ground or neutral. Sure, it will turn the lights off but will present a safety hazard for anybody who turns the switch off, assumes the power is off and attempts to work on the lights or wiring.

Use a 2 pole single throw switch that will disconnect both sides of the line.

-Hal

I don't really care much about trying to brother in law proof things. A real electrician will know what is going on and/or test it and/or not rely on a wall switch as a disconnect.

 

[Dsg319]

Think about it. Just opening one leg of a 120/240 circuit will still allow there to be 120 volts from the unswitched side to ground or neutral. Sure, it will turn the lights off but will present a safety hazard for anybody who turns the switch off, assumes the power is off and attempts to work on the lights or wiring.

Use a 2 pole single throw switch that will disconnect both sides of the line.

-Hal

That’s what I began to think about was the safety of it. It’s not my doing, I’m just a worker bee on the job. I’d say upper management sent the material assuming it was 120volt lighting. Will see what will come of it.

 

[hbiss]

I don't really care much about trying to brother in law proof things. A real electrician will know what is going on and/or test it and/or not rely on a wall switch as a disconnect.

Same reason they want a 2 pole breaker on a MWBC.

There are some instances like electric heat thermostats where breaking only one side is common. But I would not expect to see it with any kind of lighting circuit.

What about 2P 2T Maintained switch.
See Fig 3 .

That would work but it is a three position center off switch.

-Hal

 

[electrofelon]

Same reason they want a 2 pole breaker on a MWBC.


-Hal

Yup, and that was one of the worst dumbest changes in a while.

 

[LarryFine]

There are some instances like electric heat thermostats where breaking only one side is common. But I would not expect to see it with any kind of lighting circuit.

If I'm not mistaken, temperature control is permitted to break only one line, but a labeled "off" position must open both.

 

[drcampbell]

I don't really care much about trying to brother-in-law-proof things. A real electrician will know what is going on and/or test it and/or not rely on a wall switch as a disconnect.

A person could get shocked removing a light bulb if the unswitched hot leg is connected to the shell. Surely you don't expect people to bring in a real electrician to replace every burned-out light bulb?

And if the unswitched hot leg is connected to the tip, (presumably, to prevent his hazard) a person could get a shock removing the remaining core of a broken light bulb.

 

[augie47]

If I'm not mistaken, temperature control is permitted to break only one line, but a labeled "off" position must open both.

also allowed for motor "controllers" but not for motor "disconnects" but in all likelihood don has the answer in Post #2

 

[Cannotlogin]

The use of a a switch that has a marked "off" position for that application is not permitted by 404.20(B).

Just change it to a 3 way switch

 

[augie47]

 

[Dsg319]

also allowed for motor "controllers" but not for motor "disconnects" but in all likelihood don has the answer in Post #2

The use of a a switch that has a marked "off" position for that application is not permitted by 404.20(B).

thanks

 

[mbrooke]

thanks

The use of a a switch that has a marked "off" position for that application is not permitted by 404.20(B).

Doesn't this just apply to the switch itself and not the branch wiring?