240volt lighting ckt (single pole switch)

Status
Not open for further replies.
Dsg319

Dsg319

Senior Member
Location
West Virginia
Occupation
Wv Master “lectrician”
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.
 
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).
 
drcampbell said:
Unless the 240 volts is derived from a 240Y416 circuit and the unswitched leg is grounded. (speaking of oddballs ... )
Click to expand...

don_resqcapt19 said:
The use of a a switch that has a marked "off" position for that application is not permitted by 404.20(B).
Click to expand...

Dsg319 said:
Is this done very often to just open the one “leg” of the 240 to turn the circuit off?
Click to expand...

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
 
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.
866B9E9B-ED99-4773-B45F-2005014C668B.jpeg
 
hbiss said:
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
Click to expand...
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.
 
hbiss said:
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
Click to expand...
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.
 
electrofelon said:
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.
Click to expand...

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.

Bluegrass Boy said:
What about 2P 2T Maintained switch.
See Fig 3 .
Click to expand...

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

-Hal
 
hbiss said:
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.
Click to expand...
If I'm not mistaken, temperature control is permitted to break only one line, but a labeled "off" position must open both.
 
electrofelon said:
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.
Click to expand...
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.
 
LarryFine said:
If I'm not mistaken, temperature control is permitted to break only one line, but a labeled "off" position must open both.
Click to expand...
also allowed for motor "controllers" but not for motor "disconnects" but in all likelihood don has the answer in Post #2
 
Last edited:
Status
Not open for further replies.
Top