# One Single Pole Breaker turns off 240V



## swimmer (Mar 19, 2011)

I have a new restaurant customer. The building is early 1950s vintage. I was able to switch off 240V to the food warmer by switching off one single pole breaker. What does this mean?
I was tempted to investigate but decided against opening the ancient panel until necessary


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## BBQ (Nov 16, 2010)

It could mean you still have a hot leg at the warmer.


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## HARRY304E (Sep 15, 2010)

swimmer said:


> I have a new restaurant customer. The building is early 1950s vintage. I was able to switch off 240V to the food warmer by switching off one single pole breaker. What does this mean?
> I was tempted to investigate but decided against opening the ancient panel until necessary


Like BBQ said I'm willing to bet that the electrician did not have a two pole breaker on hand when he hooked up the the 240 volt food warmer,So he just used two single pole breakers ,The warmer will not work with just one hot leg.


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## swimmer (Mar 19, 2011)

I know that both wires were dead after I turned off the breaker. I'm pretty sure one was a neutral and one carried 240V.


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## Hippie (May 12, 2011)

swimmer said:


> I know that both wires were dead after I turned off the breaker. I'm pretty sure one was a neutral and one carried 240V.


Eh? Either you have a 120 circuit or that other wire isn't a neutral


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## Awg-Dawg (Jan 23, 2007)

Is the panel 3 phase?


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## BuzzKill (Oct 27, 2008)

208v?


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## BBQ (Nov 16, 2010)

It's starting to sound like a high-leg service but I don't have much experience with them. (OK almost none at all )


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## drspec (Sep 29, 2012)

swimmer said:


> I know that both wires were dead after I turned off the breaker. I'm pretty sure one was a neutral and one carried 240V.


uh.....?


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## Hippie (May 12, 2011)

BBQ said:


> It's starting to sound like a high-leg service but I don't have much experience with them. (OK almost none at all )


That's possible, depending on poco supply you might read 220-ground on the high leg but if so that would be a unusual and hack install


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## BBQ (Nov 16, 2010)

If he has a delta hig leg service he would have 208 to neutral on one phase.


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## BBQ (Nov 16, 2010)

Hippie said:


> that would be a unusual and hack install


Yep.


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## swimmer (Mar 19, 2011)

HARRY304E said:


> Like BBQ said I'm willing to bet that the electrician did not have a two pole breaker on hand when he hooked up the the 240 volt food warmer,So he just used two single pole breakers ,The warmer will not work with just one hot leg.



There were 2 wires going to the food warmer with 240V between them. After I turned off the breaker they were both 0V to chassis. I wanted to make sure everything was dead before I started disassembling stuff. Had there been any live wires after I turned off the breaker then I would have been zapped or seen sparks from live wires hitting the chassis.


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## BuzzKill (Oct 27, 2008)

I bet that's it.


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## Big John (May 23, 2010)

What'd you take your voltage measurement with?


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## swimmer (Mar 19, 2011)

BBQ said:


> If he has a delta hig leg service he would have 208 to neutral on one phase.


I don't recall any 3-pole breakers in the panel but there were doubles. It looks like you can get 120V and 240V from N, B, C on this transformer. As this restaurant seems to have several pieces of 240V equipment and few 120V outlets, this may be what's happening. I don't know if there is any 208V equipment. Do you ever see where N,B,C (but not A) are run from a transformer to a panel so that single pole breakers are either 240V or 120V?


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## Big John (May 23, 2010)

Even with a high leg, it wouldn't be possible to get 240 on a single conductor, that's why I'm wondering what you used to see that voltage.


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## BuzzKill (Oct 27, 2008)

how about mixed hots in a jbox somewhere? back feeding N?


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## Deep Cover (Dec 8, 2012)

What if you turned off a control circuit for a contactor? I've seen contactors used in lieu of shunt trip breakers.


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## EBFD6 (Aug 17, 2008)

Corner grounded delta maybe?

One Phase is grounded so you would read 0v to ground


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## swimmer (Mar 19, 2011)

Deep Cover said:


> What if you turned off a control circuit for a contactor? I've seen contactors used in lieu of shunt trip breakers.



Good point. 2 other restaurants I've worked in had contactors upstream of deep fryers.


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## HARRY304E (Sep 15, 2010)

swimmer said:


> There were 2 wires going to the food warmer with 240V between them. After I turned off the breaker they were both 0V to chassis. I wanted to make sure everything was dead before I started disassembling stuff. Had there been any live wires after I turned off the breaker then I would have been zapped or seen sparks from live wires hitting the chassis.


It is possible that , the single pole breaker is feeding The coil of a two pole contactor and/or a time clock fed from another panel, it is posible that they want that to shut off after a certain time.. ,,


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## swimmer (Mar 19, 2011)

Big John said:


> What'd you take your voltage measurement with?


A $30 DMM that I carry in my tool bucket.


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## Big John (May 23, 2010)

EBFD6 said:


> Corner grounded delta maybe?
> 
> One Phase is grounded so you would read 0v to ground


 Yeah, but where would he be getting his 120V loads from...?


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## swimmer (Mar 19, 2011)

Awg-Dawg said:


> Is the panel 3 phase?


There were no equip tags and it was old and nasty so I didn't remove the cover or dead front because it wasn't necessary to complete my job. However, I do not recall any 3-pole breakers. I only recall single and double.


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## Hippie (May 12, 2011)

swimmer said:


> There were no equip tags and it was old and nasty so I didn't remove the cover or dead front because it wasn't necessary to complete my job. However, I do not recall any 3-pole breakers. I only recall single and double.


What size breaker did you turn off?


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## Wireless (Jan 22, 2007)

What were they to ground? Is it possible there is a contractor somewhere?


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## Wireless (Jan 22, 2007)

Big John said:


> Even with a high leg, it wouldn't be possible to get 240 on a single conductor, that's why I'm wondering what you used to see that voltage.


High leg to ground is 240


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## Hippie (May 12, 2011)

Hippie said:


> What size breaker did you turn off?


How many amps I mean.. if only a 20 or 15 it would support the contactor theory


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## Awg-Dawg (Jan 23, 2007)

Wireless said:


> High leg to ground is 240


 

Look at BBQs drawing.


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## swimmer (Mar 19, 2011)

Hippie said:


> How many amps I mean.. if only a 20 or 15 it would support the contactor theory



Good point. I think it was a 20A.


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## Southeast Power (Jan 18, 2009)

swimmer said:


> Good point. I think it was a 20A.


Contactor.
Maybe interlocked with the hood fan too


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## Awg-Dawg (Jan 23, 2007)

Ive never had to drop a food warmer out.


Also, most if not all, are small heaters.


Probably 2-3000 watt. (from memory)


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## ponyboy (Nov 18, 2012)

jrannis said:


> Contactor.
> Maybe interlocked with the hood fan too


Bingo


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## wendon (Sep 27, 2010)

ponyboy said:


> Bingo


Just curious, is it possible he shut off the breaker for the fire alarm/fire suppression system? That would shut off the power if it's powered by a contactor.


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## ponyboy (Nov 18, 2012)

wendon said:


> Just curious, is it possible he shut off the breaker for the fire alarm/fire suppression system? That would shut off the power if it's powered by a contactor.


Depends. Possible


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## EBFD6 (Aug 17, 2008)

Big John said:


> Yeah, but where would he be getting his 120V loads from...?


good point, there wouldn't be any single pole breakers with a corner grounded system. 

It's got to be either a high leg or operator error with the meter.


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## Shockdoc (Mar 4, 2010)

He single phased it off the high leg. The breaker is not rated for that . I've run 240 volt room ACs like that when I had to balance out a hi leg motel service.


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## Jbird66 (Oct 26, 2010)

Could there have been a second service in the building that provided the single phase loads and this actually been a 240 volt delta?


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## ponyboy (Nov 18, 2012)

I bet if you would've opened the panel and food warmer the answer would've revealed itself. I've opened panels before and found contactors and relays IN the panel. Usually the most simple explanation is the correct one. There's a ton of easy and varying ways to produce your scenario


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## Big John (May 23, 2010)

Why would they put the warmer on a contactor? Timer or something?


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## 480sparky (Sep 20, 2007)

If the SP breaker that's been turned off is a shunt trip, then it most likely controls a contactor.


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## wendon (Sep 27, 2010)

Big John said:


> Why would they put the warmer on a contactor? Timer or something?


I've got a local restaurant that has it's electric griddle on a contactor. The contactor is energized all the time and is connected with the fire suppression system which also shuts off the gas supply.


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## GEORGE D (Apr 2, 2009)

Is there a chance that this piece of equipment isnt grounded which is why your not getting voltage to ground? Maybe lost its equipment grounding conductor and one of the 2 legs still has voltage but meter not picking it up. That's when a hot-stick is handy.


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## ponyboy (Nov 18, 2012)

At least let us know what you find because this is a good one


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## polyphase (Nov 1, 2011)

I haven't had to work on many delta services but if I recall the last one I worked on my readings were 240v from phase to phase and 120v from A to N and C to N and 277v from B to N. how do u get 208v?


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## crazyboy (Nov 8, 2008)

Big John said:


> Why would they put the warmer on a contactor? Timer or something?


Everything under the hood in a commercial kitchen has to turn off when the ansul system goes off. Typically done with shunt trips or contactors.


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## ponyboy (Nov 18, 2012)

crazyboy said:


> Everything under the hood in a commercial kitchen has to turn off when the ansul system goes off. Typically done with shunt trips or contactors.


Not the exhaust


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## crazyboy (Nov 8, 2008)

ponyboy said:


> Not the exhaust


True, some places want it to turn on the exhaust too.


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## BBQ (Nov 16, 2010)

crazyboy said:


> Everything under the hood in a commercial kitchen has to turn off when the ansul system goes off. Typically done with shunt trips or contactors.


Not everything, only sources that fuel a fire.

For example the electricity can stay on to say a gas fired fryer becuse the gas will be shut down.


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## Big John (May 23, 2010)

I guess I gotta go back to square 1 here:

When someone says "warming table" I'm imagining something like a steam table or a serving station the public has access to. Nothing that would be under a hood or associated with an Ansul system. No?


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## Deep Cover (Dec 8, 2012)

The way kitchens are run, you never know what is plugged in under there. My question would be that if you were sent to troubleshoot a piece of equipment, and that piece of equipment had unexpected voltage readings, why would you not investigate?


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## swimmer (Mar 19, 2011)

GEORGE D said:


> Is there a chance that this piece of equipment isnt grounded which is why your not getting voltage to ground? Maybe lost its equipment grounding conductor and one of the 2 legs still has voltage but meter not picking it up. That's when a hot-stick is handy.



I would have been zapped and I would have seen sparks while disassembling the equipment.


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## swimmer (Mar 19, 2011)

Deep Cover said:


> The way kitchens are run, you never know what is plugged in under there. My question would be that if you were sent to troubleshoot a piece of equipment, and that piece of equipment had unexpected voltage readings, why would you not investigate?



Infinite switch input spec is 240V. It was getting 240V. I determined that the problem was this switch and replaced it and was done.

Opening the ancient electrical panel, behind the swinging door may have helped to answer the question but that had the potential to cause problems.


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