Quick question 120/240 stuff

[Designer69]

hey guys, quick little situation came up at work today... the guys on the field want some 120 power only for some control I&C stuff power.

so what they want to do is take 120 off of panel "A" from one of the breakers only and run that to panel "B" and jump the bus bars so that one pole is powering both busses.

they were told to use good engineering practice and not do that but for my own education I was wondering what would happen.


Thanks

 

[don_resqcapt19]

I don't see any issues with that as long as the panel is marked 120 volts only and you do not land two conductors in a line side termination that is only rated for a single conductor.

 

[Designer69]

so what would happen if you took a two pole breaker and connected it to both busses to try to get 240?

I suppose the answer is you wouldn't but how come? is it because theyre both at the same potential and the phase angles wouldn't allow for 240?

I can't understand that part... thanks

 

[mull982]

so what would happen if you took a two pole breaker and connected it to both busses to try to get 240?

I suppose the answer is you wouldn't but how come? is it because theyre both at the same potential and the phase angles wouldn't allow for 240?

I can't understand that part... thanks

Yes this is indeed because both poles would be at the same potential. In order for current to flow there needs to be a difference of potential and hooking a device up to the same potential on both poles would not allow current to flow.

 

[Designer69]

oh ok... makes sense so then you would get nothing at all out of that 2 pole bkr huh?

 

[charlie b]

oh ok... makes sense so then you would get nothing at all out of that 2 pole bkr huh?

Quite true.

Why would they not want to bring both phases from Panel A to Panel B, buy using a two-pole breaker on Panel A as the source?

 

[mull982]

oh ok... makes sense so then you would get nothing at all out of that 2 pole bkr huh?

That is correct all you would have is the same voltage on both poles. Essentially what you have done is created an expensive distribution terminal strip.

 

[qcroanoke]

oh ok... makes sense so then you would get nothing at all out of that 2 pole bkr huh?

Right.
You could only get 120 volts to neutral or ground but nothing between
the two poles of the breaker because they are on the same phase.

Mull beat me to that! LOL

 

[eprice]

Another point to remember: the guys in the field should not attempt to run a multiwire branch circuit from this 120 only panel. Doing so would result in a possible overload of the neutral. Since both "phases" in this panel are actually the same phase, current on the neutral would add rather than subtract as happens in a true multiwire branch circuit.

 

[LarryFine]

so what would happen if you took a two pole breaker and connected it to both busses to try to get 240?

To add: It would be the exact same thing as placing two 1p breakers on the same phase in a 120/240v panel.

Another point to remember: the guys in the field should not attempt to run a multiwire branch circuit from this 120 only panel.

Absolutely correct. Every circuit must be a 2-wire circuit.