120vac grounded neutral two pole breaker

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cukele

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Are there any Nec requirements or safety concerns to support not using a two pole breaker on a 120vac grounded neutral system?
 
nmdesign said:
Are there any Nec requirements or safety concerns to support not using a two pole breaker on a 120vac grounded neutral system?
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No. UL test breakers for every possible loading configuration, 2-pole breakers are tested for 1-pole loads.
 
Is a 2pole on 120vac safe?

Is a 2pole on 120vac safe?

I have never seen the grounded leg of a 120vac circuit protected by a circuit breaker before now. I am not sold on the idea of a 2 pole breaker on a 120vac, but am struggling to come up with an argument for the client that is requesting the 2 pole breaker.
If a fault occured and the 120vac neutral leg opened could you possible have a charged leg awaiting a source to ground. What problems could occur if the neutral leg opened on a fault or overload?
 
nmdesign said:
I have never seen the grounded leg of a 120vac circuit protected by a circuit breaker before now. I am not sold on the idea of a 2 pole breaker on a 120vac, but am struggling to come up with an argument for the client that is requesting the 2 pole breaker.
If a fault occured and the 120vac neutral leg opened could you possible have a charged leg awaiting a source to ground. What problems could occur if the neutral leg opened on a fault or overload?
Click to expand...
Use a common-trip breaker. If the customer wants to waste money, that's their problem.
 
What is the second pole being used for -- as a neutral/grounded conductor over current device, or is it just unused?
 
nmdesign said:
I have never seen the grounded leg of a 120vac circuit protected by a circuit breaker before now. I am not sold on the idea of a 2 pole breaker on a 120vac, but am struggling to come up with an argument for the client that is requesting the 2 pole breaker.
If a fault occured and the 120vac neutral leg opened could you possible have a charged leg awaiting a source to ground. What problems could occur if the neutral leg opened on a fault or overload?
Click to expand...

There is nothing wrong with that concept (on can argue its safer), as long as both hot and neutral are opened at the same time on a fault or manually (ie internal common trip with handle tie breaker or a double pole switch are ok). In Europe and many other parts of the world opening both simultaneously or the ability to open the neutral after the hot is opened is very common and often considered a significant safety advancement since a neutral is often considered an "active conductor" outside the US. Though its at ground potential, if anywhere it begins to fail such as a lug or splice it can easily rise to 120 or over in Europe to 240 when measured to ground. By disconnecting both hot and neutral back feed from a failed neutral upstream can be eliminated, a concern to say someone who may be servicing a branch circuit or hard wired appliance. I know one real case where a guy got nailed working on a 120volt lighting circuit that had the breaker shut off and was originating from a 120/240volt sub-panel. Only thing that made the voltage go away was jumping the neutral to ground. Turns out the neutral screw was loose in the main panel; the other 120volt loads were back feeding it.

(Also in place when a main breaker has RCD/GFCI protection in it and a branch circuit has developed a neutral to ground fault; but that in particular doesnt apply in the US)


What application is this being used for BTW?
 
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