Only 1 pole of a 2 pole breaker used

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Re: Only 1 pole of a 2 pole breaker used

I agree it is pretty much a blanck check if there is nothing elsewhere that does not specifically permit a particular type of install.There are uses permitted and uses not permitted .But I have never seen a section of uses might be or might not be permitted.Look at the thread about LFNC that is a prime example.
 
Re: Only 1 pole of a 2 pole breaker used

SqD breakers have the 120/240 rating because they can be used in a standard 120/240V system, or in a straight 240V(Grounded B) system.

Bob, I believe that your statement that this code section is 'carefully worded' is correct, but not for the reason you state. When it states that the means shall be provided, I feel it is specifically NOT referring to a single breaker installation (double pole). This wording is telling me that I have to now provide some kind of means to tie together the 2 or 3 circuits present. This doesn't limit it to only
'handle ties', so I believe the wording is not limiting you to just handle ties.

In regards to your switch problem, I read it as 'where the circuit originates', and you read it as 'at the panel'. I see your point.
 
Re: Only 1 pole of a 2 pole breaker used

Originally posted by iwire:
Originally posted by LarryFine:
Actually, that means it is okay to feed line-to-line loads.
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Larry I think you are forgetting the 120 part of 240/120.
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No, I said "it is okay", not required, as in either/or. ;)
 
Re: Only 1 pole of a 2 pole breaker used

Steve,
SqD breakers have the 120/240 rating because they can be used in a standard 120/240V system, or in a straight 240V(Grounded B) system.
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Please take a look at 240.85. A 120/240 volt rated breaker cannot be used on a straight 240 volt system.
Don
 
Re: Only 1 pole of a 2 pole breaker used

Please take a look at 240.85. A 120/240 volt rated breaker cannot be used on a straight 240 volt system.
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Ever start brewing up an argument, just to think it all the way through and end up seeing the light? :D

I was going to argue until it clicked. A two pole breaker feeding a 3? load would experience the 'square root of 3' phenomenon. So a 120/240 1? breaker would experience what would seem to it to be a voltage of 415 volts! That's wild. :p
 
Re: Only 1 pole of a 2 pole breaker used

George,
The "square root of 3" has nothing to do with it.

A 120/240V breaker (i.e. SQD QO215) is only rated for 120V to ground due to it's internal construction. A 240V breaker (i.e. SQD QO215H or QO315) is built for 240V to ground like found in grounded-phase and wild/high-leg systems.

As Don stated, this has been spelled out in the NEC for several code cycles.
 
Re: Only 1 pole of a 2 pole breaker used

Originally posted by jim dungar:
A 120/240V breaker (i.e. SQD QO215) is only rated for 120V to ground due to it's internal construction.
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But Jim, with no reference to ground, what difference does the breaker see?

Picture a pure two-pole load, such as an A/C condenser. In a 1? 120/240 system, I install my two-pole breaker, and do not run a neutral to the unit. The breaker sees 240V. The 120 portion of the rating means nothing in this case.

It's the same for a corner-grounded 240 system Electrons flow the same way. Still a two-wire circuit. The breaker doesn't miss the neutral that it never knew existed.

Now, we swap out the condenser for a 3? unit. We install a three-wire, with two ungrounded conductors landed on the breaker, and a grounded conductor on the B-phase bus. We use the same breaker. Suddenly, the breaker is completing circuit for more than just A-C, C-A like it was before. Now, A-B, B-C, C-A is going on, we have a 3? load. That 1? breaker would not stand up to what it perceives as 415 volts for long.

Nothing changed for the 120 portion of the 120/240 breaker.

Notice 240.85 makes a deal about the breaker being "marked 1?-3?" for this application. Nothing is said that the breaker must be "240 only" or "480 only". :eek:
 
Re: Only 1 pole of a 2 pole breaker used

A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker?s voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker?s voltage rating.
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Okay, I'm frying my brain. :D

I was wrong.

I think.

My mind is burning doughnuts right now. :D
 
Re: Only 1 pole of a 2 pole breaker used

Is the EGC considered part of the circuit in this sense?

If not, then Scenario 2 above is cool with a 120/240 Breaker.

But if the unit faults line to EGC, then the breaker is not rated for this condition.

So I suppose the EGC is considered part of the circuit, then, right?

I'm getting dizzy. I must sleep. :D
 
Re: Only 1 pole of a 2 pole breaker used

You guys are right. The 120/240 Rating identifies this breaker for use in a 120/240V panel (not 3phase like I mentioned before).
This does not mean that it can be used for 1 or 2 120V circuits. This rating shows what the maximum fault (line to ground) voltage potential the breaker is rated for.

I still have yet to see someone show me where you can put 1 or 2 individual 120V circuits on a 2pole breaker.
 
Re: Only 1 pole of a 2 pole breaker used

Ever seen a multi-wire circuit, on a single yoke?

Requires a two pole, OR two singles tied togather, buy a LISTED handle tie! ;)
 
Re: Only 1 pole of a 2 pole breaker used

Ever seen a multi-wire circuit, on a single yoke?
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Multiple circuits on a single yoke are required to have a 'means to simultaneously disconnect...'
That is not telling me to use a 2 pole breaker.
My argument is this code rule doesn't say I can, and that the 2pole breaker itself is not rated for use with individual or 2 separate/idividual 120 V circuits.
 
Re: Only 1 pole of a 2 pole breaker used

Steve,

The only way for you to see it in writing, is to purchase a copy of the UL test procedures or the NEMA AB1 standard.
 
Re: Only 1 pole of a 2 pole breaker used

Originally posted by milwaukeesteve:

My argument is this code rule doesn't say I can, and that the 2pole breaker itself is not rated for use with individual or 2 separate/idividual 120 V circuits.
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Well, then your argument would be wrong. The burden of proof is on you to show me where this is forbidden. You have it totally backwards.
 
Re: Only 1 pole of a 2 pole breaker used

Steve when UL test two pole breakers it test them for a single pole to ground fault and for a single pole to neutral over load. If they didn't they would not need the slash rating as this is what it is there for. The slash rating is the voltage rating that the breaker may safely open a fault at the available fault current level that breaker is rated for. This can be many thousands of amps which could cause the breaker to fail to open. IE contacts weld or fail explosively.

We install two pole breakers all the time intended to serve single pole loads even you do it. Think! every main breaker, feeder breaker that feeds any panel will be feeding single pole loads. and to go one father, what about the UL listed combo device where you have a 120 volt receptacle and a 250 volt receptacle all on the same yoke? 210.4(C)Exception 2 not only allows this device but requires that it be fed from a two pole breaker.

If there was a safety problem using a two pole breaker to feed a single line to neutral load then the same problem would also be with any two pole breaker that feeds a sub panel.
Are we required to use a special two pole breaker to feed these sup panels? I think not.
As long as it has the 120/240 volt slash rating.
Is there a problem with certain ratings on breakers that would be a problem with this? Yes if the voltage rating exceeds the rating of the circuit it will slow too act in the event of an overload.
So don't use a 277/480 volt rated breaker to feed a 120/240 volt sub panel.
But you can use it to feed a multiwire 277 volt lighting circuit with no problems.
You cant use a straight rated breaker to feed a sub panel either.
This is why the NEC is silent on this is because it is done and has to be done in just about every installation. Just about every type of building there is a two pole breaker feeding single pole loads, The Main Breaker!
I have never seen a problem with it?

With that info, what you might have heard was crossed up with straight rated breakers, so I would say you have the requirement partly right. But it depends upon the rating of the breaker.

I hope this will clear this up. ;)

[ October 29, 2005, 01:45 AM: Message edited by: hurk27 ]
 
Re: Only 1 pole of a 2 pole breaker used

Wayne,
Is there a problem with certain ratings on breakers that would be a problem with this? Yes if the voltage rating exceeds the rating of the circuit it will slow too act in the event of an overload.
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Why?
 
Re: Only 1 pole of a 2 pole breaker used

Maybe I'm wrong on this but wouldn't a lower voltage effect the heating element in the thermal part of the breaker causing it to require more current to produce the same amount of heat to cause the breaker to trip? a heating element in series with a load would run cooler at a lower voltage thus requiring more load to produce the same heat.

Oh wait a minute It is the amount of current flowing through the conductor that produces the heat, :eek:

Been working to much overtime. :D :D

I need another vacation :D

Thanks Don for getting me straight :D

[ October 29, 2005, 03:54 PM: Message edited by: hurk27 ]
 
Re: Only 1 pole of a 2 pole breaker used

Yeah, but can you fit square current through a round conductor? :p
 
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