OT: any electricians?

Money Pit

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here is the situation; have an older 240 volt sub panel in an outbuilding that uses circuit breakers. i have all of the single pole circuit breakers filled but want to add a few more circuits for outlets. what i do have are some two pole breakers. wondering if it would be ok to use them but only use one pole? thinking if its a 15 a breaker it should trip at 15 amps regarless right? i would leave the other pole empty so if it did mtrip there wouldn't be nay guessing about which circuit it is. space in the panel isn't an issue. and i do know i want to keep the loading balanced between the 120 volt legs.

just trying to save some $$$ but not at the expense of safety.
 
How many more circuits will you need and what brand is the panel?
An ITE type breaker is only about $6, Square D a little more depending on whether you have the homeline or QO.
I not a safety nanny by any means but I would just go buy the right breakers.
I do a lot of wiring for my remodeling work
and always figure for the amount of dough I'm saving my customers by not having to hire a real electrician they can darn well afford to go first class on electrical parts, equipment and supplies.
I've applied the same measure when I rewired my own houses.
 
Almost every breaker box manufacturer offer "duplex breakers". Actually it makes 2 circuits from one breaker slot.

I use a lotta Square D duplex breakers to "free-up" a full breaker box.

HTH John,Pa.
 
square d panel. not a homeline. this uses the breakers with a metal clip that attaches to a rail (not a conductor) and then the metal clip that attaches to the power supply strip in the middle. if i remeber right the homeline only has the metal lug for the electric connection.

figuring on 4 - 5 more circuits.

agree if i were doing this for somone else wouldn't be asking hte qusstion. of course then it would be theri cost not mine.

aint looking for pretty. on the other hand safety is a no compromise area. if what i'm describing has safety issues it wont be done.

if i have a chance to save $25 i'll do it. not many folks in my circle that would walk away from that savings.
 
Ok, if they are what's called a tandem breaker (I always called them splitters) then I would do it.
I thought you meant using each side of a 240V double breaker for a seperate 120V circuit.
I would not do that.

047569008962lg.jpg
 
no; not a tandem that fits two breakers into one opening. talking about a 240 v breaker that gets one 120 v source from each incoming leg. the kind that takes up two spaces in the panel.

based on that and UD response above doesn't seem like a good idea. looks like time to let some moths out of the wallet. thanks for the feedback.
 
I believe it would take 30 amps at 120 volts to trip one side of a 15 amp 240 volt breaker; or it may not even "trip" since there would be no internal pressure on the open side of the breaker. I don't believe it is a good idea.
 
"I believe it would take 30 amps at 120 volts to trip one side of a 15 amp 240 volt breaker;"

WHY would you "believe" that?

A double 30 Amp breaker (as an example) for 240 Volts is simply two 30 Amp breakers "stacked" together, with a common-trip linkage between them.
The "common trip" is required so a "trip" results in the power being removed from both "legs" of the circuit for safety.

From a standpoint of function, there"s no reason why what the O.P. proposes won"t work (and be safe), and I've done it a few times.

If one side alone is used, and loaded to 30 Amps it will trip, kicking the other, unused half out with it.

Of course, if the job is subject to inspection, there MAY be a technicality in the code requiring an inspector to "flag" it.
 
Not really up to code but it can be done and yes it works just fine. BTDT many times over the years. Shoot my shop has a 3 phase breaker box in it but I have only single phase power
 
I've never taken apart a breaker, but I thought the number of electrons passing/flowing (amping at 30) via 120 volts of pressure would be the same as 15 at 240; thus whatever electromagnetic force and/or heat build-up that tripped the breaker would recognize the limit and shut it down. If it's just two breakers physically, but not electrically connected, then so..., I yield to your higher intellect.
 
The breakers are mechanically, but NOT electrically connected, and when either (or both) "see" 30 Amps (in this example), they trip.

NO adding or combining of Amps.
 
(quoted from post at 11:38:31 08/12/14) I've never taken apart a breaker, but I thought the number of electrons passing/flowing (amping at 30) via 120 volts of pressure would be the same as 15 at 240; thus whatever electromagnetic force and/or heat build-up that tripped the breaker would recognize the limit and shut it down. If it's just two breakers physically, but not electrically connected, then so..., I yield to your higher intellect.

Amps is amps. If you think about it you will realize the two poles are simply two single pole breakers in a common housing. They are in series on the same circuit and have a mechanical tie between them. The mechanical tie insures that when one pole interrupts one side of the circuit the other "hot" side gets disconnected as well.

TOH

TwoPoleBreaker.jpg
 
in series on the same circuit? don't think so. 15a 2 pole breaker would supply the two 120v legs to the circuit. if each leg has a 15a load wouldn't putting them in series up the amperage for the circuit to 30a? think the breakers are in paralell electrically - which would allow independant 15 a protection to each leg - and physically tied to one trip lever.

i'll check that with the ohmmeter tonight.
 
(quoted from post at 14:26:25 08/12/14) in series on the same circuit? don't think so. 15a 2 pole breaker would supply the two 120v legs to the circuit. if each leg has a 15a load wouldn't putting them in series up the amperage for the circuit to 30a? think the breakers are in paralell electrically - which would allow independant 15 a protection to each leg - and physically tied to one trip lever.

i'll check that with the ohmmeter tonight.

No. They are 15A (or whatever) interrupters in series on a 240V circuit fed from two 120V (with respect to neutral) legs that are 180* out of phase with each other. See my sketch.

The panel design gauratnees they are connected to separate legs (buss bars) of the 240V service drop. Wired in that fashion ALL of the current flowing through that 240V circuit passes serially through BOTH interrupters.

If [u:6f28d0dbcd]either[/u:6f28d0dbcd] of them sees more than 15A (or whatever) flow in either direction they interrupt the circuit at their respective point of connection. Because they are internally tied together with a mechanical trip bar they also cause the other breaker to interrupt and are designated as "multi-pole common trip" type breakers. No different than two single pole switches in series - both have to be closed for current to flow from end to end in the circuit. But because BOTH ends of the circuit are hot the common trip guarantees that if you open one the other will also open de-energizing the entire circuit.

Wanna bet :D

TOH

PS> I did a little checking over on the NEC discussion forum and the strong consensus is that using a common trip two pole breaker (one or two handle) to feed two independent 120V branch circuits is just fine as far as the National code goes. It is in fact a "standard but less than common practice" Often used with a shared neutral to squeeze a few pennies extra out of certain jobs. When used in this fashion labeling the usage inside the box is "strongly suggested". Using two one pole breakers with handle ties to protect a 240V circuit is not permitted because handle ties don't guarantee a common trip. :!:

PPS> If you really want to know if it's OK in your local jurisdiction check with your local inspector
 
Back years ago before the Arc Fault circuit breakers there was a code that all 3 wire home runs had to be connected to a two pole breaker.
So yes you could use a two pole 20 amp breaker for two 120 volt 20 amp receptacle circuits.
The problem arises when you try to instal a GFI receptacle or Arc Fault breaker you cannot share a neutral for these types of circuits.
Go buy the proper breakers and call it done and done right!
The bad thing about electrical work is you can wire receptacles with reversed polarity ( hot and neutral are reversed) and it will still work. But it creates a potential problem down the road.
That can kill someone.
A couple of circuit breakers are cheap compared to a hospital visit.
Make sure you ground everything you wire up it is the most important conductor when the circuit faults.
Bart the Master Electrician
 
I picked this one to reply to for no particular reason, just to get my two cents worth in...

I have done this in this way: I took a dual breaker that has the two handles connected with a little round bar going between them and removed the bar, pushing it out one side. After doing that the only connection between them were the rivets holding them together. I then had two single circuit breakers that, when installed in the box, were on two different legs, both being 120 volts. Each breaker in this case was a 30 amp.

I have also used the kind that takes the one circuit and splits it into two, but never went more than 15 amps with these. One of these is pictured in one of the posts. Since they are on the same leg they cannot be used to make a single 240 volt circuit. Many mobile homes have these. Nothing is really wrong with using these but one has to remember that the original circuit is being split and not to load it up too much. Add up all the breakers and don't exceed the overall load rating of the box/main breaker.

Disclaimer: Not an electrician, learned what I know by watching others and making my own mistakes.
 
(quoted from post at 23:39:32 08/13/14) I picked this one to reply to for no particular reason, just to get my two cents worth in...

I have done this in this way: I took a dual breaker that has the two handles connected with a little round bar going between them and removed the bar, pushing it out one side. After doing that the only connection between them were the rivets holding them together. I then had two single circuit breakers that, when installed in the box, were on two different legs, both being 120 volts. Each breaker in this case was a 30 amp.

Disclaimer: Not an electrician, learned what I know by watching others and making my own mistakes.

I think this may be another of those learning experiences. According to Schneider Electric (Square D):

[i:de90e96f10][b:de90e96f10]Independent trip[/b:de90e96f10] – Multi-pole circuit breakers are constructed with either a common trip, where all poles are mechanically tripped when one of the poles trips, or an independent trip construction where only the pole that is involved with the overcurrent condition trips. If a 2-pole circuit breaker does not have an [b:de90e96f10][color=red:de90e96f10]internal[/color:de90e96f10] [/b:de90e96f10] common trip feature, then it must be marked “Independent Trip” or “No Common Trip.” NEC 240.20(B) is the foundational requirement for a common trip function in a circuit breaker; however, it also goes on to explain where independent trip is permitted.[/i:de90e96f10]

Note the word "internal" which I highlighted in red. Unless that breaker is marked "Independent Trip/No Common Trip" removing the external handle ties does not disable the internal common trip mechanism and when one pole interrupts it will still pull the other one with it. The handle ties are just a convenience for manually operating both of the handles together. And if it is labeled as an independent trip breaker then by code it could not have been used on a 240V circuit (NEC 240.20 (B)).

TOH
 

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