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rws
12-21-2011, 05:38 PM
I have a Cutler Hammer panel. There are quite a few slim half size breakers in it, been there since I've owned the place. I assume they are legit, Home Depot sells them.

Looking at it, depending on how you stack the breakers, you could snap in a double pole breaker, where it would connect to the same buss, instead of connecting to both.

Assuming the loading in the panel isn't too unbalanced, is this OK?

daveo
12-21-2011, 06:01 PM
I think they are called piggy backs. A electrician told me once they are not for use in some areas. I didnt ask him to elaborate...

flylo
12-21-2011, 06:07 PM
Just ran into this. I put 2 thin 240V in the box for elect heat. They were marked 120/240 with holes drilled in the handles to put a bolt or wire to make them dbl pole. Heaters woundn't work. checked at the heater & had 120 on both legs. Then it dawned on me it's the same 120 because it only snaps into 1 buss. I traded the whites on the breakers so eack heater drew off both busses & every thing worked fine. I'm going to replace them but I can't see how the sell them for 240V?

becksmachine
12-21-2011, 06:32 PM
Just ran into this. I put 2 thin 240V in the box for elect heat. They were marked 120/240 with holes drilled in the handles to put a bolt or wire to make them dbl pole. Heaters woundn't work. checked at the heater & had 120 on both legs. Then it dawned on me it's the same 120 because it only snaps into 1 buss. I traded the whites on the breakers so eack heater drew off both busses & every thing worked fine. I'm going to replace them but I can't see how the sell them for 240V?

Move the entire breaker up or down one space. Or maybe more correctly move the 2 pole, half width breaker, 1/2 space, so that each half of the double pole breaker makes contact with each buss.

What a way to mangle the english language! :)

Dave

firbikrhd1
12-21-2011, 07:43 PM
I make no claim to be an expert, but I think it has to do with the design of the panel itself. I have a panel, for instance, that allows two of the half size breakers to be installed next to each other, depending on position, and deliver 120 volts from each buss, i.e. 240 volts. They must be tied together to do this via the holes mentioned previously. My panel has the buss set up so that each full sized breaker position connects to an alternate buss. So, depending on where the half breaker is placed it will deliver current from a different leg. Two half sized breakers placed properly will deliver 120 volts each, each on a different "phase" or pole, giving 240 volts. Placed differently each will deliver 120 volts on the same "phase" or pole.

As long as each pole is balanced relatively closely there should be no problem. Although I can't state this in Building Code terms, consider this; throughout your house or shop you never have all of your circuits in use at the same time. There is no way to tell which pole is being more heavily used at any given time and you never give it a thought. In fact, if you were to add up the amperage of all your breakers you would likely find the total is higher than the total your panel is designed for.

Black_Moons
12-21-2011, 08:34 PM
When using dual breakers to service one run, you MUST make sure they connect to opposite phases, or you can end up overloading your neutral if you use the service for 120v to neutral loads.

(Same phase = Neutral current combines, Opposite phases Neutral current cancels out)

lakeside53
12-21-2011, 09:39 PM
They are legal so long as the panel label lists them as an option.

If you are using 3 wire split phase feeds for 120 (common neutral) , the NEC 2008 code (check you local adoption) now requires the breaker handles to be tied togther.

flylo
12-21-2011, 10:14 PM
I didn't make myself clear. it was marked 120/240 but it was sng pole & only had 1 clip or lug to attach to 1 buss so it was a double 120V. Without 2 poles it can't be 240V. But it was marked 120/240V & drilled like a dbl pole.

becksmachine
12-21-2011, 11:39 PM
I didn't make myself clear. it was marked 120/240 but it was sng pole & only had 1 clip or lug to attach to 1 buss so it was a double 120V. Without 2 poles it can't be 240V. But it was marked 120/240V & drilled like a dbl pole.

Ok, let me display some (much??) ignorance here. Maybe we are talking about two different styles. Is this a 1/2" wide "piggyback" 2 circuit style that fits in a 1/2" slot? What brand?

I can see where the 120/240 volt designation is applicable if the breaker was also approved for use in a system (UK?) where the normal phase to neutral voltage was 240V, but that isn't the case anywhere in North America is it?

Dave

J Tiers
12-22-2011, 12:09 AM
A problem with the dual breakers is that often they are very sensitive..... There wer a ton of them in the office / lab panels at a prior employer.... we couldn't turn on a variac without a 50% chance of popping the breaker on inrush. had to move them around and install some HID lighting types in place.

Also they can be oversensitive if the other one in the housing is loaded heavily... they are thermal breakers generally, and heat from the other side can pre-sensitize" them. Not supposed to happen, the ratings are the ratings, but it can.



Ok, let me display some (much??) ignorance here. Maybe we are talking about two different styles. Is this a 1/2" wide "piggyback" 2 circuit style that fits in a 1/2" slot? What brand?

I can see where the 120/240 volt designation is applicable if the breaker was also approved for use in a system (UK?) where the normal phase to neutral voltage was 240V, but that isn't the case anywhere in North America is it?

Dave

No, usually it is either 277V L-N, or the 240 is between phase wires.
The 240V L-N would be for european 380 to 415V 3 phase.

flylo
12-22-2011, 12:41 AM
I believe they are Westinhouse that also stated they fit Bryant & several more. They are striclty a double 120 sng pole in the US but not marked or sold as such. Now to turn on 1 pr of heaters I flip the center 2 & the 2nd pair the outer 2. I will take these back to Home Depot & put in full size.

rws
12-22-2011, 08:00 AM
I'm not at home right now, but I know the slim breakers are half the width of a normal breaker, and you can install 2 in the space of one. There is also plastic "dividers" down at the buss that you could assume will keep this issue in check, but it still can be bypassed. There is no doubt that a slim 2 pole breaker could be installed and connect to one buss.

flylo
12-22-2011, 09:16 AM
Thats what happened it connected to 1 buss which is going to give you the same 120V on both halves of the breaker so you end up with the same 120 leg twice. Not 240V.

garagemark
12-22-2011, 11:29 AM
These 120 volt breakers are great for residential lighting and convenience power duty. It lets a homeowner or builder split many more circuits up, which in turn lightens the load on any given breaker.

They are, however, known to be less robust than their full size cousins. For heavy 120 volt loads, it is usually preferable to use a full size circuit breaker.

I have installed many of these piggyback breakers, and have had a few failures with heavier loads. I no longer use them unless there is a real need for them. If I'm completely out of spaces for, say, a remodel, I'll look for the lighter loads in the panel and install them in those locations.

They are a nice option when needed.

Mark