Electrical Service Box Question & Half Thick Circuit Breakers ?

Hello:
For new electrical service boxes:
Are they "generally" constructed to take either two of the half-thickness breakers or a single full thickness one ? I guess I am asking if the slot positions are generally designed for either the two, or one, but you don't have an option ?
How about the older ones; how were they designed ?
Is there any disadvantage to the half-thick circuit breakers ?
Thanks, B.
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It varies by manufacturer. There is usually a label inside the panel or the panel cover stating what breakers the panel is approved for. If you are shopping for an electrical panel you might see a designation on the box that reads 20/24 or 30/40 or something like that. In the case of a 30/40 it would interpret as 30 full size breakers total or if you want 40 circuits you can use 20 full size breakers with 20 thin or 10 tandem (Twin) breakers.
I tend to like the full size breakers because they usually fit into the panel with less trouble.
John Grabowski http://www.mrelectrician.tv
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yeah most boxes will take the thin breakers but I dont believe they are as durable. my old boxes have. thru 2 or 3 homes. thin breakers cost a littlke more
if your upgrading to a new service get the biggest cabnet you can with 200 amp service. it will leave room for expansion.
200 amp usually has more slots than 100 amp
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wrote:

The boxes aren't designed to fit the breakers, the breakers are designed to fit the boxes. Specifically, a duplex breaker is designed to fit in a single slot in the panel, and serve two hots, independantly.
The only drawback (other than cost) is that the enclosure itself is only rated for a certain number of connections, so you can't just keep swapping duplex breakers for normal ones until you run out of space.
If you're lucky, the upper limit is written on the box somewhere. It does NOT appear to be related to the number of open spaces on the ground and nuetral bars, which are always undersized. (Can anyone explain why that is?)
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Depending upon the manufacturer, some panels can use either full or half sized breakers in all buss locations, some buss locations or not at all. For example if a panel is designed to use 40 full sized breakers, it won't use any half sized breakers as the maximum amount of poles allowed in any panel is 42. Some panels will use 20 full sized or 40 half sized, or any variables with a max of 42

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Aside from the other points. A double breaker might be connected to the same phase or opposite phases in the panel. If they are on the same phase, you need seperate branch conductors each with its own neutral but if the two poles of the double breaker are on different phases, you can use a 3 conductor cable to feed two branches with one common neutral.
In my new square D homeline panel, double breakers use one phase but on my old panel double breakers were fed from both phases. It just depends on the box and design.

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I think your talking about two separate things. There are splits or half size breakers, some are tandem and some are not, but regardless, the two breakers occupy one section of panel buss. Then there are double pole splits and quads, which occupy two sections of panel buss and are for 240 volt circuits

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Robert11 wrote:

In their standard for panels UL limits the number of 'poles' that can be installed in a panel (a 220V breaker is 2 poles). The maximum number of poles in a 100A 120/240V panel is 20. (In a 200A panel 40.) If a 100A panel has positions for 16 full sized poles it could have 4 more poles and stay under the 20 limit. These can be installed as 8 120V half-thickness breakers (12 full + 8 half = 20). To prevent more than 8 half-thickness breakers from being installed, the breakers have a feature at the bus end or the rail end that only allows them to be installed in special positions. In this case only 8 panel positions can allow this feature and half-thickness breakers will only fit in those positions. These breakers are called class CTL (circuit limiting). (A 100A panel may be designed so fewer than 20 total poles can be installed.) Previous to the class CTL panels, half-thickness breakers did not have a limiting feature and in most panels could be installed in any position (or all the positions). Last I heard these non-CTL breakers were still available for use in non-CTL panels. The panel, on its label, should have a list of the number and type of breakers that can be installed in that panel. A class CTL panel will not have non-CTL breakers on the list and it is a code violation to install a breaker that is not on the list.
(A 100A service disconnect breaker/fuse could feed 2 200A main lug panels for 80 poles.)
bud--
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