Non-conforming breakers - please explain? - Contractor Talk - Professional Construction and Remodeling Forum

DetailHandyman · 02-03-2009, 06:13 PM

Someone please explain why there is a need for a non-conforming breaker.

I have seen this on only on tandems. Of course, the NC breakers are more expensive.

For example, there are two styles of tandem for the Siemens / ITE box in my house. The breakers look exactly alike, except that the cut out for the bus bar tab is smaller on one than the other. So the larger cut out will fit the box, while the other doesn't. I see the same issue on the thin SqD breakers: the mounting tab is different.

I figure there must be a reason for this difference, although nothing good comes to mind.

Please enlighten me on the need for such things.

Celtic · 02-03-2009, 06:46 PM

Here is a "text book" answer:

Quote:

“Class CTL” is the Underwriters Laboratories Inc. designation for the Code requirement for circuit limitation within a lighting and appliance branch-circuit panelboard and means “circuit limiting.”
Class CTL panelboards incorporate physical features that, in conjunction with the physical size, configuration, or other means provided in Class CTL circuit breakers, fuseholders, or fusible switches, are designed to prevent the installation of more overcurrent protective poles than the number for which the panelboard is designed and rated.
It should be noted that switchboards, unlike panelboards, are not limited to 42 overcurrent devices or 42 switches or devices.

DetailHandyman · 02-03-2009, 07:09 PM

Thanks Celtic.

OK, then by that explanation....

The panel is designed to only accept conforming breakers, to keep someone from replacing all the normal single pole breakers with tandems.

But, the manufacturer also provides NC tandem breakers that I can buy off the shelf, and install all I want anyway.... I'm confused. So, why have both types?

And, as an extension of that...

If I had a panel with space for (30) 1" single pole breakers, such as the Siemens, and filled it to capacity with tandems...now having 60 available single poles...what is the issue there?

Celtic · 02-03-2009, 07:39 PM

Quote:

Originally Posted by DetailHandyman

Thanks Celtic.

OK, then by that explanation....

The panel is designed to only accept conforming breakers, to keep someone from replacing all the normal single pole breakers with tandems.

But, the manufacturer also provides NC tandem breakers that I can buy off the shelf, and install all I want anyway.... I'm confused. So, why have both types?

And, as an extension of that...

If I had a panel with space for (30) 1" single pole breakers, such as the Siemens, and filled it to capacity with tandems...now having 60 available single poles...what is the issue there?

IF you used the proper breakers for the panel, you would not be able to have more than 42 ckts. [under the '05 and earlier editions]

This limitation has now been lifted under the '08 ~ but if the panel was installed under a prior code cycle, IMHO, you are still limited to the number of OCPDs.