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Circuit breakers and old panelboard; will anything work?

Posted By Underwriters Laboratories, Monday, March 01, 2010
Updated: Wednesday, January 23, 2013

Question

I have an old panelboard made by a company that was sold and no longer produces panelboards or circuit breakers under their old name. How do I find circuit breakers listed for use in the panel when the manufacturer is no longer in business, can I use any circuit breaker that fits?

Answer

Over the years the electrical industry has undergone a lot of consolidation. Where there once were many companies that made panelboards and circuit breakers, there are now only a few. That leaves a big hole in sourcing replacement breakers for these panelboards that may now seem obsolete. The circuit breaker compatibility marking on some of these older listed panelboards may specify types of circuit breakers that are no longer in production and difficult to find. If the original equipment manufacturer (OEM) circuit breakers specified on the panelboard cannot be found, it is not acceptable to just install any circuit breaker that fits.

A panelboard to which a unit, such as a circuit breaker, switch, or the like, may be added in the field is required to be marked to identify the units that can be added. Units made by different manufacturers or of a different style are not identical in all details and therefore may not be interchangeable.

Plug-in clips and blades must be matched if poor connections and overheating are to be avoided. Additionally, over-surface and through-air electrical spacings, between live parts of opposite polarity and to grounded metal, often depend on the proper mating of units and the bases into which they are plugged or bolted.

The only exception is for UL classified molded-case circuit breakers rated 15 to 60 A, 120/240 V ac, that have been investigated and found suitable for use in place of other listed circuit breakers in specific listed panelboards.

The circuit breakers are classified under the product category Circuit Breakers, Molded-Case, Classified for Use in Specified Equipment, (DIXF) located on page 95 in the 2009 UL White Book and are limited for use with panelboards rated 225 A or less, 120/240 V ac. These circuit breakers are classified for use in specific panelboards in accordance with the details described on the circuit breaker, or in the publication provided therewith. These breakers are suitable for use in equipment connected to circuits having a maximum available system short-circuit current of 10 kA.

Classified breakers are required to comply with the same Standard for Safety for Molded Case Circuit Breakers, UL 489 as listed molded case circuit breakers; however, they are typically manufactured by a different OEM than that of the manufacturer of the panelboard.


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Tags:  March-April 2010  UL Question Corner 

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