Are non-fused safety switches reqruied to be provided with "series rated" labeling per the NEC where applied in applicaitons whree the fault current exceeds 10kAIC? In looking through different manufactures literature [Sq.D, Siemens, etc.] they all state that the non-fused safety switch is rated for 10kAIC [Short cirucit current rating, really a withstand rating not an interrupt rating]. However each manufacturer also list higher ratings based on specific OCPD ahead of the safety switch [see attached excerpt from a Siemens Document]. The standard safety switch is rated for 10kAIC for any UL breaker, however only 18 & 25 with listed Siemens breakers as the OCPD or higher [200kIAC] with the listed fuse type. If the switch is applied where the avaliable fault current is greater than 10kAIC and the upstream breaker allows for an 18kAIC rating [per the manufacturers chart] or even the 200kAIC if fuses are used upstream is the safety switch requried to be labeled with a "series rated" label indicating the series rating with the upstream OCPD? The NEC [110.22] talks about equipment enclosures for circuit breakers or fuses applied in compliance with series combination ratings ? ? Shall be marked in the field as directed by the engineer to indicate the equipment has been applied with a series combination rating.? And it goes on to provide examples of labels. however the non-fused safety switch is not an "enclosure for cirucit breakers or fuses".??:?
Safety Switch - Series Rating?
- Thread starter Mike01
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If I'm not mistaken, a label similar to that will be inside of a non-fused disconnect switch now, indicating a higher SCCR when used down stream of a specific breaker, usually of the same make as the disconnect. It would be required now as part of their UL listing and labeling process. Older switches made before that requirement may not have it, so that may be a problem if you buy used or surplus parts, but for anything new you should be OK. Might end up as an AHJ issue however.
But in general, "series rating" is a term used in discussing INTERRUPT ratings of series devices used to protect against faults, such as fuses or circuit breakers. Although the same similar concept exists for SCCR, I don't think it is referred to as being a "series rating" per se, I think they refer to it as being a "tested combination" or words to that effect (on my iPad, no documents available to look at). With SCCR becoming a requirement in 2005, its really about what we used to referr to as the "Withstand Rating", as in how much mechanical force from the magnetic effects of high current flow can this device withstand before becoming shrapnel. It has nothing to do with this device trying to interrupt anything, but it IS dependent upon the current limiting effects of anything up stream of it, if any. Hence the "tested combination" issue, but why would Sq. D test their switch with a Siemens breaker or vice versa? This, by the way, has become a big problem for smaller niche players in the disconnect switch world who don't make breakers too. They either have to pick one other brand to rely upon, test multiple brands at great expense, or just tell everyone fuses, no breakers ahead of their switches.
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