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code question: CT allowed inside disconnect?

code question: CT allowed inside disconnect?

code question: CT allowed inside disconnect?

(OP)
Hello,

Code question!  Is a current transformer (CT) allowed inside a fused disconnect/fused safety switch?  Seems like the NEC doesn't say... I've looked in article 312 and article 404.

Also, if the CT is allowed inside the FSS, would a tap for the voltage (for a power meter) also be allowed inside the FSS?  My brain is telling me that a CT is a little different from a voltage tap because the CT operates by electromagnetic induction & doesn't require direct connection.  

Basically it looks like someone is trying to avoid having a separate CT cabinet for the meter.

Thanks,

Brian

 

RE: code question: CT allowed inside disconnect?


If the CTs/PT taps are for revenue metering, it's unlikely that the serving utility wound permit them installed in other than a separate sealed compartment.
  
 

RE: code question: CT allowed inside disconnect?

I don't think the NEC directly addresses CT's. If the voltage tap is sharing a lug with the main conductor, you may have a violation if the lug is not listed for more than one wire.

Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.

RE: code question: CT allowed inside disconnect?

Some inspectors might consider the CT's are part of the "listed" equipment for that enclosure.  

I know of several installations where small metering CT's were placed in fused disconnects because that was a convenient place to connect the metering for monitoring some processes.  I can't say if it was according to code.  I did not find a definitive answer when I investigated one of those installations.

IMHO, the installation was safe, but that opinion would never stand up in court if something happened inside the switch.

RE: code question: CT allowed inside disconnect?

Good point on violating the listing. IMO, it would be a stretch to say a small properly installed CT should be a problem for the listing of the switch, but as rcwilson suggested, you never know how a jury will see it.

Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.

RE: code question: CT allowed inside disconnect?

(OP)
Thanks for the advice, folks!

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