use of foreign-supplied cable

[samyer]

I need to find out if the use of British wiring cable is accepted in the US. We purchase equipment from a UK manufacturer that requires a 3-phase 208-240VAC input. Their equipment has a 32A/phase breaker supplied at the rear. The wiring they provide is only labeled BS 6007 which is a British Standard. The manufacturer claims that the wiring is BS6007, 4 core 4sq.mm EPR
(rubber) insulated. It has a current rating of 34 amps, continuous. Each phase wire appears to have a physical diameter of 12AWG wiring, making it appear to be too small in my mind. The equipment draws about 22A per phase. My concern is that if I supply the wiring and 32A breaker with a properly sized supply fusing arrangement or breaker, it will need to be around 60A, since it wouldn't be good practice (or code-passable) to put two fuses or breakers of the same size in series. That would seem that the wiring would then be too small. What is your suggestion?

 

[roger]

Re: use of foreign-supplied cable

The equipment already has it's own OCP.

The equipment should also have a CE listing. (not that it means much)

This being the case you can serve this equipment with a 40 amp circuit in acordance with NEC methods and be safe.

Roger

 

[samyer]

Re: use of foreign-supplied cable

THANKS!!!!

 

[c-h]

Re: use of foreign-supplied cable

12AWG is 'only' 3.3 sq.mm and the Brits will probably allow the cable to run a bit warmer than you would in the US. Still, 34A is pushing it rather hard, but since 'The equipment draws about 22A per phase' there should be no problem.

 

[samyer]

Re: use of foreign-supplied cable

Thanks. The nominal current drops to about 17A after warmup. Any ideas where I can find in the code where selective coordination of fuses is covered, i.e., sizing of fusing/circuit breakers upstream from a 3-phase load?

 

[don_resqcapt19]

Re: use of foreign-supplied cable

In general, selective coordination is not required by the NEC and is a design issue. There are some exceptions, like elevator feeders, but these are rare.
Don

 

[iwire]

Re: use of foreign-supplied cable

Originally posted by samyer:
The manufacturer claims that the wiring is BS6007, 4 core 4sq.mm EPR (rubber) insulated. It has a current rating of 34 amps, continuous. Each phase wire appears to have a physical diameter of 12AWG wiring, making it appear to be too small in my mind. The equipment draws about 22A per phase. My concern is that if I supply the wiring and 32A breaker with a properly sized supply fusing arrangement or breaker, it will need to be around 60A

How did you come up with a 60 amp breaker?

22 amp load you could use a 30 amp breaker with 10 AWG and the 32 amp breaker is now just a local disconnect although it is still any ones guess if there was a fault as to which breaker would trip first, or both.

You could certainly do what Roger suggested and go with a 40 amp breaker and receptacle.

A 30 amp cord cap and receptacle will be much cheaper than one rated for 40 amps.

As for the wire that seems like a 12 awg, as C-H pointed out it is between 10 and 12 awg, also even though we are required to use a 20 amp OCPD, do not forget that our 12 awg is rated 25 to 30 amps.

[ September 10, 2003, 05:10 PM: Message edited by: iwire ]

 

[samyer]

Re: use of foreign-supplied cable

Thanks to all for your help. The 60 amp value I came up with was what I was considering, but it occurred to me that this system is dedicated on this circuit, i.e., nothing else is being supplied. The concept of selective coordination kept coming up in my mind. The response I got about the device having its own OCP turned on a light - I only really needed to be concerned about how I wanted to protect that circuit, not just trying to accomodate what the manufacturer decided he needed.