4X70mm XLPE/SWA/PVC good for 250 Amps?

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kV

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I'm working with a subcontractor that swears his buried 4x70mm2 cu XLPE/SWA/PVC is good for a projected load of 250 Amps per phase. According to Table 310.16 of 2005 NEC the max ampacity for 70mm2 or about 1/0 cu before corrections is 170 Amps. Am I missing something or is 4x70mm2 cu XLPE/SWA/PVC unacceptable for this load?

Thanks
 
Re: 4X70mm XLPE/SWA/PVC good for 250 Amps?

I dont understand your wire and insulation xlpe is not in ampacitie table
 
Re: 4X70mm XLPE/SWA/PVC good for 250 Amps?

70mm2 is 0.1085 sq in., roughly the same as 2/0. I assume that this is a 4 conductor cable assembly with 3 phase conductors and a ground, insulated with XLPE (XHHW) with a shield and PVC jacket. NEC Table 310.83 is the closest approximation which has a 260A rating at nominal conditions. Be aware that ambient temperatures over 20C, nearby heat sources, or thermal resistance over 90 rho will require derating the cable.
 
Re: 4X70mm XLPE/SWA/PVC good for 250 Amps?

That is a big part of the problem. I think it is a European naming style. After searching on the web, it appears that XLPE/SWA/PVC is most similar to XHHW-2. I am overseas enforcing American code on an international hodge-podge of wires, breakers, transformers, etc. I guess I'm looking for somebody with experience in European cabling/engineering/code work as well as American code work.

The problem is that the manufacturer states the allowable ampacity is much higher than the NEC allows (of course) so I'm thinking the subcontractor wants to go with cabling the NEC considers is undersized. They go by the British standard but the NEC is the only code acceptible for this work. Having them switch cables is expensive but may be required.

Any experience with British Standard or European cabling/engineering?
 
Re: 4X70mm XLPE/SWA/PVC good for 250 Amps?

By the way, this is for a system at aprox. 400V so I'm thinking Table 310.16 is applicable instead of 310.83. Is that right?
 
Re: 4X70mm XLPE/SWA/PVC good for 250 Amps?

KV
Table 310.83 is for cable rated above 2000 volts.
It is not applicable for your installation.
 
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