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Participant

Join Date: Apr 2017
Posts: 1

Can I Use Two Different Cables Instead of Single Cable?

04/01/2017 5:30 AM

dear sir,'

i have 400 amps output transformer. i want to upgrade my main power cabling because before only 150 amps load . my question is that in old cabling is already 70 sq mm single core pvc wire install that time only 150 amps load . now we have 400 amps load so i can use 120 single core sq mm xlpe cable and old 70sq mm single core pvc both together for running 400 amps load in factory unit.

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Guru

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#1

Re: i can use two different cable insted of single cable

04/01/2017 5:35 AM

If you've got a factory unit, then you've got fire and business loss indemnity insurance. Your insurance provider may want to know why you're going to an anonymous internet engineering forum instead of consulting a local Electrical Engineer directly, Mildred, with all the indemnity involved that your insurance company might expect.

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#2

Re: i can use two different cable insted of single cable

04/01/2017 6:08 AM

Your local regulations may require all paralleled cables to be the same size.

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#3

Re: i can use two different cable insted of single cable

04/01/2017 6:16 AM

BS7671 allows parallel conductors of the same CSA with no derating. A 120mm² and a 70mm² is a NoNo. You could use 3 off 70mm²

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#4

Re: Can I Use Two Different Cable Instead of Single Cable?

04/01/2017 9:29 AM

I usually go 200% load, wire gage for a significant safety factor. DO NOT cut corners or try to cheap out on an application.

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#5

Re: Can I Use Two Different Cable Instead of Single Cable?

04/01/2017 10:59 AM

Consult with a a local licensed(?) electrician or electrical engineer. They will know which codes pertain to your location. We do not know at all where this transformer resides. Those of us who have the authority to give this type of advice get paid for this service.

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#6

Re: Can I Use Two Different Cable Instead of Single Cable?

04/02/2017 1:13 AM

what about the fault current?

You have to rate your cable not only for the load but the fault current too!

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#7
In reply to #6

Re: Can I Use Two Different Cable Instead of Single Cable?

04/02/2017 9:06 AM

Technically, however, two smaller cables will have a (slightly?) higher current carrying capacity*, due to larger surface area from which heat can be radiated / conducted / convected -

(*Than a larger cable of the same total cross section)

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