Parallel Feeders 1000A DC

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alphite

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This will be reviewed by an electrical engineer, but I'd like a general sanity check.

I have two different DC power supplies for a heater, and would like to see what cable options are possible.

Power supply #1: 400V, 200A
Power Supply #2: 100V, 1000A

Is it possible to use three welding cables in parallel? And can these be run in an open cable tray?

Thanks
 
The length of the run is approximately 75 ft, room temp, temp controlled environment (20C).
 
Is this covered by the NEC? There are a handful of "it depend"s there. Assuming it is...

"Welding cable" isn't an NEC cable type, do you need flexibility? Most other NEC cable types suitable for cable trays will do the job, size per tables for the particular type.
 
Welding cable is covered under 630.41, but there's not a whole lot of guidance. Flexibility is definitely desired, as well as the smallest cross sectional area possible. The American Welding Society has guidance for running 1,000 amps, but these aren't typically in cable trays.

See page 8 for guidance on paralleling:

It's a DC welding power supply, but it's not far off in application, especially if I only consider the 100V power supply.
 
I agree with Z. if this is a permanent installation welding cable is not a permitted type of conductor.

Having said that, often welding cable is also ual rated as something that is a NEC style conductor.

I don't see why you cannot use a suitable conductor in cable tray.

I don't see that you need flexibility so I would be inclined to use THHN.

You are not allowed to parallel conductors under 1/0 except in a few special cases, so if you want to use parallel conductors for some reason (2) 1/0 conductors for the 200 A heater is what you would need to use.

For the 1000 A heater, you would need 1250 Amps worth of ampacity. if you used three conductors in parallel that would be (3) 600 MCM copper.
 
alphite said:
Welding cable is covered under 630.41, but there's not a whole lot of guidance. Flexibility is definitely desired, as well as the smallest cross sectional area possible.
Click to expand...
If this isn't a welding load (first post says "heating"), then 630 won't apply. Also, consider the duty cycle of whatever it is and whether it counts as a continuous load.

As for cross-section, the only way you'll reduce the overall cross-section is thinner insulation like one of the X types. (You can't practically reduce the area of the conductors unless you can find higher-conductive wire, but then it won't be copper.)
 
alphite said:
Welding cable is covered under 630.41, but there's not a whole lot of guidance. Flexibility is definitely desired, as well as the smallest cross sectional area possible. The American Welding Society has guidance for running 1,000 amps, but these aren't typically in cable trays.

See page 8 for guidance on paralleling:

It's a DC welding power supply, but it's not far off in application, especially if I only consider the 100V power supply.
Click to expand...

Welding cable doesn't get used as building wire for heater. For your application, the welding cable needs to also have a listing found in Article 310

NEC
630.41 Conductors. Insulation of conductors intended for use in the secondary circuit of electric welders shall be flame retardant.
Handbook Editorial: Listed welding cable is intended to be used for the secondary circuits of electric welders and cannot be used as “building wire” for circuits operating at 1000 volts or less unless the cable is also one of the types covered in table 310.104(A). the fine stranding allows for the flexibility necessary in manual and automatic welding operations. terminals used with this type of cable must be suitable for use with the fine stranding used in this type of cable construction. See 110.14 for more information regarding terminations used with conductors having other than class B or c stranding.
 
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