DC wiring from battery storage to UPS

W

woodduder

Senior Member
Location
West Central FL.
I am looking for some feedback for wire sizing for DC cables that run from battery storage cabinets to a 300KVA UPS. I have been in this business for 40 years, but 99.99% has been involved with 120/208 and 277/480 volt AC systems.

I now have a UPS system with a separate battery storage cabinet, that I must connect with cables. I just need some reassurance that I am thinking correctly since this is not AC wiring.

The battery cabinet has a maximum voltage of 575VDC and a max current of 511 amps. My thoughts are to install 2 individual 2" conduits between the battery storage and the UPS. Each conduit to have two (one red, one black) 300 KCMIL conductors. 300KCMIL THHN good for 285 amps at 75 degrees = an ampacity of 570 amps. Seems good so far. Let me know if I am wrong so far.

Next issue. The wiring space is tight. I have been told I should be using "welding cable" as it would bend better in the tight space. I have never used "welding cable". I received a quote for OMNI CABLE B225001 (this is 250 KCMIL). What is the ampacity of this cable? I cannot find this info. Cable has an EPDM insulation, but this is not in NEC. I am going to call OMNI, but any input would be great.
 
A couple of parallel runs of 250 kcmil DLO cable would put you where you need to be. Just use the appropriate terminals for the fine strands.
 
DLO cable is dual rated usually. As another poster mentioned, use the correct terminals for fine stranded cable.
CoolWill said:
A couple of parallel runs of 250 kcmil DLO cable would put you where you need to be. Just use the appropriate terminals for the fine strands.
Click to expand...
The OP indicated 511 Amps. Two parallel runs of 250 is only 510 Amps of ampacity from the 75 deg C column.

However, you might find that the terminations are rated for 90 C.

I might be looking at cable tray instead of conduit.
 
ask the manufacturer for guidance :D ?

After that, any fine-strand cable, like SC, W, or RHH/RHW will do the job. As above, make sure all the termination temperatures are in order and that you allow extra time (and lube) for pulling; this often makes cable tray more attractive. (How long are we talking about?)

However, most equipment should have enough space to bend Good Ol' THHN, and there are specific tools to help do it.
 
petersonra said:
DLO cable is dual rated usually. As another poster mentioned, use the correct terminals for fine stranded cable.

The OP indicated 511 Amps. Two parallel runs of 250 is only 510 Amps of ampacity from the 75 deg C column.

However, you might find that the terminations are rated for 90 C.

I might be looking at cable tray instead of conduit.
Click to expand...
I have to say that I wouldn't let 1 amp stand in my way. I would sleep just fine.
 
Usually the freestanding battery cabinet has an output breaker. Size the conductors based on that trip rating.

Fine strand conductor is often referred to as welding or DLO conductors. No special ratings, be sure it has an insulation type seen in the NEC, such as XHHW-2 or RHW-2 which is what I usually see. Fine strand requires special connectors, usually compression type, so be sure you are not terminating in a mechanical lug.
 
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