[RE-wrenches] Changing from 2 battery cable setup to single cable for Outback?

[scot.arey at solarcentex.com]

Greetings,




My team is installing a Outback Radian 8048 to replace an older dual Xantrex/Trace 5048 inverter setup where one failed either due to lightning or old age.  We did not install the original system.




Battery setup is 48V bank with Rolls 6CS21P Series 5000 batteries (to be quite honest, largest I've ever seen - 271 lbs per battery, 683AH, 1740CCA).  4 parallel strings of 4 batteries.




The cable from the battery bank to the inverter is two 4/0 RHH cables.  Two for the positive cables and two for the negative cables.  I keep asking the original designer why he used two cables (4 total) and I never quite get the same, straight answer.




Now enter the new Radian inverter and its load center.  While there is a positive load plate to bolt the positive cables onto, there really is not lots of space through the load center to maneuver the cables.  Even less for the single negative bus bar connection.  The load center has dual 175A circuit breakers built in (one for each of the 4KW inverters that makes up the 8048)




So my question(s) is (are): can I go from a  pair of 4/0 cables to a single 2/0 RHH cable to enter the load center and carry the battery load?  Why would a designer use dual cables?  How does one calculate the battery short circuit current in order to even determine cable ampacity requirements?  Or for that matter, to determine if the load center 175A dual circuit breakers are of sufficient size to negate the need for additional OCPD IAW 694.70C?




I want to make sure I'm doing this right and whenever I'm upgrading a component, I try to remember that other components likely need adjust/upgrading…thanks all.






Howard "Scot" Arey

Solar CenTex
254-300-1228

"Use the Texas Sun!"
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