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

[William Miller]

Scot:

 

I won’t comment on the battery wiring sizing here.  What I will say is that the Radian distribution panels are poorly designed.  I have numerous complaints and if you want detail I can dig up my report to Outback.  Short answer is I suggest anyone do the following:

 

1.    Do not order a prewired system.

2.    Remove all AC distribution components from the Outback Radian power panel and relocate them to two outboard off-the-shelf breaker panels.  One will be Gen fed and one will be Inverter fed.

3.    Create your own interlock to provide for generator bypass.  This can use an off-the-shelf breaker interlock but you can do better with a small aluminum plate, jig saw and drill press.  I can provide more insight on this as well.  Will build a lot of custom interlocks and we are very pleased with the results.

 

William Miller

 

 

Gradient Cap_mini
Lic 773985
millersolar.com <http://www.millersolar.com/> 
805-438-5600

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of scot.arey at solarcentex.com
Sent: Saturday, August 09, 2014 11:11 AM
To: re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Changing from 2 battery cable setup to single cable for Outback?

 

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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