Author Topic: PreWired Combiner Box Termination Ratings  (Read 1393 times)

Surfpath

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PreWired Combiner Box Termination Ratings
« on: January 30, 2015, 11:08:37 AM »
I have a quick tech related question.

I am trying to determine if my current combiner box to charge controller wire run is appropriately sized for a proposed PV expansion. My current run of #6 AWG ANCOR Boat Cable with (105 degree C insulation), technically can carry higher current than typical #6 AWG (rated at 60 degrees C). However that seems to be dependent on IF the terminal connectors in a) my Midnite combiner box and b) my FM80 are also rated at a higher temperature than the usual 60 degree C connector.

So my question for Midnite is, what are the termination ratings for the pre-wired Midnite combiners (I have the MNPV4). Are they 60 degrees C or 75 degrees C rated, or something different??

This technical bulletin from Cooper Bussman explains exactly what I am referring to:
http://www.cooperindustries.com/content ... cities.pdf
Thanks!

ps. I've asked Outback a similar question.

Vic

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Re: PreWired Combiner Box Termination Ratings
« Reply #1 on: January 30, 2015, 12:53:11 PM »
Surf  ..,

Believe that it is very common to find circuit breakers with a maximum terminal (connection point)  rating of 75 C maximum.  This is the limiting factor in the ability of the conductor to handle current.  The MNEPV and MNEDC breakers all appear to have this 75 C maximum rating,  and quite probably the large frame breakers also have this 75 C  max rating as well ... have not looked in some time,  though.

EDIT:  However,  in looking at the specs fot the MNPV-4,  it does say that the Lugs have a 90 C temperature rating.  So,  if you are connecting to the "Lugs",  then it appears that you could use the 90 C Ampacity of the cable connected to the Lugs:
http://www.midnitesolar.com/pdfs/pvCombiner_spec_sheet.pdf

I should wait for the MN Tech folks to reply ...
FWIW,   Vic
« Last Edit: January 30, 2015, 01:29:33 PM by Vic »
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Surfpath

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Re: PreWired Combiner Box Termination Ratings
« Reply #2 on: February 02, 2015, 07:58:22 AM »
Hi Vic,
Nice sheet.  Thanks for that preliminary data on the combiners.  I did not see that one in my search.  -SP

Seems like my link to the Cooper article above got messed up.  Here it is again. 

(http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/solution-center/technical_library/BUS_Ele_Tech_Lib_Conductor_Ampacities.pdf)
« Last Edit: February 02, 2015, 08:01:51 AM by Surfpath »