Author Topic: what sized wire for MC4 connectors  (Read 559 times)

sunbelt57

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what sized wire for MC4 connectors
« on: August 12, 2021, 05:52:02 PM »
I have an array of panels - 3 in series, 4 parallel strings that use MC4 connectors. Its a 48v system and the panels are 350W, 46.6 VOC, 37.7 VMP & 9.32 ISC. I would like to use 6AWG going to the Classic 150 Lite, which is about 25 feet from the panels. (The panels are 20 feet from the building and the CC will probably be 5 feet up on the wall. I could probably get by with 10 AWG connecting the panels together?

Vic

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Re: what sized wire for MC4 connectors
« Reply #1 on: August 12, 2021, 06:05:34 PM »
Hi sunbelt ..,

You will have four strings of PVs,  so,  you will need to use a Combiner (box),  with one DC circuit breaker for each string:
https://www.solar-electric.com/mnpv6.html

Circuit breaker example,   you can use a breaker,  sized to the "Maximum Fuse Rating" for your PVs:
https://www.solar-electric.com/mnpv6.html

You can make the transition to #6 AWG cable,  at the output of the Combiner.

Your Voc is probably a bit high for a Classic 150   ...   IIRC,  you have already posted the String Sizer output,  in an earlier Thread   ...

You probably know all about Combiners and DC breakers,  but ...

More later,  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!

sunbelt57

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Re: what sized wire for MC4 connectors
« Reply #2 on: August 12, 2021, 06:15:51 PM »
For some reason, I was under the impression that you could just tie the wires together. I'm glad I asked now. I'll order one.

Vic

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Re: what sized wire for MC4 connectors
« Reply #3 on: August 12, 2021, 06:46:08 PM »
For some reason, I was under the impression that you could just tie the wires together. I'm glad I asked now. I'll order one.

To reduce the risk of a fire,  caused by a shorted PV module,  a DC circuit breaker (or fuse) is needed when there are three,  or more PV strings,  or  three, or more PVs in parallel.

Regarding the wire size for the PV wiring to the Combiner,  #10 AWG is often used,  and for relatively high power PVs,  #10 cable is used by the PV manufacturers.  If you are making your own MC4 cables,  the manufacturer of these MC4s should specify the range of cable sizes that those connectors will accept.

Many of us will order pre-made MC4 PV extension cables,  of the correct length,  cut them in two,  and use each half on the respective polarity on the PVs,  example of such:
https://www.solar-electric.com/mc4-extender-cable-1000-volts-15-feet.html

FWIW,  it is great that you are asking some good questions,    Vic
 
« Last Edit: August 12, 2021, 08:10:11 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!

ClassicCrazy

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Re: what sized wire for MC4 connectors
« Reply #4 on: August 12, 2021, 09:56:43 PM »
For some reason, I was under the impression that you could just tie the wires together. I'm glad I asked now. I'll order one.

To reduce the risk of a fire,  caused by a shorted PV module,  a DC circuit breaker (or fuse) is needed when there are three,  or more PV strings,  or  three, or more PVs in parallel.

Regarding the wire size for the PV wiring to the Combiner,  #10 AWG is often used,  and for relatively high power PVs,  #10 cable is used by the PV manufacturers.  If you are making your own MC4 cables,  the manufacturer of these MC4s should specify the range of cable sizes that those connectors will accept.

Many of us will order pre-made MC4 PV extension cables,  of the correct length,  cut them in two,  and use each half on the respective polarity on the PVs,  example of such:
https://www.solar-electric.com/mc4-extender-cable-1000-volts-15-feet.html

FWIW,  it is great that you are asking some good questions,    Vic

Vic , I thought you probably would have a good solar connector crimper and a spool of solar wire to roll  your own cables !

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

Vic

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Re: what sized wire for MC4 connectors
« Reply #5 on: August 13, 2021, 01:29:33 AM »
Hi Larry,

YES,   I do have crimper,   cable and some connectors.

But am not in the position to recommend crimpers to others.   For many,  buying extension cables is much better than rolling one's own,  for the price of doing so.

Some folks solder these connections,   etc,   doing so,  IMO,  is not worth the risk,   and so on.

All personal preferences.    IMO.

73  Take care,   Thanks,   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!

ClassicCrazy

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Re: what sized wire for MC4 connectors
« Reply #6 on: August 13, 2021, 11:28:53 AM »
Hi Larry,

YES,   I do have crimper,   cable and some connectors.

But am not in the position to recommend crimpers to others.   For many,  buying extension cables is much better than rolling one's own,  for the price of doing so.

Some folks solder these connections,   etc,   doing so,  IMO,  is not worth the risk,   and so on.

All personal preferences.    IMO.

73  Take care,   Thanks,   Vic


Okay got you - yes for the non pro easier to get cable already made and cut it in half like you say.
I need to get one of those real crimpers - or maybe borrow one next time I need it.
I soldered mine but learned that can cause problems if getting too hot and then you burn some tinning or coating off the end of connector.
So far no fire here but then again I dont' run 600 to 1000 volt strings here !

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie