Y connectors or Combiner box?

shadyshabin

New Member
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Apr 28, 2022
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Hey there people,

I am currently designing my first solar system for an off grid cabin, with 2s4p due to shading (each panel 230W, Voc 37V, Vmp 30.3V, Isc 8.2A, Imp 7.6A, Max fuse rating 15A).

I was originally planning on connecting each string to MC4 15A inline fuses, and then using three pairs of these 2 to 1 connectors (https://www.solamart.com.au/product/mc4-y-connector-2-to-1-pair-genuine-mc4/) to join all to 1 output to disconnect and then Victron 150/60 mppt charge controller. I then learnt of combiner boxes and am now wondering if that would be the better option here?

I was looking at Eco-worthy combiner boxes (https://www.amazon.com.au/dp/B01N96GJFT/ref=emc_b_5_t?th=1) but wondering if the 10A fuses would be suitable, or would I need to opt for 15A fuses?

Any opinions or advice would be greatly appreciated!
 

rmaddy

Full-time Solar-powered Trailer Life
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but with MC4 you may run up against the max amp rating of those connectors.
Which is typically 30A.

with 2s4p due to shading (each panel 230W, Voc 37V, Vmp 30.3V, Isc 8.2A, Imp 7.6A,
This puts the Isc of your array at 32.8A and the Imp at 30.4A. That's too high for MC4 connectors. The last pair of Y connectors will be carrying too much current. Seems like a combiner box would be the correct approach for your planned 2S4P array.
 

shadyshabin

New Member
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Apr 28, 2022
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7
It probably can be done with Y connectors, but with MC4 you may run up against the max amp rating of those connectors.
Which is typically 30A.


This puts the Isc of your array at 32.8A and the Imp at 30.4A. That's too high for MC4 connectors. The last pair of Y connectors will be carrying too much current. Seems like a combiner box would be the correct approach for your planned 2S4P array.
Thank you both. The MC4 connectors I am planning on getting are rated at 39A, so in this case it should be okay?
 

DThames

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Nov 22, 2019
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I don't mind using a Y connector if the amps are low, like 20 amps or less. As you approach the rating most connectors will get warm and even start getting hot. A proper connection is based on spring tension inside the metal sleeve of the connector. When this tension is less (like from getting hot) the connection resistance goes up and the connector gets hotter still.
 

HRTKD

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Apr 24, 2020
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Depends on solar wire Size

That's a good thing to check. Some MC4 connectors say they work with 10 to 14 gauge wire. If you require 8 gauge wire then the MC4 connector has to also support that size wire.

That have been some forum members that made 10 -14 gauge MC4 connectors work with 8 gauge. But not many and I wouldn't be one to try it unless it was a critical, short term, need.
 

12VoltInstalls

…myself everything do I…
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some forum members that made 10 -14 gauge MC4 connectors work with 8 gauge.
I have used the Bouge connectors with 10ga and 8ga fine fwiw
Don’t mix brands - something I learned the hard way. Buy a 24pak, change ‘em all and have spares.
 

shadyshabin

New Member
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Apr 28, 2022
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Thanks all for the advice. I've actually decided to go with 4S2P to start off with and see how things go with that - seems it will end up being simpler and cheaper, and I can always rewire if the shade is impacting too much. Some good takeaways from this post though.

For reference I was planning on using 6mm sq wire, which I believe sits somewhere in between 9 and 10 gauge, which is the max the Y connectors I was looking at fit (https://www.solamart.com.au/product/mc4-y-connector-2-to-1-pair-genuine-mc4/)
 
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