Combiner box

basewindow · January 2012

I have decided to buy another panel for my system.

Current Set up: 1x120w 12v panel, 30A reg, 2x100AH 12v AGM in parallel.

I'm going to need a combiner box for my second panel which is another 1x120w (same panel with same stats)

I was simply going to get a waterproof junction box, put a neg and pos bus in it and connect the panels in parallel.

Question: Do I need to fuse or put breakers in, or reverse diodes etc. The panels already have diodes and the array has a main breaker further down the line before the Reg.

The 30A Reg should allow enough scope for 1 other panel in the future.

Cheers,

Cam.

vtmaps · January 2012

Re: Combiner box

With only two panels (or strings of panels) in parallel you do not need to fuse each string. When you have more than two strings you do need to fuse each string. The reason is that if one string is defective, it can handle the current from the other string. When you have two strings feeding into a defective third string, that third string may not be able to handle the current from the other two.
--vtMaps

niel · January 2012

Re: Combiner box

you can do as you proposed with a junction box and you can use something like these to tie them together.
http://www.solar-electric.com/tbb.html
now you won't have need for all of those available spaces, but it will give lots of options on wire sizes. even some places like lowes or home depot have this type of thing, but without the plastic feet so one would need to mount them on an insulated surface like a plastic j box so as to not short them out. if the j box is big enough then maybe you could have room for a few fuses or circuit breakers some time down the road if you expand even further.

does your present pv have a j box on it that can have wires entering it or is it the newer style set up for mc connections that do not allow access into the j box?

basewindow · January 2012

Re: Combiner box

Thanks for replies, and taking time to answer my questions. Having only a fairly limited knowledge of electronics and electricity back from High School, it's been an interesting experiance setting this up over the last year and a steep learning curve. Thanks to the internet and forums like this it's made it a lot easier.

Anyway.

I have a couple of bus bars very similar to those which I was going to use.

I seem to have the old style PV with wires, but the wires will fit well into those bus bars!

I shall have a go making up a combiner box and I'll let you know how it goes.

Cheers,

Cam.

Combiner box

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