Circuit Breakers Either Side of Battereis

gengwall

Wow am I learning a lot reading these forums.

Still in the design phase of my off grid solar system. I am finding it easy getting info on the combiner box and breakers between the solar array and the CC but not so easy finding what I need to do between CC and battery bank and between battery bank and inverter. I mean, I get that I need breakers between everything, but the solar sites I've visited really don't cover those topics nearly as well as they do the solar array combiner box topic. Any resources or product suggestions that will give me more in depth info? Any help is appreciated.

I have looked through the forum quite extensively using a variety of searches. The topic is discussed extensively on the fringes but not really to the depth I need to make decisions.

Thanks.

Cariboocoot

Re: Circuit Breakers Either Side of Battereis

The requirements for breakers or fuses are the same everywhere.

Your power system consists of four separate but inter-acting circuits: array to controller, controller to battery, battery to inverter, inverter output. Each of these circuits has its Voltage and current ratings. The wire is sized to handle the power need of the particular circuit, and the breaker/fuse is sized to suit same.

So the output of the charge controller is 'X' Amps and the wiring must be at least large enough to handle that. Likewise the fuse or breaker used must also be large enough to accommodate that. The NEC standard is 1.56 multiplier: so for a 60 Amp controller output the fuse or breaker would be (60 * 1.56 rounded up) 100 Amp. It is not necessary for the over-current protection to be that large if the output is not going to be at the maximum. Not all inspectors understand this.

Most charge controllers and inverters have sections in their manuals covering wiring needs specific to them, including the sizing of over-current protection.

vtmaps

Re: Circuit Breakers Either Side of Battereis

gengwall wrote: »

Still in the design phase of my off grid solar system.
<snip>
I mean, I get that I need breakers between everything
<snip>
Any resources or product suggestions that will give me more in depth info? Any help is appreciated.

Do some research on Midnite's ePanel. Look at the wiring diagrams they have on their web site.

--vtMaps

BB.

Re: Circuit Breakers Either Side of Battereis

Ignoring the Combiner box/solar panel fusing/breakers--The battery bank is (almost always) the source of very high current into short circuits.

The standard installation is to ground the negative battery bus (ground rod to battery negative, to any water/metal pipes, etc.).

The battery + leads go to a common bus connection. Every wire/cable that leaves that bus should have a breaker or fuse in the positive lead that is no larger than that one wire can carry (i.e., 14 AWG + wire, uses a 15 amps fuse if you follow the National electric code). The fuse/breaker should be as close as practicable to the battery + bus (little chance for short circuit--Wires well supported, insulation around any sharp edges, etc.).

If you have parallel battery strings (especially if you have three or more parallel strings), you should have a fuse/breaker per battery string--then connect to the battery + bus.

You want to ensure that any short circuit (those you can predict, and those you cannot) will not pass any more current than the wire is rated--By ensuring there is a fuse/breaker in every "Hot" wire circuit path.

With grounded returns, we typically do not place any fuses/breakers/switches in the return leads (fuse blows, kills hot circuit--A fuse in the return blows, the upstream wiring is still "Hot").

-Bill

gengwall

Re: Circuit Breakers Either Side of Battereis

Do some research on Midnite's ePanel. Look at the wiring diagrams they have on their web site.

I did! So these ePanels are kind of Tolkienesque - "one panel to rule them all". That was exactly what I was looking for in terms of product.

jcheil

Re: Circuit Breakers Either Side of Battereis

gengwall wrote: »

I did! So these ePanels are kind of Tolkienesque - "one panel to rule them all". That was exactly what I was looking for in terms of product.

I just got one myself and I tell you what, it saved SO much time wiring the system up not to mention EVERYTHING is in one nice clean small package. However, I wish I had ordered the WIDE version. The standard (narrow) version was a tad tight to work in. Especially fitting the extra 2 shunts in. I was able to mount them where the optional DC breakers went (since I was not using those spaces anyways). And if you calculate the price of all the items, it is really only a few hundred dollars more to buy the e-panel.
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