Putting Fuses in a Solar System

2oldman wrote:
I don't know how a solar panel is going to surge enough to burn up a wire.

Depends on the rating of the solar panel and the size of the wire.
Either way, we're not talking about only 1 solar panel. If we were then no fuse would be needed in line with it. We're talking about 4 solar panels in parallel. If one shorts then the other 3 will try to send their current thru it. Thus, we need fuses.
Also, code requires it if you apply NEC to RVs.

No fuse is needed from the panels to controller. The panels will never ever accidentally produce more than Isc amperage. The wire does need to sized to carry 125% of Isc. Usually not an issue after sizing to minimize voltage drop.

Fuses on the panel side are only needed in a combiner box where the total Isc exceeds the individual panel fuse rating. Commonly 15 amps.

Fuse Breaker or Switch is often installed to cut power for service. But you can short the wires from the panels and not open any fuses.

Here's a good chart for figuring fuses and cables from Bluesea.

http://assets.bluesea.com/files/resources/reference/20010.pdf

DC breakers instead of fuses work too.

I don't know how a solar panel is going to surge enough to burn up a wire.

Lots to take in...

I haven't installed the panels pending my decision on fuses. My panels are 4 x Renogy 100 Watts 12 Volts Monocrystalline Solar Panel wired in parallel. I've never seen a diagram placing fuses between each solar panel. Gotta look that one up.

The charge controller is a Renogy Tracer 4210 40 Amp MPPT Charge Controller, 12/24V 100VDC Input. The instructions don't mention the CC at all but base all calculations on the panels.

Batteries are 4 x T105 wired for 12v.

Inverter is a Go Power! GP-SW3000-12 3000-Watt Pure Sine Wave Inverter. Have a 400 amp slow burn fuse for this guy.

So, I take from all this that plastic fuse holders are ok. I like the idea of using a breaker panel for disconnect.

Fuse to the wire size. Most folks do not fuse between the panels and the controller. A DC switch may work nicely for a disconnect.

Wouldn't you use a fuse to match the amps rating of the wiring or the Charge Controller?

There are only certain sizes of fuses and obviously 27.6 isn't one of them. The NEC states that when your calculations don't fall on a standard size you round up; so yes, a 30A is appropriate.
Fuses also have voltage ratings. Many automotive fuses are only rated for 32 volts. You didn't say what panels you're using but unless you have a big 60 or 72 cell panel the 32 volt rating should be fine.
You apparently have 4 panels in parallel?
If so you need a fuse inline with each parallel panel sized according to the label on the back of the panel. It will likely call for a 12A or 15A fuse. In a solar installation parallel panels are combined with a "combiner box" which would have spots for the fuses or breakers to protect each string.
You would still want the main one in between the combiner box output and the charge controller input. Really, it ought to be a breaker to make disconnecting power easier.
I would use MidNite Solar combiners and DC breakers for your installation.

I went with ATO for the panel to controller line as I only have one 160w panel, and ANL for everything else. Used Xscorpion plastic fuse holders for the ANLs from SonicElectronics, based the model on the wire gauge.

I got a small breaker box and breakers from AZ wind and sun, solar-electric.com; they are Midnight Solar. According to the NEC fuses or breakers on solar systems should be de-rated by 15% but that is for grid tie systems. RV's are a gray area. I prefer breakers to fuses for two reasons.
1. Gives a means to disconnect for trouble shooting.
2. Fuses are more subject to failure due to heat loss at the connections.

My panels call for a 12 amp fuse, and I used 15 amp 150vdc breakers.
For the CC output I used a 50 amp 150 vdc breaker. The CC is rated for 45 amp and its de rated value is 36 amps.