Solar Installation FAQ

[Kidkraz]

Brad,

My battery is on the tounge it came that way from the factory with an 85 watt solar panel installed. All I have to see what's happening with my system is this panel, again installed by the factory.

[LoveToCamp]

kidraz's post makes me ask the question - in layman's terms, what is the impact of a 12' run of 10ga wire from the controller to the battery, vs. a 3' run? My controller is on the wall inside my door, as it appears kidraz's. Not real close to the battery (I ran under the TM, then in the front of the slide to get to the battery under my dinette seat).

Wonder if it has a noticeable impact, or just one that is measurable, but not significant?

[BradS7535]

Originally Posted by Kidkraz

Brad,

My battery is on the tounge it came that way from the factory with an 85 watt solar panel installed. All I have to see what's happening with my system is this panel, again installed by the factory.

I think your controller and monitor are all in one. If you looked on the inside of that cabinet at the back of that monitor panel I bet you would see 4 wires, 2 going to your solar panels and 2 going to your battery.

I was thinking that is where I would install my controller, in the cabinet next to the fridge.

LoveToCamp, that is the essence of my question as I will probably have about a 10' run from inside to the battery. Want to know if it makes a big impact.

[BradS7535]

Ok, so looking for the electrical experts to chime in and let me know what they think of my proposed setup below. Hopefully my research has paid off.

Questions:
1) Can I use circuit breakers to combine the functionality of a fuse and a cut-off switch?
2) Based on my equipment below, did I size the breakers appropriately?
3) Is a fuse/breaker needed from the battery to the TM, if so what size? I know many of you have installed the battery cut-off switch, but do you also have a fuse there? If a fuse is needed, can I use a breaker to combine fuse and battery cut-off?

Equipment:
1 x Renogy 250W Panel
1 x Tracer 3215BN MPPT
1 x 10A Circuit Breaker?
1 x 40A Circuit Breaker?
1 x Battery Cut-Off switch (or breaker?)
10AWG wiring

[Padgett]

I understand your reasoning but used a pair of 30A circuit breakers not a 10A and 40A. for two 100W cells in parallel.

Also used 2ga wiring and a 100A CB for the 1KW inverter line. (Coffee maker pulls 64A of12v - 770W of 120VAC).

[Bill]

Originally Posted by BradS7535

Questions: <snip>
3) Is a fuse/breaker needed from the battery to the TM, if so what size? I know many of you have installed the battery cut-off switch, but do you also have a fuse there? If a fuse is needed, can I use a breaker to combine fuse and battery cut-off?

Yes, a fuse is needed, and TM wired one in when the trailer was manufactured. If it is not there, you need to add one. This is completely independent of whether you have solar or not, and independent of whether you have a battery cutoff switch or not. The fuse must be within a few inches of the battery - do not try to move it into the circuit breaker box in the converter.

To look for it, follow the wire from the battery positive post toward the TM about 8-10 inches. You should/must encounter a fuseholder. The value of the fuse is 30 amps, and should not be changed. Take a look at this picture in my Tech Stuff album. If you have the first type of fuseholder, you should change it out to the second type. The change is easy - you can find the automotive fuseholder at WalMart or any hardware or big box or auto parts store.

http://www.trailmanorowners.com/foru...&pictureid=760

Bill

[BradS7535]

Originally Posted by Bill

The fuse must be within a few inches of the battery - do not try to move it into the circuit breaker box in the converter.
Bill

Bill, in my circuit diagram I have a battery cut-off switch, but I'm not showing a fuse. If the fuse is there would it be possible to swap the fuse with a 30A circuit breaker that would combine the 30A fuse with a battery cut-off, or is it better to just keep the current 30A fuse (assuming it is the blade type) and add a battery cut-off switch?

[BrucePerens]

NEC since 2008 has required a DC GFI on solar panels installed on homes. I expect to connect enough to get to 150V, so it makes sense.

Midnite solar makes this GFI. Amazon has the 80 amp one for less than the 63 amp one here. You could put this in series with a properly-sized DIN breaker. You'd need a waterproof DIN breaker enclosure to mount them, like this, but I don't have a good U.S. source.

As you can see, nobody's really produced the right product for RV use. This really belongs on the roof with the panel, before any flexible wire run.

[klpauba]

Since you have only a single panel, I would think that any circuit breaker (or even a switch) that is rated a 125% or more of the short circuit current rating of the panel will suffice. Many sources (Midnight Solar was one of them) mention that no overcurrent protection is required for a series-connected PV array. If you have 3 or more parallel-connected PV panels then overcurrent protection is mandatory.

I've also read that if you're using an MPPT controller (which you've mentioned that you are), you don't need to protect the solar panel wiring from the battery since the MPPT controller will not pass current to the panel connections in a failure condition. This is not necessarily the case for PWM controllers.

I will not argue Bruce's point that DC GFI would be desirable especially at the voltages he's talking about.

I merely bring this up for discussion since I'm sharing what I've read (on the internet, no less) and I'm an engineer, but not an electrical one. I could very well be wrong (and welcome the critique by those more knowledgeable).

[Padgett]

My solar panels have built in diodes to prevent reverse or excessive currents.