Fusing small RV setup?

Jonesz · January 2011

I will shortly be picking up some solar supplies which have been shipped to a pickup point on my trip South. Think I have a handle on most things but have some specific ?'s I was wondering about. Trying to think ahead as to what I'll need to hookup!
-FYI the setup will start with one Kyocera 135 W panel, a morningstar mppt 15A controller, 2 UB121100 110AH batteries. I have not purchased but am seriously considering a Morningstar Suresine 300 W inverter. I also have another battery which will be seperately switched via a Blue Sea 9001e switch.
-My questions are:
1. Was going to put the controller and inverter in the same front battery storage area of my Fifth wheel. The series 27 battery is in a closed vented box, the UB121100's are not. Is that OK. Just saves drilling holes to another storage compartment backing on to the battery location with the additional cable length.
2. I understand no fuse is needed between the panel and controller but that I should put one between the controller and the battery? What type and size I do not know but the panel will be about 7.6A Max so I was thinking of a 15 A inline type fuse.
3. The Kyocera will not be permanently mounted at this time but will be deployed daily as required (if we are boondocking or not) and put on a stand I have. The panel is the type with the J box connection rather than MC4 so I was also wondering the best way to establish a quick connect between the panel and controller?
Sorry for the long post but was trying to anticipate any info that you might need. Also if anyone can tell me the best type and size of fuse to put in the +ve inverter line from the battery for the 300W inverter that info would also be appreciated. I thought something along the lines of a 50A fuse would suffice.
Thanx in advance, I have learned a lot from this site so far-but still a bit confused as you can tell.
Jonesz
editted to change Freudian "South Seas switch" to Blue Sea. Maybe I wish I was on the South Seas as it is -25C here as I type this

icarus · January 2011

Re: Fusing small RV setup?

For the quick connect, look at the site host site for Anderson connectors. They make for a very easy connect/disconnect that prevents plugging in a DC system backwards!

http://www.solar-electric.com/ansb50amppop.html

Also consider using BlueSea fuses at the battery terminals. Very elegant solution for battery based systems. Remember that every wire needs a fuse relative to it's size. Because you fuse the wire from the battery to the controller with say a 50 amp fuse because you are using large wire, you will further need to fuse any current carrying conductors such as your branch circuits and loads. These allow you to stack fuses so that they can protect wires of different current carrying capacity.

http://bluesea.com/category/5/22/productline/overview/379

http://bluesea.com/category/5/21/productline/overview/378

http://bluesea.com/products/2151

As for sizing, the fuse for the PV might be say 15 amp, could be smaller as your panel is never going to push anywhere near that. Ideally, use as big a wire as possible, coupled with as small a fuse as possible, with the fuse size at least rated for the ampacity of the wire.

For the 300 watt inverter (great inverter by the way) would need ~ 30 amp fuse depending on how much surge load head room you need. 300 watts at 12 vdc would be 25 amps. I think the Suresine suggests 30 amps. Make sure that the wire size between the battery and the inverter is big enough both for the current, but for the length of run as well. Maybe #2 if the run is not too long?

Tony

Jonesz · January 2011

Re: Fusing small RV setup?

Thanks for the info re connectors and fuses Tony-as to the Morningstar being a good inverter it was Bill and you who recommended it in the first place. Looks like it will do the trick for me. As I said before I really like the low standby power draw.
Jonesz

BB. · January 2011

Re: Fusing small RV setup?

Remember that the Morning Star inverter can run a 600 watt load for something like 10 minutes... If you go through all the math (apparently everyone hates me now for making everything overly complex

):

600 watts * 1/10.5v inverter cutoff voltage * 1/0.85 efficiency * 1.25 NEC margin of safety for fuses/wiring = 84 amps recommended minimum branch wiring (round up to next standard size)

From the MorningStar 300 watt TSW inverter PDF Manual:

Required Parts (not included):
3A AC in-line fuse

100A DC in-line fuse

Toggle switch (if remote switch is used)

Remember fuses/breakers are rated to trip at rated load (tens of minutes/hours/etc.)... Running at 80% of rated load (1/1.25 NEC requirement.) means that you should not have any nuisance trips.

Bill "Making the Complex Unintelligible" B.

icarus · January 2011

Re: Fusing small RV setup?

We don't hate you Bill because you make things complicated,, we hate you because you are almost always right! LOL!

Fusing the inverter is largely a matter of what your loads are going to be. I never have more than 100 watts on the inverter, so that is only ~ 8 amps. I think I have mine wired with a 30 amp fuse on # 2 wire. The 100 amp that the Morningstar book calls for is too big for my tastes, as it would protect against ~ 1200 watts of surge, not a likely scenario.

Keeping it simple through error ridden arithmetic,,,Tony

BB. · January 2011

Re: Fusing small RV setup?

icarus wrote: »

We don't hate you Bill because you make things complicated,, we hate you because you are almost always right! LOL!

That is wrong on so many levels...

-Bill "The Law of Averages" B.

icarus · January 2011

Re: Fusing small RV setup?

Noticed I said, "almost"! Happy New year Bill, thanks for the continued learned help over the years!

Tony

Fusing small RV setup?

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