Fuse size question.

Well I crawled under the trailer to have a good look see and took a couple pics so since I took them you guys get to see them.

It appears that I have about 6ga wire coming off one battery to my disconnect switch.


Off the other battery there is about 4ga wire that runs into the genny compartment so I assume its the genny starter cable? As you can see there is just a little bit extra all coiled up.



Here is an overall look at the mess, guess I should tie up my propane hose as well, didn't realize it was hanging down that far.



Not sure why they are upside down, there facing right until I upload them into the photo app?

Hi,

Get some copper pipe 3/4 inch and press it flat. Instant buss bar material.

Muddydogs wrote:
Thanks westend, I have seen your picture before and was planning on outright stealing your design. I have the 2 plug boxes already, an electrician friend is going to scrounge me up a couple pieces of copper for the bus.

You're welcome. Steal away, that's what Forum friends are for. :B

Fuse is determined by wire size as others have said.. I will not bother with links to charts since they have done it

Instead of upgrading grom 24's to27's.. Why not go with a Pair of GC-2 in series

Here is the math
Group 24 73 amps hours each, MARINE/deep cycle
Group 27, 95 amp hours each, MARINE DEEP CYCLE

GC-2 210-230-250 amp hours.. A bit taller.. DEEP CYCLE

(There are different sub classes. all fit the same tray but they get taller as you go up in amp hours) the amp hour numbers are for the pair, in series)

That is more amp hours than your 27's will give plus being DEEP CYCLE you can use up to HALF the battery capacity.. MARINE/deep cycle you should not use that much.

Thanks westend, I have seen your picture before and was planning on outright stealing your design. I have the 2 plug boxes already, an electrician friend is going to scrounge me up a couple pieces of copper for the bus.

Bus bar connecting inverter, converter, and solar controller:



At the battery terminal is a 125A fuse connected to the 1/0 battery cable.

You need to figure out what you're protecting with the fuse. That's what determines its size. Generally this will be the wiring after the fuse (so that it doesn't start a fire).

For the bus bar connections, you can size the fuse based on the safe current carrying capacity of the bus bars and their feeder lines. If this is greatly more than could ever be expected to flow through them, it may make sense to use a smaller fuse than this maximum. Wiring that connects to the bus bars, if of lower capacity than the main fuse, should have its own fuse or circuit breaker to keep it from being overloaded and starting a fire. Usually this is the case when you have a bus bar—the main fuse for the bus bar is larger than most or all of the connected system's safe current carrying capacity.

For 2 gauge wire, it appears the NEC permits 95A (for 60°C insulation), 115 (75°C), and 130A (90°C insulation). The inverter probably would be better served with heavier wiring than 2 gauge. You presumably need to size the system for the maximum inverter draw plus the maximum simultaneous draw from other 12V systems used concurrently (lights, fans, etc.); solar if active will offset this current some, reducing the current coming from the battery. If you will have a large solar setup, the charge current from it may be the highest current you need to size things for.

#2 fairly short in plain sight I would probably not fuse. Should carry 200 amps.
Branch circuits yes.

Joe417 wrote:
The starter wires (2 AWG cable) for the generator run directly to the battery terminals. No circuit breaker.

There is a 40 amp auto resetting circuit breaker protecting the battery from all camper circuits just before the disconnect.
There is a 40 amp auto resetting breaker after the disconnect.
There is a 40 amp auto resetting breaker feeding the jacks.
There is a 30 amp auto resetting breaker feeding the slide motor.

So if there is a 40 amp from the battery to disconnect then I should put a 40 amp fuse between battery and bus since all I am doing is breaking the line from the battery to disconnect and adding a bus bar in between right? Instead of all the cables hooked to the battery i'm putting a bus in between the lines and battery. But then again I have a 750 watt inverter drawing off the cables as well?

The wire size looks to be about 2 ga, I am planning on fusing the solar charge controller and inverter off the bus. the other wire will go to the trailer disconnect. There are a couple other wires on the battery's that I am going to move to the disconnect as well so all that's hooked to the batteries is a pos neg and trailer breakaway power. As for components the fuse will protect the 2 lines off the battery supply the whole trailer with 12 volt.

I'm trying to make room so in the fall when I gang 2 more deep cycles to the other battery's I have room for the cables plus with the extra 4 gauge wires for solar and inverter just checking the water level and getting the covers back on the box is a pain.