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Adding a extra 12v fuse box


alan0043

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Hi Everyone,

 

I am in the planning stage of adding a extra 12v fuse box. The fuse box has room for 12 circuits. The fuse box is a Blue Sea brand with grounds going to the fuse box. I am planning to locate this fuse box in the driver side storage compartment. What size wire do I need ? I am thinking # 8 would work. Is there a flexible #8 wire ? Something like welding cable. What size fuse and what type should I use to supply the positive side of the fuse box ?

 

Thank you for any help,

Al

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What is the total amp draw going to be on this block? That and the distance from the power supply is what you need to determine the wire size and main fuse size.

 

I don't know what the total amp draw is going to be. I want to have this extra fuse box just incase that I need extra circuits for added on equipment to the truck. That is the best answer that I can give. Right now I don't see any high draw equipment being added.

 

Al

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Alan I ran 2/0 welding cable from batt bank into compartment to blue sea power posts. Have a 200amp fuse at batts.

 

That allows the inverter a place to connect very close short run. Then from the posts fed the Blue Sea fuse panel for extra circuits. Mine only had spaces for 8 circuits. Used #4 wire. Short run. All my users are low amps.

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If you have the "standard" Blue Sea fuse panel the rating should be 40 amps. 8 AWG copper tinned marine grade wire is the best choice for a 40 amp feed. Be careful what you buy, a lot of the wire out there is copper coated aluminum and may not really be 8 AWG (Pyramid is an example). Marine grade is tinned and more resistant to oxidation/corrosion. You will have a short run from the battery's to the fuse panel so you most likely only need about 5' of hot and ground. I would not use a fuse in the 8 AWG from the battery - an automatic resetting marine circuit breaker is my choice. Don't forget your feed through bushings where you come through the floor. Bushings for RG-6 coax are cheap and sized right for #8 AWG wire. The links I provided are strictly for "examples", not an endorsement of a specific product.

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I can definitely recommend welding cable over automotive battery cable. Used it on many projects over the years. You will find it to be better quality, much less expensive, and far more flexible than battery cable. It is way cheaper, so just oversize it a gauge or two to be on the safe side for peace of mind if you want. They will also have reasonably priced brass terminals at the same welding supply, and generally will crimp them on for you with a smile and no extra charge. If not, pick up a cheap hammer crimper tool and install them yourself.

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No argument with above recommendations but we did it a little different.

 

We added a couple small fuse panels and connected them through a Midnite Solar Baby Box with DC breakers. I wanted to be able to isolate the loads and sized the breakers to to protect the downstream wire and panels. Also rerouted the main DC fuse panel through the breaker box.

 

For wire, we used 4 awg and 8 awg wire connected to 60A and 30A breakers respectively. As i recall, the 8 awg is MTW and 4 awg is welding cable. Blue Sea has a handy DC wire selection chart which will give you guidance for sizing. For our short runs, go with the heavier gauge wire; cost difference is minimal between sizes.

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Just as a point of interest, consider adding 2 boxes, one switched (at the ignition key) and one unswitched. Hook lights and similar stuff to the switched box so you can't walk away and leave something on, and the unswitched for things where you want (or need) to use the native switch of the item you're connecting.

 

Good Luck

 

Paul

 

BTW - I used some flexible plastic conduit to route the wire. Makes future circuits MUCH easier to install.

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The above advice is all pretty good. For the BEST wire run, use the marine wire that Randy mentions. It is always best. But the welding wire is generally what I use because it is more available. You can "mail order" either one, though. I ALWAYS dd both a switched (ignition) and unswitched (constant) loadcenter. You will not regret doing that over the course of time. I usually also add a few relays when I put in the loadcenter. Eventually you will use them, if you don't right away. I mount the Jackaloppee, the loadcenters, etc. on a plywood backer and build it on the bench. then just install the entire thing at one time.

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