How to pair wire size, fuse blocks etc.

[mraz72]

I am in the process of adding some electronics and I think a first good step would be a fuse block at the helm.

I'm unsure of sizing of cables and the block itself.

For example, How do I know the fuse block can handle my garmin a USB charger and a few sets of lights etc?

For example a blue seas block I am looking at has this in the info

"Max Amps: 100A per block, 30A per circuit, Max Volts: 32V DC,"

So, an individual item can only emit 30A max and the block handles a total of 100A. Is that something that is listed on each device, garmin chartplotter = 15A, USB charger = 2.5A etc? I'm not sure about the 32V DC, I have 2 batteries at 12V DC each.

Then I assume I should look for a cable that can handle the MAX the block can handle, so I need POS and NEG cables that handle 100A routed back to the batter?

 

[watdog]

I am by no means any kind of trained professional, but don't over think it. I just installed a fuse block for all the same things you are wanting to add. What I did was kind of an overkill because my VHF and my Garmin are only on 5 amp circuits. Unless you are adding an amp to the sound system 100 amp should be more than enough. Here is my video of what I did and used.

 

[mrcleanr6]

None of the items you want to install have anywhere near a 30amp draw. That fuse block has mor capacity than you could ever possibly use. You can look on any electrical item and it will tell you the current draw. A chart plotter is prob only an amp or two. You will need to fuse each circuit accordingly. Not just a 30 amp fuse for each.

 

[HangOutdoors]

Run Marine duplex, so much easier. I ran 6awg to helm fuseblock and also put a circuit breaker close to the batteries after a buss bar.

The fuse block is fine and you will have more than enough capacity

Keeps everything clean and protected and the duplex fishes nice and smooth, easy to zip tie and very flexible.

If you are going to add an amp someday that should be on its own run with its own circuit breakers

Flat Duplex Wire by the Foot | West Marine

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[HangOutdoors]

Here is the path i took and my materials list, of course you omit the portions you are not using.

https://jetboaters.net/threads/wiring-and-battery-addition.32539/

 

[mrcleanr6]

Yes since @HangOutdoors brought up the wiring. Always use marine marine wire like he posted. Not automotive or any old stranded wire. Marine wire has much finer strands and its tinned so the wire wont be bare copper and corrode. Wire strands will always be silver on marine wire

 

[mraz72]

Thanks all, I'll take pics of the fuse block once installed.

Three more dumb questions.
1. Tools for fishing wires? What do the pros use?
2. I noticed on Julien's cable run he had cable tubes (no idea what these are called) that matched the OEM, west marine have something similar?
3. I plan on wiring the block to the house battery, but I, thinking I should wire the block so the battery switch still works. If I wire the block directly to the battery, this bypasses the switch

 

[HangOutdoors]

1) I have a Steel Fish, but I didn't need it for the Helm run. You could just use a pole etc. or a broom handle, or extension docking pole if you have one. run it along the wires you have. If you need to run it through a compartment this is what I use. I use it around the house as well. Tie a string or tape a string on the end and then fish it through in the opposite direction you are pulling. One through undo string and pull fish out. Attach string to wire and pull wire through by string not the fish metal tape. Klein Tools 65 ft. Steel Depthfinder Fish Tape-56002 - The Home Depot

2) That is typcially split Plastic tube. If you run just individual wires you should put them in split plastic tube. If you run the sheathed duplex like I linked above you do not since the sheathing is the protection. Much easier and cleaner if you haven't bought your wire. I much prefer the duplex, if I can get it in the size I want. Also it could be a bit cheaper since you are getting both wires.
3) Wire it to the switch so that the switch cuts it off. I have mine wired to the switch side of my switch but I put a buss bars in to make everything easier. Would recommend a 60 amp or greater circuit breaker on the run as close to where you connect it either to the switch or battery as you can get it. You will see mine on the bottom of my wiring diagram. That runs to the helm. You want a resettable one for ease of use.

 

[mraz72]

I ordered Klein Tools steel fish (1/8" @120'), even if I don't need it for the fuse block, I'll need it in the future. I plan on ordering a roll of cable, various cable ends to fit the various connectors and a crimper. Doing a quick online search, I don't see many USA brands that make crimpers. Amazon is flooded with Chinese crap, which I try to avoid, but it seems for crimpers, it's almost the ONLY option. What are you guys using?

I was looking at a chart (on westmarine.com) listing wire run length vs the size of the wire. Here is the chart



If I plan on running ~30' of cable from the helm to the battery and the bus is 100A, I should run 1 gauge (or whatever 1 is). This is taking the max of the fuse block (100a) which I probably won't hit, but I wanted to do the job correctly.

Wiring to the switch, is that as simple as removing the switch and adding the new cables to a terminal (I never looked behind it)?

 

[HangOutdoors]

You will never be pulling 100 amps across that wire at the same time. Add up max draw. I have tabs, chart plotter, Vapor Alarm, USB x 2 and room for 1 more. Barely 15 amps continuous max with everything running at the same time and moving tabs up and down. As I indicated above, 6-2 is fine and more than enough. You are not going to put anything there that will draw big loads and if you amp you would give it it's own run. If you feel the need you can run 4 ga, but it would be a waste imho. 6-2 duplex in this situation is your friend and easy to pull and secure.

 

[mrcleanr6]

X2

 

[HangOutdoors]

For continuous on use as an example see the following.

1) Garmin 93SV UHD - Draws 1.5 amps.
2) Phone Charging 1.5 amp per phone. So 3 phones will be 4.5 amps.
3) Tabs 1 amp
4) Vapor Alarm .5 amp.
5) 1 Tablet 2.5 Amps Charging
6) 1 Laptop Charging 3 Amps


So as you can see, full up, with everything working and charging I can barely crack 15 amps. I would estimate that on average, on an average day I am using about 6 amps or so continuous and that could be a high estimate.

 

[mraz72]

Thanks, good to know. I was just looking at the raw numbers (fuse block max and length of run). I won't be adding anything other than what you listed, so that will save A LOT of cash lol. I added 35 feet of red and black @2/0 gauge to my westmarine cart and it was like 650 bucks lol.

I'm having trouble estimating what length to buy, I'm going to go with 30', sound about right? Helm to batteries through engine bay. Next up is heat shrink and cable ends

 

[HangOutdoors]

30' may be a lot. In my boat I did it with 22' but go run a tape measure through and then get some extra. You want a continuous run. This is what I used at $5.99 per foot. 6-2 Guage duplex.

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