new helm and wiring

[jjc23]

I made a new helm for my 1979 glasply to try and give it a updated look. I also want to update my wiring to something more current. The original setup has a AC/DC panel near the cabin door which houses 4 AC breakers and 6 DC fuses. for now the AC will remain the same but the DC fuses are being replaced with 2 bluesea 4306 switch panels that have the fuses built in. Each panel is rated for 6 15amp fuse or 90amp. The original has 6 wires I believe 12awg that run about 18' to the helm switches. Since the new switch panels have fuses built in I need some clarification on how to get adequate power to the panels. I wont be using all 90amps of each panel but I will need power for other items up there such as nav equipment and other small items. From what I read for my amps and footage I need to run a 1awg wire to supply 80amps. My thought was to use 2 bus bars to run 4awg wire to each one giving me approx 40amps each bus. From the bus I can run short distances to the switch panel with 10awg. Is there something not right with this plan? I made a little diagram of what I'm thinking. thanks for any help you can give

 

[gonzo]

Make sure the ground wire can handle the total amperage of 66A. This chart should be helpful

 

[philSweet]

jjc23, you seem to be on the right track, but without a more complete sketch of the system, it is hard to say. In order to size the wires, you need to know the distance round trip to the batteries (not the switch), and any switches and fuses along that path. There may also be some loads that are best not run on the common bus such as sensitive electronics. Typically, there are a few small loads that bypass the disconnect switch - Bilge pump circuits, stereo standby, perhaps a security circuit, perhaps the anchor light. 1 of the pump circuits can be unfused, but all the others would have inline fuses or run to the panel. I use a solar panel that is able to run all the circuits that bypass the disconnect switch. Usually that can be a tiny one for battery maintenance between uses.

 

[Poida]

Because I an slack. I noticed you are running different gauge wires to different places, I am not sure if you think that is necessary (except from the battery) but I run one gauge wire everywhere regardless of the Amps as long as it can carry the largest current required.

Saves buying different gauges.

I usually use trailer wire 7 core and run the current to several points in one cable run.

They are also coloured so you know what is going where.

But as I said, I am slack.

Poida

 

[jjc23]

Gonzo, thank you that was something I over looked, I will probably try to keep each panel separate so I'll split the load between 2 wires.

Philsweet, thank you for the info I'll see if I can easily explain this. My thought was that the cables going to my battery switch from the batteries are providing 120 amps at less then 3% drop. So I thought I would be safe calculating from there. If not my run just got 9' longer and now im going to need to run larger cables. The power I'm bringing to theses panels is for them only. I will have a circuit breaker at the helm for each wire but nothing else will be hooked up to these runs. Basically I need to provide around 65 amps to the helm. Id like to have a 40amp capacity for each and move some items around the equal out the panels. My biggest miss understanding is I have never seen a boat this size (28') with basically battery cables running to the helm to power the switches. I'm used to seeing 10awg wire to the panels. It just seems I'm missing something here. I will then run a 3rd wire up to run the delicate electronics so they can be as clean as possible.