Rewiring thoughts

[Stemar]

I'm gradually finding out how the wiring on Jazzcat works or, more accurately, mostly doesn't work.

I'm going to scrap the existing ceramic fuses and their holders because I've too many bad memories of grief from them in old cars and bikes, and use blade fuses. Most circuits will go through a master switch so I can turn everything off when leaving. So here are my thoughts so far. I'm thinking that the lead from the battery isolator to the master should be 4mm and have a 30 A fuse and, for simplicity's sake everything else will be 1mm.

Circuit	Fuse	On Master?	Separate switch?
Nav lights	2​	Yes	Yes
Steaming light	2​	Yes	Yes
Deck Flood	2​	Yes	Yes
Anchor Light	2​	Yes	Yes
Interior Lights	5​	Yes	No
Fresh water pumps	10​	Yes	Yes
Chargers/12 outlets	15​	Yes	No
VHF	5​	Yes	No
HH VHF Charger	2​	Yes	Yes
FM radio	5​	Yes	No
Instruments - depth, log, wind, plotter	5​	Yes	Yes
Autopilot	5​	Yes	No (can just unplug it)
Windlass	5​	Yes	Yes (power to up/down switches at bow that work the relay)

Any thoughts, suggestions, things I've missed?

Thanks in advance

 

[dansaskip]

I would be tempted to have a separate switch for everything partly for the sake of uniformity and to be able to isolate things, but maybe because everything electrical on my boat has a separate switch.

 

[Boater Sam]

Unless you are wiring a coracle, with those wire gauges and 12v you will have excessive volt drop to most circuits.
Why fuses when MCBs are better?

 

[prv]

Do the volt drop calcs for larger items as Sam suggests; 4mm and 1mm feel small to me. Otherwise seems reasonable.

I like having a master switch for cabin lights - it lets you be sure during daylight hours that there isn’t a forgotten reading light in a corner somewhere draining power all day. Also convenient to turn everything off with one flick as you head out to the pub, and everything back on as you come back. But depending on the size of boat and your pattern of use, those may matter less to you than me.

I agree that there’s no point having a switch at the panel for devices that have their own effective on/off switch. And I approve of the switch for the windlass control circuit; I have the same having once laid on the foot-switch on a charter boat while wrestling with a stuck jib, and had the windlass start grinding away at my oilies…

For what it’s worth, my light, windlass, and deck socket switches are in the cockpit next to the plotter, rather than at the chart table. Not everything electric has to be on a single panel.

I too have blade fuses, they’re compact and simple and the slight extra effort of replacing one rather than resetting a breaker is irrelevant since they shouldn’t be blowing or tripping regularly in the first place. The only time I’ve had to replace a fuse in nearly ten years was when I foolishly left the instruments circuit turned on while rewiring one of the displays.

Pete

 

[Stemar]

The only time I’ve had to replace a fuse in nearly ten years was when I foolishly

... did something similar

I reckon if fuses are blowing regularly, somethings badly wrong. The fuse boxes I'll use have LEDs that tell me which fuse is blown.

 

[prv]

The fuse boxes I'll use have LEDs that tell me which fuse is blown.

I don't need that because by the time I'm looking in the fuse box, I already know what's not working ?

Pete

 

[PaulRainbow]

I'm gradually finding out how the wiring on Jazzcat works or, more accurately, mostly doesn't work.

I'm going to scrap the existing ceramic fuses and their holders because I've too many bad memories of grief from them in old cars and bikes, and use blade fuses. Most circuits will go through a master switch so I can turn everything off when leaving. So here are my thoughts so far. I'm thinking that the lead from the battery isolator to the master should be 4mm and have a 30 A fuse and, for simplicity's sake everything else will be 1mm.

Circuit	Fuse	On Master?	Separate switch?
Nav lights	2​	Yes	Yes
Steaming light	2​	Yes	Yes
Deck Flood	2​	Yes	Yes
Anchor Light	2​	Yes	Yes
Interior Lights	5​	Yes	No
Fresh water pumps	10​	Yes	Yes
Chargers/12 outlets	15​	Yes	No
VHF	5 10​	Yes	No
HH VHF Charger	2​	Yes	Yes
FM radio	5​	Yes	No
Instruments - depth, log, wind, plotter	5 10​	Yes	Yes
Autopilot	5​	Yes	No (can just unplug it)
Windlass	5​	Yes	Yes (power to up/down switches at bow that work the relay)

Any thoughts, suggestions, things I've missed?


Thanks in advance

Most of the wiring and most of the fuses are underrated. The autopilot should have a switch, plugging in/unplugging live equipment is a bad idea.

Use 10mm cable to the panel.

All other cables should be 1.5mm, except the ones i've marked in red, which should be 2.5mm. Suggested fuse rating in blue.

I have assumed LED lights.

Autopilot will depend on the exact pilot and cable run, most definitely not 1mm. 5A fuse looks low for an autopilot.

Double check all other fuse rating, don't fuse too low, for instance, everything except the 12V outlets and possibly the autopilot could simply be 10A, they only protect the wiring.

 

[Stemar]

Thanks for the responses. That's exactly what I wanted.

My wire sizes were a first guess, influenced by what I have in stock, and I didn't allow for cable length.

 

[pyrojames]

I like to have two fused (CB) circuits for cabin lights (roughly port/stb) so that a fault on one light doesn't leave you completely in the dark.