New Electrics

Common sense will tell you to have at least two light circuits on separate fuses as you don't want to be in the dark trying to replace a fuse should one blow.

I wouldn't worry about this refinement on a 20' boat. Come to think of it, I don't have it on my 34' boat either.

It used to be necessary because the total load of dozens of incandescent bulbs would necessitate a large fuse, and this in turn would mean large wire, even though each individual fixture didn't need it. By splitting the lights across two circuits the fuses can be smaller and then you can use a more appropriate size of wire. The fact that you also had redundancy in lighting in the event of a fuse blowing was an additional bonus.

With LEDs, the overall lighting current remains low even with everything on, so that reason to split goes away. Given the rarity of fuses blowing in a decent installation (I can't remember the last time) and the fact that we have plenty of torches scattered around the place, having two lighting circuits just so that you can see to change a fuse seems unnecessary to me.

Pete
 
It's a 20' boat, not 43'. I would expect 6 circuits will be fine.

6 might be Ok for just the basics but things rapidly grow. 12 I'd agree are unnecessary

Look at my circuit nothing fancy there 7 fuses in use. The 8th could supply a bilge pump perhaps or an anchor light.

My main criticism of what I have there is that all the nav lights are on the same fuse. If I were doing it again I would wire it so that the tricolour, at least, was on a different fuse to the deck level lights.
 
On old boats it is traditional to use wires of assorted sizes and colours, basically whatever you can lay your hands on, special marks are given for having the wires change colour halfway through a run, all wires should be connected with cheap choc blocks especially in damp locations, wired directly to battery posts, fuses are an unnecessary complication.

Seriously though as part of the rewiring process buy yourself a decent crimping tool makes life so much easier coupled with decent heat shrink crimps.
 
My main criticism of what I have there is that all the nav lights are on the same fuse. If I were doing it again I would wire it so that the tricolour, at least, was on a different fuse to the deck level lights.

Agree. My design for this winter's rewire has individual fuses for each light - they have individual cable runs back to the panel anyway, and a 6-way automotive fuseholder is only a couple of quid on ebay. Individual fuses for bow, stern, steaming, tricolour, all-round white, and windex-illumination then mean that a short in one cable doesn't take out anything else.

Because the fuseholder and cables are all plugged together with spade terminals, this also gives me flexibility to use odd light combinations if I want to for some reason. Can't think why I would, but this is sometimes cited as an objection to the automatic combination controller that means I normally select "Sailing Low", "Motoring High" etc rather than manually turning individual lights on and off.

Pete
 
You will need (probably) two fuse boards (each X6 fuses).

I agree - you might get away with one (X6 but I think that would be an absolute minimum). The fuse boards are not expensive anyway.

Lighting
Bilge pump
Anchor Light
Tricolour light
12V outlets
Radio
 
Are we talking about the same thing? These switch panels are quite small

Yes, we're talking about the same thing. Are we talking about the same boat? The Vivacity 20 is also quite small...

vivacity_20.jpg
 
Space on a 20' boat is limited. Doubt there's room for 2. The recommendations need to take into account the size of the OP's boat.

There is plenty of room on the Vivacity for 3 or even 4 panels (I just replaced the wooden panel mine sits on so am confident). That said, mine manages fine with a 6 switch panel and a separate volt meter.
On my Vivacity I have:
1. Anchor/steaming light - these are the same thing on the Vivacity since it's so small
2. Tricolour - no deck level lights required for sail or motor on a Vivacity
3. cabin light
4. nav instruments (depth guage)
5. Stereo and 12v power socket
6. VHF and GPS

Separately I have the auto tiller. The battery lives in the port cockpit locker and has a local switch to turn everything off. The outboard connects to the batter through the stern and the auto tiller connects via a socket under the sheet runner. There is a battery charger which connects direct to the battery but lives in the cabin connected to the shore power. The fuse panel lives in the locker on starboard side inside the companionway and the VHF is on the starboard side.
 
1. Anchor/steaming light - these are the same thing on the Vivacity since it's so small
2. Tricolour - no deck level lights required for sail or motor on a Vivacity

Howzat work, then? Assuming the tricolour is at the masthead, anyway.

If you take the attitude that displaying correct lights doesn't matter on such a small boat, fine - but in that case why bother with a "steaming" light at all?

Pete
 
Howzat work, then? Assuming the tricolour is at the masthead, anyway.

If you take the attitude that displaying correct lights doesn't matter on such a small boat, fine - but in that case why bother with a "steaming" light at all?

Pete
Tricolour for sailing, all around white for motoring maybe. Under 7m you only need a white all around
 
Doh, of course.

Though you are supposed to show sidelights if practicable :)

Pete

No you're not, they are completely optional on a boat this size in the colregs. I realise you've not had a boat in this category but trust me, I've checked what is needed and my lights are correct!
 
Though you are supposed to show sidelights if practicable :)

No you're not, they are completely optional on a boat this size in the colregs.

Rule 23 d ii:
a power-driven vessel of less than 7 metres in length whose maximum speed does not exceed 7 knots may in lieu of the lights prescribed in paragraph (a) of this Rule exhibit an all-round white light and shall, if practicable, also exhibit sidelights;

(I'm not trying to persuade you to change your setup, just playing rules pedant :) )

Pete
 
No you're not, they are completely optional on a boat this size in the colregs. I realise you've not had a boat in this category but trust me, I've checked what is needed and my lights are correct!

Not sure though that I follow your logic of fitting a tri-colour to use when sailing but don't bother with sidelights, or a bi-colour, when motoring

All you are actually required to to when sailing is to have a torch or lighted lantern available.

IMHO a set of deck level lights is worth having for the day the tricolour does not work or for when it would be difficult to see against a background of shore lights.
 
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