Circuit Protection

[Kristal]

I am currently designing a new wiring and distribution system for my boat, and naturally, the first consideration is safety. Crystal is a traditional boat (1927) and therefore I am aiming to fit the system with as traditional a look as is possible - for instance, I want to use those hefty push-pull marine switches rather than the superb but modern-looking combined switch/circuit-breaker items.

Using the latter, however, would mean every piece of equipment is protected separately - highly desirable. Using traditional-looking switches means that, without a long and complicated cable run for each circuit, I can't place individual protection on each piece of kit.

Is it acceptable to calculate the largest current flow likely to run through each main circuit (Maintained, Primary & Auxiliary) when all bits of kit are operating, and protect it at that rating? I suspect not, as ideally one would want the protection to trip the moment one item of equipment malfunctions or shorts - but then again, the fuses on my old Triumph car numbered two for the whole system.

Advice welcome, and fear not, I will have the system checked and installed by a professional marine electrician - I just want to eradicate any potential design flaws at this stage.

Thanks very much,

Kris

 

[steve_cronin]

I don't know how much this suggestion will be considered by you as a compromise of the boat's originality but have you considered in-line fuseholders or even the push button CBs made by Index Marine? The latter can be rather expensive though at £41 each.

I once made a distribution box for a 60s boat using a seven fuse "Wylex" domestic distribution/fuse box, drilling holes below each switch, in the hard plastic to take automotive push/pull switches. It's cream colour looked very much in place and had a fuse ever blown (none did in 17 years) they would have been simplicity itself to re-wire.

Steve Cronin

 

[Kristal]

That's a good suggestion, and one that I had stupidly not thought about. I would prefer circuit breakers if possible, but as you say, they are rather pricey and I need almost 20 of them.

In-line fuse holders, an LED, and a push-pull switch would look very nice - after all, I'm only worried about the look being original. A high level of sophistication is equally important.

Thanks very much for that.

/<

 

[Benbow]

I have not had good experiences with inline fuses, in my hands they often fail to make proper contact with the holder and lead to an annoying intermittent fault.

Why not just a marine or car-type fuse box behind your switch board ? You could common the inputs and use the outputs to feed your switches.

 

[Evadne]

LEDs would be a nice touch, I've always fancied doing (one day!) one of those boards you see on the bridge of a big ship for the nav. lights, an outline of the ship with an LED in the place where the light is. I've never seen one on a yacht so I'll have to carve it myself.
If the panel is big enough you can also do panel mounted fuse holders, with the fuse under each switch.

 

[Kristal]

Cor! The outline & LEDs idea is a cracker... totally over the top for a 30' yacht, but that's never stopped me before. I'll have to have a think about that...

I've always found in-line fuses to be a bit hit-and-miss, too, which is why I fancied circuit breakers. Weighing up against the cost, though, might prove to be the issue - with 20 of them all told, it starts to get rather costly, and the money would be better spent on the new kit. The separate fusebox idea is an attractive option, as I'd quite like all the serious bits of the system to be hidden away beneath the chart table, I'm just worried about excessive cable runs.

/<

 

[Gunfleet]

I think you'll find the traditional electrical layout on a 1920s yacht was 'none'. You could keep plenty of paraffin in the lazarette!

 

[moondarra]

You can buy individual panel-mounting fuse holders which fit through a small (15mm) drilled hole: these are at least better than in-line holders and can be bought quite cheaply from CPC (08701 202531)

12 volt: Order part no FF01014 for 23p each

240 volt: Order part no FF00852 for £ 2.19 each

For indicator lamps use panel mount lampholders

12 volt (11mm hole) SC00460 at £ 1.80 each

240 volt (9.5mm hole) SC01019 at £5.60 each

Suggest you contact your marine electrician to help with the design: good design will simplify the installation and reduce the amount of wiring and components needed. Also cable diameters are dependant on circuit length: otherwise voltage drop will give you problems.

Best wishes with your project

 

[pvb]

I\'d consider blade fuses...

You certainly need individual fuses/breakers on each circuit. Breakers are nice, but costly. In-line fuseholders can be problematical. Fuseboxes using those ceramic fuses are very prone to corrosion. So I'd consider using automotive-type blade fuses, which are very neat, have sound contacts, and are inexpensive. Index Marine have fuseboxes for 4, 6 or 8 blade fuses.

 

[Graham_Wright]

Don't forget Beaulieu Boat Jumble.

I bought a box of 50 breakers for £5 each.

 

[snowleopard]

Egg-sucking instructions follow. Grandmas please ignore /forums/images/graemlins/smile.gif

It's a common but incorrect assumption that the fuse is to protect the bit of kit on the end of the circuit. There is an element of that but the main function is to protect the circuit from carrying more current than the wire can handle. A short inside a gizmo is possible but more likely is one caused by accidental bridging of wires. Your aim therefore should be to set the rating of the fuse or breaker to just below the maximum the thinnest bit of wire in the circuit is able to carry. The fuse must blow before the wire gets hot.

There is no harm in reducing the fuse rating as long as the value is more than the total load the kit can draw. Remember that some items, particularly those containing motors and filament lamps, draw more current on start-up than during use.

There's no harm in having several items hanging off one fuse as long as all the cabling in all the circuits is rated above the rating of the fuse that protects it. For this reason you wouldn't want to put an anchor windlass on the same fuse as a depth sounder.

 

[tome]

Reading the responses, I think by now you'll be aware that you need individual circuits rather than large groups.

I've built a few panels for traditional boats over the years, and have done a simple artwork for each and taken it to a professional panel maker to have it cut and engraved - cost about £30-40.

Circuit breakers (see Fatipa's thread) are available which serve as both switches and thermal protection. These are about £7 each. They will not look out of keeping on Kristal.

As for the indicating panels on ships, there's no reason why you couldn't include this provided you have space.

If you want something like this and have a suitable drawing package to alter it to your own design (AutoCAD, CorelDraw etc) PM me and I'll send you some files to get you started.

 

[Kristal]

Thanks, tome, and to everyone for this illuminating advice - my original design did incorporate individual breakers for each (albeit of the combined switch/breaker design) but now I think that using the smaller type circuit breakers is the best plan. It makes things one hell of a lot simpler and avoids lengthy runs for trifling reasons.

Aesthetically, the switches will be laid out over several panels, all of which will need to be custom-etched and cut, so I'm pleased to know this can still be done at a reasonable price.

So, large groups having been avoided, how about small ones? For instance, my current thinking is this: there will be a master switch for Nav Lights, fuse protected at about 10A (estimate - I will heed snowleopard's advice about cable tolerance etc), and then, on another panel (etched with the outline of the boat, hee hee) individual switches for sidelights, stern light, steaming light, anchor light etc. These, I imagine, will be fine under the protection of the matser 10A breaker, provided the right cable is used.

An aside question regarding the LEDs to indicate which lights are on - would it be reasonable practice to connect these in series with the lamps they indicate, so that if there is a malfunction with the lamp, the LED won't light?

Again, my basic design will undergo the scrutiny of a qualified engineer, but as a jumping off point, I think this is a good start.

Thanks again, everyone - am learning the black art of marine electrics slowly but surely!

/<

 

[Stemar]

For the panel, if the cost of a pro job iturns out to be prohibitive, you could print out your design then attach it to a board and cover with clear fablon. If you want light lettering on a dark background, letraset is still available.

 

[TheBoatman]

Dave
I've seen just what you want, they are made by a company in Rochester (the name of which fails me) but if you want the name I'd be happy to get it for you.
The pannel is about 6 ins sq with the engraved outline of a yacht on it with an LED at every point that you should have a light.
Peter.

 

[William_H]

Hello Kristal gemerally no it is not practical to put an LED in series with the loads ie Nav light. An LED melts at more than 50 ma (typically) and needs or drops .8 volt up to 2 volts to operate. You would need a low value resistor to drop about 2 volts say 1amp the lamps are drawing ie 2 ohms at about 5 watts. Across this you connect the LED in series with a resistor of about 20 ohms to limit the LED current. This would work but leaves you losing 2 volts to the lights. A more elegant solution is to wrap a coil around a reed switch (that is a tiny glass tube about 4mm in diameter 25 mm long with an iron switch which contacts in a magnetic field. You would need about 20 turns of wire capable of carrying the lamp current with low volt drop. The swith connects the LED with a series resistor 470 ohm to the 12 volt supply. So I am guessing that you see current sensing indicators are too hard unless the sophistication becomes an end in itself.
Snowleopard has given you the best advice. Firstly you can and should common circuits to reduce the number of fuses. (My boat has one.) You must accept that a fuse or more likely a fuse holder failure, will kill multiple systems (probably not life and death) For light load applications up to Nav lights then the wire you will use will be 20 gauge. Don't know the new MM sqaured measurement but we are talking ordinary plastic covered wire like you use in cars rated for 10 amps. You need robust wire to improve the durability in corrosion climate. this is typically protected by a 5 or 10 amp fuse. You need to check the data here. This will cover I imagine all of your services if you are only using simple nav gear radio and a few lights. Or you could go more sophisticated with 2 or more fuses.
I reckon these fuse panels with multiple switches and fuses are made by electricians to line their own pockets it just isn't necessary even if it looks flash. Sophistication gives frustration cos with electrics and water, water always wins. just adding a bit of controversy here good luck olewill

 

[Benbow]

I would add two points to all this.


If you go with circuit breakers, remember that unlike fuses they have a MAX current that they can isolate. If exceeded, they can weld themselves closed. You should therefore have a single high current fuse in the feed to the entire board sized to blow above the trip current of the biggest breaker but below the max current of the smallest.

When I rewired my boat, I tried to separate circuits so that any one failure would not be too much of a problem. Thus I fed the GPS from a separate circuit to the other nav stuff. I also split the interior lighting into two, each with a separate switchable circuit. I was very grateful I had done this, when one blew a fuse (and its replacement) in the middle of the night. I did not need to worry about finding and fixing the fault while we were bouncing around.

 

[Alex_Blackwood]

Also with circuit breakers. You should ensure that the current rating for the breaker is the DC and not the ac rating (Some are quoted in both and some are ac only). DC will give a much bigger arc on breaking and can result in welding of the contacts. Therefore the DC rating is usually much lower than the ac rating!
The above should be taken into account when installing any elctrical devices such as switches, fuses and contactors etc.

 

[halcyon]

A couple of items, when planning a switch board, make sure you have dual options, i.e. fit nav lights with two supplies, one feeding bi / stern, the other feeding tri-light. Cabin lights, split port and starboard, not by the cabin. The reason is that should a circuit breaker fail, you have a back-up circuit, may not be 100% right, but you have lights.
Use a simple circuit breaker, the little button and bigger button/switch type, we found more likley to fail. In the 80's and 90's we used around 80,000 Otter breakers ( not available now), and a square one with a rocker type pop out for marine switch panels, both appear to be still going fine 20 years later. The advantage of the simple bi-metal breaker with a blade that isolates them on trip , is that if you have a major fail, instead of welding together it blows the bi-metal blade.
With switches, look for silver plated, with contacts, a number of marine switches in the past have been plain brass with pressed contacts, going geen very quickly.


Brian