NB wiring

[Guest]

How likely, in a used boat am I to encounter the type of wiring system whereby a unit sends a 'signal' along a single cable to activate individual electric device at the other end'

(sorry I don't know the technical name but I'n sure somebody on here will know what I'm going on about)

 

Call me old fashioned but I would rather have a simple out and return for each circuit rather than rely on electrickery and jiggery pokery to do things like switch the lights on. I understand the stated benefits of these type of systems (and indeed similar principles are used in motor vehicles now) - but I do worry about the reliability and the possible risk of being tied into a particular electronics manufacturer when things need replacing.

 

Or are my concerns unfounded and should a get my self into the current century??

[musicman]

Relays are commonplace these days. They allow you to run power the length of the boat to service several circuits that can be "switched" by a relay and are a reliable way of doing things and actually, could save you money in the long run as the chunky cable you need to avoid voltage drop over such a long distance need only be run once rather for each out and return. The relay, alternatively, can be energised by a much smaller (and cheaper) cable.

[Tony Brooks]

How likely, in a used boat am I to encounter the type of wiring system whereby a unit sends a 'signal' along a single cable to activate individual electric device at the other end'

(sorry I don't know the technical name but I'n sure somebody on here will know what I'm going on about)

 

Call me old fashioned but I would rather have a simple out and return for each circuit rather than rely on electrickery and jiggery pokery to do things like switch the lights on. I understand the stated benefits of these type of systems (and indeed similar principles are used in motor vehicles now) - but I do worry about the reliability and the possible risk of being tied into a particular electronics manufacturer when things need replacing.

 

Or are my concerns unfounded and should a get my self into the current century??

 

 

Unless you buy a very modern exceptionally high spec boat built to the customer's requirements you are very unlikely to find any Canbus type electrics.

 

It is juts possible you may find you have a sort of very heavy DC ring-main with everything taken off that by fused T connectors or possibly similar with distribution boxes (say) at the back, front & one in the middle.

 

By far the most likely layout will be a fuse/mcb distribution box at the back of the boat feeding the main components individually (like the water pump) but the lights may have several fed from one fuse.

 

Typical diagrams in the electrical notes on my website.

[bag 'o' bones]

How likely, in a used boat am I to encounter the type of wiring system whereby a unit sends a 'signal' along a single cable to activate individual electric device at the other end'

(sorry I don't know the technical name but I'n sure somebody on here will know what I'm going on about)

snip

 

I think they call it 'multiplex' well, thats what VW call their system.

 

I'm not sure how reliable the latest systems are but I know some systems are affected by static electricity causing all manner of strange things such as central locking key fobs winding windows down rather than locking the car!

 

Personally I think multiplex systems are a bad idea on a boat, I always think along the lines simple circuits are more simple to fix if theings go wrong!

Edited February 28, 2010 by bag 'o' bones

[Guest]

Unless you buy a very modern exceptionally high spec boat built to the customer's requirements you are very unlikely to find any Canbus type electrics.

 

It is juts possible you may find you have a sort of very heavy DC ring-main with everything taken off that by fused T connectors or possibly similar with distribution boxes (say) at the back, front & one in the middle.

 

By far the most likely layout will be a fuse/mcb distribution box at the back of the boat feeding the main components individually (like the water pump) but the lights may have several fed from one fuse.

 

Typical diagrams in the electrical notes on my website.

 

Canbus - that's the word I was looking for, cheers Tony.

 

and I'm very unlikely to be be buying "a very modern exceptionally high spec boat built to the customer's requirements" as you aptly describe. Have just watched Narrowboat and seen what was fitted to Dover which is what prompted the question.

 

Thanks for the pointer to your web site link too.

 

I think they call it 'multiplex' well, thats what VW call their system.

 

Thanks B 'O' B, that's certainly the name for it on cars and I think the principles the same as what I was asking about on boats.

[Guest]

Relays are commonplace these days. T

 

Cheers but I didn't mean relays - I'm familiar with those, and have been since I fit air horns to my first Mini.....

Thanks,

[springy]

An air horn is the one place where I have used this - rather than run chunky cables all the way to the

front just for the horn compressor I ran a thin one to a relay & picked up the power from the already

chunky cables installed for the cabin supplies. I thought about doing the same for the tunnel light

but as the cables were already in place for that and were (just about) adequate I left that as it was.

 

springy

[capnthommo]

An air horn is the one place where I have used this - rather than run chunky cables all the way to the

front just for the horn compressor I ran a thin one to a relay & picked up the power from the already

chunky cables installed for the cabin supplies. I thought about doing the same for the tunnel light

but as the cables were already in place for that and were (just about) adequate I left that as it was.

 

springy

 

sorry to hi-jack the thread, but i didn't want to start a new one for what is a really minor query. i just wondered exactly what degree of chunkiness you had for the tunnel light cable. i need to jury-rig one very soon and don't want to under specify on cabling. i will have to run it about 15 metres each way so a total run of about 30m and quite a low wattage of lamp - certainly not 50watts. i worked it out using the usual formulae but the local cable supplier seems to think i need about double the thickness, so i'm wondering if they are not either a) not very expert or trying to make a bit more from the deal.

again sorry to hi-jack.

cheers

nigel

[Chris Pink]

sorry to hi-jack the thread, but i didn't want to start a new one for what is a really minor query. i just wondered exactly what degree of chunkiness you had for the tunnel light cable. i need to jury-rig one very soon and don't want to under specify on cabling. i will have to run it about 15 metres each way so a total run of about 30m and quite a low wattage of lamp - certainly not 50watts. i worked it out using the usual formulae but the local cable supplier seems to think i need about double the thickness, so i'm wondering if they are not either a) not very expert or trying to make a bit more from the deal.

again sorry to hi-jack.

cheers

nigel

 

Perceived wisdom says economise, a tunnel lamp does not have to be super bright so the losses are neither here nor there.

 

Also the engine will be on at the time so your voltage calculations should be on 14.4V not 12V.

 

In fact a bright tunnel lamp will not make you very popular.

 

My 70 foot boat has 1.5mm² running a 40W bulb (?) and I have yet to get lost in any tunnels.

Edited March 1, 2010 by Chris Pink

[capnthommo]

Perceived wisdom says economise, a tunnel lamp does not have to be super bright so the losses are neither here nor there.

 

Also the engine will be on at the time so your voltage calculations should be on 14.4V not 12V.

 

In fact a bright tunnel lamp will not make you very popular.

 

My 70 foot boat has 1.5mm² running a 40W bulb (?) and I have yet to get lost in any tunnels.

thanks chris, i admit i had overlooked the engine running factor. that alters things slightly. but even so, it's good to have confirmation. why the supplier were suggesting something in the region of 6mm² i have no idea. and just so you don't worry about meeting me coming the other way in a tunnel, the light is only about 40w too, i was just erring on the side of caution - a thing i can be prone to do.

cheers again

nigel

[Keeping Up]

Also, by running the tunnel lamp at a slightly lower voltage you will get many many times more life from the bulb.

[Guest]

sorry to hi-jack.

cheers

nigel

 

No problemo - my query has been answered.

 

But on the subject of bright tunnel lights

 

- is this not also as much about the direction they point in, ie should be elevated upwards

 

a to light the roof

 

and

 

b so as not to dazzle an oncoming boat in a two way tunnel

 

>??

[Keeping Up]

No problemo - my query has been answered.

 

But on the subject of bright tunnel lights

 

- is this not also as much about the direction they point in, ie should be elevated upwards

 

a to light the roof

 

and

 

b so as not to dazzle an oncoming boat in a two way tunnel

 

>??

They must not be pointed so as to dazzle oncoming boats. That means ideally they should have a flat beam like a foglamp (this actually used to be mandatory) or if not they must be pointed slightly to the right. They should be pointed either upwards to light the roof or else (and this is my preference) ever so slightly downwards so that they light the waterline at the edge of the tunnel.

 

This latter does need careful positioning though: obviously it must be set below level so as not to dazzle an oncoming boat, but it must not be set so far down that the light will reflect off the surface of the water and dazzle them. I set mine - which is a car foglamp - so that the beam strikes the water about 100 ft in front of the boat and that seems to keep oncoming boaters happy.

[Tony Brooks]

Perceived wisdom says economise, a tunnel lamp does not have to be super bright so the losses are neither here nor there.

 

Also the engine will be on at the time so your voltage calculations should be on 14.4V not 12V.

 

In fact a bright tunnel lamp will not make you very popular.

 

My 70 foot boat has 1.5mm² running a 40W bulb (?) and I have yet to get lost in any tunnels.

 

 

Although I agree with most of this post there is, I think, one thing to add.

 

It is my view that unless you know exactly how the cables are run you should still do the voltdrop calculation for tunnel lamps, not because of voltdrop, but to minimise cable heating. Many cables are bundled together and then encased behind trim or between cabin lining and insulation. Add to that the extra current capacity quoted on modern "thin insulation" cables and you have the conditions for long term overheating and I suspect loss of insulator strength.

 

FWIW, when I took the head lining down on the boat I found some cables had melted a plastic cable clip even though their description gave them as being of adequate size when I checked. In fact they were 2sq mm.

[alan_fincher]

My 70 foot boat has 1.5mm² running a 40W bulb (?) and I have yet to get lost in any tunnels.

Ah, but you have thed benefit of a 70 foot boat.

 

With a wide tunnel, 7 foot boat, no headlamp, and a poor sense of direction, then it's just about possible, I think!