TRI cable

[DHutch]

Re: bus-bar, is that the type of solid metal bar we use for connecting several earth cables?

People do all sorts of things, but that what i would be using.

- As i say, we have actutally used a normal domestic consumer unit for the 24v wiring in our boat. In the form of an MK sentry unit.

- The breakers work very well for us, the box is very nice and spacious, and there are plenty of conections for our needs.

 

 

 

Daniel

[Bert]

Come on guys simmer down, I did not want to start a row.

 

Many thanks to everyone for their replys. You can all join me onboard for pint when I finish this project.

All the best to you all

Bert

Edited August 18, 2006 by Bert

[Gary Stacey]

'I also doubt the positive advantage of building in voltage drop and would be curious what an RCD surveyor would say when viewing a schematic containing undersized cables. I reckon he would find the idea that its for bulb life reasons to be quite comical, he may even consider it as a fire risk'

 

 

You can 'downrate' cables to increase voltdrop and still be well within the current rating of the chosen cable. Infringing the latter is what would cause fires etc. Surely all boat exiaminers are interested in is that the aplliance current demands do not exceed the current ratings of the cable?

 

Gary

[John Orentas]

'I also doubt the positive advantage of building in voltage drop and would be curious what an RCD surveyor would say when viewing a schematic containing undersized cables. I reckon he would find the idea that its for bulb life reasons to be quite comical, he may even consider it as a fire risk'

You can 'downrate' cables to increase voltdrop and still be well within the current rating of the chosen cable. Infringing the latter is what would cause fires etc. Surely all boat exiaminers are interested in is that the aplliance current demands do not exceed the current ratings of the cable?

 

Gary

 

 

If anyone wishes to use Tungsten Halogen lamps on a boat without paying some regard to increased voltages they should aquire 'Automotive' specification lamps. Automotive lamps are in fact 14 volt rated units for the very reasons described on this thread, the lamps on your car will very regularly see up to that voltage perversely when the battery is a 'bit flat'.

 

In practise the automotive lamps are not available so you must either put up with a shorter lamp life or reduce the voltage in some way, a voltage drop in an electrical circuit is always present, what we are talking about is the degree of that reduction. Very often this is done for you without being aware of it.

 

For example if you have a 20 watt lamp midway along your boat, supplied through say 20 metres of wire, if you use 1.5mm cable it will will have a volt drop per metre 0.117 per amp.

A 20 watt 12 volt lamp will draw 1.7 amps

 

So 1.7 x 20 x 0.0117 = 0.4 ...... You have lost close to half a volt well onto the region you are looking for.

 

By the way for anyone concerned that you may produce a fire ball by down-rating your cable a little. A typical Tri-rated cable 1.5mm has a current rating of 21 amps so it is not going to happen.

 

For wiring a boats 12 volt system when selecting a cable size you should be guided only by the calculated volt drop for a particular size, the current rating of cable concerns only the thermal spec of the insulation and is only appropriate for 230 volts systems. For most applications you should aim for a minimum drop but remember there is no such thing as a zero volt drop. For a water pump for example half a volt drop is quite acceptable, using the same 20 metre length of wire and assuming the pump may draw up to 10 amps the calculation using say 6mm cable. 6mm cable will drop 0.003 volts per amp per metre.

 

So. 10 amps x 20 mtr x 0.044 = 0.6 volt drop.

 

For a shorter shorter cable run you can reduce the cable size, longer runs and you should increase it.

[Bernie]

Whilst this topic is extremely helpful and instructive there are a couple of quite sarcastic and uncalled for replies which I don't really think are helpful to anyone. I feel the person who wrote them should apologise, if not then they could probably be removed from the subject.

[Bert]

Hi Daniel,

Yes I will use one of these consumer units, I have seen them being offered complete with breakers at very good prices. I did read an article about fitting a reversed polarity indicator to these units, but I cant remember where I found it. Not sure if this type of indication is something that now has to be fitted or not.

Cheers

Bert

[John Orentas]

Hi Daniel,

Yes I will use one of these consumer units, I have seen them being offered complete with breakers at very good prices. I did read an article about fitting a reversed polarity indicator to these units, but I cant remember where I found it. Not sure if this type of indication is something that now has to be fitted or not.

Cheers

Bert

 

 

Hi Bert.

 

Yes using a domestic consumer unit is a good idea, that is what most people do these days, but you will need to make arrangement for a very high current feed, perhaps 10mm or even more, as I have said previously the breakers may well be marked only with an AC rating but don't worry about that. The reversed polarity indicators are only of value with 230 volt systems where you have more than one power sources, if I am thinking about the same thing.

 

You will also need an isolator capable of switching the heaviest current on the boat, the starter motor many boats have fitted on them those automotive ones with the red handle you see advertised, I don't like them as they have real problems with contact pressure but if you do go for that type, buy the biggest you can get hold of, 300 amps or even more. Personally would look for an industrial unit, I managed to find a 300 amp job made for stacker trucks.

 

If you are buying a cruiser style boat, try and get as many of the electrics and other sensitive stuff in the cabin area, that damp oily atmosphere under the deck can be a problem in the longer term.

[Bert]

 

 

Hi Bert.

 

Yes using a domestic consumer unit is a good idea, that is what most people do these days, but you will need to make arrangement for a very high current feed, perhaps 10mm or even more, as I have said previously the breakers may well be marked only with an AC rating but don't worry about that. The reversed polarity indicators are only of value with 230 volt systems where you have more than one power sources, if I am thinking about the same thing.

 

You will also need an isolator capable of switching the heaviest current on the boat, the starter motor many boats have fitted on them those automotive ones with the red handle you see advertised, I don't like them as they have real problems with contact pressure but if you do go for that type, buy the biggest you can get hold of, 300 amps or even more. Personally would look for an industrial unit, I managed to find a 300 amp job made for stacker trucks.

 

If you are buying a cruiser style boat, try and get as many of the electrics and other sensitive stuff in the cabin area, that damp oily atmosphere under the deck can be a problem in the longer term.

 

 

 

 

Hi John,

Glad you pointed that out ,I would have been busy trying to find out how to fit indicator to DC pane l

I shall come back to that when I get on to the 230v system.

The isolator, does that need to be fitted close to the batteries or can it be sited next to the consumer unit.

I am going for the Trad, so I think the first cabin area is ok for electrics.

Cheers Bert

[nmptwentyone]

tb-training.co.uk

 

what an excellent website, thanks for posting the link!

[DHutch]

Yeah, the indicators are for the 230vac boards.

 

The MCBs in the sentry box are actally rated for DC, upto about 50v i think. But as john said, there doesnt seam to be any problem with using non-dc rated switchs.

 

We also have a smaller sebry box for the 230vac electrics, with three, MCBs in for The ring main, The battery charger, and the 240v lighting circuit. (one large florence in the enigne room only)

- This doesnt have and indicators fitted, as its 15years old, when they wernt reqired. However, we plan to add them somtime...

 

As you can see the cabling we have used to bring up the DC supply is fairly huge, it is infact 35mm^2 arc welding cable (used for the earth cable)

 

Our electics (batterys, mains charger, disboard, are actally closer to the middle of our boat about 2/5th from the stern.

- Our engine has no electrical requirement, so it made sence to have everything more central.

- The alternator is actually as the back of the boat, so thats a fiarly long cable run. But even being machine-sensing, it seams to charge well enough for our (limiited) needs)

 

 

The supply cables run from the batterys (4*110Ah 12v batterys, wired into two 24v banks) thought the (large two-way vetus) isolator switch, and then stright upto the disboard. Behind the removable plank seen clearly in the second photo.

 

 

Then about half the cables run back down again, under the floor in a flexable conduit, and then up the wall, and run forward and backwards under the gunnels to where every they go.

- Then the other half run thoght the back of the box, over the ceiling (inside the coal bunker actally) then down to the other gunnel, to all the stuff on that side. (inculding the 240v disboard, at th back of the boat)

 

 

Daniel

[Bert]

Thanks Daniel,

I see you have used the vetus isolator switch, i'm looking for suppliers now, and maybe some alternative isolators.

Cheers

Bert

[DHutch]

I see you have used the vetus isolator switch, i'm looking for suppliers now, and maybe some alternative isolators.

Yeah, we used two, one for the domestic batterys, using it to its full potential, switching to one other, or both of the two banks. And one for the bow batterys (its a eectric vetus bow thruster, 3kva, 24v), just using it as an on/off switch for the single bank. With a

150amp inline fuse.

 

Mailspeed have them:

http://www.mailspeedmarine.com/ProductDeta...30-1d3198326770

 

 

Daniel

[Bert]

Yeah, we used two, one for the domestic batterys, using it to its full potential, switching to one other, or both of the two banks. And one for the bow batterys (its a eectric vetus bow thruster, 3kva, 24v), just using it as an on/off switch for the single bank. With a

150amp inline fuse.

 

Mailspeed have them:

http://www.mailspeedmarine.com/ProductDeta...30-1d3198326770

 

 

Daniel

 

Hi Daniel,

Thanks for the web site link.

I have just found this site, very good prices. http://www.gscontrols.com/index.asp?functi...LAYCAT&catid=22

Cheers

Bert

[david and julie]

I got most of my cables etc from vehicle wiring products, and found them to be OK too.

 

I don't know how it compares (pricewise) with the Tri-rated cable you mentioned earlier, but the thinwall version of cable is certainly a lot easier to work with. Especially when you have a lot of cables to get into conduits or small areas.

 

It is also wise to make a simple schematic with cable sizes/colours and any fuse/breaker/isolator values and locations, as you go along, rather than at the end. This will help you in the future if you have any problems and if you intend going for RCD the surveyor will probably also want to see it.

 

I also used a third smaller dedicated isolator and fuse just for the 12v fridge. This way you can isolate the rest of the boat if you want too leave it anywhere unattended.

 

www.vehicle-wiring-products.co.uk

[DHutch]

I have just found this site, very good prices. http://www.gscontrols.com/index.asp?functi...LAYCAT&catid=22

Yeah, looks like the same badger.

- A lot of vetus' products are infact just other products branded, including i know our anchorchain winch.

 

 

Daniel

[Bert]

I also used a third smaller dedicated isolator and fuse just for the 12v fridge. This way you can isolate the rest of the boat if you want too leave it anywhere unattended.

 

www.vehicle-wiring-products.co.uk

 

Hi David,

A good site to add to my list. The thinwall is a bit cheaper.

I am going to work to the wiring schematic that is shown in Narrowboat Builders Handbook, then I can print a copy and mark cable sizes fuses etc. onto that for future reference.

A little concerned about selecting correct cable sizes for this 12v system, but I now have a cable rating chart to follow, so should be ok.

Thanks for the tips

Regards

Bert