New fit out cable sizing and layout

[Northernboy]

My first question is do I need a fancy panel as I enter the boat with isolation switches for everything. I am looking at 12way fuse blocks feeding straight out to circuits. I have attached a picture.

 

Then comes the question of cable sizing. I found a formula on the fit out pontoon site and have applied it to the circuits I will have. Again I have attached a drawing and just wanted to know I was on the right track. The ??m refers to the distance in meters there and back.

 

Please be gentle with the replies. Help, advice and constructive criticism greatly accepted.

[WotEver]

Hi.

 

No, you don't need a fancy panel, your fuse boards are adequate. However, in future years you will wish you'd installed a fancy panel. Pulling fuses to switch off circuits isn't nearly as convenient as switching a switch. You'll also have to have them covered (BSS requirement) yet easily accessible. I'm also unsure if those connectors will accept 6mm² cable terminations; they look somewhat small to me. What is their current rating?

 

As for cable sizes, I'll study your sheet later and revert.

 

Tony

[nicknorman]

You'll need a much bigger cable for the webasto. 3.3A may be the running current, but the glowplug during the startup phase means it will be taking around 25A and they are sensitive to low voltage during startup.

 

I'd suggest you are putting in a lot of wiring, do you really need seperate circuits for so many of the lights e.g. in the bedroom? Presuming they are switchable at the fitting I'd have at most 2 fused circuits per room, with several lights on each circuit. I think most people have just one.

Edited October 18, 2016 by nicknorman

[Alan de Enfield]

What type of lighting are you proposing to use ?

 

You are showing the

Saloon lighting at 14 amps

Port pelmet lighting at 14 amps

Starboard pelmet lighting at 14 amps

 

That is about 175 watts for each installation

[Northernboy]

Wotever reply....Take your point about the switches but not sure how often you need to isolate circuits. The block comes with a purpose built cover and I will double check the 6mm suitability. The blocks themselves are rated 30amp per fuse and 100amps per bank. Thanks for your input and any further input on cable calculations is much appreciated.

 

Nicknorman reply....thanks for the webasto comment, these are the things that I cannot find out without help and yes you are correct about a lot of wiring but as it is all a bit new to me I was just trying to keep things separate as it is easier for me to understand and if I spend an extra few quid on cable it's not such a problem but I might look at it again.

 

Alan de enfield reply....these lights are concealed strip lights and they are 13m long and are around 170 watts each at max brightness. The outside ones will not be used much and the inside lounge one will be used but on a very low brightness setting.

[Tony Brooks]

Wotever reply....Take your point about the switches but not sure how often you need to isolate circuits. The block comes with a purpose built cover and I will double check the 6mm suitability. The blocks themselves are rated 30amp per fuse and 100amps per bank. Thanks for your input and any further input on cable calculations is much appreciated.

 

Nicknorman reply....thanks for the webasto comment, these are the things that I cannot find out without help and yes you are correct about a lot of wiring but as it is all a bit new to me I was just trying to keep things separate as it is easier for me to understand and if I spend an extra few quid on cable it's not such a problem but I might look at it again.

 

Alan de enfield reply....these lights are concealed strip lights and they are 13m long and are around 170 watts each at max brightness. The outside ones will not be used much and the inside lounge one will be used but on a very low brightness setting.

 

Mains or 12V? This seems stupidly high to me and in my view is just asking for battery problems in the winter unless you only use them when on shorepower. Please rethink this and look at the option for 12V LEDs with voltage stabiliser built in.

 

 

[Alan de Enfield]

 

Mains or 12V? This seems stupidly high to me and in my view is just asking for battery problems in the winter unless you only use them when on shorepower. Please rethink this and look at the option for 12V LEDs with voltage stabiliser built in.

 

 

 

That was the reason for my question - glad I'm not the only one.

[WotEver]

...these lights are concealed strip lights and they are 13m long and are around 170 watts each at max brightness.

What type? 3528 smd led strips are 4.8W/m which would be around a third of that 170W for 13m. Even 5050 strips would only be 93W.

 

Either way, that's a huge amount of power for background lighting off batteries.

[Northernboy]

Point taken about strip lights....think i got figure from one i had but now see their are diiferrnt types so will look again at lower consumption options.

[spadefoot]

I've used exactly the same fuseblock on my build. It can take 6mm cable.

I may well change it at a later date for a switch panel once I am happy with the functioning of all the circuits.

[Tony Brooks]

I still think you are talking about mains lights as you decline to clarify. Please spend time looking at 12V boat/caravan type LED lighting. Possibly apparently more expensive but far cheaper than battery sulphation and frequent battery changes in the long run.

 

Look here.

 

A12v led bulb equivalent to a 27 watt halogen only draws 207 milliamps and that is plenty bright enough to read by.

Edited October 18, 2016 by Tony Brooks

[Northernboy]

Thanks again to all the replies. One further question.....the cable itself. Have been looking around and although I know the cable should not be solid core. Does the cable have to be tinned or tri rated as this all adds onto the cable price but not sure if necessary.

 

And where would you recommend to buy the cable, I have seen a lot of stuff on the net but worry slightly about inferior quality cable.

 

Ok.....I know, that was two questions.

[Tony Brooks]

It SHOULD be multi-strand but if you are only building to the BSS you juts might get away with solid BUT you would also be building a greater number of failures into it. Please use multi-strand. If Building to the RCD note there is a minimum number of strands so what used to be 14/0.30 (1sq mm) is now something like 21/0.28.

 

Inland boats can get away with non-tinned cable but when they are the cables might corrode under the insulation. This can cause problems if you need to fit a new terminal. On salt water boats non-tinned cables can corrode right away.

 

As you will be doing voltdrop calculations rather than looking at the current rating for the cable (you will, won't you!) it will not matter much which cable you use. they both have the same number of strands, strand diameter and conductor cross sectional area. It might matter more where space to run thicker cables is at a premium. This is less likely on a boat especially if you heed the advice not to provide a separate feed to each light. I would use one fuse and feed for the port side lamps and one for the starboard so if one circuit failed you will still have some lights.

 

I have yet to come across any poor quality cable from reputable suppliers. If it has the right number of strands of the correct diameter and the insulation is OK it should be fine. In any case it seems nominally 12V cable is actually insulated for a far higher voltage running poor quality cable at 15 volts max. is unlikely to cause a problem if the insulations is a bit low spec.

[WotEver]

These folk are pretty popular for cable:

http://www.vehicle-wiring-products.eu

 

And this is a popular range:

http://www.vehicle-wiring-products.eu/section.php/198/1/single-core-pvc-thin-wall-cable

[cuthound]

Tri-rated cables are designed to meet British and North American standards, are rated at 1000 volts and are fire retardant.

 

Not necessary for a 12 or 24 volt boat, but can often be competitively priced as it sells in large volumes, so possibly justifiable on cost.

 

https://en.m.wikipedia.org

 

Most people use automotive type cable, as suggested in earlier posts.

 

Edited to add the last sentance.

Edited October 21, 2016 by cuthound

[OldGoat]

I bought mine from a motor factor in varying sizes and wired the 240v stuff in 2.5mm three core.

[WotEver]

... and wired the 240v stuff in 2.5mm three core.

With bootlace ferrules of course

[Guest]

Tri-rated cables are designed to meet British and North American standards, are rated at 1000 volts and are fire retardant.

 

Not necessary for a 12 or 24 volt boat, but can often be competitively priced as it sells in large volumes, so possibly justifiable on cost.

 

https://en.m.wikipedia.org

 

Most people use automotive type cable, as suggested in earlier posts.

 

Edited to add the last sentance.

I used tri rated in our fit out. It is OK 13 years on. Always used ferrules on cable ends.

Looked at some light fittings in a well known chandlers recently, and the switch connections were soldered

With bootlace ferrules of course

Best way.

[Robbo]

Hi.

 

No, you don't need a fancy panel, your fuse boards are adequate. However, in future years you will wish you'd installed a fancy panel. Pulling fuses to switch off circuits isn't nearly as convenient as switching a switch. You'll also have to have them covered (BSS requirement) yet easily accessible. I'm also unsure if those connectors will accept 6mm² cable terminations; they look somewhat small to me. What is their current rating?

 

As for cable sizes, I'll study your sheet later and revert.

 

Tony

Instead of that fuse block you can get a breaker block...

https://www.bluesea.com/products/5051/ST_CLB_Circuit_Breaker_Block_-_12_Independent_Circuits

[WotEver]

Instead of that fuse block you can get a breaker block...

https://www.bluesea.com/products/5051/ST_CLB_Circuit_Breaker_Block_-_12_Independent_Circuits

Much nicer but noting the make I wouldn't mind betting that it's at least three times the cost.

Looked at some light fittings in a well known chandlers recently, and the switch connections were soldered .

Why does that not surprise me?

[Guest]

Much nicer but noting the make I wouldn't mind betting that it's at least three times the cost.

 

Why does that not surprise me?

Also I have some switches from the same place which are sold for use on boats at 12V dc. Look closely and they are AC rated switches! I don't have a problem with using AC switches providing they are downrated, but i think it is naughty to just sell them thus.

[Robbo]

Much nicer but noting the make I wouldn't mind betting that it's at least three times the cost.

 

Why does that not surprise me?

This one maybe better as it has a negative bus as well as a common positive bus...

 

https://www.bluesea.com/products/5054/ST_CLB_Circuit_Breaker_Block_-_12_Position_with_Negative_Bus

[NMEA]

You'll need a much bigger cable for the webasto. 3.3A may be the running current, but the glowplug during the startup phase means it will be taking around 25A and they are sensitive to low voltage during startup.

The boats cabling should have no impact at all on a properly installed Webasto, the supplied loom should be connected direct to the battery bank, the cable supplied is more than adequate for the maximum 16a draw.

[WotEver]

Also I have some switches from the same place which are sold for use on boats at 12V dc. Look closely and they are AC rated switches! I don't have a problem with using AC switches providing they are downrated, but i think it is naughty to just sell them thus.

The problem with many AC switches is that they don't even have a DC rating. A 5A AC switch might only have a 200mA DC rating if it were to be tested for it but because that's not their intended use they're not specced for DC at all.

[ditchcrawler]

The boats cabling should have no impact at all on a properly installed Webasto, the supplied loom should be connected direct to the battery bank, the cable supplied is more than adequate for the maximum 16a draw.

How can you say that when you dont know where his batteries are and where the Webasto will be mounted. Of course if you do know his boat I take it all back.