Wiring size

Richardnhunt · 20 November 2016, 10:00

Hi all

After some advice. I am looking to do a rewire on a 5m RIB. I need to wire in the normal run of items - lights, plotter etc. My question is on wiring size. I have a grip (ish) on the normal formulas for wiring size, but given that I need to buy a reel of wire to run the wiring in a small rib, I am looking for some advice on:

a) a good general size of wire to use
b) suppliers
c) terminals

cheers

Rich

Nos4r2 · 20 November 2016, 11:00

Vehicle Wiring Products are rather useful for cable and glue lined heatshrink connectors.

They do a very good thinwall single and multicore tinned cable, and they state the power handling capabilities on the website.

You'd have to be running some pretty hefty kit to overload even the thinnest they sell.

Firefly · 20 November 2016, 12:12

Quote:

Originally Posted by Richardnhunt

Hi all

After some advice. I am looking to do a rewire on a 5m RIB. I need to wire in the normal run of items - lights, plotter etc. My question is on wiring size. I have a grip (ish) on the normal formulas for wiring size, but given that I need to buy a reel of wire to run the wiring in a small rib, I am looking for some advice on:

a) a good general size of wire to use
b) suppliers
c) terminals

cheers

Rich

To be on he safe side, I would recommend 18 to 16 awg for nav lights and 20 to 18 awg for navigation equipment. (18 awg for the VHF).

The best terminals are Amp or Thomas and Betts. The sea is a harsh environment for electrical wiring so invest in ratchet crimpers (Thomas and Betts are reasonably priced)

Suppliers: RS components, Farnell, CPC.

Have you drawn or obtained a circuit diagram?

Good luck

Richardnhunt · 20 November 2016, 12:42

Fab - so if I go for 1.5mm or 2mm, that would cover all?

Pikey Dave · 20 November 2016, 14:33

Go for tinned cable & heatshrink terminals. I've used this company in the past. Good prices & service.
http://kojaycat.co.uk/epages/9500004...hops/950000457

Firefly · 20 November 2016, 18:34

Quote:

Originally Posted by Richardnhunt

Fab - so if I go for 1.5mm or 2mm, that would cover all?

The problem with 1.5 to 2 mm is that it is very thick cable for nav equipment but it certainly will handle the current. You can always double up for high current stuff such as nav lights.
the heatshrink terminals sound good or use conventional terminals and apply your own adhesive heatshrink.

By-the-way. If you need heavy duty battery cables, there are people how make them to order on ebay.

A1an · 20 November 2016, 18:46

Nav lights high current?

Even if you have the 3 of them wired together its going to be 2.5A at most

Poly · 20 November 2016, 19:01

Quote:

Originally Posted by Firefly

The problem with 1.5 to 2 mm is that it is very thick cable for nav equipment but it certainly will handle the current. You can always double up for high current stuff such as nav lights.
the heatshrink terminals sound good or use conventional terminals and apply your own adhesive heatshrink.

By-the-way. If you need heavy duty battery cables, there are people how make them to order on ebay.

Not sure I like the idea of doubled up wiring. A corroded/broken-wire/failed connector on one half of the circuit will not show a fault but potentially give you a fire hazard. On boats like ribs where electrical failure is almost inevitable at some point that would make me nervous.

MatFromPoland · 20 November 2016, 19:03

Quote:

Originally Posted by Pikey Dave

Go for tinned cable & heatshrink terminals. I've used this company in the past. Good prices & service.
Cable, connectors and wiring parts for car, motorcycle and boat

Really nice stuff.
Cables on mine boat for Bilge Pump were not "Marine Grade".
I have changed Bilge to Whale Pump and discovered that long parts of cables are rusty. So maybe next year will fix new cables to end of old cables and try to pull them out. But I think that the man who made wiring tight all cables together under floor.

So next think is to use flexible Marine Grade tiny cables for 10A (If I remember 6A is max for this bilge). And try to use some equipment which electrician people use to fit cables in some ducts.

The question is which cable can you recommend "Marine Grade" for bilge pump. Max 10A thin, solid but flexible.

>>>>>>>>>>>>>>>>

Mine Bilge (fuse 7.5A)
http://www.whalepumps.com/marine/pro...Orca-Auto-1300

Pikey Dave · 20 November 2016, 19:10

Quote:

Originally Posted by MatFromPoland

Really nice stuff.

Cables on mine boat for Bilge Pump were not "Marine Grade".

I have changed Bilge to Whale Pump and discovered that long parts of cables are rusty. So maybe next year will fix new cables to end of old cables and try to pull them out. But I think that the man who made wiring tight all cables together under floor.

So next think is to use flexible Marine Grade tiny cables for 10A (If I remember 6A is max for this bilge). And try to use some equipment which electrician people use to fit cables in some ducts.

The question is which cable can you recommend "Marine Grade" for bilge pump. Max 10A thin, solid but flexible.

Either this http://kojaycat.co.uk/epages/9500004...e_Tinned_Cable

Or the 1.5mm twin

MatFromPoland · 20 November 2016, 20:01

I prefer thinner cable like 14/3 like this one mentioned below
Made in US but shipping cost is horrible (Fuse is 7 A):

Manolism · 20 November 2016, 21:39

Read the attachment wiring diagram from Blue sea. Basically is not only the amp of the device but also the wire length from the source.

gtflash · 20 November 2016, 22:01

Quote:

Originally Posted by Manolism

Read the attachment wiring diagram from Blue sea. Basically is not only the amp of the device but also the wire length from the source.

Exactly what I was thinking. You need to work out ur current draw and distance of cable runs before spec ing cable size. Consider battery placement, fuse/circuit breaker location, switch panels etc.

A1an · 20 November 2016, 22:04

its a 5m rib, voltage drop will be negligible.

Firefly · 20 November 2016, 23:01

Quote:

Originally Posted by Poly

Not sure I like the idea of doubled up wiring. A corroded/broken-wire/failed connector on one half of the circuit will not show a fault but potentially give you a fire hazard. On boats like ribs where electrical failure is almost inevitable at some point that would make me nervous.

If doubled up cables make you nervous, don't ever fly again. Doubled up cables are commonly used on aircraft systems. Note, I mentioned wire gauges ranging from 20 to 16 awg. A 5 meter rib is unlike to have any system that would present a fire hazard due to loss of 1 of these wires. In any event, if the wires are doubled up and crimped together in the terminal, what are the chances of just one wire corroding and failing? One other point. How is electrical failure almost inevitable? I have many hours on RIBS under my belt, most of these, I have rewired entirely from scratch and I have never suffered electrical failure. Of course, if you have an old with old wiring, you are asking for trouble; or indeed a new RIB with poor wiring.

Firefly · 20 November 2016, 23:04

Quote:

Originally Posted by A1an

its a 5m rib, voltage drop will be negligible.

Common sense prevails....

Anyone would think we were talking about rewiring the Titanic.....in situ

Firefly · 20 November 2016, 23:21

[QUOTE=A1an;735258]Nav lights high current

I take your point. However on an average 5 meter RIB, with the exception of the VHF on transmit and the starter circuit, I would suggest the nav lights have, by far, the highest current draw and in most cases the longest wiring runs.

Dirk Diggler · 21 November 2016, 09:02

Quote:

Originally Posted by Firefly

However on an average 5 meter RIB, with the exception of the VHF on transmit and the starter circuit, I would suggest the nav lights have, by far, the highest current draw

Hmm, you sure?

Most nav light nowadays are LED, with a wattage of maybe 0.8, or if old style with an Incandescent Bulb, 10 watts. What do you reckon a fully submerged bilge pump draws?

Manolism · 21 November 2016, 09:37

Quote:

Originally Posted by Firefly

Common sense prevails....

Anyone would think we were talking about rewiring the Titanic.....in situ

the length of a boat when we talk about safety It' irrelevant . The spark may cause fire and finally the same result to any boat in an accident. Safety come first in my opinion.

Iron Dials · 21 November 2016, 09:52

Tinned cable, over engineer by 1 size, it's a harsh environment we leave our ribs to live in.
The extra cost is negligible. 30m reel of twin core tinned £23 versus £34 for 1.5mm versus 2.5mm

If you are replacing in-line fuse protection with fused switches then use the correct rating fuses.
I got a quote last year from "an electrical engineer" who told me, "nah, I just put 30A fuses in them all, sure if it's blown its blown". Apparently the extra current/heat involved didn't worry him as the fire risk wouldn't be his problem.

Use good quality, heat shrink connectors, any faults that develop are unlikely to be mid cable, much more likely to be mechanical or corrosion at the connectors so worth reducing the potential for failure here.
Secure the loom to reduce mechanical wear when using rib.

IMO doubling up on cable is a way of introducing twice as many weak points.
To suggest its ok as used in commercial transport ignores the rigorous certification requirements and engineering expertise involved.
Would you fly on an aircraft where the tech advice came form an internet forum, albeit one as good and helpful as ribnet?