240v cable

[smudgersboat699]

Hello, can someone please point me in the right direction of what is the correct cable to buy for wiring up 240v sockets in my boat and where best place is to buy it.  I am running the cable around to where the sockets are going. I'm not an electrician my friend is conecting everything for me but I can not get hold of him to ask his advice. As we i'm  in lockdown on my boat  thought it would keep me out of trouble. Thank you for any help or advice

[Alan de Enfield]

2.5mm2 (2.5 mm squared) flexible conductors stranded 50/0.25.

 

DO NOT USE DOMESTIC TWIN & EARTH

 

PVC insulated and sheathed, the most common type is 'Arctic Grade colour Blue', but that's not mandatory.

Edited January 6, 2021 by Alan de Enfield

[smudgersboat699]

Thank you for your quick reply will look it up

Is 1.5mm or 2.5mm best for sockets? 

[Tracy D'arth]

I usually use 2.5mm Arctic cable from Screwfix, its blue 3 core round flex so obviously not the 12v services. Stays flexible when cold, stands the heat of the hot steel on a boat in summer. Makes a good land line too.

[smudgersboat699]

Just now, Tracy D'arth said:

I usually use 2.5mm Arctic cable from Screwfix, its blue 3 core round flex so obviously not the 12v services. Stays flexible when cold, stands the heat of the hot steel on a boat in summer. Makes a good land line too.

Thank you

[Alan de Enfield]

3 minutes ago, smudgersboat699 said:

Thank you for your quick reply will look it up

Is 1.5mm or 2.5mm best for sockets? 

2.5mm. as per post #2

Edited January 6, 2021 by Alan de Enfield

[smudgersboat699]

Cheers

[TheBiscuits]

Another vote for 2.5mm² Arctic flex. 

 

If your electrician friend thinks it's the wrong stuff, then don't let him wire anything on your boat.  The rules are completely different for boats compared to houses.

Edited January 6, 2021 by TheBiscuits

[smudgersboat699]

No it's not that I just forgot to ask him and as I'm sitting in the boat was wondering what jobs to do during lockdown and thought I can at least run the cables to where they have to go to save him a job 

[Alan de Enfield]

4 minutes ago, smudgersboat699 said:

No it's not that I just forgot to ask him and as I'm sitting in the boat was wondering what jobs to do during lockdown and thought I can at least run the cables to where they have to go to save him a job 

Just a question (or two)

 

Where are you running the cables ?

What type of insulation does the boat have ?

[smudgersboat699]

It's a Piper Semi Trad built in the early 90's and there is a wooden trim. I was going to remove that and run it along the back as there is a nice size gap there and there is 12v cable already running in there. The insulation is polystyrene  

[smudgersboat699]

Found this seems good value 50 meter role 

Arctic grade cable available in Blue

Size 2.5mm (25amp) 50 meters £35

 

[TheBiscuits]

2 minutes ago, smudgersboat699 said:

The insulation is polystyrene  

 

That's what Alan was concerned about.  Polystyrene must never be allowed to come into contact with PVC cable insulation, so the wire needs to be run in a protective sleeve or a conduit.

 

There is a chemical reaction between polystyrene and PVC that makes the cable insulation brittle and it cracks off leaving bare wires that can short out.  Bad Things happen after that!

 

If all this is news to you, I'd very strongly advise you NOT to run any cable anywhere, even if you think it would help.

[smudgersboat699]

Ok mate appreciate the advice. Will do some more research on it. 

[nicknorman]

5 minutes ago, smudgersboat699 said:

It's a Piper Semi Trad built in the early 90's and there is a wooden trim. I was going to remove that and run it along the back as there is a nice size gap there and there is 12v cable already running in there. The insulation is polystyrene  

Ah that is a bit of a problem. Polystyrene insulation can react with the cable sheathing and insulation to make it go brittle. Something about leeching of plasticiser. It may be an overstated issue and only become a problem after many years, but probably best to run the cable inside some trunking. Google polystyrene insulation and electrical cable.

[Alan de Enfield]

1 minute ago, TheBiscuits said:

 

That's what Alan was concerned about.  Polystyrene must never be allowed to come into contact with PVC cable insulation, so the wire needs to be run in a protective sleeve or a conduit.

 

There is a chemical reaction between polystyrene and PVC that makes the cable insulation brittle and it cracks off leaving bare wires that can short out.  Bad Things happen after that!

 

If all this is news to you, I'd very strongly advise you NOT to run any cable anywhere, even if you think it would help.

 

Exactly.

 

Polystyrene attacking PVC cable

 

 

[smudgersboat699]

Thanks bud, glad I posted this topic as had no idea

Just now, Alan de Enfield said:

 

Exactly.

 

Polystyrene attacking PVC cable

 

 

Wow had no idea. See what you mean

 

[Alan de Enfield]

Just now, smudgersboat699 said:

Thanks bud, glad I posted this topic as had no idea

 

Not a problem - no one knows anything until they are told it (or read about it)

 

Boats are not domestic and different techniques are used - dont assume - don't guess - always ask

[smudgersboat699]

The good thing is there is a reasonable space so will look into flexible trunking for the cable

[Alan de Enfield]

2 minutes ago, smudgersboat699 said:

Thanks bud, glad I posted this topic as had no idea

Wow had no idea. See what you mean

 

I had 10 years working for a cable company designing new cables and materials, everything from 'termite resistant runway lighting cables to special non-migratory PVC for use where polystyrene could come into contact with the cables.

2 minutes ago, smudgersboat699 said:

The good thing is there is a reasonable space so will look into flexible trunking for the cable

 

Either Polyethylene or Nylon trunking / conduit is fine.

[smudgersboat699]

Thank you everyone for your help

[TheBiscuits]

4 minutes ago, nicknorman said:

leeching of plasticiser. It may be an overstated issue and only become a problem after many years, but probably best to run the cable inside some trunking.

 

You can get away with it for years in a house, but a boat gets a lot more vibration so it fails and falls off much sooner.

 

It's still a bad idea though - I have seen a few houses like Alan's picture where the insulation is sticky, and a few where it's fully flaked off. 

 

All you need in a house is someone to poke a cable when putting something in the attic, but all you need to do on a boat is start the engine ...

[Tracy D'arth]

Your 240v cables must be separated from all gas pipes and all 12v cables, certainly must not touch. The polystyrene problem can be avoided by using aluminium sticky tape on the polystyrene or on the cable to ensure no contact.

Or thin oval conduit for the cable, that type of plastic is not affected by the polystyrene.

You need plastic boxes for the sockets, if you want them flush the box can be  let into the insulation and stuck to the steel with PU18 or OB1 gun glue. Don't use metal boxes because then you need rubber grommets and the sockets will earth them which gets complicated avoiding the earth touching the hull and creating stray currents in the steel.

[Keith M]

I have seen cables in lest than half a year, the copper in a three core cable was exposed.

[smudgersboat699]

2 minutes ago, Tracy D'arth said:

Your 240v cables must be separated from all gas pipes and all 12v cables, certainly must not touch. The polystyrene problem can be avoided by using aluminium sticky tape on the polystyrene or on the cable to ensure no contact.

Or thin oval conduit for the cable, that type of plastic is not affected by the polystyrene.

You need plastic boxes for the sockets, if you want them flush the box can be  let into the insulation and stuck to the steel with PU18 or OB1 gun glue. Don't use metal boxes because then you need rubber grommets and the sockets will earth them which gets complicated avoiding the earth touching the hull and creating stray currents in the steel.

Thanks for the advice will definitely do more checking