What cable to use

[jake1953]

I'm at the point of electrics being fitted into the van. I have fitted the 240 volt hook up to the side of the van and want to run a cable from it to a 240v consumer unit(fitted under the rear seat.) From the unit i will run 2 lengths of cable to a double socket on the end of each. we are talking A telly/toaster/kettle/heater to be used between the 2 sockets. Without going ott but wanting to be mega safe what thickness/amp rating of cable do you suggest I use?
Is 2.5mm x 25a too much?

[Red Westie]

Effectively this is a ring main so 2.5mm2 twin and earth.
I would be inclined to use flexible multicore round cables (moving vehicle)
And be especially careful to use grommets through holes plus cable ties to prevent movement and chafing.

RCD
MCB like a fuse rated at the maximum draw on the circuit
mini consumer unit

The problem is buying one small enough with suitably rated RCD and MCB's

Martin

[1664]

Effectively this is a ring main so 2.5mm2 twin and earth.

No it isn't, and sorry but even if it were there'd be no need for 2.5mm for a ring circuit in this case.

Maximum hook up rating is 16A so no point fitting larger than that.

There are different ways you can wire your consumer unit and sockets etc but the bog standard method when these vans were new was a 2 way consumer unit with a 40A rated 30mA RCD incoming switch. The rating of the 2 m.c.b's (circuit breakers) was 6A and 10A (6A+10A=16A). The reason for this is because an RCD protects against earth faults NOT 'over-current'. Two single sockets were fitted; one for the fridge connected to the 6A m.c.b and another single for general use connected to the 10A m.c.b. Both these circuits were 'radial' circuits, not a 'ring' circuit. They were wired in 2.5mm twin & earth cable with solid conductors because back then there were no regulations specific to camper van wiring so they used that. The wiring from the hook up socket to the consumer unit was done in 2.5mm 3 core flex.

These days of course, campers DO have specific regulations applicable to them which knocks the use of domestic twin and earth cable into touch and "sheathed flexible cables" are specified unless you are prepared to install PVC conduit with single stranded cables in it which frankly is more hassle than it's worth.

In the example above, 1.5mm flex is perfectly capable of supplying both 6A and 10A – it can even supply 16A but that's at it's upper rating limit and drops if it's in contact with thermal insulation so people generally use 2.5mm for peace of mind. Problem is 10A isn't quite big enough for a 3kW heater running at full pelt and it might 'trip', but my fan heater isn't a problem....

You could, if you prefer, just fit a consumer unit with an incoming 16A 30mA RCD without any m.c.b's at all but you MUST ensure that it conforms to BS 61009-1 with integral over-current protection and NOT BS 61008-1 which does not have integral over-current protection. Then you just wire a radial circuit out from that with as many sockets on it as you like.....it'll just trip if you try and drag more than 16A through it.

As Martin said, cables must be protected from mechanical damage, sharp edges etc and be securely supported

[Red Westie]

A good explaination with lots of very detailed info but you still conclude most people use 2.5mm2 and that was the original question.
This is a home install so although I recognise that there are current regs for campers is to use sheathed cable, normal domestic cable can be used but caution is needed.
The main cautionary notes are around routing and the avoidance of sharp edges/screws/nails and routing through holes in panels. This is where common sense should prevail and you should be using grommets/cable ties and packing to avoid chaffing etc.
Whilst I accept camping mains is a max of 16 amps the difference in cable price over these small cable lengths equates to pennies.

Again..your main problem is finding a suitably small consumer unit with appropriately rated RDC/MCB's

Martin

[1664]

A good explaination with lots of very detailed info but you still conclude most people use 2.5mm2 and that was the original question.

I didn't conclude anything. I said that 1.5mm is adequate for both 6A and 10A but using it for 16A was pushing it in thermal insulation.

This is a home install so although I recognise that there are current regs for campers is to use sheathed cable, normal domestic cable can be used but caution is needed.

Being a 'home install' is irrelevant. There is no ambiguity here - if you want an installation that conforms with recent electrical safety standards you cannot use domestic cable. Frankly, you can install wet string as far as I'm concerned, I'm just pointing out what is required under the regulations.

The main cautionary notes are around routing and the avoidance of sharp edges/screws/nails and routing through holes in panels. This is where common sense should prevail and you should be using grommets/cable ties and packing to avoid chaffing etc.

Couldn't agree more

Whilst I accept camping mains is a max of 16 amps the difference in cable price over these small cable lengths equates to pennies.

I'm just saying what used to be used and what can be used, I was not considering cost as like you say, pennies, and that you don't bother wiring it as a 'ring' circuit - it's a camper with a couple of sockets, not a house.

Again..your main problem is finding a suitably small consumer unit with appropriately rated RDC/MCB's

No problem, walk into any electrical wholesaler and ask for a 2 way consumer unit with an 30mA RCD incomer and a couple of circuit breakers. They should have them on the shelf.

[Red Westie]

Bren, we are both trying to do the same thing here, help this guy with advice, I didn't realise it was a competition.

I acknowlege what you have said has been sound advice, I admit my 'ring main' comment was not completely accurate thats why I said 'effectively' meaning, treat it as, I wasn't saying it actually was a ring main.
if for any reason I have contradicted you then I'm sorry, it wasn't intended.
I don't really know why you have highlighted and answered each line of my post, it looks as if I've done something wrong?.
I offered an opinion, you offered yours, let the man take from each what he will, there is no reason to disagree over this.

Martin

[jake1953]

OK, So erring on the side of safety, I bought 2.5mm 25 amp flex cable and a bundle of grommets. (Local C.E.F. electrical wholesaler miles cheaper
than B&Q.) I already had bought off fleabay a 2 way consumer unit with 30 a incoming and 2 circuit breakers a 10 amp and a 6 amp.
The sockets are wired in and am now working on the lights.
Thanks for your help on this one guys.
Jake