Using 7 core trailer wire for mains lights

[Andrew Gabriel]

Flex is sometimes marked (mains will typically be marked 300/500, or H05VVF or similar for mains flex in the UK).

However, you can check the manufacturer's spec, and for the sources I can find online, the manufacturer rates trailer cable at 50V.

It might work fine at mains voltage, but you have to prove that, as the manufacturer doesn't (and the manufacturer probably won't provide you with enough details of the manufacturing process for you to prove it yourself).

Also, ISTR that the earth wire is never allowed to be covered with anything other than green/yellow for mains wiring, and given there is no such conductor (nor a bare conductor which would also be OK), even if you can prove the cable is OK for mains use, it could only be for appliances which were double-insulated and thus not earthed.

[Andy Burns]

But it will often have a BASEC approval number marked on it.

Even when the TW in TW07 stands for "thin wall"? The car flex I've used for random 12V jobs has thinner insulation than mains flex.

[Andrew Gabriel]

Well, the EU started by drawing on the EIC colours, but went on to do its own thing. The UK was late to adopt because we refused to use the EU 3-phase colours, and we did eventually persuade the whole EU to change its 3-phase colour code to brown, black, grey to meet our concens of being unable to identify phase rotation with the EU's original scheme, whereas that had always been possible (and relied upon) with our previous red, yellow, blue scheme for 3-phase.

[Dave Plowman (News)]

I'm sitting alongside my cable hooks here. Loads of assorted mains leads. Very few have any markings on the cable. Nor do the drums of mains flex I have here.

I can see that. They're hardly going to rate it at higher than needed. And current ratings tend to be different for car and mains flex of the same size too.

That is the main reason for not using it.

[Dave Plowman (News)]

Oddly, I've got some heavy duty trailer stuff here. Handy for some speaker apps. I'd say the insulation is if anything thicker than I'd expect with mains flex. For mechanical protection and strength. It can lead rather a harder life than plain mains flex.

[Bill Wright]

There's a lot on mine.

Bill

[Andrew Gabriel]

Or to put it another way... In the UK, we connect the Earth to the ground, In the US, they connect the Ground to the earth.

Since cars aren't earthed/grounded at all, a better name is Chassis.

[Adam Aglionby]

It`s been the common cable in use by mobile discos for a lot of years, took them about 20 years to start using a line female, Bulgins used to be male to male leads.

Perhaps like to ask a major retailer the manufacturers voltage rating on the cable used:

Maplin`s are getting better , less use of cable ties to hang lights in store nowadays...

Disco world uses Bulgins and 7 core to run 3 or 4 channels with a combined earth.

Event presentation uses 18 core cable and Socapex for 6 channels with separate earth and neutral per channel, only one core is typically green/yellow.

[charles]

Bulgin (a manufacturer) make all sorts of different connectors. Do you mean one that uses an octal valvebase as its model?

[Andrew Gabriel]

Doesn't say what cable is used, or even what the voltage rating of the assembly is.

There are a number of multicore cables manufacturered for mains use, such as YY cable. It has numbered cores, plus one green/yellow core e.g.

(CY cable is similar, but with a protective earthed screen too.)

[Dave Plowman (News)]

But most don't have a chassis these days. ;-)

[Chris Green]

It's a dilemma I always ponder on when I draw circuits of bits of my boat/car/bike electronics. What does one call the circuit/wire which is the -ve return to the 12 volt (usually) battery? The possibilities are:-

Earth - but it isn't really

Chassis - harks back to big, old valve radios built on a metal chassis, my boat doesn't have a chassis, nor do modern cars.

0v - this is what I usually end up using

[Roger Mills]

Caravans *do* have a chassis but I'm not sure it's used as an electrical conductor.

When I were a lad, car batteries had their positive terminals connected to the chassis. Nowadays - maybe from when alternators replaced dynamos?

- the negative terminal is connected to the chassis. As far as I am aware, both systems are still referred to as positive or negative - wait for it - *earth*!

[Dave Plowman (News)]

Ground does for me. Don't care if it means something else in other countries.

But on car electrics, you generally just expect everything to ground to the bodywork, so it's not confusing.

It's more confusing with Hi-Fi etc gear where you can have a 0v rail, connection to chassis and connection to earth.

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[Dave Plowman (News)]

It was more the introduction of car electronics that brought about the change back to negative ground. It wasn't forced by alternators as they were available positive ground - as were things like rev counters and radios. More that most of the rest of the world had never changed to positive ground, so made sense we went back to conforming with them. Thus allowing cheaper electronics.

Some people do talk about earth on a car. Doesn't make it right, though.

[tabbypurr]

It's purely semantic. Car chassis are at earth potential, now that tyres are a bit conductive. That they don't perform the safety function of a mains earth is immaterial. Earth, chassis, ground, 0v, -ve, frame, common and return are all correct.

NT

[The Natural Philosopher]

-ve is incorrect on positive earth cars ;-)

[Tim Lamb]

Bit late to this thread. Isn't there some link between electrical polarity and corrosion? One way the car bodywork corrodes and the other it is the wiring loom?

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[Chris Green]

Oh yes, there's 'ground' as well isn't there. It's not on my shortlist though as it's US usage to my mind (nothing wrong with that but is like using 'trunk' for 'boot' on a car).

Hmm, not so true nowadays is it, many have a single earthing point near the battery and return wires from everywhere else don't they? It helps with corrosion and, possibly, with 'earth loop' problems. Certainly on boats it is de rigueur to have only a single connection to the hull (on steel hulled boats).

Isn't that just the 'single earth point' thing again?

[Chris Green]

Surely -ve (or +ve) is always incorrect or, at the very least, misleading. It's quite likely nowadays that there will be wires carrying voltages on both sides of 0v isn't it?

The only place I might use -ve or +ve on a wiring diagram would be to annotate the actual battery terminals.