Author Topic: Electric light bulb wiring/cable/flex plug thing  (Read 4424 times)

Electric light bulb wiring/cable/flex plug thing
« on: 23 February, 2014, 07:43:16 pm »
I need to install a couple of temporary lights in a studio space. When I say install I really mean dangle the cord over a metal beam... so I need to wire up some bayonet fittings to a cord/cable (not sure what the correct terminology is) and put a plug on the other end. Is there anything I should be aware of to prevent my burning the building down etc.? I'm pretty ignorant when it comes to electrical stuff but I assume there's no real way to screw this up(?).
Some web searches reveal the fact that there's a variety of types of cable... I'm after cheap and simple. I guess the cable ought to be thin/flexible in order to drape over the beam.

Kim

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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #1 on: 23 February, 2014, 07:54:42 pm »
Not a lot to it, if you know how to wire a plug.  You'll want stranded cable with a round outer sheath - 2 core should work unless the lamp holders have exposed metal parts, in which case you'll need 3 core to connect the earth.  0.5mm should be sufficient.  3A fuse in the plug.

Main fire risk is probably from hot lamps coming into contact with something flammable, unless you really make a pig's ear of the electrics.

Re: Electric light bulb wiring/cable/flex plug thing
« Reply #2 on: 23 February, 2014, 08:04:24 pm »
Cable advertised as 'lighting cable' etc., is it in any way specific to lighting applications?

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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #3 on: 23 February, 2014, 08:49:16 pm »
Wilkinsons shops are ideal for the cable, lamp holders and plug you need.  The cable doesn't have to be lighting-specific, but get cable described as "mains" to guaranty safe insulation.

Cable with silicone insulation is extra flexible and flame retardant, but overkill for this application.  Just ensure the cable won't touch the bulbs.
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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #4 on: 23 February, 2014, 10:56:42 pm »

Main fire risk is probably from hot lamps coming into contact with something flammable

Less of an issue lately, what with "Energy Saving Bulbs" (compact fluorescent lamps) being not has hot. And LED ones even less hot.
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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #5 on: 23 February, 2014, 11:27:40 pm »
Buy an extension cord with a built-in RCD. plug into that
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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #6 on: 11 March, 2014, 08:49:31 pm »
Flex is flexible.  Cable is only designed to be bent into position, and then fixed there.  Cable only has a single copper wire for each conductor (L, N and E) unless it's something esoteric like a high power cooker circuit; flex has lots of very thin wires which can happily bend back and forth without breaking.

The exception is the wiring from the wall to a free-standing electric cooker, which nearly always has to be (not very flexible) cable, because flex isn't made big enough.  The wiring regulations allow this because it is considered to be fixed wiring, although it's just hanging there and the cooker can be slid in and out for cleaning or decorating.  This offends me in some indefinable way.
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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #7 on: 11 March, 2014, 09:26:36 pm »
Flex?  Flexible what?  A flexible tyre?  A flexible sausage?  It's flexible cable!  :)

Incidentally, I just got some of this deliciously flexible cable: www.ebay.co.uk/itm/171246343965.  I love the way it feels in my hands.
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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #8 on: 11 March, 2014, 09:35:09 pm »
The exception is the wiring from the wall to a free-standing electric cooker, which nearly always has to be (not very flexible) cable, because flex isn't made big enough.

Sure it is.

http://www.tlc-direct.co.uk/Products/CA4F3.html

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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #9 on: 11 March, 2014, 09:47:24 pm »
How many cookers could you run off one 3-core 6 mm flex?  www.ebay.co.uk/itm/130931080754  :)
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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #10 on: 26 March, 2014, 07:39:55 pm »
Well, that proved to be easy peasy. Having done that my next task is to wire a couple of lights in parallel... so my question is how one should connect the cables in a way that's reasonably secure? Do I need twist on wire connector cap thingies?

Re: Electric light bulb wiring/cable/flex plug thing
« Reply #11 on: 26 March, 2014, 07:59:27 pm »
Choc-block connectors are cheap and easy, Wago connectors are nicer. Wrap them in insulating tape if you're a semi-responsible adult who can trust yourself to keep them out of reach and not to poke screwdrivers in, or put them in proper boxes if you want to do a proper job or there's any chance people might fiddle. Junction boxes may be a better choice if this is a fixed installation, especially if you can fix them in place. Think about strain relief on the connections too, if only to ensure that you're not simply suspending fittings from the connectors.

Re: Electric light bulb wiring/cable/flex plug thing
« Reply #12 on: 26 March, 2014, 09:46:38 pm »
Junction boxes? About time to mention part 'P'. -Although the OP was not about fixed wiring.

Kim

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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #13 on: 26 March, 2014, 11:02:51 pm »
Do I need twist on wire connector cap thingies?

Those are a work of Stan and an abomination of the highest order.  The design brief appears to have been to come up with the cheapest way of setting as many American houses on fire as possible.   :hand:

At least with choc blocks it's reasonably obvious when you've made a naff connection.  Junction boxes with some sort of strain relief would get my vote.

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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #14 on: 27 March, 2014, 06:24:35 am »
The exception is the wiring from the wall to a free-standing electric cooker, which nearly always has to be (not very flexible) cable, because flex isn't made big enough.

Sure it is.

http://www.tlc-direct.co.uk/Products/CA4F3.html
Most cookers demand 6mm cable now. Even that is a bit marginal when you have two ovens and a grill; there is a fudge factor called "diversity" which gets round the fact that even a 30A circuit isn't big enough for a range cooker with everything turned on, but people don't want to rewire back to the consumer unit.

I've never tried turning on both ovens and the grill simultaneously; I imagine the MCB would trip, looking at the specification of the elements.
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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #15 on: 27 March, 2014, 07:36:56 am »
Most cookers demand 6mm cable now. Even that is a bit marginal when you have two ovens and a grill; there is a fudge factor called "diversity" which gets round the fact that even a 30A circuit isn't big enough for a range cooker with everything turned on, but people don't want to rewire back to the consumer unit.

I've never tried turning on both ovens and the grill simultaneously; I imagine the MCB would trip, looking at the specification of the elements.

We have a fully electric range cooker. We occasionally have both ovens all rings the warming plate and the slow cooker/warming oven on at the same time (Christmas day or a big family meal). It's never tripped the 30amp MCB. It's an induction hob though so maybe its a bit more efficient than one with a traditional electric hob.
I think you'll find it's a bit more complicated than that.

Re: Electric light bulb wiring/cable/flex plug thing
« Reply #16 on: 27 March, 2014, 08:13:41 am »
But even when all the ovens, rings and warming drawers are 'on', then the stats for each will switch the individual heating elements on and off to maintain the appropriate temperature, so not all of the elements will be drawing current simultaneously.

And even if you turn everything on from cold at the same time to maximise current draw, an MCB will pass a fairly substantial overcurrent for a very long time before it trips.

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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #17 on: 27 March, 2014, 01:13:21 pm »
The exception is the wiring from the wall to a free-standing electric cooker, which nearly always has to be (not very flexible) cable, because flex isn't made big enough.

Sure it is.

http://www.tlc-direct.co.uk/Products/CA4F3.html
Most cookers demand 6mm cable now.

Ah, I accept you might have to go to an industrial supplier for that.  It's not unobtanium though (I've used it often enough on dimmer racks), and if cookers are in the habit of using it, I'd expect the sheds to start stocking it eventually.


Quote
Even that is a bit marginal when you have two ovens and a grill; there is a fudge factor called "diversity" which gets round the fact that even a 30A circuit isn't big enough for a range cooker with everything turned on, but people don't want to rewire back to the consumer unit.

That's a posh term for "most things are okay for twice their rated value if you do it for a short enough time that nobody notices", isn't it?   :)


And even if you turn everything on from cold at the same time to maximise current draw, an MCB will pass a fairly substantial overcurrent for a very long time before it trips.

Varies considerably with the age of the MCB and ambient temperature IME.  They're finicky things, but fundamentally there to stop wiring catching fire, not enforce ratings.  As with fuses, the rating tells you the condition that *won't* cause it to trip.

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Re: Electric light bulb wiring/cable/flex plug thing
« Reply #18 on: 27 March, 2014, 02:19:15 pm »
Can get 6 mm flex via the link I posted above, albeit in yellow or blue only - caravanning colours, apparently.
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