Extension leads

[Fred]

Thanks. I wasn't sure whether you could do this or whether you needed

2.5mm^2 for the whole length of the extension lead. I'm guessing it is permissible to use the 1.5mm to fit the plug because you are just using a short length, so not long enough to drop voltage or limit currents? Is that right?

On the subject of these plugs, I've often wondered about fitting one of these wall inlets onto my house wall:

the other side I would connect it to a socket and if I had a power cut plug the boiler in one side and a cheap 2 stroke generator into the other. I've never got round to it because, touch wood, we've not had a power cut for a couple of years (cue a cut tomorrow).

I'm sure CPC describe these as IP44. Now according to this:

x4 means protection from water sprayed from all directions. I can't see how this is possible when the pins are exposed. Or does it only have ip44 protection when in use and coupled?

[Fred]

Thank you, that's taught me a lot.

CSA x 10

I have a 25m lead from Wickes and IIRC it is 1.25mm^2, possibly

1.5mm^2 (it's cold and dark outside so I'm not going to check ;)). It certainly is not 2.5mm^2 because as other posters have said, it wouldn't fit a plug.

FIL has a massive 50m lead from Argos. Made by Masterplug possibly? The cable is fat but I'm sure it's not that fat. Even if it was, according to your table, even 2.5mm^2 would be too small anyway.

I saw some 2.5mm^2 flex in B&Q. I was surprised how wide it was and also that they sold it. I can't imagine anyone who shops at B&Q needing to buy some. Since it won't fit plugs, I guess it must be used for fixed appliances. What would they be: cookers? I thought many now just used 13A plugs.

Thanks again.

[js.b1]

Consumer extension leads have often been very long and often a bit "skimpy".

The reason is they expect people to use them on a hedge trimmer (500-950W) or lawn mower or drill (900W), but pressure washers can be quite a beefy load at the higher end of the market (1.7kW induction).

Welders on the other hand use the thickest cable they can afford.

For an IP44 inlet with a shield, search for "16A inlet" on

- there is a picture of a Mennekes with a spring loaded shutter to keep rubbish out when not in use. Obviously, never ever connect an inlet connector in such a manner that it can become live (just a general comment).

[Dave Osborne]

Well the amount of voltage drop is a function of the current and the length and is measured in V/A/m or voltes-per-amp-per-metre. So, if your 1.25mm2 or 1.5mm2 cable is very short, it's not going to drop much voltage, even at max current.

or

Only IP44 when in use and coupled, but as they're not live when they're not connected, they don't need a lid (although you can get them with lids): -

[Fred]

Thanks, I thought the short length was the key factor here. Andrew Gabriel was talking about fault current, does the fact that you have used 1.5, even for a tiny length, affect fault current and the maximum length of flex?

If you have a very long lead such that you are concerned about fault currents, is there any way to make things safer (other than use a fatter cable or install a permanent socket)? Would plugging an RCD in the distant end of the lead, i.e. where you are using the tool, help?

Thanks, that explains it. I'm not sure I'll ever get round to it because I couldn't put a genny the other side of the boiler because that would be in the car port and though one side is open, I imagine it would accumulate deadly exhaust fumes, so I'd have to move it further away and then we come back to issues of cable length and earthing and all these complications and us not having many power cuts are the reason I haven't done it yet!

Thanks again.

[Tabby]

yes against L-E faults, but not against L-N faults.

I dont recall you giving details of length, load etc, maybe you did.

Picking/designing your overload protection to suit the lead can make all the difference.

NT

[Fred]

No, I didn't. I don't have a particular application in mind. I only have a small garden so I don't really need to worry about cable length. I'm guessing I'd wouldn't need anything over 5m, if that, here. I just found comments on another thread interesting and wanted to learn more, which thanks to the replies here, I have. Thanks again.

[Dave Osborne]

Not really.

Table 4F3B of the wiring regs gives the following voltage drops for flexible cords:

CSA (mm2) Volt Drop (mV/A/m)

1.25 37 1.5 32 2.5 19 4.0 12

Let's say your load current is 5 Amps.

The volt drop of 25m of 1.5 is 32mV/A/m x 5A x 25m = 4000mV or 4V. The volt drop of 25m of 2.5 is 19mV/A/m x 5A x 25m = 2375mV or 2.375V

Now, if we make up the 2.5 extension in industrial connectors and have a

0.5m adapter cable in 1.5mm2 the volt drop is increased by only 80mV.

32 x 5 x 0.5 = 80mV = 0.08V

Giving a total volt drop of 2.375V + 0.08V = 2.455V.

So you see a short length of 1.5 makes hardly any difference.

[Fred]

Thanks very much.

[Dave Plowman (News)]

The way it's done for location filming where you're getting power from normal 13 amp sockets in say a house for lighting etc, is to use a short

13 amp to 16 amp tail (with RCD) using 1.5mm TRS, and then a 2.5mm TRS extension lead. With a 16 amp to 13 amp tail at the other end if needed. I can't remember how long that main extension can be and still comply, but it's probably enough for most things. On a large rig you'd use a generator, and run out distribution points.

[Fred]

Thanks. That sounds an exciting way to make a living, how did you get into that? I thought it was hard to get into film and tv, or is that only if you want to be the other side of the camera?

[Dave Plowman (News)]

Like any job you find out about it first. Plenty of low paid jobs around to start with - but not everyone's cup of tea because the hours can be long and anti-social.

It may sound exciting but in practice it tend to be lots of hanging around followed by periods of frenzied activity.

I did enjoy my career, though. Not sure I'd go into it these days. The salad days were when TV was made by enthusiasts at all levels - not just another business controlled by accountants.

[Fred]

I guess even brain surgeons get bored of doing the same thing every day though.

Too true. Too many "talent" shows now where the accountants are more interested in the money they can make from the phone lines that the channel's output.