electrical socket in the loft ?

[Owain]

If it's got a flex, cut the plug off and wire it into a junction box on the lighting circuit.

If it's the sort that has a plug as part of the case, things are more awkward. One suggestion has been to glue a single extension socket to the case, to connect to a length of flex/cable that can be wired in to the junction box. What is to be avoided is a 13A socket into which other things could be plugged.

Although if one is running coax cable all round the house for a TV system it shouldn't be beyond the wit of man to run a spur up to the loft at the same time.

Owain

[Andy Luckman (AJL Electronics)]

Cut the plug off and hardwire into a 5A switched spur from the lighting circuit. You will hardly notice the load.

[Andrew Gabriel]

If you can find one, a clock point is excellent for this. They are designed to be connected to a lighting circuit, can be unplugged for maintenance, and they take a fuse.

[Christian McArdle]

Are these the same as BS546 round pin sockets?

Christian.

[dave stanton]

LIke I have done many times, feed from lighting circuit into FCU, amp wired directly into FCU with 3 amp fuse or smaller if poss. Only prob is if amp dies you cannot just unplug.

Dave

[google]

If they don't work then they're not even protecting the lighting circuit *before* he's added the socket.

Andrew

[Andrew Gabriel]

No, and there's no standard style for them (they aren't interchangeable between different manufacturers, and they're sold as a plug and socket matched pair). Some take the small cartridge fuse used in some shaver adaptors, and some take a regular BS1362 plugtop fuse. They were normally available in surface mount or BESA box mounting types. There's usually a screw or knurled nut to stop the plug dropping out (not that it's likely to -- this was probably to act as a bit of a "safety chain" if the clock fell off the wall).

A fused 2A BS546 round pin plug/socket would be pretty equivalent.

[Andy Dingley]

My workshop dust collector doesn't have a 2kW fan !

I once lived in a flat where the (windowless) bathroom lights were fed from the shower feed. If you used the pull-cord switch to isolate the shower, all the lights went out.

[Owain]

A good idea. Clock points are also good for 100V loudspeaker installations, but not everyone's house boasts a 'tannoy' system.

Owain

[Aaron]

Ah but by protection I mean a L-E fault... during which tens of amps can be drawn very quickly and that would trip the MCB.[1] If you were to take say 7amps on a 5amp MCB it may not trip straight away. The MCB uses an electro magnet that generates magnetic flux depending on the amount of electrons (current) flowing round the coil. As I understand it, they are designed not to trip when just over the threshold current is being drawn, because you may well get trips if say you had a fan light or tube that draws more current than usual when it starts up.

[1] A L-N fault cause by say a bulb blowing and causing one filament to come in contact with another could also do this since the filament support wire can drive more current without buring out. I also think it's worth mentioning that you may not be protected by L-Person fault since a person may not be able to conduct enough current.. Hence the modern use of RCD protection.

[Martin Angove]

From tables in the back of BS7671:

6A type B MCBs need 30A to trip in 0.4s. They need 13 or 14A to trip under 100 seconds. 9A looks like about 2,000 seconds. Less than about 8.5A is unlikely to cause it to trip at all. 1mm2 cable is rated up to 16A in normal ("clipped direct") installations, or 12A partly in insulation.

A 5A BS3036 (rewireable) fuse link needs 24A to blow in 0.4s. 10A will blow it in about 100 seconds.

Hwyl!

M.