6A lighting cct to supply a 13A socket

Now now Andy, did I suggest any of those things?

I thought that 100W on a 100A circuit was yours (or someone else using your account?). The 20A circuit was geoffsd's (I don't think I suggested it was yours). I did say they were subtle points rather than fundamentals - but still something to keep in mind I think. All the same the point that it's not just cables but all conductive parts of the circuit that need to be protected from faults (e.g. lightswitches & lampholders) is a valid one I think.

There is nothing in the regs to stop a 13A socket being fed from a 'lighting' circuit fused at 6A.

How about 433.1 - and small overloads of long duration? We can't completely rely on overcurrent protective devices to protect cables - a small overload may overheat the conductor and so degrade the insulation to some extent without tripping the MCB. In conventional circuit arrangements we don't totally rely on the OPD but also attempt to restrict the load - e.g. by limiting the floor area served.


OK a 6A MCB and 1.0mm² usually has a good margin available, but that's not necessarily the case, and a simple mower isn't likely to be a problem (unless it's one of the old electric flymos and being used to mow half an acre or more) but if the socket could regularly be used for something more powerful, or there's insufficient spare capacity on the circuit, there could be issues.


  - Andy.

Now now Andy, did I suggest any of those things?

I thought that 100W on a 100A circuit was yours (or someone else using your account?). The 20A circuit was geoffsd's (I don't think I suggested it was yours). I did say they were subtle points rather than fundamentals - but still something to keep in mind I think. All the same the point that it's not just cables but all conductive parts of the circuit that need to be protected from faults (e.g. lightswitches & lampholders) is a valid one I think.

There is nothing in the regs to stop a 13A socket being fed from a 'lighting' circuit fused at 6A.

How about 433.1 - and small overloads of long duration? We can't completely rely on overcurrent protective devices to protect cables - a small overload may overheat the conductor and so degrade the insulation to some extent without tripping the MCB. In conventional circuit arrangements we don't totally rely on the OPD but also attempt to restrict the load - e.g. by limiting the floor area served.


OK a 6A MCB and 1.0mm² usually has a good margin available, but that's not necessarily the case, and a simple mower isn't likely to be a problem (unless it's one of the old electric flymos and being used to mow half an acre or more) but if the socket could regularly be used for something more powerful, or there's insufficient spare capacity on the circuit, there could be issues.


  - Andy.