Fault finding advice

[Wilson12]

Any fault finding advice
It’s always been said to clients to unplug everything if a fault on socket circuits but can you
Turn off counter top fused spurs for e.g washing machine instead of the hassle to get to the back of plugs.
So I’m asking are fused spurs double pole.
Also the same question with sockets is switching to off enough.
Light switches are single pole so I take it
E.g if it’s a outdoor light with water line to earth or neutral fault it can be switched off and will clear the fault but neutral to earth. Turning the switch off will do nothing.

 

[westward10]

A switched fuse spur is double pole however a switched 13A socket is not necessarily double pole.

 

[Lucien Nunes]

E.g if it’s a outdoor light with water line to earth or neutral fault it can be switched off and will clear the fault but neutral to earth. Turning the switch off will do nothing.

Since the light (or any load) can create a path from line to neutral of much lower resistance that the insulation, switching off the line only will not isolate an earth fault no matter whether it is from line or neutral. Even a PIR light where the light itself is off, will often have a circuit from line to neutral powering the sensor electronics. If the electronics are powered by a capacitive dropper, then a DC insulation test might not 'see through' from supply neutral to a fault on the line, but this is not a good test to do anyway as one should normally have L & N connected together when testing circuits with connected loads to prevent the test voltage appearing across the electronics.

 

[happysteve]

The vast majority of switched fused spurs are double pole, but I've come across one or two very old ones which are single pole - they had more of a toggle type (plastic) switch, rather than a rocker style. The number of these still in use is diminishing over time, though, and in general it's reasonably good odds that a switched fused spur will be double pole.

The chance of a socket-outlet having a double-pole switch is quite a bit less than 50/50 at the moment, though as time goes on the chances will get higher, as many are now supplying double pole switches as standard on their sockets. Manufacturers are still making and selling single pole switched sockets: for instance on USB sockets, and sometimes 1G sockets (in both cases where space is more limited).

So I'd say carry on with your advice of getting customers to unplug (rather than switch off) everything; asking them to switch off the SFCUs will almost certainly disconnect both L and N, unless it's a very old one.

Your example of the outside light having a N-E fault is the reason I always fit a double-pole isolator switch (which may coincidentally be an SFCU, if derived from a socket circuit) for outside sockets and lights, if I'm installing from scratch.

 

[nicebutdim]

The chance of a socket-outlet having a double-pole switch is quite a bit less than 50/50 at the moment, though as time goes on the chances will get higher, as many are now supplying double pole switches as standard on their sockets. Manufacturers are still making and selling single pole switched sockets: for instance on USB sockets, and sometimes 1G sockets (in both cases where space is more limited).

At the risk of further diverting the thread, this is something that recently irked me.

To keep my father from continually buying pound shop USB adaptors, I recently changed several sockets for USB A/C versions. Legrand Synergy accessories fitted throughout the house (well thought out terminal access) and all sockets had been DP, but the only option for the USB units was SP.

Maybe space would have been an issue with manufacturing DP switching, but it would be nice to have the option.