13A fused-spur to 3 external connections

[Tim Kedwards]

Hello

I am in need of some council wrt safety of below setup. Essentially single internal plu socket has been fitted with a 13A fused-spur whic then feeds 3 external (ie., outside)

So a single internal 13A fused-spur feeds

1 Outside socket - used to plug-in lawn mower 2 Outside 60w lamp & switch 3 Outside small water feature pump and switch

None are used concurrently

I have had a new fusebox and circuitry installed which has RC protected fuses for all sockets throughout the house.

Is the above setup ?safe?? Or do I need to replace the 13A spur with a RCD-protected spur ? or is this double counting wrt the new fusebo having this already ?

Many thanks

Ti

-- Tim Kedwards

[Stefek Zaba]

Na, you don't. Councils know naff-all about electrical safety. That's why Prescott, who knows naff-all about anything (well, naybe throwing punches, and being a Tough Bluff negotiator) put them in charge of Part Pee. Counsel, now that's different ;-)

So far as overload and short-circuit protection goes, this is (almost certainly) fine - by fusing the spur through the fused connection unit you provide appropriate protection to the cable. It's just possible the water-feature cable wants a lower-value fuse on its final run of cable - do you know its rating and what the manufacturer specifies?

The RCD in what I'm guessing is a split-load consumer unit provides the necessary added protection against faults to earth for your outside sockets and water feature. There's an argument that a specific RCD for your outside supplies would be more convenient - if there was such a fault out there, which is relatively more likely than indoors, having the CU's RCD trip will take out power from *all* socket-supplied equipment. But without running a dedicated circuit to such an RCD, there's no point using an RCD with integral RCD, as both it and the one in the CU which feeds it are equally likely to trip - indeed, both are quite likely to trip.

HTH - Stefek

[Owain]

"Tim Kedwards" wrote | I am in need of some council wrt safety of below setup. Essentially | a single internal plu socket has been fitted with a 13A fused- | spur which then feeds 3 external (ie., outside) | So a single internal 13A fused-spur feeds | 1 Outside socket - used to plug-in lawn mower | 2 Outside 60w lamp & switch | 3 Outside small water feature pump and switch | None are used concurrently

That is fine, as the max load that can be drawn is limited to 13A by the fuse in the fused-connection-unit (FCU) -- providing the socket is not itself a spur from a ring circuit i.e. your FCU must be connected directly to the ring circuit.

| I have had a new fusebox and circuitry installed which has | RCD protected fuses for all sockets throughout the house.

I hope this is a split-load consumer unit. Whole-house RCDs are deprecated, as they will turn off all the lights whenever the lawnmower gets damp.

| Is the above setup ?safe?? Or do I need to replace the 13A | spur with an RCD-protected spur ? or is this double counting | wrt the new fusebox having this already ?

There is no gain in safety from cascading RCDs -- indeed, if they are both rated the same (usually 30mA in this application) either or both may trip on a fault i.e. there is no discrimination between them.

Owain

[John Rumm]

If the house RCD also protects the spur and has a trip current of no more than 30mA, then you are most of the way there. Depending on how the pump and light are wired, you may also want to check that they are protected by their own fuses where required.

[Christian McArdle]

All sounds fine to me, although the 60W lamp might require fusing at below 10A (or even 6A), so might need additional fusing down. If so, go all the way down to 3A. The pump may also need fusing below 13A.

Christian.

[Dave Plowman (News)]

I've got a few RCD sockets scattered around the house. But have recently changed to a split load CU. Are there any disadvantages to having two in circuit - other than those you've given? And would the socket one be more likely to trip than the 'main' one?

[Stefek Zaba]

The 'main' one's more likely to trip on a marginal fault - it's got other sources of imbalance on the other circuits which are 'sensitising' it to trip with an added, say, 10mA of imbalance (positing here, for argument's sake, an existing 10mA imbalance on those Other circs). With a small added imbalance (bit of damp in your mower's 3-pin extension lead connector, say) your CU RCD will get a cumulative imbalance over its trip threshold, while the dedicated one is still sitting there happy enough.

But it's far from serious enough that I'd spend any tuits on rewiring your existing integral-RCD sockets on their very own radial or ring on the non-RCD-side-of-the-split if I were in your position...

HTH - Stefek