Outside socket spurred from the ring main. query! (I am a long Serving electrician)

[michaelw6]

Ok i may get slated for this one but here goes; A bit of background info first.
Its been a while since ive looked at my iee regs, and ive not done my 18th edition but get the updates. i no longer practice much electrical due to a career change.
But for friends, family old customers when i get time i still do the odd little job.
I have been asked to install an outside socket which normally is never an issue just to spur of an internal socket.
This time ive been asked to install a socket 6m away for one of those inflatable hot tubs.
As i remember the regs state you can spur off a socket in 2.5mm t&e im sorry but i dont recall it ever mentioning lengths.
Now a 2.5mm twin and earth is only capable of 25A approx if you plug in two 13A sockets thats 26A. That all works but are we forgetting its on a 32A MCB that cable would burn out before the mcb trips if there was an overheating issue?
Im pretty sure the 6m is not that much of an issue. but if i do a cable calc for this little job it says the cable should be 4mm, im assuming due to the 32a mcb.
Im contemplating installing a XLPE SWA 2.5mm² 6943X 3 core to a single socket, the cable being rated at 31A and a single socket at 13A.?
So putting all the questions to one side and working on the above assumptions.
Would you install a 2.5mm or 1.5mm armoured or a 4mm?
To either a single or double socket?
to be safe than sorry and to future proof i could just install a 4mm to a double socket!!

 

[DPG]

Ok i may get slated for this one but here goes; A bit of background info first.
Its been a while since ive looked at my iee regs, and ive not done my 18th edition but get the updates. i no longer practice much electrical due to a career change.
But for friends, family old customers when i get time i still do the odd little job.
I have been asked to install an outside socket which normally is never an issue just to spur of an internal socket.
This time ive been asked to install a socket 6m away for one of those inflatable hot tubs.
As i remember the regs state you can spur off a socket in 2.5mm t&e im sorry but i dont recall it ever mentioning lengths.
Now a 2.5mm twin and earth is only capable of 25A approx if you plug in two 13A sockets thats 26A. That all works but are we forgetting its on a 32A MCB that cable would burn out before the mcb trips if there was an overheating issue?
Im pretty sure the 6m is not that much of an issue. but if i do a cable calc for this little job it says the cable should be 4mm, im assuming due to the 32a mcb.
Im contemplating installing a XLPE SWA 2.5mm² 6943X 3 core to a single socket, the cable being rated at 31A and a single socket at 13A.?
So putting all the questions to one side and working on the above assumptions.
Would you install a 2.5mm or 1.5mm armoured or a 4mm?
To either a single or double socket?
to be safe than sorry and to future proof i could just install a 4mm to a double socket!!

I don't understand reasoning behind the difference in taking your feed from a single or a double socket?

The distance will obviously affect the volt drop, but as you say it's not a particularly great length.

What current is required by this hot tub?

 

[Moley]

I don't understand reasoning behind the difference in taking your feed from a single or a double socket?

I may be wrong but I think he means fitting a single or double socket to the end of the spur not at the feed.

 

[DPG]

I may be wrong but I think he means fitting a single or double socket to the end of the spur not at the feed.

Ah yes. I've just read it again and I think I misunderstood.

 

[littlespark]

It’s standard to think of a double socket as taking only 20A between the two outlets, not 26…. 2 x 13A

Spurring off a rfc with 2.5 to a double socket is permitted, whether it’s 6m away or only 6 inches.


An inflatable hot tub may only be rated at 10A anyway….


For risk of overloading, I’d avoid taking a socket for a hot tub off the same circuit as washing machines, dishwashers, tumble dryer etc.

 

[oscar21]

A twin socket will destroy itself long before the cable ever does with 2 x 13A loads plugged into it.

 

[Jamie2011]

A double socket is permitted in a 2.5mm spur from a 32a ring main due to secondary protection (26 amps - 2x 13amp plugs is the maximum load that 2.5mm will see).

Secondary protection allows a whole load of things that most guys wouldn’t do. An example - a 1.5mm fed from a cooker outlet (32amp) to fed a cooker hood - as long as the hood is fed via a fuse spur or single socket there’s nothing wrong with it.

 

[Markyd]

Hopefully there is RCD protection

 

[michaelw6]

hot tub about 11Amps.
So in theory if its just a double socket i could get away with 2.5mm 3c armoured. no FCU. and yes it has RCD of course!
Its coming off the kitchen ring as its the only nearest power supply.
i will put a single socket on it though as i dont like the idea of them plugging something else in like a 2kw heater as well as the hot tub.

 

[pc1966]

While no need to feed of a FCU in only one single/double socket, there is an argument for having some means to switch it off if faulty so rest of RFC can be kept on. Any DP switching FCU would achieve that as well as allowing a double socket and no worries of stupid levels of current being drawn.

If cabled in SWA and done by someone like yourself then a fault is unlikely, but future damage might see water in outdoor socket tripping RCD, etc.

 

[michaelw6]

While no need to feed of a FCU in only one single/double socket, there is an argument for having some means to switch it off if faulty so rest of RFC can be kept on. Any DP switching FCU would achieve that as well as allowing a double socket and no worries of stupid levels of current being drawn.

If cabled in SWA and done by someone like yourself then a fault is unlikely, but future damage might see water in outdoor socket tripping RCD, etc.

I did contemplate a FCU, and thought about the isolation issue. But that only lasted a second!!! LOL
No honestly a FCU would be an idea rather than a wiska box on the back to back of the socket.

 

[Jamie89]

As long as its RCD protected at the DB why don't you just put in a fused Spur?

 

[DPG]

As long as its RCD protected at the DB why don't you just put in a fused Spur?

An FCU has already been suggested.