Outside socket question

peter212693 · 17 May 2016 at 00:08

Hi all,

I am thinking of installing some outside sockets for easier access for the lawn mower etc, save running an extension cable through the house which with a 2 year old isnt ideal.

I am looking at something like this:

http://www.toolstation.com/shop/p27175?table=no

Couple of questions... with this being classed as a special install with it being outside will I need to apply for inspection under part p? I have read not as its not altering internal wiring and is deemed as temporary?

I will be plugging it into the sockets in the utility room which from what I can tell is on a 20a breaker at the CU using 2.5mm2 cable (Written on the CU). If i was to use an extension from the newly installed outside sockets will this be ok as long as im not loading it up too much?

The whole house was re wired before we moved in back in 2014 so nice and up to date. I have 2 RCDs at the CU already but I presume with the RCD on the socket anything tripping from outside will just trip this kit rather than the rest of the stuff on the RCD at the CU?

Werewolf · 17 May 2016 at 03:14

With something like that from my understanding as it's only a "temporary" thing and basically a wall mounted extension lead you won't need to worry about part P or anything like that.

You should be able to use an extension from the socket outside, as long as it's in line with the rating of the cabling etc in use, and the RCD on the socket will likely be a lower trip current (as it's only protecting one or two items) than the consumer unit.

We fitted a similar socket to the back of the house and the side of the garage no issues.

We also had my nephew cut through the cable of the hedge trimmer last year (he didn't pay attention to the position of the cable), which was plugged into a normal plug in RCD, which tripped but left the RCD on the consumer unit running.

Lopéz · 17 May 2016 at 05:59

Yes to the best of my knowledge these class as temporary as they plug in - from what I've read online electricians really dislike them but they do the job.

My hot tub has the same RCD plug - I've found then a touch unreliable (had 2 fail in a year, no faults with the tub itself) so if it trips and won't reset get it swapped under warranty first.

kefkef · 17 May 2016 at 09:16

I've got the built in RCD version of that socket. Has worked very well, only issue I've had is that some plugs have to be 'rammed' is as the housing is very tight, should be ok when used with the RCD not being built in though.

valve90210 · 17 May 2016 at 09:22

Lopéz said:
from what I've read online electricians really dislike them but they do the job.

Of course they dislike them, it means your average non-electrician can do the job and not have to shell out for an electrician at what, £50 an hour or so?

Gaygle · 17 May 2016 at 09:47

There is no need to have two RCD's on the same circuit. The RCD at the CU will provide the protection, just as it does for any of the other sockets in your house. As I understand it, the sockets you've linked were invented for people in old houses who don't have modern RCD's built into the CU. My parent's house, for instance, still uses strands of fuse wire - so they need things like this, not a person with a house rewired with the latest stuff in 2014.

I also don't understand how you have two RCD's for the same circuit at your CU?

peter212693 said:
I will be plugging it into the sockets in the utility room which from what I can tell is on a 20a breaker at the CU using 2.5mm2 cable (Written on the CU). If i was to use an extension from the newly installed outside sockets will this be ok as long as im not loading it up too much?

What else is shared on the circuit? Does the breaker *just* supply that one socket? If so, it should be fine, provided you haven't got appliances plugged in that will overload the circuit. To illustrate - even if you you plugged two 1250w electric heaters into your outside sockets and they were using 100% peak power (which they would only do for a very short amount of time and probably not at the same time aka diversity) it would still use up around 10A peak.

kefkef · 17 May 2016 at 11:28

Gaygle said:
There is no need to have two RCD's on the same circuit. The RCD at the CU will provide the protection, just as it does for any of the other sockets in your house.

Convenience? If I tripped the RCD at the CU i'd have to take my boots etc off, traipse through the house from back to front, reset RCD, traipse back again, but boots on and get back to it. Whereas with one on the socket I can just reach/walk over, reset it and get on with things.

Gaygle · 17 May 2016 at 11:38

kefkef said:
Convenience? If I tripped the RCD at the CU i'd have to take my boots etc off, traipse through the house from back to front, reset RCD, traipse back again, but boots on and get back to it. Whereas with one on the socket I can just reach/walk over, reset it and get on with things.

Huh?

A) You've got two 30ma RCDs on the *same* circuit, if someone gets electrocuted it's more likely that the more sensitive main CU one will trip, if not both tripping. The net result is that you still have to walk into the house.

B) If someone has been electrocuted or you've cut through a cable and just seen a gigantic blue flash and a loud crack, are you really going to be moaning about having to walk to the CU to reset the RCD?

kefkef · 17 May 2016 at 11:49

I've tripped the outside socket a number of times recently whilst building an extension/landscaping using a 110v Belle mixer that had some dodgy wiring (it wasn't my mixer or I would have fixed it and the hire place were pretty poor), if it had tripped the inside RCD I would have had to pretty much strip naked to go inside 3 or 4 times a day and reset the RCD, whereas in reality I just walked over to the socket and pushed the reset button.

Mercenary Keyboard Warrior · 17 May 2016 at 12:59

Im in the process of installing an outside socket myself, under the guidance of our electrical manger at work. Hes happy to provide the advice as from our conversations hes judged me to be competent

He said to me you shouldn't really put two RCDs on the same circuit as they often dont play nicely together and that I should rely on the MCU RCD, and revert back to a fused spur where necessary.

Gaygle · 17 May 2016 at 13:07

Mercenary Keyboard Warrior said:
He said to me you shouldn't really put two RCDs on the same circuit as they often dont play nicely together and that I should rely on the MCU RCD, and revert back to a fused spur where necessary.

I have also been told this by several electricians before. Two RCDs on the same circuit can cause issues.

peter212693 · 17 May 2016 at 13:49

Gaygle said:
There is no need to have two RCD's on the same circuit. The RCD at the CU will provide the protection, just as it does for any of the other sockets in your house. As I understand it, the sockets you've linked were invented for people in old houses who don't have modern RCD's built into the CU. My parent's house, for instance, still uses strands of fuse wire - so they need things like this, not a person with a house rewired with the latest stuff in 2014.

I also don't understand how you have two RCD's for the same circuit at your CU?

What else is shared on the circuit? Does the breaker *just* supply that one socket? If so, it should be fine, provided you haven't got appliances plugged in that will overload the circuit. To illustrate - even if you you plugged two 1250w electric heaters into your outside sockets and they were using 100% peak power (which they would only do for a very short amount of time and probably not at the same time aka diversity) it would still use up around 10A peak.

I have uploaded a pic I took of the CU the other night. It seems to be just so the up and down is separated a little.

I was hoping with the RCD on the sockets it would stop and trip at the plug if any problems where to occur with the outside sockets.

Beer_MonsterUK · 17 May 2016 at 16:36

it really just depends which RCD is more sensitive. Unless you test the tripping times and the mA at what the RCD's actually trip at, it's a toss up which RCD will trip in the event of a fault.

There is a regulation relating to discrimination of RCD's in series, but it really relates to discrimination necessary to prevent danger i.e, 100mA on the main switch ,30ma covering the socket circuit & 10mA covering the external socket.......even then, it would likely be a toss up which would trip 1st in the event of a short circuit, it would be a race to isolate the quickest, as you would want, you'd just want any of the protective devices to do their job.

You should have no worries using the bit of kit in OP. It's basically a bit of Portable Appliance. You could in theory just make up a plug and socket and plug it into a RCD protected Internal socket.

peter212693 · 17 May 2016 at 16:56

Beer_MonsterUK said:
You should have no worries using the bit of kit in OP. It's basically a bit of Portable Appliance. You could in theory just make up a plug and socket and plug it into a RCD protected Internal socket.

I was thinking of buying the sockets and cable separate and then as you say swapping the sockets inside to a RCD socket but what I read is you have to use the "pre made CE approved kit" or its classed as electrical work and will fall under part p and need building regs.