RCD Protection for Outside Socket

[kencoburn]

My consumer unit has RCD protection for the main power sockets in my house. I want to tap off one of the internal sockets (drill through the wall) and connect a weatherproof socket on the outside wall to give me easy access to electrical power in my garden.

(1) Does this outside socket need to be RCD protected?
(2) Would it do any harm to have both the consumer unit and the external socket RCD protected (effectively in series with one another)?

The latter question is because I have a spare weatherproof RCD socket that I could use.

 

[rjm2k]

I am no electrician and will overlook notification requirements.

I assume you will go straight through the wall so no cable is exposed.

The outside socket does need to be RCD protected, which it is from the sound of it on your main CU.

Using an additional RCD socket is not needed but afaik will cause no harm, however if the RCD fires, you will probably find that both RCDs fire! I personally would view that as extra protection since RCDs can fail so having 2 of them I would assume makes that less likely.

What is important is that you are able to fully isolate the external socket in the event of a fault, so use a DP FCU/FSU to make that easy.

 

[kencoburn]

Many thanks for the prompt advice and particularly the point about being able to isolate the external socket.

 

[rjm2k]

It's also a good idea to have a slight diagonal when you drill from the inside to the outside so that water doesn't enter the wall though the hole, maybe stick a bit of sealant in the hole too

 

[PrenticeBoyofDerry]

(1) Does this outside socket need to be RCD protected?

Yes, but this will be okay from CU only

(2) Would it do any harm to have both the consumer unit and the external socket RCD protected (effectively in series with one another)?

There is no need to have two RCDs rated the same, protecting the same equipment.

The latter question is because I have a spare weatherproof RCD socket that I could use.

Use it if you wish but no added benefit really.
What I would recommend, is when installing outside socket, use an internal two pole isolator to take supply from feed socket and load to external socket.
Then you can isolate the outside socket without having to isolate the internal sockets. This is useful in the event that the external socket is faulty, therefore you can isolate it, without causing internal power loss.

 

[Nemo2000]

What I would recommend, is when installing outside socket, use an internal two pole isolator to take supply from feed socket and load to external socket. ..... This is useful in the event that the external socket is faulty, therefore you can isolate it, without causing internal power loss.

I can see the logic in that suggestion, but.....other than the fact that the socket is outside, what difference is there from any other "socket on a spur" arrangement? Assuming that the external socket has a good IP rating and is robust, thereby avoiding water or physical damage, is it at any more risk of being faulty than an indoor socket on a spur?

Just curious....

 

[PrenticeBoyofDerry]

Assuming that the external socket has a good IP rating and is robust, thereby avoiding water or physical damage, is it at any more risk of being faulty than an indoor socket on a spur?
Just curious....

Never assume!
Outside socket are more at risk to ingress of moisture, which could cause RCD trips and power loss, not just the socket outlet, the socket circuit but also any other circuits on the same RCCB. So the wise move is to have two pole isolation as single pole isolation will not prevent the RCBO from functioning.
It's a logical precaution worth taking, it could well be that an internal socket could also cause power loss through RCCB trips, but independent two pole isolation on all internal socket outlets, is simple not practically.
So really you have answered your own question.

 

[rjm2k]

Assuming that the external socket has a good IP rating and is robust, thereby avoiding water or physical damage, is it at any more risk of being faulty than an indoor socket on a spur?

Even if the outdoor socket was no more at risk of being faulty, the consequences if it is are higher. As it is, an outdoor socket has to survive in a much harsher environment so there are more factors to go wrong than with an indoor socket. An indoor socket is never waterproof, but water should never be near it anyway. An outdoor socket must be waterproof and if that fails it absolutely will get wet, with the consequences associated with that.

 

[LearningSpark]

It is also worth having it switched from inside to stop other people using your electricity if the socket is accessible by neighbours etc.

 

[Scoby_Beasley]

It is also worth having it switched from inside to stop other people using your electricity if the socket is accessible by neighbours etc.

Damn!! Now I'll have to put the fan heaters back in the garage.

 

[rjm2k]

It is also worth having it switched from inside to stop other people using your electricity if the socket is accessible by neighbours etc.

And so you don't have to go out to switch off the christmas lights

 

[kencoburn]

Many thanks to all the contributors to my request for information regarding the RCD socket. I have enough information now.

 

[SimonH2]

... and will overlook notification requirements.

This ceases to be notifiable work on 6th April

 

[EFLImpudence]

This ceases to be notifiable work on 6th April

So, do the work now and plan it after April 6th.

 

[rjm2k]

... and will overlook notification requirements.

This ceases to be notifiable work on 6th April

Hurray!