Question about reinstating socket in shed

[kissinger]

I’ve had a partial rewire and the electrician removed the old shed socket because the shed was being demolished. The original 2.5 mm² T&E that supplied that socket is still in place from the kitchen to the shed location, and it forms part of an RCD-protected socket circuit at the main consumer unit. Now that the new shed is installed, I want to reinstate a socket by fitting a BG Nexus Storm IP66 13A weatherproof RCD double socket directly onto the end of the existing T&E. I’m not creating a new circuit; I’m simply putting a socket back where one used to be.

Before I go ahead, I’d like a second opinion. Is it acceptable to terminate the T&E directly into the weatherproof socket without adding anything else? Are there any safety or regulatory issues I should be aware of when reinstating the socket on this spur?

I am aware that armoured cable is preferred, but the T&E is already installed underground with a protective sheath and I don't fancy digging up my patio (it's crossig a roughly 2m stretch of patio to the shed). Any advice appreciated.

 

[ericmark]

1) Location, Wales likely need to register the work, England no longer required I think.
2) Unless using a 10 mA RCD socket then pointless fitting a RCD protected socket when already RCD protected.
3) Twin and earth not rated for external use, but as long as it passes the testing then I would not be too worried, however for my own shed used SWA and have abandoned the old twin and earth.
4) As long as nothing goes wrong, no one is likely to question what you have done, if something does go wrong then paperwork will be asked for, so unless a very poor job even if it does not comply then unlikely to get caught.
This from the IET is rather dated 2005 however not that much has changed, unless you are going to charge an EV from the shed, or install solar panels, then following the 2005 instruction set and you will not go far wrong.

 

[securespark]

I can't see an issue. You are in effect just replacing an accessory, like for like.

But if you are in Wales, it is notifiable.

What I would be tempted to do is protect the cable (my choice would probably be black PVC conduit) where the cable comes out of the ground so it is protected against damage from tools etc...

 

[endecotp]

RCD-protected socket circuit at the main consumer unit.

BG Nexus Storm IP66 13A weatherproof RCD double socket

There's not much point having two RCDs; either one or the other (or both?) could trip. Don't imagine that the more-downstream RCD will always trip first.

 

[SimonH2]

I’ve had a partial rewire and the electrician removed the old shed socket because the shed was being demolished. The original 2.5 mm² T&E that supplied that socket is still in place from the kitchen to the shed location, and it forms part of an RCD-protected socket circuit at the main consumer unit.

Can you clarify: is this existing cable connected to anything or not ? If it's still connected at the house end, what's on the other end ?

2) Unless using a 10 mA RCD socket then pointless fitting a RCD protected socket when already RCD protected.

There is (in practice) no discrimination between a 10mA and 30mA RCD (and 100mA RCD for that matter) - in the event of anything but a fairly high resistance fault, the current imbalance is likely to be above any of those values and so will trip all of them (or some indeterminate subset depending on detect times, and mechanical operation times). That's why we have time-delayed RCDs to provide such discrimination.

 

[ericmark]

There is (in practice) no discrimination between a 10mA and 30mA RCD (and 100mA RCD for that matter) - in the event of anything but a fairly high resistance fault, the current imbalance is likely to be above any of those values and so will trip all of them (or some indeterminate subset depending on detect times, and mechanical operation times). That's why we have time-delayed RCDs to provide such discrimination.

I see your point, a nail through a cable can take out the 5 amp 1-minute delay RCD with the 30 mA 40 mS I have seen that happen, but in the main, water is the cause, and it slowly gets worse, so we see using an approx x3 between RCD's the 10, 30, 100, 300, 1amp and 5 amp does in the main give discrimination.

 

[SimonH2]

But considering the primary function for most RCDs - pritection against direct contact. You'll conduct "considerably more" than 30mA - and trigger all the RCDs. The only one's that won't trip will be thise that are slow enough not to have triggered before another has physically opened its contacts.
There's a period between the point in time when the unit "will trip" and when the mechanism has physically opened the circuit. This means that it often isn't just the fastest that trips - it all depends on how those periods overlap (or don't) between the different devices.

 

[morqthana]

1) Location, Wales likely need to register the work,

But if you are in Wales, it is notifiable.

Why do people keep mentioning Wales?

 

[morqthana]

There's not much point having two RCDs; either one or the other (or both?) could trip. Don't imagine that the more-downstream RCD will always trip first.

If the socket is the type that also trips on loss of power it might be worth having, depending on what gets plugged in.

 

[ericmark]

If the socket is the type that also trips on loss of power it might be worth having, depending on what gets plugged in.

I have used an active RCD to power grinding wheels and the like, so it will not re-energise when power returns, but that is hardly the case here.

As to location, not sure how I missed it, but people do read replies and act on them without posting, so it does not harm to say it depends on where one lives as the rules change will location.

 

[Harry Bloomfield]

Before I go ahead, I’d like a second opinion. Is it acceptable to terminate the T&E directly into the weatherproof socket without adding anything else? Are there any safety or regulatory issues I should be aware of when reinstating the socket on this spur?

That sounds OK in principle, but what's at the supply end? If it's simply spurred straight from the kitchen ring circuit, it would be better to ensure it can be isolated separately, and maybe limited to 13amps, via a double pole, fused spur, fitted with a 13amp fuse. Double pole, so both L and N can be isolated, in case of problems, so kitchen power can be easily restored, in case of outdoor faults.