Relocating ring as surface mount

[IT Minion]

Hi All,

I have a cable running through my cavity wall. I'm doing some work in the room it emerges into and also want to put cavity wall insulation in at some point soon. As such I want to move it.

Is it safe (and legal?) for me to do it or should I book a qualified sparky in?

I would like to move the cable to the underside of the stairs. There is a bit of trunking shown on the image below that I want to remove and replace with something a bit bigger then re run the cable in it. My reading implies that surface mount wires are ok without any armoured conduit but if that's better I'm ok with that.

The CU is in the cupboard under the stairs (purple), the new route is to replace the trunking below the orange line.



At some point we'll (with qualified help) be looking at rerunning the cable and rationalising the number and location of rings, so bonus points if I can find a way of doing this that makes the Sparky's work easier in the future.

 

[ericmark]

It is an open question as to if a DIY person can safely work on a ring final, there is no formal qualification to become an electrician, it is down to if they have the skill or not, although to become a scheme member you would need some paper qualifications, you could still work for a company who are scheme members as an electrician and have no qualifications. (Although unlikely)

So it comes down to what do you need to know.
There are some building requirements, like ensuring in a fire the cables can't fall and trap a fireman. Stick on trunking still needs metal fixings at intervals to stop wires blocking routes in a fire.

You need to be able to test it is a ring, and that in a fault it will auto disconnect.

So in England you should be able to DIY most electrical work, Wales is more restrictive, if following the regulations (and BS7671 is not law, but can be used in a court of law) then you should complete the electrical minor works or installation certificate, and sign it to say you have the skill. No one can do this for you, it has to be done by the person in control of the work, so if an electrician says run a wire here, and you do it, then he tests he can sign, but if you run the wire then ask him, then he can't sign, as he was not in control.

So you will need test equipment to fill in the certificates, likely will cost £200 plus even second hand, clearly most DIY people take a chance. So your question is like asking some one who has never driven a car, could they drive it around a private track, most likely could with some practice, and guidance, but if you don't have that practice or guidance what then?

So forget legal bit, ask is it safe? With a ring final as name implies it goes round in a ring so every socket has two supplies, the wire is good for around 20 amp, the protective device is around 32 amp, so unless it has supply from both sides you can overload the cable, so you need to skill to test it is a ring.

 

[IT Minion]

Lots of information in there. My reading supports your statement of it being a grey area depending on what you're trying to do. In this case I believe I'm competent enough, but I'll give you and the internet a bit of time to point out that I'm wrong.

In this case I'll be disconnecting a wire, looks like 2.5m twin and earth, from a junction box under the floor.

Pulling the wire back down the cavity and then inserting it into some (mechanically fixed) trunking.

Then reconnecting it to the junction box, relocated outside the room into the hallway but still under the floor. No new wires added, but a few sockets removed that currently spur off the junction box.

To restate the final issue,the (hopefully not fatal) flaw is that once I've connected it then I don't have any way to test that the ring itself is complete and it's not acting as a radial (eg by pulling the wire through and breaking one or more of the cores)? Is there a way for a DIYer to do that?

Edit: it's also probably worth pointing out that the electrics aren't, as far as I can tell, in a standard ring that meet current rules. Junction boxes under the floor and too many spurs etc. I'm not even 100% sure it's a ring Vs a radial.

 

[JohnD]

As for "legal," if you are in England, the work is not notifiable.

But all electrial work in domestic premises is supposed to comply with the 28 words of Requirement P1 of the building regulations. If you read the entire document, observe where the word "shall" is used. Everywhere else says "should."

You mention continuity testing of the ring. That's pretty easy. At every point (for example a socket or the CU) there should be continuity between the two brown or red; and between the two blue or black; and between the two G&Y.

Junction boxes are undesirable, and are not supposed to be hidden under a floor.

 

[ericmark]

The easy way if not sure a ring is use 25 A over current protection instead of 32 A and then there is no overload problem. As to testing the EZ150 plug in tester does most functions, all maths so a B25 MCB should trip on magnetic part at 125A (5 times thermal rating that is what the B is for) so 230/125 = 1.84Ω and the EZ150 will show 1.5Ω as on a 25A B type if the EZ150 says OK then it would also pass with a more expensive tester. At 32A then 1.44Ω so EZ150 does not really help. Yes it seems odd to market a tester that does not work with a ring, but non of the go/no go testers do.

As to the RCD well you can't check it trips within 40 ms with a stop watch, but using the test button built in is good enough for most people. My son has one, but I have yet to borrow it and test all my RCBO's I just cross my fingers they will work, which I would guess most DIY people do the same.

To be frank with today all RCD protection if the earth loop impedance is a little over the limit not really an issue as the RCD will still trip with a fault.

All shown have a loop test, all under £50 some even have a basic RCD test, but the ones without loop test are not really good enough, it has to have loop test. The last Non-trip earth loop impedance ranges 0 - 1.7 - 5 - 10 - 100 - 200 - 500Ω as said not low enough for a ring final but about the best you can get without paying around £200.

 

[Taylortwocities]

Then reconnecting it to the junction box, relocated outside the room into the hallway but still under the floor.

Junction boxes with screw terminals (I'll bet you have one of those) are not permitted unless they are accessible.
Under the floor doesn't count as accessible so you would need a "maintenance free" junction box. One of these would suit you, sir!

 

[IT Minion]

Junction boxes with screw terminals (I'll bet you have one of those) are not permitted unless they are accessible.
Under the floor doesn't count as accessible so you would need a "maintenance free" junction box. One of these would suit you, sir!

Hah, shows what you know, I've got at least two!

But good point. I'll get a handful of those to replace the under floor ones as I find them. Shame Screwfix doesn't stock 32A ones, I've got one right next door.

 

[winston1]

There is no limit to the number of spurs, only the amount of sockets on each (one). Ordinary junction boxes were permitted under the floor for many years and as regs are not retrospective there is no need to replace them. Never heard of any problems with them either.

 

[Taylortwocities]

The use of screw terminals in hidden boxes are not now permitted for a reason.
I know the reason and you @winston1 dont,
because you have never had to find a hidden joint that has failed under a floor. A fault that has been found when carrying out an inspection.

Now, it is true that regulations are not retrospective and, should the OP have discovered these boxes then there is no compunction to change them for maintenance free. BUT
he is doing new work on the circuit, moving the cabling and probably running some new. In my opinion, it would be absolutely criminal not to do things properly while he has the opportunity. And you always bellowed from the mountaintops that work should be done properly. Good grief.