Extend existing ring or whole new ring?

[Welshjeff1000]

Let me start by saying I have zero electrical knowledge so forgive obvious ignorance.
Query relates to adding further domestic plug sockets upstairs.

Renovating a 1960's house. Bedrooms have 1 or 2 sockets each so need to add more taking 6 to 15. Appears to have had a modern rewire and the consumer box looks fairly modern.
I'm doing the donkey work such as running cables beneath the floor boards and chasing in the new metal boxes.
Electrician mate (certified) advises extending existing ring by adding new sockets in with junction boxes under the floorboards to the existing sockets.

My query, is this safe? While house is empty, shouldn't I just replace the whole plug ring circuit rather than have the extensions in each room? Electrician is connecting everything up but wouldn't a new circuit be more reliable than cuts and junc boxes in the old? Is electrician taking a shortcut?

 

[JohnW2]

Electrician mate (certified) advises extending existing ring by adding new sockets in with junction boxes under the floorboards to the existing sockets. My query, is this safe? While house is empty, shouldn't I just replace the whole plug ring circuit rather than have the extensions in each room?

That would certainly be preferable (although you may be able to retain some bits of the existing wiring).

Electrician is connecting everything up but wouldn't a new circuit be more reliable than cuts and junc boxes in the old?

Yes.

Is electrician taking a shortcut?

Yes.

What your electrician is suggesting would, if done properly, be essentially 'safe' (and compliant with regulations), and there are probably millions of homes out there with such circuits. However, if the opportunity exists whilst the house is empty, it would be far better/'nicer' (and more certain to remain 'safe' for very many years) to do things 'properly' - particularly given the extensive degree of 'extension of the circuit' that you are talking about.

You should be aware that if you did take the electricians approach, and used (I would imagine several) junction boxes, the regulations require that if they are not "accessible" (for inspection, maintenance and testing) (e.g. if they are under floors or above ceilings), the JBs must be of a special ('maintenance-free') type.

Kind Regards, John

 

[PrenticeBoyofDerry]

Firstly the new sockets and newly buried cable require RCD protection, so how new is your consumer unit/fuse board can it offer this protection?
If the property is empty and you have access to all areas, then using junction boxes to extend the ring final is sheer laziness and unprofessional in my opinion. You could save parts of the existing circuit without having to form junctions, by using the parts of the circuit that go directly between sockets and replace for new the lengths that require extending or alteration.
If junctions are made that are inaccessible for inspection,test and repair then maintenance free methods of jointing would be required.
If you are doing the donkey work such as routing cable, chasing walls and sinking sockets, you must make yourself fully aware of the permitted safe zoning of cables in floors and walls.
This would include depths and location of chases, permitted depths and location of holing of joist and if notches need to used their location and depth plus the addition of mechanical protection.
In answer to you question with regards to safety, yes it is perfectly safe providing it is done competently! But not recommended!

 

[ericmark]

There is a limit to how much cable one can use with a ring final considered as 106 meters which by time you weave back and to using 1/3 rules when drilling beams it is easy to exceed.

So working on existing ring final step one is to work out how much cable has already been used. In theroy this is easy, you measure the impedance or resistance of existing cable. However in practice not so easy as the meters and the readings have errors we are only talking about 0.59Ω allowed for the cable total.

So yes to measure the resistance and subtract that from the total so you are told before starting you can add x meters of cable it is possible. But far easier to say here is a 100 meter role don't use any more than that in your ring.

As to non RCD protected you could use surface or special cable and RCD sockets but rather an expensive option. DIY wise the RCD FCU is likely the best option as using fused spurs. But this would not be a professional method, professionals have the meters and the ability to self certify so would tend to extend the ring final.

There is nothing wrong with using a mate. And getting the home owner to do as you say the donkey work is no different to using a mate. But the electrician must be in control, it's not a case of you deciding on cable runs and he just simply connects up, he has to decide what is done and check it has been done the way he wanted. I have heard the phrase "Done exactly as asked, but not as wanted." going away and leaving a mate to do work there is always a chance he is not doing as one expected and the work may need re-doing. The better way is to do work at the same time as the electrician is there so he can catch anything which is not to his liking.

My son made the mistake of allowing a home owner to help. He estimated 10 days without help, with help should have been 6 days, but so much had to be re-done still took 10 days so that was last time he allowed owner to help. After that we question electricians who allow home owners to help. For the owner to cut chases to lines and make good plaster great. But does not take long to pull in cable why would an electrician ask some one else to do it?

 

[flameport]

Forget about rings and install new radial circuits.

 

[Welshjeff1000]

Thanks guys, I'm going to start the circuit again as it would be mad not to take advantage of the house being empty. I'll do some research on correct laying of cable first and keep all the wiring exposed for the electrician to check before everything gets connected.

 

[PrenticeBoyofDerry]

I'll do some research on correct laying of cable first

You can start your research by browsing the information in Wiki
//www.diynot.com/wiki/Electrics:Installation-Techniques

 

[winston1]

Forget about rings and install new radial circuits.

So says someone who does not like rings. But rings have been tried and tested since 1947 and have been found to be perfectly acceptable and safe.

 

[Welshjeff1000]

I'll do some research on correct laying of cable first

You can start your research by browsing the information in Wiki
//www.diynot.com/wiki/Electrics:Installation-Techniques

Many thanks

 

[oldbutnotdead]

Adding sockets to the existing ring is fine (subject to square metreage of rooms and max cable length), junction boxes under the floorboards are a rubbish idea though. If you have existing ring final circuits then map the legs (to make sure you don't have any spurs on spurs or other nasty tricks like that) then extend intelligently (depends what your map looks like) with new cable to your new sockets. There are requirements for where you can bury cables in walls (only horizontally and/or vertically from outlets or within 150mm of ceiling or wall corner) and where you can drill (0.25-0.4 of span, on centreline of joist, max hole diameter 0.25 of joist depth) or notch (0.07-0.25 of span, max notch depth 0.125 of joist depth).

 

[sparkwright]

You say this 60s hose has had a 'modern rewire', so, depending on how new the cables may be, it may or may not be a waste of time rewiring all of the circuit.

I suppose a good indication would be whether the cables contain red and black or brown and blue cores.

Brown and blue wouldn't be any older than 11 years (assuming it is proper T&E cable, as it almost certainly will be) so really wouldn't need changing unless badly done.

It may of course be practical to replace all or nearly all of it if there is to be lots of extra sockets.

Always worrying hen someone says they have zero electrical knowedge, then start running cables.

I advise you check with your mate first before running cables he hasn't asked for.

Also, when running cables, keep them nice and straight. Kinks and twists make a bad job.

Also leave a little slack on the cables under floors just to allow for any future alterations (like moving an accessory a few inches or adding a junction for a future addition).
Photographs would be most welcome, out of general interest.

 

[Welshjeff1000]

I took some photos which I'll upload asap. I opened 2 existing sockets and both have 2 red, 2 black and 2 green&yellow.

 

[sparkwright]

Yes, please do.

It could well be that your 60s house wasn't rewired, merely 'upgraded'.

Photos will tell us a lot.

 

[sparkwright]

Forget about rings and install new radial circuits.

So says someone who does not like rings. But rings have been tried and tested since 1947 and have been found to be perfectly acceptable and safe.

I prefer rings.

One advantage being if a cable gets damaged, the ring can be converted into two radials.

 

[Welshjeff1000]