Extending a ring into extension 1

[shabbaranks]

Hi guys
Just after some info concerning extending my ring main. Got all the planning application in and it will all be signed off - I want to extend the ring main into my extension all the current sockets are fed from under the floorboards so not just a question of adding some junction boxes and extending that way.

My thought is I have a socket which is the closest and access underneath while the ceiling is down. My thoughts are to pull those 2 cables back and join the new cable using a wago chase the top of the socket and run the new cable up into the loft around and down to feed the new sockets and then back to the original socket as above joining to the other cable again with a wago.

My question is, is this is the best way? And am I ok to use one of these cables to feed the socket here and effectively having tge other just passing through so to speak?

Excuse the crappy picture

 

[shabbaranks]

Hi guys
Just after some info concerning extending my ring main. Got all the planning application in and it will all be signed off - I want to extend the ring main into my extension all the current sockets are fed from under the floorboards so not just a question of adding some junction boxes and extending that way.

My thought is I have a socket which is the closest and access underneath while the ceiling is down. My thoughts are to pull those 2 cables back and join the new cable using a wago chase the top of the socket and run the new cable up into the loft around and down to feed the new sockets and then back to the original socket as above joining to the other cable again with a wago.

My question is, is this is the best way? And am I ok to use one of these cables to feed the socket here and effectively having tge other just passing through so to speak?

Excuse the crappy picture

 

[SUNRAY]

Assuming the existing socket is on a ring circuit an idea is to join one of the new cables to one of the existing to extend the ring. I've shown it as looped round the outside of the existing socket but in reality the join (wagos?) should be within the backbox. If there isn't space I'd consider changing the existing socket and backbox to a double.

The person signing to say he has designed, installed and inspected is the person to verify it is a ring and whether the existing circuit is suitable for so much additional cable etc.

 

[ericmark]

Step one is look at the original installation certificate or measure R1 + R2 or at least the prospective short circuit current or loop impedance and work out if extra cable can be added to the ring final. 106 meters is considered to be maximum length to comply with volt drop, but also depends on the over current device, for example a B32 MCB will trip on the magnetic part of the trip with 5 times rated valve, so 160 amp, using ohms law, this equals approx 1.44Ω and add 5% for safety, 1.36Ω so step one is be enquiry (reading installation certificate) or by testing, (using the loop impedance meter or low ohm meter) work out if you can add to the ring final.

Using a twin back box and two single sockets, or a double back box and two grid sockets, is likely the easiest way to split the ring. To add to the circuit the circuit will need to be RCD protected, and I think the new edition is now in force, so will need to be a type A, can't use type AC any more.

But before jumping in first is to ensure the LABC will let you do it. When I came to do the electrics in my mothers wet room, I had a problem getting the LABC inspector to allow me to do it, he did in the end, but it seems there is a tick box on the building application and when you make the application you need to select if using a scheme member or not to do the electrics, my LABC wanted me to pay for some one to come in and test the installation which I would need to pay for, the cost of the inspection would be more than the cost of using a scheme member electrician.

So you need to have the calibrated test set to show the LABC inspector, and some proof you know what you are doing, like a city & guilds 2391 certificate.

When Part P came out it was one fee, which in Wales was £100 plus vat for first £2000 worth of work, and the LABC inspector had to either test and inspect himself, or the LABC paid for the third party inspector, but that changed, and now the LABC can charge you with cost of inspector, so it can get rather expensive if your not doing your own inspecting and testing.

It is the same for a lot of the building work, windows for example need a certificate or you pay the LABC, so in real terms near impossible to build an extension without the LABC being involved, and the last thing you want, is for it to be nearly complete, but the LABC will not issue the completion certificate without some other paperwork, like the compliance certificate issued by the scheme members electricians scheme.

So do check with your LABC inspector what he will let you do, we found Liverpool very helpful, and no real problems, but Flintshire were really strict, so a lot depends where you live.

 

[Taylortwocities]

@ericmark the OP seems to have already posted this topic.

Extending a ring into extension

Hi guys Just after some info concerning extending my ring main. Got all the planning application in and it will all be signed off - I want to extend the ring main into my extension all the current sockets are fed from under the floorboards so not just a question of adding some junction boxes and...

www.diynot.com

Probably he/she thinks this forum is a 24 hour a day service!!

 

[bernardgreen]

Using a dual box provides an extra socket and removes the need to have cables jointed in terminal blocks behind a socket,

 

[ericmark]

In the old days of fuses, if one exceeded the loop impedance a little, then likely the disconnection time also was exceeded a little, no big problem, but with modern trips, be it a MCB or RCBO the over current protection is split into two, the thermal part, and the magnetic part, and the thermal part is slow. So if you exceed the loop impedance then short circuit tripping time jumps from 0.01 seconds to minutes, that is a huge jump.

So measuring the loop impedance or prospective short circuit current becomes rather important.

Unfortunately the cheap plug in devices

seem to be designed for radial circuits, the pass mark is based on a 20 amp B type MCB, at around 1.9Ω depending on the make, so to work on a ring final the test equipment jumps from around £40 to £200, although since we really want to work out what the earth loop impedance will be after the extension is fitted, we really want to be reading down to 2 decimal places, so we know what can be added.

The cheap (£32) insulation tester

has no low ohm range, to get a low ohmmeter with the required 200 mA test current is expensive. Lucky I have one, but again looking at £200 mark to buy one.

As to calibration certificates I really think a test resistor is enough, but likely the LABC inspector will want to see them, so after doing the wet room, I wanted to get whole of mothers house rewired, by which time the meters I had were out of calibration, and some had stopped working, so to DIY was going to cost between £500 and £1000 to get the meters required and pay the LABC, the house would either be let out, or sold soon after, depending on mothers condition, so needed all the boxes ticked.

So I decided it was going to cost that little extra to get a scheme member firm to do the job, it was simply not worth all the effort. And likely with an extension the LABC is already involved, so to not follow regulations is really not an option.

If it was not an extension i.e. LABC not involved, I would say fit a FCU (fused connection unit) and feed the extension with a spur, the cheap plug is tester will be good enough with a 13 amp fuse, the pass was 2.42Ω not sure if changed when the 5% for safety was added? But it is unlikely to be a problem, but the big question is not so much what is safe, but what will the LABC accept.

 

[SUNRAY]

@ericmark the OP seems to have already posted this topic.

Extending a ring into extension

Hi guys Just after some info concerning extending my ring main. Got all the planning application in and it will all be signed off - I want to extend the ring main into my extension all the current sockets are fed from under the floorboards so not just a question of adding some junction boxes and...

www.diynot.com

Probably he/she thinks this forum is a 24 hour a day service!!

I believe this thread was not showing when I responded to the latter thread (3 minutes between them) with the second image of his proposal.
I have managed to do the same thing myself while adding a picture during an ammendment, since the new software, I've also found it's happened where I click 'post reply' but for some reason the site doesn't take it straight away but a second 'post reply' does.
When I've been aware I amend one with something like 'deleted double post'.

 

[ericmark]

Yes done the same myself, the problem is when you don't realise two are running, so miss half the answers, is there a way to get sysop to combine them?

 

[SUNRAY]

In the old days of fuses, if one exceeded the loop impedance a little, then likely the disconnection time also was exceeded a little, no big problem, but with modern trips, be it a MCB or RCBO the over current protection is split into two, the thermal part, and the magnetic part, and the thermal part is slow. So if you exceed the loop impedance then short circuit tripping time jumps from 0.01 seconds to minutes, that is a huge jump.

So measuring the loop impedance or prospective short circuit current becomes rather important.

Unfortunately the cheap plug in devices View attachment 276138seem to be designed for radial circuits, the pass mark is based on a 20 amp B type MCB, at around 1.9Ω depending on the make, so to work on a ring final the test equipment jumps from around £40 to £200, although since we really want to work out what the earth loop impedance will be after the extension is fitted, we really want to be reading down to 2 decimal places, so we know what can be added.

The cheap (£32) insulation tester View attachment 276139has no low ohm range, to get a low ohmmeter with the required 200 mA test current is expensive. Lucky I have one, but again looking at £200 mark to buy one.

As to calibration certificates I really think a test resistor is enough, but likely the LABC inspector will want to see them, so after doing the wet room, I wanted to get whole of mothers house rewired, by which time the meters I had were out of calibration, and some had stopped working, so to DIY was going to cost between £500 and £1000 to get the meters required and pay the LABC, the house would either be let out, or sold soon after, depending on mothers condition, so needed all the boxes ticked.

So I decided it was going to cost that little extra to get a scheme member firm to do the job, it was simply not worth all the effort. And likely with an extension the LABC is already involved, so to not follow regulations is really not an option.

If it was not an extension i.e. LABC not involved, I would say fit a FCU (fused connection unit) and feed the extension with a spur, the cheap plug is tester will be good enough with a 13 amp fuse, the pass was 2.42Ω not sure if changed when the 5% for safety was added? But it is unlikely to be a problem, but the big question is not so much what is safe, but what will the LABC accept.

Like you I have meters well out of calibration. While having many of their meters calibrated a few years back a company I worked for paid for my insulation/low resistance meter

as it was used it so much for them.
I suggested putting the RCD

and loop

through as well but quickly shied away when they said how much it would cost me.
I originally purchased my set of 3 complete with a bundle of test leads for £50 when a company downsized (read that as; lost the 'on site' maintenance contract at a number of locations) 20 years on I still see these going for £50-150 each on ebay

 

[SUNRAY]

Yes done the same myself, the problem is when you don't realise two are running, so miss half the answers, is there a way to get sysop to combine them?

have you reported it yet?

 

[ericmark]

No have you?

 

[SUNRAY]

Is this not one of those things which you do if you think it needs doing?

There you go, I've done it for you.

 

[SUNRAY]

Thank you mod.

 

[shabbaranks]

@ericmark the OP seems to have already posted this topic.

Extending a ring into extension

Hi guys Just after some info concerning extending my ring main. Got all the planning application in and it will all be signed off - I want to extend the ring main into my extension all the current sockets are fed from under the floorboards so not just a question of adding some junction boxes and...

www.diynot.com

Probably he/she thinks this forum is a 24 hour a day service!!

Hi Mate

As far as I know I only posted it once - but thanks for the comment (did you get out the wrong side of the bed?)

I like others appreciate forums like this where people share their knowledge - Im sure in life we all have something to contribute. I dont expect people to jump on and answer me straight away (or at all) but for those that do its really helpful.