Odd ring main??

Postby Buzzard73 » Fri Mar 20, 2009 10:37 pm

I'm completely renovating the downstairs of my house at the moment and started replacing some of the sockets with a view to either extending the ring main or adding a couple of spurs.

The house was built in 1974 and is a 3 bed semi. The kitchen has been done with a new consumer unit fitted but the rest of the electric are on an old style 4 fuse box (ring main, lights, heating, immersion) and I'm intending to have the ring main split and a new consumer box fitted at some point (budget allowing).

The dining room has one double socket and as I rewired that, there was only one set of wires which is a spur - from the back of the other wall which is the kitchen.

I have 2 double sockets in the living room - 1 on the joining wall to next door and one on the joining wall with the kitchen.
I replaced the socket today and that only had one set of wires suggesting a spur also. I haven't looked at the one behind the tv yet as have to move a 42" tv stand and dvd,sat receiver, tuner box etc, but I expect it will also be a spare taken from upstairs!

Is that normal????

So in order to fit 2 extra sockets downstairs, 1 in dining room and 1 in living room - will I need a qualified sparky to do the work?

Any idea how much I expect to pay for a new consumer unit, a split ring main and a couple of sockets?

Just when I thought I would finish within budget.........
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Simply Build It

Postby kbrownie » Sat Mar 21, 2009 2:33 pm

a non fused spur can feed only one socket out-let (this can be either a single or a double or one multi out-let).
You can not spur from a spur, you can spur a string of socket-outlets if a FCU (fused connection unit) is used.
You could also extend the ring final circuit if you wished
At present it sounds like you have one ring final circuit supplying both upstairs and downstairs of your property, this is very common to a house built of that period and I have no doubt that sockets have been added since the original installation as the demand for more socket out-lets
has increased since.
You can add or extend to an existing circuit as a DIYer, without notification to building controls. It's not something I recommend as the work will still have to comply to BS7671 and a minor works certificate issued and if you don't have the required knowledge of intalling and certificating/reporting. How can anyone expect to do this correctly.
You can not without notification or a suitable qualified electrician doing the work add a new circuit from the cu/fuse box. This will also need an electrical installation cert/report.
Cost depends on area you live in, get a few on site quotes and weigh up your options. It's difficult times for most at the moment but finances should not be compromised for safety.
Kind Regards
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Joined: Mon Mar 05, 2007 9:36 pm

Postby Buzzard73 » Sun Mar 22, 2009 2:43 pm

Thanks for your response.

All the downstairs sockets in the dining and living room appear to be spurs taken from the ring main which appears to be entirely upstairs.

There are 3x 2.5mm wires running from the fuse box straight upstairs, 2 thinner ones (probably lighting) and another 2.5mm wire that heads into the kitchen and into the sockets there.

The lighting accounts for 2 out of 6 wires which leaves 4 others on 3 fuses and all 3 (the total amount) downstairs sockets have only a single 2.5mm wire going in and none out.

This leads me to think that the ring main only runs through the upstairs and every downstairs socket (excluding the kitchen) is a spur. I also believe that as a result, I could not add any additional sockets from those downstairs, and would have to chase the cables up the entire length of the downstairs walls and into the ring itself unless I use an FCU.

If I reconnect the spur back into the ring main itself (upstairs)can I then then take a new spur from this socket safely??
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Joined: Fri Mar 20, 2009 7:15 pm

Postby kbrownie » Sun Mar 22, 2009 9:43 pm

Hi Buzzard,
It doesn't supprise me in regards of the dinnig room, as houses of that age they did not always fit a socket in the dinning room.
I'd expect at least one original in front room though but that may have been a spur!
When you say wires do you mean single cables, line/live, neutral and earth cables?
I think firstly we must be sure it is a ring final circuit, once that has been confirmed.
As mentioned can't take a spur from a spur, you can extend the ring and add a socket or two and spur from them or you could add FCU in the ring and take a string of sockets off of that.
This is not notifiable work but does need minor works cert to confirm it complies with BS7671. This will involve essential test to be made.
It's not a job i'd recommend to a diyer with little knowledge of electrics. Safety is paramount for you, family, friends and the property.
Kind Regards and be safe.
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Postby Buzzard73 » Mon Mar 23, 2009 12:23 am

When I say wires I mean the the live,earth and neutral contained within the grey sleeve.

It sounds like an FCU is the way to go in the interim as this will allow me the two spurs I'd need In the area I need them.

As I want the old fuse box replaced with a consumer unit, I'll get the ring main split at that time. What concerns me is the possible amount of power being drawn at any one time - My PC has a 1kw PSU which draws about 1.2kw at full load (usually consumes no more than 80% when I'm working it hard) and that the thought of having the big TV on whilst the missus is running the tumble dryer, ironing and making a cup of tea at the same time (plus the thermostats in the two vivariums) might be pushing the limits.

Everything was going soooo well up to now too!

Thanks for all your help - really appreciate it!
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Joined: Fri Mar 20, 2009 7:15 pm

Postby kbrownie » Mon Mar 23, 2009 11:01 am

I appreciate your concerns and ideally when you have your new CU installed, I would expect your electircian to split the power circuits evenly as that is what should be done. If I understood correctly that your kitchen circuit is seperate to that that supplies the ring final circuit so that's a bonus.
The regulation has no limits on the number of socket-outlets it supplies on a ring final circuit, but we don't expect you to have 15 double sockets all doing work at the same time
The FCU will be protected by a 13amp fuse so any overload on that string will cause that to blow before the fuse in the fuse box. So not to overload whole circuit, I'd make use of those sockets to prevent a total loss of power.
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Joined: Mon Mar 05, 2007 9:36 pm

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