Radial Circuit off a Spur

solavie · May 9, 2015

I seem to have located a radial circuit in the loft conversion. The Circuit is the Ring circuit from the Middle Floor which supplies only 4 single sockets on the Middle Floor, 2 single sockets in each room. In Each room there is a ring circuit and a spur.

My Problem is when i Removed 1 of the 3 double sockets in the loft and tried to do L/L, N/N and Cpc/Cpc, I got a reading on the cpc/cpc but no readings on the L/L or N/N. So I left the socket 1 disconnected and switch the power back on and tested the sockets. Sockets in room one - ring power ok, spur - no power, room 2 - power in both sockets, loft power only at the disconnected sockets on 1 wire only. When reconnected the socket wires I get power back in the spur in room 1 and the other sockets in the loft

The wire supplying the middle floor is the grey strand 2.5 mm and the one supplying the loft is white 2.5 mm T&E.

I have opened all the sockets in the middle floor and there is only two wires in one socket and 1 wire in the spur for both rooms - all in grey wires. There is no 3 wires in any sockets.

At consumer unit: Cpc to cpc - 0.41 ohm, L to L =0.34 ohm, N to N= 0.32 ohm. I also get a resistance of 0.56 ohm between the L and N ends.

With Figure of 8, R1+Rn in room one is 0.05 at socket wired as a ring and 0.66 ohm at the spur coming back from the loft, second room is 0.07 by socket wired as ring and 0.36 at spur socket and in the loft it is 0.47, 0.33 and 0.19 at the first socket.

R1+R2 is 0.12 at consumer unit then bedroom one 0.23 ohm at the ring, 0.86 at spur, Bedroom 2 - 0.47 at the ring socket and 0.19 at the spur socket and in the loft it is 0.63, 0.49 and 0.31 at the first socket.

IR - L to N - 0 (interconnection somewhere), L to CPC >299 and N to CPC >299 Mohms

I need to find out how to circuit is wired or where the loft connection comes from. My job was to add a couple of extra sockets as the loft conversion is being extended.

If not I might have to run a new circuit to the loft from the Consumer Unit. I have found a boiler in a cupboard in the loft at the end of the day as I was leaving, and a quick switching off the MCB for that circuit and the boiler was still powered.

Will appreciate any ideas or thoughts on this circuit.

Leesparkykent · May 9, 2015

solavie said:
I seem to have located a radial circuit in the loft conversion. The Circuit is the Ring circuit from the Middle Floor which supplies only 4 single sockets on the Middle Floor, 2 single sockets in each room. In Each room there is a ring circuit and a spur.

My Problem is when i Removed 1 of the 3 double sockets in the loft and tried to do L/L, N/N and Cpc/Cpc, I got a reading on the cpc/cpc but no readings on the L/L or N/N. So I left the socket 1 disconnected and switch the power back on and tested the sockets. Sockets in room one - ring power ok, spur - no power, room 2 - power in both sockets, loft power only at the disconnected sockets on 1 wire only. When reconnected the socket wires I get power back in the spur in room 1 and the other sockets in the loft

The wire supplying the middle floor is the grey strand 2.5 mm and the one supplying the loft is white 2.5 mm T&E.

I have opened all the sockets in the middle floor and there is only two wires in one socket and 1 wire in the spur for both rooms - all in grey wires. There is no 3 wires in any sockets.

At consumer unit: Cpc to cpc - 0.41 ohm, L to L =0.34 ohm, N to N= 0.32 ohm. I also get a resistance of 0.56 ohm between the L and N ends.

With Figure of 8, R1+Rn in room one is 0.05 at socket wired as a ring and 0.66 ohm at the spur coming back from the loft, second room is 0.07 by socket wired as ring and 0.36 at spur socket and in the loft it is 0.47, 0.33 and 0.19 at the first socket.

R1+R2 is 0.12 at consumer unit then bedroom one 0.23 ohm at the ring, 0.86 at spur, Bedroom 2 - 0.47 at the ring socket and 0.19 at the spur socket and in the loft it is 0.63, 0.49 and 0.31 at the first socket.

IR - L to N - 0 (interconnection somewhere), L to CPC >299 and N to CPC >299 Mohms

I need to find out how to circuit is wired or where the loft connection comes from. My job was to add a couple of extra sockets as the loft conversion is being extended.

If not I might have to run a new circuit to the loft from the Consumer Unit. I have found a boiler in a cupboard in the loft at the end of the day as I was leaving, and a quick switching off the MCB for that circuit and the boiler was still powered.

Will appreciate any ideas or thoughts on this circuit.

Boiler on its on dedicated radial? If it is could this be used for adding the two new socket outlets?

solavie · May 9, 2015

Will check exactly how boiler is connected when I go there next week. I might have switched off the wrong MCB or it could be wired into the light circuit. Did not see any new connections at consumer unit as all the wirings were original though consumer unit has been changed and some circuits RCD protected.

Also I would like to Know why I am getting different R1+Rn reading at each sockets when it should be r1 (0.34) plus rn (0.32)/4 should be about 0.16 ohms

Pete999 · May 9, 2015

Not having a dig mate, but it probably would be better if the folks on here knew what they are dealing with, and tailor our answers accordingly, i,e, are you an Electrician, Trainee etc

solavie · May 10, 2015

I am a new electrician

Richard Burns · May 10, 2015

The results do sound odd, though it is possible you had the ring interconnections for figure 8 the wrong way round.
However because the loft was a later addition and there are only two single sockets in each bedroom it is possible that it is an old spider ring that has been inappropriately modified to include the loft, perhaps by taking the feed from the spur in room one up to the loft and bringing it back round the loft and reconnecting back to the spur socket.
I have not thought it through in detail but the attached diagram is one possible way of getting results similar to yours, I have ignored the R1+R2 measurements as I do not know what you were testing there.
View attachment 29074

solavie · May 10, 2015

Hi Richard

Cannot open the attachment 29074 - not too sure why.

I had both wires completely seperate when doing the figure of 8 (there is not much wiring in the consumer unit) but will double check it. What is a spider ring as I cannot see the attachment?
Cheers.

Richard Burns · May 10, 2015

Hmm do not know what happened there, the forum does seem to be messing up a bit at the moment.
I have reattached here.
I have also thought that your reading of 0.56Ω between line and neutral indicates that there is something electronic still connected to the circuit that is giving a false reading, if there were only 0.56Ω beween line and neutral then 400A of current would flow through the circuit when switched on and trip the breaker, so you may not have covered the whole circuit.

[ElectriciansForums.net] Radial Circuit off a Spur

shanky887614 · May 10, 2015

solavie said:
Hi Richard

Cannot open the attachment 29074 - not too sure why.

I had both wires completely seperate when doing the figure of 8 (there is not much wiring in the consumer unit) but will double check it. What is a spider ring as I cannot see the attachment?
Cheers.

a ring through jb's then a link from each jb to a socket

solavie · May 10, 2015

Thanks for the diagram. It seems to make sense. Will be Checking how the connections have been made tomorrow.

solavie · May 17, 2015

I have lifted some floorboards and looked at some on the wiring. I have found 2 juntion boxes in the corridor but there seems to be other spur wires going I do not really know where. The boiler was on that circuit as well. I have decided to run a new circuit for the loft sockets - instead to spending more time in sorting out this one and it will be quicker too as the staircases are being moved around on all 3 floors.

Thanks for you help