Ring Final Circuit Problem

[AA410]

Hi all hope you can help had a spur to fit on an old ring final circuit today that is made up of the old 3092 and old twin and earth were it has been extended in the past the readings i got end to end L 0.16 N 0.16 E 0.32 added together 0.16+0.32/4 = 0.12 but when i carried out a figure of 8 i got 0.07 on all outlets could this be because the different types of earth conductor any thoughts please

 

[markc123]

With L and N readings of 0.16 (which are abit low IMO) i'd be expecting a E (if its smaller than L&N) to be around 0.26.

Thus, doing the prediction for R1+R2 (0.16+0.26)/4 i'd be expecting a reading of around 0.11.

When conducting the figure of 8 for R1+R2 making sure you have the L and E of opposite legs connected together, you should be getting around 0.11 at each socket.

The reason you are getting 0.07 is almost definitley going to be parallel paths somewhere. What you must remember, are that when parallel paths are in circuit the reading will be drawn down towards 0 depending on the strength/amount of parallel paths.

Try disconnect the boiler and go again.

 

[RichardMoore]

Either you have a good ring because you can allow 0.05 reading either way for external factor temp and loose connection or good connections even Orr you have a interconnection a ring with in a ring. Did you take a reading at ever socket on the circuit then?

 

[RichardMoore]

Also true a parallel path nice1

 

[markc123]

I was just trying to put it, as you would if the installation was installed properly. However, i agree Richard it sounds like the ring main will resemble a spaghetti bolognaise.

 

[AA410]

The readings were taken at every s/o x5 not a large ring and no boiler but a bowl of spaghetti come to mind

 

[RichardMoore]

There might be a supplementary bonding conductor going somewhere creating a path you now how the old boys use to just tap onto to anything

 

[AA410]

Thanks lads will have a chat with the owner circuit in need for further investigation

 

[Octopus]

Look for a bare earth cable running from a socket...to a pipe probably!

 

[AA410]

Thats worth a look at the thing is the installation is of age not sure what under the floor the IR is good and the customer i don't think wants to have this looked at the same old story

 

[somersetsparks]

If you for your figure of 8 at the fuseboard the parallel paths shouldn't come into it. It is likely it could be a 'spider' ring with a short ring with many spurs to sockets. IMO I wouldn't worry to much if you get good readings at each point

 

[AA410]

Thanks as you say not to worry its only minor works i will right it on the sheet