Domestic Socket outlet problem

[freedomrun]

Domestic PME, have two 2.5mm t&e on a B32 mcb, if this was a ring at sometime then the continuity is broken somewhere and i cannot locate the break. No access to underfloor, no spare ways in the CU, has RCD protection to 30mA. I'm thinking it is not compliant to put two Skt Radial cct's on one breaker even if i downrate to B20? Any advice on what to do here please. Thanks.

 

[Zeespark]

Not a problem to put 2 legs of an RM on a B20 MCB, PME is nothing to do with us, only TT/TNCS/TNS is.

AndyGuinness

 

[freedomrun]

I would'nt put, say two or three lighting cct radials on a single mcb, so why is it Ok to do this on a Skt outlet Radial CCT?

 

[Zeespark]

Because the legs are on the same circuit?

AndyGuinness

 

[sparkytim]

+1

Think of it as ONE circuit, you can spur off a radial circuit anywhere you like including the MCB.

Even a lighting circuit can have as many feeds direct from the MCB as can fit into the terminals, as long as the total load does not exceed the rating of the MCB.

 

[Doc Hudson]

From basic principals, a radial can have branches, a branch can be at a CU. which regulation are you worried about?

Doc H.

 

[Evans Electric]

Freedom , you are talking yourself out a solution , which,TBH, quite a lot of sparks seem to do these days. Eventually we will be frightened to open our tool boxes.

The ring is open ended.

No access under the floor.

No spare ways in board.

So if board is not being upgraded , its two radials on a 20A .

 

[shed69]

Or.... Trace every leg out to see where the ends are and see if you can wire a new leg between them?? More work admittedly but would be better for customer to have ring complete than one radial... What rooms are the sockets affected, if it's kitchen then you could be in for calls from customer asking why it's now tripping with kettle toaster and washer on but it never used to before...

 

[circleoftrust]

as above trace the two legs out and make it a ring it makes good sense in the long run

 

[Sharpend]

Is the standard of training that poor these days that we are unable to carry out some simple fault finding?? Half hour at most and this break should be found and ready to be resolved surely or have I missed something? :C :C:coat

 

[Theorysparky]

furthest sockect half split

find which leg has got the fault

power up that leg

socket test those sockets

job done

or you could dead test at each socket..

etc

 

[Doc Hudson]

Is the standard of training that poor these days that we are unable to carry out some simple fault finding?? Half hour at most and this break should be found and ready to be resolved surely or have I missed something? :C :C:coat

I think you have not missed anything and yes training is poor, or rather it is just a money making exercise by training providers where passes = profits. Actually imparting understanding of a subject or how to resolve an issue not covered in the classroom is of secondary importance.

Doc H.

 

[kerching]

I do despair, and I am sure it is not just me. It woll not be too long before we are into the culture of : swap it, bin it, put up with it or replace it! 'Fix It' will be removed from the English Language....sorry, rant finishes! If you had seen some of the carp AND some of the quotes that I have seen this week you would understand/weep.............. :coat

 

[ProDave]

If this WAS a ring, and the ring has got broken, lets not discount the possibility that the neutral break and the live break may not be at the same place.

Split that into two separate radials, and it could get interesting.

Some proper investigation is needed to determine exactly how and where the break is, then determine whether to repair the break and restore it back to a ring, or properly deal with the break and set it up as two radials.

 

[remustered]

Humble offering...Iirc from docs book, you can meter the wire and calc how far along wire the break is. If you did this for both , would it not show if both breaks are together? Or is theory not useable in practice?

 

[SPECIAL LOCATION]

Domestic PME, have two 2.5mm t&e on a B32 mcb, if this was a ring at sometime then the continuity is broken somewhere and i cannot locate the break. No access to underfloor, no spare ways in the CU, has RCD protection to 30mA. I'm thinking it is not compliant to put two Skt Radial cct's on one breaker even if i downrate to B20? Any advice on what to do here please. Thanks.

ALL three legs open circuit? L, N & E....?

On the balance of probability I would guess this NEVER was a ring...

Just someone (DIY bob or his brother) banging radials onto a 32A MCB cuz thats what they think sockets must be on irrespective of the cable size.!

What to do????

As the total number of sockets on this circuit is not Infinite it would not take too long to asses which sockets are fed off which leg of cable.....

1/ Do an Insulation Resistance test between the L-L & N-N of the alleged two half's of the ring...

just to verify there is absolutely NO continuity at all between them..

e.g. if it is a bad joint.. screw undone in the back of a socket.. you may get a high resistance reading.

2/ Take one cable OFF the MCB...

3/ Re energize the other cable..

go round with your ELI tester.. read AND note the Earth Loop Impedance at each socket...

4/ Write figures onto a floor plan sketch..

5/ As this is a radial the numbers should get bigger the further along the cable...

6/ Open up the socket with the biggest ELI

have a look if it has 1 or 2 cables into it!

7/ Do steps (2) thro (6) for the other cable.....

8/ If you have too "end" sockets that BOTH only have one cable in them..

then its more than reasonable to assume that it was never a ring in the first place....

9/ The longer way to do the above is to open up every socket and do dead resistance tests along the lengths of the various sections of cable.

Tell the customer you need to investigate the circuit as the previous electrician appears to have been negligent in either labeling of circuits, selection of protective device, testing prior to energizing a ring...

quote it at 10mins per socket + half hour thinking & mug of tea time..

If they say no....

walk away and leave it as it is!

:coffee

---------- Post Auto-Merged at 10:28 ---------- Previous post was made at 10:26 ----------

I think my post was just the slightly longer version of what Theory say in shorthand on post #11 :Salute

:^O

 

[ProDave]

Humble offering...Iirc from docs book, you can meter the wire and calc how far along wire the break is. If you did this for both , would it not show if both breaks are together? Or is theory not useable in practice?

Power up one leg and go round with a socket tester. If you find one with a missing neutral, you know the breaks are not in the same place.

If one leg tests okay, repeat for the other leg.

 

[freedomrun]

If i have no way of determining how the cable runs in the property or maybe to an outbuilding, in walls, ceilings ect - then calculating how far along the cable the break is? Also, the customer is paying the cost and if they are not willing to pay for testing time is it wise to do all i can to make the installation safe, by replacing the B32 to B20 and making a note on the paperwork that this is a possible defect in the installation that requires further investigation - at least i'm protecting myself that way, i'm not going to spend hours fault finding when i'm not getting paid to do so. Agree on payment terms and then i can go to town on fault finding it.

 

[Sharpend]

Before I can agree with what you are proposing, will need some clarification on the extent of the break in the ring. Is it one leg broke? Is it two? At same place or different or is it all three broke and

Is that at same place?

It is one thing to have a broken ring, and split as two radials but it is another thing to have a safe broken ring, as radials.

Further detail required as regard extent of break. I note that this is posted in DIY section is this correct,??

 

[Theorysparky]

Can we have more info as Sharps has requested

then we can provide a more logical fault finding process for this fault

could we then put it in the Student learning area

I dont think the Op is a diyer,,,,,,