Original and strange ring main readings RCD Tripping

[Roger]

Need some guidance from the wise old forum please

Have a issue with a rcd tripping,Thought I had issue with original marked downstairs ring so did continuity end to end at CU all ok after I did R2 cpc ,all ok whole house lights and everything,good values for cpc so that was ok .Did Cross connection l/cpc and n/l out and in, you know the figure of 8 to get the R1 and R2 readings.All the sockets in the whole house both floors seemed ok apart from 3 ! .1 socket in the UPSTAIRS bedroom and 2 sockets in the Downstairs front living room had high readings of 24.9/25 ohms everything else seemed ok with readings no higher than 1.10.For info front room had 4 socket the other 2 were fine.All sockets were wired as rings and had 2 cable entries no spurs.

Very strange so reconnected CU back up and then checked original marked upstairs ring,end to end ,cross connected and the 3 sockets with high readings seemed fine with acceptable readings.Out of interest checked other sockets that were ok with first tests and they all had voltage so could confirm that they were all feed from the so called downstairs ring.

Question why the high readings ? ,ring main crossed somewhere ?

For info they had a socket in the toliet,only a small room and a child could pee on it easily.I think every light switch needs replacing as they all feel very worn and gritty when switching.Old house again for info she did want the meter relocated moved down the into the hall about 4 foot ,Electricity board quoted £1500 and could not do it for 9 weeks.No more than 4 hours work tops.,

She's just getting the house back together she will be very annoyed if I have to pull floorboards up.

Any ideas ?

 

[Roger]

Just a quick note mate, if you carry out an IR test on the whole circuit, or indeed the whole installation, you shouldnt need to test every cable individually (presuming that the 'whole circuit reading' was clear of course).
A 'figure of 8' test is very important as well, especially on the neutrals, to make sure that you have the correct neutrals connected to the correct RCD. Personnaly, I would connect the live and neutral, and then check all sockets on that circuit. I would also test all sockets on the OTHER circuit as well, to try to eliminate shared neutrals. An IR/continuity test between the different neutrals at the board, and in the field may be usefull as well.
If your unsure, its always best to carry a martindale, or volt stick (ducks for cover) when you are sticking your IR tester on something which 'could' be live.
Not sure what the first line of your post means.

Are you refering to the original post or the one tonight,basically I had a rcd that covered the downstairs ring tripping all the time ,I did some quick tests and found some errors which I need to correct .I am hoping something will become very apparent and soon.I spoke to a sparky friend tonight and he has suggested that every socket be removed and I check as above.He is a senior lecturer and guess he know whats what.Very handy to bounce ideas off him with technical issues every now and then.The shared neutrals seems to be a common mistake so I will check for that first,thank you.For info he immediately suggested crossed rings.Just had a text come in and the client now wants all new switches and sockets throughout the whole house,now to figure out a price incorporating a day testing as well.
Regards,

 

[Davey101]

Was refering to not understanding post number 14.
Wasn't suggesting that you dont take socket fronts off, just that you 'shouldnt' have to test each cable seperatley(sp). Very often with fault finding, there wont be a definitive answer that someone can give you, the best place to start is certainly with the basic tests, in order (ring-ring, continuity, IR, loop, rcd), the rest will be a mixture of experience and luck in finding it quickly.
Do you have an RCD tester? Have you checked the times, especially the 1/2 times test?

Good luck mate, let us know how you get on.

 

[Roger]

Was refering to not understanding post number 14.
Wasn't suggesting that you dont take socket fronts off, just that you 'shouldnt' have to test each cable seperatley(sp). Very often with fault finding, there wont be a definitive answer that someone can give you, the best place to start is certainly with the basic tests, in order (ring-ring, continuity, IR, loop, rcd), the rest will be a mixture of experience and luck in finding it quickly.
Do you have an RCD tester? Have you checked the times, especially the 1/2 times test?

Good luck mate, let us know how you get on.

Aha I understand and yes will do.I was passing the clients house tonight so i thought i would pop in and ask hows things and explain in detail what i would be doing first.Asked about tripping and she said the RCD covering the upsatirs ring had tripped when she was ironing.Checked that out and the cable was so perished you could see the bare wires.It was very old and she threw it in the skip outside straight away.Then she said she was running it through a extension lead when using it downstairs and surprise checked that and you could also see bare wires through the insulation,looked like it was trapped in the door or a dog had chewed it.
Back thursday for a full day,report more then.
all rcd's tested ok with 1652 and double checked with Megger.However not done 1/2 checks and would not normally ,what should i expect ?
Thank you

 

[Davey101]

1/2 times check simply checks that the device will not trip 'too easily', for want of a better term. It literally tests the RCD at 1/2 the rated current of the RCD (as lond as you have set your tester to match the RCD of course). 99+% of the time the RCD wont trip, if it does it points to a faulty RCD. I'm sure others can give a more technical answer though.
Anyway, I doubt thats the problem, so I wouldnt get too hung up on it.
Sounds like you might have solved half the problem with the iron/extension lead.

 

[Roger]

1/2 times check simply checks that the device will not trip 'too easily', for want of a better term. It literally tests the RCD at 1/2 the rated current of the RCD (as lond as you have set your tester to match the RCD of course). 99+% of the time the RCD wont trip, if it does it points to a faulty RCD. I'm sure others can give a more technical answer though.
Anyway, I doubt thats the problem, so I wouldnt get too hung up on it.
Sounds like you might have solved half the problem with the iron/extension lead.

Ok RCD was not faulty,and have had no more problems with tripping since RCBO fitted,Had a lengthy chat with client today and she said they had more sockets added a few years ago.To be honest i think most of the problems have been with faulty household goods or appliances.
I checked the ring in more detail today and so far have upstairs ,3 double sockets from downstairs ring one as a spur and 4 double sockets actually feed from upstairs ring.
Downstairs I only have 2 double sockets feed from upstairs ring.A number of other sockets around the place are on single radial circuits.Insulation tests on radial and upstairs ring came back ok so now to check the downstairs.
If the circuits check out ok what is the rules about the sparadic position of the sockets.Against rules even if i identified each one with a printed label as to the feed.2 Upstairs bedrooms have one double socket feed from each ring.Handy if the loose one of the rings i guess,

Thoughts and advice welcome

 

[Davey101]

Might be worth posting another thread to get some more (knowledgeble?) replies, but as far as I can see, you can wire a ring how you like (I havent checked regs). Its easier to wire 1 half (upstairs and downstairs) of the house on one ring, and the other half (up and down) on another. I've been told that one well known electrical contractor that specialise in new house builds, wires the upstairs on a ring, and just spurs off for the downstairs, sounds a little unlikely tbh. You should defo change the DB labels to something a little less confusing.

 

[electricAl]

The reason why its unacceptable as it is, is due to the requirement to provide for safe isolation of ccts for maintenance etc
As you`ve been contracted to change the CU, Roger, and not re-wire the house, it`d be unreasonable for you to be expected to physically improve the situation too much. You`ve hopefully already fulfilled your obligation to leave the install in no worse a state of safety than already existed - i`m sure its much safer.
However, complying with The Regs as closely as you can manage would mean you really should go to the trouble of making the layout as clear as is possible for the next unsuspecting party to have a go...
Can see you`ll need to suppliment your cct designations at the board with diagrams etc.
Personally, i certainly would.
But if you do that, for me you can do no more, "practicably" as the IET like to call it

Hope that helps you a bit

 

[Roger]

The reason why its unacceptable as it is, is due to the requirement to provide for safe isolation of ccts for maintenance etc
As you`ve been contracted to change the CU, Roger, and not re-wire the house, it`d be unreasonable for you to be expected to physically improve the situation too much. You`ve hopefully already fulfilled your obligation to leave the install in no worse a state of safety than already existed - i`m sure its much safer.
However, complying with The Regs as closely as you can manage would mean you really should go to the trouble of making the layout as clear as is possible for the next unsuspecting party to have a go...
Can see you`ll need to suppliment your cct designations at the board with diagrams etc.
Personally, i certainly would.
But if you do that, for me you can do no more, "practicably" as the IET like to call it

Hope that helps you a bit

It does and thank you ,I still feel a bit uneasy about leaving it like that however I will label consumer unit,do a seperate chart and relate to both with highlighted numbers and positions so it is clear to the client and the next sparky that goes in.The kitchen is on a new ring so most loads with all the appliances is on that ,a good thing as its all new.The rest of the house has not any real demands on the other circuits so it should be fine.It was funny that when I left on thursday it was really dark and I made the comment she should get some outside lights,she emailed me tonight with her selection and whether the ones she has chosen would be suitable.So its looks like I will be back there soon.Good job I put a 12 way board in.
It seems every job I do always has a bit more ! a good thing if I am getting paid for it.I also said that if they ever decorate upstairs give me a shout and I will come back and lift the floor boards to put it right.Both rooms upstairs have fully fitted furniture everywhere,and loads of clutter.
Thanks again

 

[electricAl]

Anytime