Fault finding

[High Tower]

Ok, one of the hardest things you guys will have to deal with as sparks will always be fault finding, it really only does get easier with experience, so........... im going to describe some of the faults i have been to.

i would like your theory's, ideas and suspicions, how you would go about testing to confirm your theoreys and any rectifications.

Please remember there are no stupid answers. soooooooo

 

[High Tower]

two bedroom terrace house, front door opens into dining room, leads to living room, leads to kitchen.

Cu s in dining room to the right of the front door.

6 way very early crabtree 60898, only 4 circuits used, 2 power and 1 shower.

Fault was catastrophic loss of lighting, breaker was in the on position and working fine, whole house in darkness apart from dining room which was working.

over to you guys

 

[Baker1988]

it sounds like the entire lighting is run of the 1 mcb so that's why it all went off except the dining room (should upgrade to a split board haha), as the board is in the dining room i would assume that the cable goes from the board to the dining room lights to start with then onto the kitchen then upstairs, there is probily a loose connection either on the live or the neutral wire in between the last light that is on in the dining room and the first light that is off in the kitchen, the first thing i would do is a visual inspection on the ceiling rose from the last light that is working to see if there are any loose cables if there are no loose connections that i can see (i wouldn't touch any cables at the moment as they are still live and this would not comply with eawr reg 12 "i think") i would go to the next light and check that ceiling rose if i could not see any thing i would go to the last point on the circuit and do a quick check to see if the line conductor is live with a voltage indicator if there was a live feed then it would make me believe that the fault is on the return path(neutral) so i would then go to the board isolate it then put a link between live and neutral (r1/rn) or put both cables in chock block then go to the furthest point and do a r1/rn continuity test and work my way back till i got a reading then i would no the problem was in between that fitting and the next fitting, so now i have narrowed it down i would check the connections and probily find a loose wire.

sorry for the essay answer

 

[High Tower]

Im going to let others join in before i digress the rest.

 

[Paul.M]

Im going to let others join in before i digress the rest.

I wont say anything HT. It may take a few days before others join in mate, its not the busiest of forum sections.

Good idea for a thread HT, I'll post one up from a fault find call out from yesterday and post up a picture of the fault. I wonder if Trev can post up fault finding scenarios as well, I'll ask him.

 

[Baker1988]

Im going to let others join in before i digress the rest.

Lol so I take it that I am wrong! haha

 

[High Tower]

I wont say anything HT. It may take a few days before others join in mate, its not the busiest of forum sections.

Good idea for a thread HT, I'll post one up from a fault find call out from yesterday and post up a picture of the fault. I wonder if Trev can post up fault finding scenarios as well, I'll ask him.

Yeah mate the more the merrier, just think its only fair to let em run for a little while so a few people can have a pop at it, yours and trevs would be great too

Lol so I take it that I am wrong! haha

Assume nothng ! first rule of faultfinding, comes just before "the DIY client is probably lying"

As i said i will let it sit for a while in case there is any more interest.

 

[Paul.M]

Lol so I take it that I am wrong! haha

Erm, not wrong but not 100% correct. Only a few pointers that would make a big difference. Lets see what others come up with.



The thread "fault find #2" is not from yesterday but its a good one to start off with.

 

[Marvo]

Can I ask if it's a single or 3-phase CU?

 

[Paul.M]

Can I ask if it's a single or 3-phase CU?

Domestic single dwellings in the UK are single phase mate unless special permission is given by the local authority or it is divided into flats that demand more than the incoming supply cable can hold. In this case it will be a single phase supply.

 

[High Tower]

Can I ask if it's a single or 3-phase CU?

Nope not telling na na na na na na

 

[Marvo]

Nope not telling na na na na na na

Lol, WTF kind of a reply is that? I think you might have a nasty dose of 'five year old' syndrome. There's been a bit of it going around in the public forums recently and I fear you may have caught it.

 

[High Tower]

Lmao, I was going to say I'm not telling you because of your superior skill and knowledge, you don't need the help, but I'm not telling you because I don't wanna lol

 

[Marvo]

Lmao, I was going to say I'm not telling you because of your superior skill and knowledge, you don't need the help, but I'm not telling you because I don't wanna lol

*tears*
I'm still at a loss how '....superior skill and knowledge' and 'you don't need the help' ended up as 'Nope not telling na na na na na na'

 

[High Tower]

On the grounds of I couldn't think of anything more witty or intelligent at the time lol

 

[Floody]

There's no lighting circuit.

2 power, 1 shower and 1 cooker. So maybe the lighting is accidentally connected to a MCB that's already in use?

I can't think how 1 room would be lit without the rest tho. I'm still working on that. Half way there?

 

[trev]

No mention of a cooker in the question mate, it might be an acceptable assumption to make that C4 is the lighting. Work with what you know not what you expect

 

[High Tower]

James,

keep going mate you will figure it out!

 

[Floody]

Guys I've read it totally wrong. Where the hell did I get cooker from?????????? Idiot!! Let me have a think ill be straight back lol

 

[Floody]

Ok, my next effort at the answer.

weve got 4 circuits

shower
power1
power2
lighting

lighting off in all rooms apart from 1. Possibly the live out from the dining room rose?


or Ill take a stab at a crossed/dropped neutral

 

[Floody]

I really want to say that's its a problem at the cu but I don't know how the dining room would be lit if that was the case. So ill stick with my answer, although its similar to Bakers. Problem with live/neutral coming out of the dining room rose into the second rose.

 

[Paul.M]

Problem with live/neutral coming out of the dining room rose into the second rose.

Ask yourselves this:- How can the first light on this circuit be working fine and the rest of the house (only one lighting circuit) not have any power to them? What would happen if there was a break in the loop in loop out from the first rose?

 

[Baker1988]

Ask yourselves this:- How can the first light on this circuit be working fine and the rest of the house (only one lighting circuit) not have any power to them? What would happen if there was a break in the loop in loop out from the first rose?

That is what we are saying the first light has both live and neutral so it works fine but the second light is not working so it has a problem/break with either live or neutral from the first light to the second so do a quick continuity test between lights this will show if they are continuously connected which more then likey they will not be

 

[Floody]

Baker im thinking exactly the same as you pal. But someone is going to fly out with the answer and its gonna be simple ... And ill be like..'doh' lol

 

[Baker1988]

Baker im thinking exactly the same as you pal. But someone is going to fly out with the answer and its gonna be simple ... And ill be like..'doh' lol

Lol yeah more then likely will be something completely different and simple like they have connected the first light from the sockets and fused it down or there are 2 different lighting circuits in the same mcb or something like that

 

[Paul.M]

No lads, you have both danced around the answer and only now you have hit the nail on the head. It will be lost of continuity on the Line or Neutral from rose 1 to rose 2. This is how I would test in the real world BUT please dont do this in college or on any form of testing exams you do, YOU do all test whilst the circuit in isolated, locked off and sign hung up.

Go to the cu and switch off all over circuits and see if the living room light still works, hence making sure it is on the lighting circuit. It is (I assume)

Go to the 2nd rose and test Live to Neutral then Live to CPC. This will tell you which leg is broken. Lets assume its the Neutral.

Power off at the mcb. Test for dead at 1st rose, check terminations on the neutral and all the others whilst your there. If terminations are fine now do an end to end test using long leads from rose 1 to rose 2 one conductor at a time. If you dont have long leads connect L + N together at one end and test at the other, do the same for L + CPC and N + CPC.

Now you have found the broken Neutral fault in the ceiling, we now have to repair or rewire that leg.

Well done lads, just do all your testing dead. I do it live just to save a bit of time on site but dont you do it in college, you will get an automatic fail.

 

[Floody]

I bloody said that on post #21

its been annoying 50 shades of grey out of me alllllll nite because I just couldn't think of anyway else that rose 2 wouldn't be live, unless there was a problem with the loop terminal in rose 2 and it needed a new rose..... But I was hardly going to say that lolol


anyway thank god that's cleared up, I can go to Austria Sunday with my head held high


we need more of these Q's up tho

 

[Paul.M]

It may not need a new rose. There is really only 3 things that could be wrong on this fault finding mission.

1. Loose or broken termination for the out going loop in rose 1.

2. Loose or broken termination for the in coming loop in rose 2.

3. Damaged/broken or burnt out conductor in bertween the two roses.

Its difficult to put down in words on here and paint the picture so to say but we all did well. I'll see if I can post up another one for tonight.


Just thought of another thing it could be.

4. Only the lamp in the living room works and all the other lamps throughout the house have blown and need replacing lol. Dont think that would ever happen but it is a remote possibility (not)

 

[Baker1988]

I bloody said that on post #21

its been annoying 50 shades of grey out of me alllllll nite because I just couldn't think of anyway else that rose 2 wouldn't be live, unless there was a problem with the loop terminal in rose 2 and it needed a new rose..... But I was hardly going to say that lolol


anyway thank god that's cleared up, I can go to Austria Sunday with my head held high


we need more of these Q's up tho

yeah i totally agree the more questions like this the better!!

 

[Baker1988]

Just thought of another thing it could be.

4. Only the lamp in the living room works and all the other lamps throughout the house have blown and need replacing lol. Dont think that would ever happen but it is a remote possibility (not)

haha i actually thought that as well but didn't put it as what are the odds really haha

 

[Floody]

Hahahahahahahah. We ALLL wanted to say that

 

[Paul.M]

Hahahahahahahah. We ALLL wanted to say that

Its not my fault finding thread so it still could be that, but I doubt it.

I've posted up another fault thread, I will post up a picture of the fault once you've answered it correctly.

 

[Floody]

I originally said in post 27 that there could be a fault in loop terminals of rose 1 or 2, but I deleted the rose 1 out of it

Reason: the switch wouldn't work, so we wouldn't know if the dining room light was working if we couldn't switch it on/off.

 

[High Tower]

Well done, with a little help from Paul, you got there, as he said you have both tickled the answer.

It was a broken loop, line conductor had broken. I found it in seconds because the dining room had a stupid decorative metal fitting, hence I knew it would be broken here and not going into the next fitting.

In the real world you use a voltage tester and work from the last known working fitting.

In college you would need to find it using dead tests.

Well done to both, the reason I left it a while was because inevitably given time you will start to doubt your ideas.

 

[Floody]

Like I said, pretty sure I tickled it before he mentioned anything

**cough post 21# cough**

haha

keep these coming high tower, same to others too. It's a massive help to us all, makes it easier in college and certainly will for the future. Ill always remember this fault as I was up for hours trying to work it out, little did I know I'd already answerd it. If this ever happens on a job ill know what to look at straight away. Little questions like these make a massive difference.

 

[Paul.M]

^^^ Agree.

Going by the info given to us in the opening post we know that the living room light is the first on the circuit, we know it works so therefore we know it has a perm Line and Neutral and a functioning perm live and switch live to and from the switch. So it could only be one of the 3 options above. By knowing this and drawing a circuit diagram in your head you have saved yourself a lot of time testing everything, you have narrowed down where the fault could be and you can concentrate on that area only.

In the field we/you charge £xx per hour and it is within our best interests to find the fault quickly and correctly so not to make us look like we are trying it on and getting more money out of the customer. Once the fault is found we can then estimate the time and materials needed to fix the fault and a solid (ish) quote can be given. This is how the professionals do it whilst the cowboys in our industry just pick a number from the thin air and makes us lot look bad.