fault finding

[james king]

hi all i was wondering what all do when u come across a fault on a cct. eg a ring final!!

what ways do u do it?

what test do u do?

split rings?

im just asking what u do i know this may sound funy and prob not make sense lol

 

[telectrix]

depends on the fault. could be low IR or high continuity, or crossed polarity, and many more. you'll have to be more specific.

 

[james king]

ok lets say all those

 

[james king]

i have nothing to be specific about...

ok lets say high IR

high cont

 

[not clever]

High IR well no fault finding required.

if the ring is small enough drop the socket fronts it'll be a poor termination

 

[james king]

may be but not all the time! what would u do if all connections are tight?

 

[telectrix]

or some scroats JB nailed under a laminate floor

 

[james king]

so i high IR results could be a loss connection?

 

[telectrix]

think you need to do a bit of reading. the higher the IR, the better.

 

[james king]

lol i mean low

 

[telectrix]

low IR could be : damaged insulation e.g. nail in cable. damp in a fitting. faulty appliance. faulty fitting.

high continuity could be poor connections

 

[nickblake]

I just love Fault finding , tripping lighting MCB , RCD tripping , open circuit on ring mains , low insulation , High Zs reading, motors humming 3 phase , machines inoperative ,

one of the most common is a lighting mcb tripping , normally this is caused by posh lights with burnt out wiring shorting , other faults i have found low IR tripping RCD , fault was caused by young lad peeing over socket , tripping RCD , extension lead in garden powering pond pump had got wet , tripping RCD , out side light full of water , Fire alarms continuosly sounding even after reset , cause burst pipe flooding detector ( shop totally flooded £250,000 worth of damage ouch) tripping MCB , fault located to Rodent attack Dead squirrel found across cables , Tripping MCB fault due to burnt out connector (originally a posted thread ) open circuit on ring main ,cause cable chopped in half then plastered ove

just a few ive come across over the years best one was a call out to no power , this was caused initially by a power cut , but when the power came on still no power , main fuse blown fault traced to a light in an elderly gentlmans lounge , it kept blowing fuses so he wrapped the fuse with 30 amp fuse wire , which in turn blew the 30 amp rewirable fuse which he then wrapped in 30 ap fuse wire which then blem the main fuse , fault was a faulty light fitting testing revealed a low IR reading on the ring circuits , cable was melted probably caused by incorrect fuse wire in fuse , and one reason to reccomend replacing rewirable boards to MCB's

 

[james king]

thats what i thought... so how can u just take the skt plates off to look for low IR??? doesnt make sense.....

say u have high continuity eg 274Kohms u will more than likly have a low IR reading correct?

so what steps would u take in order to track down the high cont reading?

 

[SMB]

okay...im really knackered (because I work now!!?)...but these are the tests you need to complete for a ring main....

Insulation resistance of the ring...

* make sure all switches are ON.
* All loads are removed.
* Remove sensitive equiptment (or link between L and N and test at 250v DC). (if not then use 500v DC).

* Use an Insulation resistance tester.
* Check the testers calibration, be sure its not damaged, check the batteries.

* Test between L-N, L-E, N-E (or link L-N and test to E).
* Minimum reading 1 Megohm, if below 2 Megohm then investigate.




Continuity of ring conductors....

* Step 1. End to end continuity...L-L (r1) N-N (rn) E-E (r2). Record results.
* Step 2. Cross connect L + N. Measure resistance at each outlet between L + N (r1 +rn / 4). Record results.
* Step 3. Cross conect L + E. Measure resistance at each outlet between L + E. (r1 + r2 /4 = R1 +R2). This is your result.


Good luck.


Im going to bed.


Zzzzz. Snore.

 

[james king]

i know this mate... just wondering what the readings could be caused by.. and how to approch it to trace the faults

 

[Golden_Boy]

thats what i thought... so how can u just take the skt plates off to look for low IR??? doesnt make sense.....

say u have high continuity eg 274Kohms u will more than likly have a low IR reading correct?

so what steps would u take in order to track down the high cont reading?

I think you realy do need to do a LOT more reading .......

 

[james king]

lol haha im asking what u lot would do as an example? any books witch explains all this i have not come across any??

 

[telectrix]

fault finding is an art on its own. you can't learn it from books. it's experience. basically, it boils down to logic and breraking down the circuit , ist in half to identify the faulty half, then thatn half in half again, and a gain, till you've found the fault , say between point 6 and point 7 on the circuit. then its time to get the crowbars and hammers out.

 

[nickblake]

hers one jigga open circuit on a ring main say live , how to locate the fault you could open every socket and inspect the wirng for disconnected conductors or do as i do , i carry out an R1R2 test or R1Rn , Rn or R2 depending on what the fault is say for instance an open circuit on the Neutral , then i would carry out an R2Rn test so from the board disconnect the tails of that circuit join the CPC and the Neutral to gether and then test the circuit at every socket and check the readings untill i get an open circuit then ill open that socket and retest then ill test from the other leg or the ring and carry out tha same tests untill i fing a sockets that has a disconnected wire , i have had this fault and traced the fault to an open circuit on a section of wire so it was replace that leg lifting the floors we traced the cable and the fault was located to a socket that was behind a radiator cut the socket out JB retested spot on all ok

 

[SMB]

i know this mate... just wondering what the readings could be caused by.. and how to approch it to trace the faults

My post explained your question mate.

 

[SMB]

lol haha im asking what u lot would do as an example? Any books witch explains all this i have not come across any??

osg

gn 3

 

[telectrix]

gthought you were sleeping .lol#

 

[nickblake]

My post explained your question mate.

nice to see your knackard mate i mean that in a good way hows the job going then

 

[Golden_Boy]

lol haha im asking what u lot would do as an example? any books witch explains all this i have not come across any??

I would work logically and use my experience to find the fault. There is no hard and fast rules, each individual has his/her own approach.
You MUST understand how circuits work BEFORE attempting to find a fault.

 

[chiplard]

lol haha im asking what u lot would do as an example? any books witch explains all this i have not come across any??

There is no book.

Every fault is different to the last. You just need to be experienced in testing to enable a more accurate assumption of what the fault might be.

And even then there is always the one that will have you chasing your tail and spending stupid amounts of time looking for!!!

 

[SMB]

nice to see your knackard mate i mean that in a good way hows the job going then

Its a bloody eye opener!!

Its great!

A rather large and steep learning curve (understatement!)

Will post about it soon.

Thanks for asking Nick.

I drempt about my work last night!!!

Alls good.



Smile...................yawn.

 

[nickblake]

i agree with golden boy on this one , fault finding can be stressfull , its how you approach it , all i will say is think logiacaly , ie lighting circuit tripping rcd mcb , first thing i think of is out side lights has it been raining , break down circuit trace the fault to a specific location , there is no real books available because there are so many reasons for faults IE defective wiring water ingress, short circuits , cable damage , i name a few

 

[nickblake]

Its a bloody eye opener!!

Its great!

A rather large and steep learning curve (understatement!)

Will post about it soon.

Thanks for asking Nick.

I drempt about my work last night!!!

Alls good.



Smile...................yawn.

you drempt of you work lol nice one to me that would be a night mare , ive never had a dream about an MCB before , ladies and food yes lol its great to see you in work . realy pleased for you .

 

[telectrix]

Rodents, Plumbers , Wood Butchers. thats 3 possibilities straight away. you can tell if it's a rodent because he will never say " It wasn't me "

 

[SMB]

osg

gn 3

when I posted this I meant the methods to test circuits are explained in these publications.....they certainly do not show how to find the fault itself, but do show the tests required to prove there is, or is not a fault present.

 

[SirKit Breaker]

MMM lots of ways to find split rings

 

[SMB]

gthought you were sleeping .lol#

Right, im now off to dream about bus-bar trunking, pyro and metal conduit......

Night Night Tel....





Grin.

 

[ezzzekiel]

usually better to test from back of sockets also to get good readings when tracing - just a bit of a pain.

 

[malcolmsanford]

Domestic fault finding ..................I always cringed when you were asked by a someone .............." when I plug this in that trips ......

So it's climbing over furniture where the one socket you want is behind a display cabinet full of Granny's best china ............or your followed around by a 5 yr old that just loves your shiney new stanley knife ................ Up into a loft that resembles the dungeon from the film national treasure, theres 150 yrs of "well we might find it useful one day" .......................... there is a rottwiler that thinks your legs are Jordan, or even worse dinner ......................every light rose as 70 yrs of accumilated paint on it .................you finally find the fault on the outside light and it would take serpa tenson and a team to scale up to it .................. it's always the outside light when it's -15........................it always in the loft when it 30c............................and finally the best "how long do you think you'll be" getting asked every 30 seconds.....................