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.