Lighting Circuit - Fault Finding

[matt.leung]

spent a couple of hours today fault finding a lighting circuit for a client.

the mcb will not re-set and i have IR the circuit and get 0 between L-N, N-E and L-E, even 0 with L,N to E.

I surspect a JB is full of water or a large nail going through all three conductors... The client siad that he has not done any DIY in the property, and in the past he has had difficulty with the same circuit, and managered to hold the mcb button in before...

back tomorrow to fault find further...

any help will be gladly recieved...

 

[SLIPSHOD & SLAPDASH]

Could be anything. You will have to start splitting the circuit to locate the faulty part.

 

[Marvo]

If it's tripping the MCB then I'm guessing the zero you talk about is actually 0 ohms rather than 0 Mohms.

 

[sellers]

turn your tester on to ohms. Get a reading. If its showing a decent short, for example 0.76ohms live earth.

Long lead on the live in the board, dash round the lights testing at the earths, your lowest reading will be nearest the fault. Measure across live earth there and check against resistance per meter to work out how far away it is. Check for continuity between all conductors at the point and any local screws nails etc.

If you do not have a dead short then its a little harder, split circuit up, check readings, look for damp in walls and outside lights.

 

[Electroglow]

As he says ^

 

[SPECIAL LOCATION]

spent a couple of hours today fault finding a lighting circuit for a client.

the mcb will not re-set and i have IR the circuit and get 0 between L-N, N-E and L-E, even 0 with L,N to E.

I surspect a JB is full of water or a large nail going through all three conductors... The client siad that he has not done any DIY in the property, and in the past he has had difficulty with the same circuit, and managered to hold the mcb button in before...

back tomorrow to fault find further...

any help will be gladly recieved...

A couple of hours fault finding and all you got is a suspect resistance of anywhere from 0ohms to 9999ohms?

Surely anytime anyone gets a reading of 0.00Mohms...

The next logical step is to find out the actual resistance????

and then compare it with the ohms/meter figures in the OSG to get a rough idea of how far up the circuit any potential fault may be......

Also...

unless you have been round unplugging and disconnecting everything off the circuit you are testing then you will most certainly get a very low IR between L & N......

is this what you get from a 5WW imitation electrician course???

I do hope the customer is not paying for this unproductive couple of hours of your time..

:|

:coat

 

[matt.leung]

a 'couple of hours' is a figure of speech.... the fault finding involved removing all the lamps, disconnecting transformers, jumping up ladders taking lamps out of outside lights (at height), IR testing, chatting to the client to see if anything electrically has changed recently,like constant blowing of bulbs or DIY projects etc... it does not help when the client has alzheimers....

anyway, i have worked my way half way through the circuit and is now all working and going bk next wk to finish off... looks like carpets and floor boards will be coming up next week... alot of the junction boxes are in inaccessable areas... and is not a loop in loop out install.

 

[Marvo]

... it does not help when the client has alzheimers....

Make sure he signs your timesheet each visit you make in case he doesn't remember you when it comes to paying the bill