Fault on ring main

[dutchy]

Hello everyone, I'm just looking for advice on a ring main fault, I'll try and keep the scenario short so as not to bore you al....

I was asked to attend this fault at an on going job our firm our firm is doing (I wasn't involved from the start) The existing kitchen ring had been broken into to incorporate a new utility room a few weeks ago. I was asked to attend a fault on the washing machine tripping out the ring.
The ring main works fine "under load" (dishwasher/tumble dryer etc) but when the washing machine is plugged in to its single socket under the worktop it takes out the mcb, but plug it in anywhere else and it works fine. (eliminating the appliance) I disconnected the leg from the spur to the single socket, and as i was testing for voltage live/neutral was fine but when testing live/earth it takes out the mcb? (I'm returning on monday as I didn't have my test kit with me)..... now without having to start stripping the ring down, does anyone have any advice on a quick way to find this fault. The house in currently having renovations done, so its possible its a damaged cable, but found it unusal that all the other appliances are working fine, without causing it to trip.....any advice would be greatly appreciated.

 

[IzzyS]

Is it taking out the MCB or an RCD/RCBO?

 

[i=p/u]

id say start from the start with r1 and r2

 

[malcolmsanford]

I would say your getting terminologies confused here and it is taking out the RCD/RCBO rather than the MCB.

I simply say this because I think you have a polarity issue on the circuit. Either somewhere in the split you have crossed an Earth/Nuetral or more likely at the CU your on 2 different neutral bars.

 

[dutchy]

Thanks everyone.... its definitely taking out the MCB... its a split load board, and the RCD stays on....only the breaker goes.

 

[tonycoysh]

Leave the washing machine unplugged and tell them go to the stream..... Sorry!

 

[malcolmsanford]

Fair enough ......................but I have never known testing LIVE/EARTH to take out an MCB, some testers take out RCDs when testing like that.

 

[dutchy]

thats the thing though...the washing machine is currently plugged in to a D/S on the same ring and its merrily working away fine, but when plugged in to its dedicated S/S via its controlling spur....pop it goes!...and its definitley not the leg between the spur and socket...already checked that...??????

 

[dutchy]

Fair enough ......................but I have never known testing LIVE/EARTH to take out an MCB, some testers take out RCDs when testing like that.

me either.... its a strange one!

 

[Hawk81]

I can never understand people attending faults with no test gear?? If you don't have test gear it's going to be very hard to fault find. I find it best to bring my test gear with me always. It's needed for all jobs anyway. Testing new installs as well as fault finding.

 

[i=p/u]

some people arnt as rich as you hawk1, they have to do caveman method and break ciruit up accordingly.. oj..

you should have it with you. as you are ment to test before installing anything and after..... but we know it doesnt happen in all cases or any at all..


what about this one was called to a fault few weeks ago in garvagh, the outside lighting wasnt working.. now i was witha spark helping him just, so letting him take lead role.. we walked around the perimeter to see circuit route and seen it split and went down a walkway to gate for a lampost floodlight. so went to middle of circuit and disconnected the live of one side and tried the the old mcb and still tripped and tried the other side and still tripped, so investigated on and we had found somone had added other lighting around the building frame itself. so opened contactor and seen one incomming and 3 or 4 out going circuits dont know where the neutrals were take too.. so disconnected one out going at a time and found the ciruit the fault was on and it turned out to be a ballast blown and causing a short... now this guy had no test gear, how would test gear of helped him here....

 

[telectrix]

he could have tested you at 500V DC.

 

[tony mc]

How can you be sure its not the spur leg if you have not tested it?

Does it trip with another appliance plugged in say a kettle!

I would start from the beginning once you get your gear and fully dead test the final ring and see what results are found for starters!!!

 

[i=p/u]

telectric i dont feel it im like plastic coated before i go to work

 

[dutchy]

I can never understand people attending faults with no test gear?? If you don't have test gear it's going to be very hard to fault find. I find it best to bring my test gear with me always. It's needed for all jobs anyway. Testing new installs as well as fault finding.

the job is 100 miles away from our office, and I was passing it to get to my job (where my test kit was) which is why I have to return on monday...just didn't want to bore you all with that detail...

 

[telectrix]

fault appears to be in kitchen... cupboards fitted... kitchen fitters..... 4" screws directly above socket?????

 

[dutchy]

How can you be sure its not the spur leg if you have not tested it?

Does it trip with another appliance plugged in say a kettle!

I would start from the beginning once you get your gear and fully dead test the final ring and see what results are found for starters!!!

I completely disconnected the spur leg, so I just had the supply connected to the spur, and thats where I was testing live/earth and the MCB was tripping...

 

[i=p/u]

and when load applied bang, legs up, lights out

 

[trev]

I remember a guy they filmed on watchdog installing a few new sockets in a kitchen, his testing procedure was plugging in a kettle

 

[dutchy]

and when load applied bang, legs up, lights out

nope!...the ring is already under load with dishwasher/tumble dryer etc.... but as soon as you add the washing machine...pop!... but the machine works fine went plugged in to another part of the ring.