Weird!!!!!

[ThrownRazor25]

Hi I had a call out tonight where the tenant said she was getting a shock from her hot and cold taps and also her sink in the kitchen.Her worktop had been changed today and when I looked under the sink the usualtrend of joiners/plumbers of cutting earth cables had taken place.the pipes where all cross bonded but a cable from one pipe was lying loose and also a6mm earth from a double socket underneath for dishwasher and washing machine had also been cut.testing between the tap/sink I was getting20v however when I switched on the dp switch for the double socket it was jumping up to 134v.why was this not lifting the rcd or mcb?zs on the sockets was 0.76.I was getting on earth continuity of 0.34 between fusebox and the pipes/sink/tap.when I connected the 2 cut earth cables back up to the sink the voltage dissapeared.I know about the need to bond all pipework so that their potentiol is the same but could someone explain this one to me please?

 

[supasparxs]

Hi I had a call out tonight where the tenant said she was getting a shock from her hot and cold taps and also her sink in the kitchen.Her worktop had been changed today and when I looked under the sink the usualtrend of joiners/plumbers of cutting earth cables had taken place.the pipes where all cross bonded but a cable from one pipe was lying loose and also a6mm earth from a double socket underneath for dishwasher and washing machine had also been cut.testing between the tap/sink I was getting20v however when I switched on the dp switch for the double socket it was jumping up to 134v.why was this not lifting the rcd or mcb?zs on the sockets was 0.76.I was getting on earth continuity of 0.34 between fusebox and the pipes/sink/tap.when I connected the 2 cut earth cables back up to the sink the voltage dissapeared.I know about the need to bond all pipework so that their potentiol is the same but could someone explain this one to me please?

your right it's werid.

However it maybe a fault outside the installation coming into it on the main water.
Did you check if the MEB was connected within 600mm of the stopcock.
I wouldn't normally ask but more often than not the stopcocck is at the kitchen sink?

reconnecting the bonding cables would bring the pipes and sink back down to earth and so the voltage would disapate.

Richard

 

[jbec-john]

Did you check that the RCD was actually working?

 

[ThrownRazor25]

I never checked that bud,but the sink and pipes were earthed before I reconnected those two earths as I done anR2 test on it.I've done a stand by/ call out for six years and never had anything like this.

Yeah done a ramp test and it lifted at 27 amps so it was fine also done x1 and x5 tests and that was ok too.

 

[jimes]

dishwasher or washing machine elements breaking down?

 

[Deleted member 9648]

If it's a TNCS system check the neutral is intact at the intake...a break or high resistance may result in a voltage appearing on metalwork connected to the earthing system. Do an insulation resistance test at the DB lives and neutral to a fly lead connected to the affected pipework ,if that pipework is isolated from the bonded pipework by plastic inserts in the plumbing - and there a fault between a cable and that pipework....
Bear in mind that technically the sink and pipework in a kitchen doesn't need to be supplementary bonded.If a voltage is appearing on it there is clearly something going on which needs to be rectified,relying on reconnecting the existing earth wires is not an option.