Discuss Can you get a back feeding voltage through tha main earth in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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power up

Power up electrical Bristol
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5
Location
Bristol
Has any one ever come a cross this. I went to a customers house that all ready had a two way rcd 63amp 30mil amp board fitted under the stairs on the ground floor with a shower connected on it. I was asked to install a some skt's and lights into the loft. So i ran a 6mm t&e from the ground floor board to a new two way board in the loft. And from the new board ran a small ring main with four skt's on it and a lighting cct with two lihgts on it.when i tested the the new cct's every thing was fine and all reading's satisfactory. But when i done the zs on the ground floor board the reading was fine 0.10 ohms. But when i went to put the earth back into the met there was a small blue spark and when i put a muti meter from the earth cable from the ground floor board to the met there was 110 volt's. I disconnected the l.n.e feeding the loft but had 60 volts on the earth from the shower. So reconnected the loft and disconnected the show and had 65 volt's. I removed the 6mm cable feeding the loft board from the loft board and put it into connector blocks but still had 65 volts even though i have tryed two insulation resistance testers and both read >9.99 across all three core's. So i got one meter of a three core flex wiyh a single skt on one end and with nothing else connected in the board i connected the flex in the board and had 30 volts i then pluged into the single skt a ten meter extension lead and the had 110 volts from the ground floor board earth to the met
 

robsparky1975

Regular EF Member
Messages
1,297
Location
isle of wight
I would personally check the dno supply at source,Ze,voltage,correct polarity,then start moving more into the installation,all circuits off test,1 circuit on test etc,maybe do an orbital IR test,thinking i have come across something similar,IR in that case but all guess work sat behind a screen.
 

rich.250

Electrician's Arms
Messages
944
Location
Cornwall
Was there anything on in the installation at the time? Just thinking leakage?
You need to work out which cable this voltage is on, I've had a similar thing on a 100 ohm TT where the gas bond was 0.3 ohms.....
 

oldtimer

Regular EF Member
Messages
4,313
Location
Edinburgh
You are picking up an induced voltage because you multimeter picks these up if you used an analouge meter it would not be their halogen light and some electron equipment can do this last one I had was a washing machine when the main earth to its socket fell of leaving the bond cable to the sink with plastic water pipes test with a multimeter 120vac with a voltage tester 0v
 
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