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Discuss 380 V neutral to earth in the Commercial Electrical Advice area at ElectriciansForums.net

J

jonboy1

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Just been to see a job in a block of flats. There was a flat that had had a leak and this has caused 3 other flats to blow there re-wireable fuses. The flats were supplied from a riser cupboard in VIR cable circa 1930's and VIR cable was run to each flat. The cables were in a terrible condition.
The fuseboard had what appeared to be 8 porcelain fuses running across the top level and 8 fuses on the bottom level all re-wireable. I believe the top level was the phase and the lower level the neutrals. I checked the voltages from phase to phase at the top and they all appear to be on the same phase. I also checked from the phase to the metal tubing coming up from riser which gave me 240V. The unerving reading came from the neutral to this metal pipe which read 380 V.

I suggested that i would come back and carry out insulation resistance test on the three cables running to the other flats to see whether the water had got into the cables below floor but really i do not like the idea of re-connecting/changing fusewire, even if they are ok when they are in such a poor condition and with this very alarming reading.

Questions:

Why am I getting this reading?
Does the neutral just need earthing correctly and what are the risks of carrying this out.
Should I just refuse to re-connect old VIR cables (tennants living in flats)
If i do re-connect what am I responsible for and can i just write out the bad stuff on limitations.

Really appreciate feedback.
 
J

jonboy1

  • Thread Starter Thread Starter
  • #4
actually went back there today and tried readings using another meter. Either the meter was playing up or the cables had dried as the neutral to earth reading was 230 V. Thanks for all the help from the "electricians".
 
S

Spudmiester

  • Thread Starter Thread Starter
  • #5
actually went back there today and tried readings using another meter. Either the meter was playing up or the cables had dried as the neutral to earth reading was 230 V. Thanks for all the help from the "electricians".
Neutral to earth should be zero, or very nearly zero. Could you have a broken neutral somwhere, or a bloody bad earth? Sounds well dodgy to me. I would refuse to do anything else apart from rewire it !:eek:
 
S

spark-doctor

  • Thread Starter Thread Starter
  • #6
From what you have posted i nthink you have a broken N and a VERY bad earth. If it was me, i would do a IR test on all the cable.
 
W

WarrenG

  • Thread Starter Thread Starter
  • #8
Needs a serious Inspection and test starting with a full visual. You have already said that the cables are in terrible condition which would be enough for me to not put the installation back in to service untill fixed.

These old VIR rubber cables need replacing because they become brittle and crack with age and lose their insulation properties. Could explain the the fuses blowing?

Sounds like a complete rewire to me.

Be interested to know what the IR readings are?
 
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