davetheglitz
Electrician
Me and another sparky did an inspection today on a house converted to 7 bedsits. Each bedsit has it's own submain to a pay meter and RCD protected DB. Each bedsit also has water services.
The whole place was a shambles and is in need of a rewire.
We had a debate about how each DB should be earthed/bonded.
One arguement is that each DB should have a substantial earth wire to the MET (10mm G/Y + cpc from 6mm T + E) to ensure bonding/earthing was adequate as PME system earths should be able to take the full neutral current in the event of neutral disconnection.
The other arguement was that if this was a house you wouldn't even be having the debate for each room. The bonding is mainly to protect from an external influence. Main bonding at source should allow for this. If a plumber decides to fit a lot of speed fit connections the 'far end ' of the plumbing installation will only have to cope with problems caused within the house - so 2.5mm supplementary bonding to water at each DB would be adequate.
I tend towards the second arguement - but I would be interested to see if I'm on my own here!
One interesting comment was made in our discussions. Britain is the only country that uses PME - no-one followed us for good reason! Now we have the 17th with the RCD protection on everything (nearly) electricians to a man should be getting rid of PME where possible and installing earth rods! I'd be intrigued to know what other people felt about this - particualrly Mr Steptoe knowing his Kiwi roots!
Cheers
Dave
The whole place was a shambles and is in need of a rewire.
We had a debate about how each DB should be earthed/bonded.
One arguement is that each DB should have a substantial earth wire to the MET (10mm G/Y + cpc from 6mm T + E) to ensure bonding/earthing was adequate as PME system earths should be able to take the full neutral current in the event of neutral disconnection.
The other arguement was that if this was a house you wouldn't even be having the debate for each room. The bonding is mainly to protect from an external influence. Main bonding at source should allow for this. If a plumber decides to fit a lot of speed fit connections the 'far end ' of the plumbing installation will only have to cope with problems caused within the house - so 2.5mm supplementary bonding to water at each DB would be adequate.
I tend towards the second arguement - but I would be interested to see if I'm on my own here!
One interesting comment was made in our discussions. Britain is the only country that uses PME - no-one followed us for good reason! Now we have the 17th with the RCD protection on everything (nearly) electricians to a man should be getting rid of PME where possible and installing earth rods! I'd be intrigued to know what other people felt about this - particualrly Mr Steptoe knowing his Kiwi roots!
Cheers
Dave