Metal - clad buildings and the confused forum member.

Sparkingchip:

If all the units are being built together, then care is taken to balance the loads and a copper earthing tape that is also sized to handle stray current is run buried as a foundation earth between the main earth terminals in each of the separate units, then the risks from lost neutrals and diverted neutral currents can be reduced can’t they?


Or is that an over simplification?

If you had N-PE links in each unit then you'd still have diverted N currents flowing through the structure - possibly reduced by having the earthing tape in parallel, but possibly still quite substantial. Years ago I worked in an office in one unit of a multiple block with conventional individual PME supplies - in one corner images on CRT monitors would always 'wobble' - it was only years later I realised that they were between our intake position and next door's and diverted N currents running through the structure were likely to blame. It's hard to balance a supply when different users feel free to turns thing on and off to please themselves.


Current DNO policy of supplying each unit using split-con from a single point outside where N and PE are split is probably an easier and more thorough solution - especially now other services are likely to be non-metallic.


   - Andy.

Sparkingchip:

If all the units are being built together, then care is taken to balance the loads and a copper earthing tape that is also sized to handle stray current is run buried as a foundation earth between the main earth terminals in each of the separate units, then the risks from lost neutrals and diverted neutral currents can be reduced can’t they?


Or is that an over simplification?

If you had N-PE links in each unit then you'd still have diverted N currents flowing through the structure - possibly reduced by having the earthing tape in parallel, but possibly still quite substantial. Years ago I worked in an office in one unit of a multiple block with conventional individual PME supplies - in one corner images on CRT monitors would always 'wobble' - it was only years later I realised that they were between our intake position and next door's and diverted N currents running through the structure were likely to blame. It's hard to balance a supply when different users feel free to turns thing on and off to please themselves.


Current DNO policy of supplying each unit using split-con from a single point outside where N and PE are split is probably an easier and more thorough solution - especially now other services are likely to be non-metallic.


   - Andy.