I have a job to change out a consumer unit in a small workshop that is currently fed by a three core 10mm SWA cable. one conductor is earthed, as is the armouring at the supply end CU. The circuit is protected by a 40amp S type 100mA RCD and 32amp MCB on a PME supply.
At the workshop end the installation has been made into a TT system. The earth from the rod has been taken directly into the consumer unit and from there to the water pipes etc. The supply is protected by a 30mA RCD and appropriate MCBs for the final circuits. The SWA has been terminated on a gland that has been fitted into a metal box. The live and neutral pass straight through the box to the CU and the spare earth conductor has been insulated with heat shrink sleeving. The metal box earth potential is naturally at the potential of the supply end rather than the local earth. Should this box be changed to plastic and should the SWA gland also be enclosed so that no one can touch both earths at the same time? Indeed could the gland be removed and aplastic one used with the armouring tidied up with heat shrink sleeving.
At the workshop end the installation has been made into a TT system. The earth from the rod has been taken directly into the consumer unit and from there to the water pipes etc. The supply is protected by a 30mA RCD and appropriate MCBs for the final circuits. The SWA has been terminated on a gland that has been fitted into a metal box. The live and neutral pass straight through the box to the CU and the spare earth conductor has been insulated with heat shrink sleeving. The metal box earth potential is naturally at the potential of the supply end rather than the local earth. Should this box be changed to plastic and should the SWA gland also be enclosed so that no one can touch both earths at the same time? Indeed could the gland be removed and aplastic one used with the armouring tidied up with heat shrink sleeving.