Discuss 16mm2 t&e supply in the UK Electrical Forum area at ElectriciansForums.net

leep82

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Ok so i might get ripped to shreds for this but here go's. Been to look at a job this morning, customer wants to move a couple of switches from a wall theyre having knocked down and have an additional socket installed. Carried out a couple of checks, gas and water bond ok, tns supply which enters the property in the garage, and here is where my concern lies. The supply to the DB is in 16mm2 t&e. Fed via a 80a kmf switch. The cable is clipped surface in the garage and then disappears into the ceiling void within the house. There is no RCD protection for this cable. Fitting any 30ma device upstream to protect it isnt really an option as the DB is split load with one side unprotected and one side having 80a 30ma RCD protection, leaving me with no discrimination. I then thought of using a 100ma time delayed RCD but realised this would not achieve the required disconnection time. In an ideal wolrd this t&e cable would be replaced for a swa but this just isnt practical as the house is immaculate and theres no way the customer will pay for this. Ive told them i'll ask a few questions and do a bit of reading before i start any work. I was thinking could it be argued that the t&e cable supplying the DB isnt actually concealed in any walls, as it is clipped direct in the garage before it disapears into the ceiling void, only to then enter the DB which is mounted right underneath the ceiling?
 
you've answered part of your query. the 16mm does not require RCD, unless required for ADS. e.g. a TT earthing system. more to the point is whether the cpc in the 16mm is adequate to carry the PEFC.
 
and if you have PME earthing and that cpc is also a main bonding conductor, then 10mm is the min. size.
 
16mm2 t&e supply

All main bonding conductors are 10mm2 and come back to an earth bar at the meter position. Doesnt look like any bonding conductors come from the MET in the DB
 
OK, so that rules out that one. do the adiabatic for the cpc after measuring the pefc.
 

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