B
Boberto
Can someone just give me some straight answers. Ive had a bitch of a day and i'm not thinking straight. These Kronenbourgs might have something to do with it. LOL.
With regards sub mains, on large commercial / industrial installations. When testing Zs on sub mains final circuits, if the circuits are large there is a chance the maximum Zs is exceeded. For example a ring main in a office on the third floor of a large commercial building. (I'm talking generally here, no particular job in question). If the Zs is measured as greater than the maximum Zs given in BS7671 then this doesnt comply. However with the sub mains circuits protected by a 30mA RCD there is no longer a problem because this provides additional protection? Correct?
Next scenario. Same as before but ring final circuit is not RCD protected. For example if all socket outlets are to be used for computer equipment with sockets labelled "COMPUTER ONLY" but the Zs is high still do we now have a problem? Would a resolve to this problem be to rewire the ring final in say 4.0mm as opposed to 2.5mm to reduce the Zs reading? Or drive a rod in at sub mains?
Finally earthing system at incoming mains is tncs. SWA supplying sub mains. PME cannot be exported. At sub mains a rod is installed. On Electrical Installation Cert for new ring from sub mains do we record the earthing system as tncs or tt? If a 3 core armoured taking a supply to sub mains is used should this be recorded as sub mains earthing system as tns even if mains is tt or tncs??
Just a couple of tea break discussion points from today. If im correct I stand to win a bacon sarnie tomorrow so whats the verdict !?
With regards sub mains, on large commercial / industrial installations. When testing Zs on sub mains final circuits, if the circuits are large there is a chance the maximum Zs is exceeded. For example a ring main in a office on the third floor of a large commercial building. (I'm talking generally here, no particular job in question). If the Zs is measured as greater than the maximum Zs given in BS7671 then this doesnt comply. However with the sub mains circuits protected by a 30mA RCD there is no longer a problem because this provides additional protection? Correct?
Next scenario. Same as before but ring final circuit is not RCD protected. For example if all socket outlets are to be used for computer equipment with sockets labelled "COMPUTER ONLY" but the Zs is high still do we now have a problem? Would a resolve to this problem be to rewire the ring final in say 4.0mm as opposed to 2.5mm to reduce the Zs reading? Or drive a rod in at sub mains?
Finally earthing system at incoming mains is tncs. SWA supplying sub mains. PME cannot be exported. At sub mains a rod is installed. On Electrical Installation Cert for new ring from sub mains do we record the earthing system as tncs or tt? If a 3 core armoured taking a supply to sub mains is used should this be recorded as sub mains earthing system as tns even if mains is tt or tncs??
Just a couple of tea break discussion points from today. If im correct I stand to win a bacon sarnie tomorrow so whats the verdict !?
