That'll get the replies coming! (Oh look, here comes one now...)Paul Barker said:
Nice way to remember it, but they actually stand for Combined and Separate, the separation originating at the cutout. (PME = Protective Multiple Earthing, the earth and neutral being combined in a single PEN conductor - Protective Earth & Neutral)
The S still stands for separate. As you rightly say, the earthing is normally via the cable armour.
Not necessarily; the earth bar inside a domestic CU is designed to do the duty of the MET.
The subject of earthing and bonding - despite actually being very straightforward - is beset with all kinds of myths. There are hard and fast rules, but for some reason sparks like to believe they are open to interpretation.
The same rules apply to boilers, but here the gas fitters like to add their own bit of confusion.
If it's got a Circuit Protective Conductor then EEBAD is still the principle means of protection. However the disconnection times are reduced for equipment with exposed conductive parts because of the lower resistance path of a body in direct contact with the general mass of the earth (reg 471-08-03)
Because safety and convenience are entirely secondary considerations in electrical installations. As everybody knows, it's cost first, safety second. If you are rewiring it is easy, cost effective and far more convenient to provide a boiler with its own supply. It is also actually simpler to provide a greater number of circuits, rather than try to run fixed equipment from spurs on socket circuits.
I hope you're not suggesting powering a shower from a ring final circuit? In any case the regs do not actually require a shower to be on an RCD (although the manufacturers usually do) but most sparks will RCD-protect all sockets anyway, as you went on to suggest.
Having said all that, not a bad stab... for a plumber.
I only have 21 ways, will this be a problem?
This is electrics UK, I cannot see anything here that Ban would take offence to!
