I did my 'leccy C&G back in 1995 and new regs seem to
zip past me like speedy zippy things. I've just got a quote
for new/replacement supplies to my flats and it mentions
the earthing needs to comply with the Electrical Safety
Quality and Continuity Regulations 2002. I've read through
the HMSO paper and it all seems to be regulations for
suppliers and distributers, other than one mention of:
"the consumer must not join the earth and neutral conductors
within an installation".
In other words, a "normal" installation, phase earth and
neutral everywhere. Is that correct, or am I missing
I think it's been worded differently to confuse the cowboys (sorry, the
unqualified or DIYer) a bit more, but nothing seems to have changed
The supplier has to make sure their bit is properly bonded, because some
supplies didn't meet the current minimum standards. But that's it, I think.
You know what those IEE people are like. Never get one went you want one,
then three come along together and disagree with each other.
I'm not an MIET (IET=IEE). All I have is a bit of DIY experience and an EAL
Level 2 Domestic Installer's qualification, which, to be honest, is pretty
basic by anyone's standards.
With that stated, I'm happy to comment...
jgharston coughed up some electrons that declared:
Yes - that's about the sum of it. There are 3 types of earthing system in
common residential use:
TN-S, supplied by the network operator by means of the sheath or armour of
the supply cable all the way back to the transformer, at which point it is
connected to the neutral tap, or centre of the star winding. Maximum
allowed loop impedance (that's phase to earth, at the meter) is 0.8 Ohm,
but a particular operator may state a lower figure.
TN-C-S: Also supplied by the network operator. Earth is derived from the
neutral at or near the supply head at your property. Neutral is usually
bonded to earth (as in the ground) at regular intervals throughout the
network as well as at the neutral point of the transformer. Max Phase-Earth
loop impedance is 0.35 Ohm unless they say it's lower.
TT: You stick your own earth rod in at your property and it's your
responsibility. Neutral is connected to ground via rod or otherwise back at
the transformer. Common with overhead lines. You can ignore a supplied
TN-C-S or TN-S if you wish and make your own TT provision.
With TT, it's usually impossible to get a low enough phase-earth loop
impedance to blow out a fuse or circuit breaker under a phase-earth short
circuit fault, so this is mitigated by using a time delayed 100mA or 300mA
RCD directly after the meter. The time delay (so called Type S RCD) is
needed to ensure that if you have RCDs on the final circuits, that they
trip without taking out the 100mA RCD, otherwise your house blacks out
everytime your lawnmower has a wibble.
Do you want to ask anything specific about what you are doing - you
mentioned "flats" so it sounds like a non-trivial thing that you're up to.
BTW - after the supplier's meter, everything will need to comply with
BS7671:2008 aka the IEE Wiring regulations, 17th Edition which is a rather
large tome. That's why I asked what you are actually doing.
You may well need paid-for professional advice if this involved tenants or
selling flats, but feel free to ask here first.
About ten years ago I bought a building that contains: basement
ground floor shop, first floor flat, second floor flat. Picture at
There are two supply meters: basement+shop, flat1+flat2. It's always
been a hassle organising the respective tenants to contribute their
respective shares of their bills. Plus, the meters are in the
inaccessible to the shop or flat occupants.
When I bought the properties I rewired everything to 16th Ed (got my
C&G in 1995, did the work in 1997), which required some fiddly working
out for the flats, see http://mdfs.net/Docs/Electrical/Supply/Multiple /
Previously, the second floor flat's consumer unit was in the basement!
The first floor flat became vacant last year, so I decided, along with
replacing windows, heating, kithcen, bathroom, carpets, decor, etc.,
to get everything properly metered on their own supplies, ie:
workshop, shop, flat1, flat2, landlord, all installed where the
relevant consumer can see their own meter.
The supplier quote mentioned the 2002 regs, which I hadn't come across
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