What, more on RDCs?

[Richard Hughes]

Rich has provided much useful information, as always, on the GFCI/RCCB/RCD
debate.  There still are a few additional points that I’d like to make:

1.  ‘Europe’ is not a single country with a single building code.  Yes
there is a series of Harmonised Documents (the HD 384 series) upon which
the national codes, such as the IEE Wiring Regulations in the UK, are
based: however, there is no single European Norm.

2.  The wiring practices within the countries of Europe vary, they even
vary within individual countries.  Firstly there is the question of whether
the supply is IT, TT or TN.  In the UK the TN supply (also referred to as a
PME - Protective Multiply Earthed) is most common but TT supplies are used
in rural areas: IT supplies are not used except for special applications
(such as chemical plants).  In France, Norway, and elsewhere the IT supply
is most common and in fact there are a couple of flavours of IT.

3.  Then there is the question of how socket outlets are wired back to the
circuit protection panel (in the UK referred to as the Consumer Unit).
Some countries use a spur system whereby a single socket outlet is wired
back to the Consumer Unit.  In the UK we like to be a bit different and so
we use the ‘ring main’ system.  (space here for a comment from Vic ……… -
not too big a space you’ll note).

These and other differences mean that there is a multiplicity of approaches
to providing earth fault current protection within the mains supply
network.  RCDs (they don’t called them RCCBs any more) can be placed in the
Consumer unit - it is also possible to get units which provide both
‘normal’ overcurrent protection (i.e. a MCB) with residual current
protection, these units are called RCBOs.  It is possible to get RCDs (and
RCBOs) with a range of tripping currents, but 30 mA is the most common & 10
mA is the lowest rating I’ve seen.  In the UK (I cannot say for other
countries in Europe) you can get socket outlets that have a RCD built in
and an overgrown mains plug that has a RCD built into it.

All in all, you pay’s your money and you take’s your choice.

Richard Hughes