Stefek Zaba wrote:

John Rumm wrote:


One might argue that the MCBs purpose is to protect the installation
from overload, not to prevent electrocution. That is what the RCD (if
fitted) is for.

One might, but one would be in error. The little slogan is "protection
by EEBADS" - that's protection of people, against electric shock, by
Earthed Equipotential Bonding and Automatic Disconnection of Supply. The
*point* of the low-resistance earthing we commonly practice (not just
the supplementary bonding in bathrooms, but earthed cases on metal
appliances) is to produce a big enough flow so that the MCB or fuse will
operate fast enough. RCD's are a useful top-up, esp. where good earthing
can't be assured (portable appliances outdoors being the clearest case),
but good old EEBADS is the design and implementation which has kept
death-by-electrocution down to very low levels in the UK for, yay, 40
yearses or more.

Yup agreed - perhaps my statement was too hard on EEBADS! it is indeed a
major life saver. However there are still catagories of faults for where
no amount of earthing is going to give sufficent protection though, like
the incident refered to above, or the classic mower/hedge trimmer
through the cable scenario.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/