On Fri, 5 Sep 2003 07:57:50 +0000 (UTC), NC wrote:
My immediate thoughts would be that as long as the pipes were properly
bonded there isn't too much of a problem. What always bothers me about
these types of arrangements, however, is that at some time in the dim
and distant future, when you no longer own or rent the flat, someone
will come along and think that it's a water pipe running along the top
of the skirting and merrily cut into a live cable.
Reminds me a bit about a quite elderly edition of GroundFarce, where
Charlie 'Nipples' Dimmock was feeding a section of cable for a water
feature through some scrap gas service pipe under a path. I complained
at the time to the Beeb, but never heard any more about it.
Or ,seeing the hole in the pipe,they might think it is an unused water
pipe and STILL cut in to it .
maybe better putting some of that hazard tape round it with suitable
labelling warning of what lies within !!!
Remove YOURPANTS before E-mailing Me
Bonding is like earthing, but without the earth !
All metal parts (pipes, shower rails, bathtubs) are connected together
with green & yellow, and this is connected to the earth terminal of
the supply to the room. There is no need to run a separate earth
connector for this metalwork, back to any centralised earth. Nor does
this bonding conductor need to be as large as many earth conductors
The difference between bonding (or equipotential bonding) and earthing
is in what they're trying to achieve.
Earthing is there so that when a live-case fault develops, enough
current flows through the earth terminal to blow the fuse or breaker
supplying the equipment. Impedances must be low, or there won't be
enough current to blow the fuse - which is why it's important to test
earth loop impedance, not just rely on a neon tester.
Equipotential bonding is there so that no two metal objects can
develop a high voltage across them. This is typical from a high
impedance fault condition - maybe a heater with failing insulation,
not enough to cause an earth fault, but still enough to make the case
give you a shock. Humans are normally high impedance, so won't suffer
such shocks - but wet humans are much more conductive, so bonding
becomes especially important in bathrooms.
or to look at it another way....
(a)even more paths for across the chest shocks
(b)more things that can become live
you are not allowed bare protective conductors
but you can have acres of bonded metal
where I work bonding causes more problems than it solves
because it just increases the chance of electrucution
Isolation, insulation & electronic protection !
A bathroom is not really like a faraday cage, since it has mains in
there that is not at the 'cage' potential. Its more like an earthed
cage with wired appliances in it, which occasionally become live.
2 issues with equipotential earthed bonding are:
a) a shock from light fitting to bonded metalwork is worse than a
shock from light to unbonded metalwork
b) should there be a fault with the earth feed lots of metal will
become live instead of a little.
Those points dont make it bad, but they do make it less great than it
But I would look at equipotential bonding from another point of
How many lives has it saved? Our of 50 deaths per year from
electrocution in the UK, how many of those were bathroom
electrocutions? And how many of those would have been saved by
Now, whats the cost of equipotentially bonding the nations bathrooms?
How much per life is that?
Now, people die en masse due to their own ignorance, eg due to stupid
eating habits. How much would a food education campaign cost? How many
lives would it save? How much per life is that? How many times the
number of lives would be saved with the same amount of money?
On 6 Sep 2003 05:31:44 -0700, email@example.com (N. Thornton) wrote:
A campaign to bond all the nation's bathrooms tomorrow "For The Sake
Of The Children (tm)" would be expensive.
But a better standard that all new work should comply with, is a much
lower incremental cost.
On 6 Sep 2003 05:31:44 -0700, N. Thornton wrote:
Occasionally? I hope not.
So you're suggesting that PME is not worth bothering with? May I
respectfully suggest that you need to go away and quietly reflect on
just what it is you're saying.
*If* an appliance or wiring installation develops an earth fault then
the various safety measures *should* act to isolate that fault.
If they don't, then the whole fabric of the building rises to some
voltage above zero with respect to earth, coz the leccy companies
connect the neutral of the distribution system to earth at the
transformer. Because you in your dripping wet state are safely contained
within a Faraday cage, formed by the equipotential crossbonding of the
installation, the risk of electric shock is minimised, because you are
at the same voltage as everything around you.
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