In article ,
Bob Latham wrote:
I'm sorry, I don't quite see the point of your comments Dave. Are
agreeing with me or correcting me? It seems to me I said pretty much all
of that in another way didn't I?

Only the bit about earthing the supplementary bonding in the bathroom.
This is against the regs.

--
*I wonder how much deeper the ocean would be without sponges*

Dave Plowman London SW
To e-mail, change noise into sound.

On Fri, 16 Nov 2007 10:56:49 +0000 (GMT), "Dave Plowman (News)"
wrote:


I've been reading through the regs, and what you describe for
bathrooms - simply joining everything together so different bits won't
cause shocks appears to be called "Supplementary Bonding", and is just
a local belt-and-braces addition.

That's it in one. But I don't know what you mean by local - it's in the
national wiring regs.

Sorry - I meant local in the "local to the bathroom" sense.

d

--
Pearce Consulting
http://www.pearce.uk.com

"Dave Plowman (News)" wrote in message
...
In article ,
David Looser wrote:
By "things that can't be touched", are you refering to the metalwork
of the heating chamber?. Because that's the one part that *should* be
earthed because it contains the heater element. Should the heater's
insulation fail then the leakage current will trip the RCD.

Again, you're confusing earthing with bonding. The supply cable
provides the earth to the appliance.

So what do *you* mean by bonding then? Are you suggesting that bits of
metal, all of which are naturally isolated from each other and from
anything electrical should be bonded together? What would that achieve?

It makes them all at the same potential. So touching two of them at once
can't electrocute you regardless of any fault condition.

But what happens when you only touch one???, a *far* more likely event and
one for which bonding makes things *worse*.

It's impossible to make allowances for any possible 'what if'. You can
only take the most sensible precautions.

Of course, take the most *sensible* precautions, bonding simply isn't
sensible.

Since you don't appear to understand the principle, are you sure of that?

I understand the principle all too well. More to the point I understand that
it simply isn't relevant in a *real* bathroom. Bathrooms aren't Faraday
cages - they are nothing like Faraday cages and no wishful thinking on your
part is going to make then anything like Faraday cages. Unless you think
that people float about in bathrooms a couple of inches off the floor, never
entering or leaving, and only ever touch bits of bonded metal in pairs then
all this "equipotential" stuff is so much theoretical nonsense. The
(electrically) safest metalwork in a bathroom is metalwork that isn't
connected to anything electrical, it's simply impossible to get a shock from
it. Bonding it to something else creates the possibility of creating a shock
hazard from it that wouldn't have existed otherwise.

Or simply not have electricity in the house. And sensible precautions
mean following the current regs to the letter.

Well no it doesn't, that's my point. The committee chairman more or
less admitted to me that this bonding rule was based on a totally
inadequate analysis of the actual situation that could arise in a real
bathroom under real conditions. Put simply the committee made a
thoroughly bad job of it. I would rather follow the spirit than the
letter of the regs.

I hope he understood the principle of equipotential bonding. Perhaps not.

Since he was from the chairman of the committee that invented this
nonsensical notion I guess he did.

David.

On Fri, 16 Nov 2007 11:08:51 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Bob Latham wrote:
I'm sorry, I don't quite see the point of your comments Dave. Are
agreeing with me or correcting me? It seems to me I said pretty much all
of that in another way didn't I?

Only the bit about earthing the supplementary bonding in the bathroom.
This is against the regs.

Hang on. One of the illustrations I've been looking at was for a
bathroom with an electric power shower (within Zone 2). In this case,
the supplementary bonding was definitely connected to the mains ground
wire of the power shower. And a pretty vital connection too, I would
have thought.

d

--
Pearce Consulting
http://www.pearce.uk.com

In article ,
Don Pearce wrote:
On Fri, 16 Nov 2007 10:56:49 +0000 (GMT), "Dave Plowman (News)"
wrote:


I've been reading through the regs, and what you describe for
bathrooms - simply joining everything together so different bits won't
cause shocks appears to be called "Supplementary Bonding", and is just
a local belt-and-braces addition.

That's it in one. But I don't know what you mean by local - it's in the
national wiring regs.

Sorry - I meant local in the "local to the bathroom" sense.

Yes - and that's the whole point. It turns that *room* into an
equipotential area - like a Faraday cage. The same principle as a bird
surviving perching on a live cable - you need a return path for current to
flow.

--
*The statement below is true.

Dave Plowman London SW
To e-mail, change noise into sound.

In article , David Looser
wrote:
"Dave Plowman (News)" wrote in message
...
In article , David Looser
wrote:
By "things that can't be touched", are you refering to the
metalwork of the heating chamber?. Because that's the one part
that *should* be earthed because it contains the heater element.
Should the heater's insulation fail then the leakage current will
trip the RCD.

Again, you're confusing earthing with bonding. The supply cable
provides the earth to the appliance.

So what do *you* mean by bonding then? Are you suggesting that bits
of metal, all of which are naturally isolated from each other and
from anything electrical should be bonded together? What would that
achieve?

It makes them all at the same potential. So touching two of them at
once can't electrocute you regardless of any fault condition.

But what happens when you only touch one???, a *far* more likely event
and one for which bonding makes things *worse*.

If you only touch one there is no return path so no current flows.

It's impossible to make allowances for any possible 'what if'. You
can only take the most sensible precautions.

Of course, take the most *sensible* precautions, bonding simply isn't
sensible.

Since you don't appear to understand the principle, are you sure of
that?

I understand the principle all too well. More to the point I understand
that it simply isn't relevant in a *real* bathroom. Bathrooms aren't
Faraday cages - they are nothing like Faraday cages and no wishful
thinking on your part is going to make then anything like Faraday
cages. Unless you think that people float about in bathrooms a couple
of inches off the floor, never entering or leaving, and only ever touch
bits of bonded metal in pairs then all this "equipotential" stuff is so
much theoretical nonsense.

Fine. Then show examples of those injured by this principle. There aren't
any I know of.

The (electrically) safest metalwork in a
bathroom is metalwork that isn't connected to anything electrical, it's
simply impossible to get a shock from it. Bonding it to something else
creates the possibility of creating a shock hazard from it that
wouldn't have existed otherwise.

The far greater likelihood is that parts of it are connected via copper
pipes to other parts of the house where a fault may well occur making it
live. An immersion heater, for example. Boiler. Shower or shower pump. and
that's before a cable rubbing through and touching under the floor
somewhere. Add into this random lengths of plastic pipe and you could
easily have two bits of metalwork in the bathroom with 240 volts between
them. We are, after all, talking of what ifs.

Or simply not have electricity in the house. And sensible
precautions mean following the current regs to the letter.

Well no it doesn't, that's my point. The committee chairman more or
less admitted to me that this bonding rule was based on a totally
inadequate analysis of the actual situation that could arise in a
real bathroom under real conditions. Put simply the committee made a
thoroughly bad job of it. I would rather follow the spirit than the
letter of the regs.

I hope he understood the principle of equipotential bonding. Perhaps
not.

Since he was from the chairman of the committee that invented this
nonsensical notion I guess he did.

So the entire committee of qualified people thought it necessary - at the
time - but you know better? They're not a trade body with axes to grind -
like making work for their companies by unnecessary regulations.

--


Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Don Pearce wrote:
On Fri, 16 Nov 2007 11:08:51 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Bob Latham wrote:
I'm sorry, I don't quite see the point of your comments Dave. Are
agreeing with me or correcting me? It seems to me I said pretty much
all of that in another way didn't I?

Only the bit about earthing the supplementary bonding in the bathroom.
This is against the regs.

Hang on. One of the illustrations I've been looking at was for a
bathroom with an electric power shower (within Zone 2). In this case,
the supplementary bonding was definitely connected to the mains ground
wire of the power shower. And a pretty vital connection too, I would
have thought.

Well if all the plumbing in the house is copper and that copper is
correctly bonded at the main earth point then yes the bathroom metalwork
will probably be at near the safety earth potential. Similarly if there
are exposed metal parts to a shower which are internally connected to the
supply earth.

--
*If all is not lost, where the hell is it?

Dave Plowman London SW
To e-mail, change noise into sound.

"Signal" wrote in message

Jim Lesurf wrote:

Well I don't like to draw direct analogies between
drug and hifi blind tests (which are far from
equivalent), but yes the underlying principle is nice
in theory. However, pertaining to controversial areas
of hifi, there are practically no DBTs of a grade
which could be called conclusive.

There I would agree with you. Most audio DBTs are
poorly designed and inadequately conducted. Which is
why the audio snake-oil merchants still make a good
living.

OK, lets take as an example the test reported a month or
so ago in the JAES. Would you say this was poorly
designed, etc? if so, can you perhaps explain in detail,
and say how you would run a better test to deal with the
problems you see? I'm curious about this as I've already
seen it dismissed in one magazine.

Sorry Jim, haven't read the JAES article. I do know that
details on the equipment used was withheld by the authors
for fear of being "nitpicked to death". That seems like a
mistake.

Simply not true. The JAES shys away from references to specific pieces of
equipment. The authors posted the contents of the test systems on the BAS
web site.

Needless to say, the component lists on the BAS web sites have already been
nitpicked to death.

Knowing the egocentric nature of most audiophiles leads me to the conclusion
that no audiophile will believe anything unless it involves their ears and
their equipment. Hence www.pcabx.com , which has also been picked to death
on other grounds. ;-)

In article , Arny
Krueger
wrote:
"Signal" wrote in message


Simply not true. The JAES shys away from references to specific pieces
of equipment. The authors posted the contents of the test systems on
the BAS web site.

Needless to say, the component lists on the BAS web sites have already
been nitpicked to death.

Knowing the egocentric nature of most audiophiles leads me to the
conclusion that no audiophile will believe anything unless it involves
their ears and their equipment.

Well, so far as I know, nothing is stopping them from repeating the JAES
proceedure using components an objector favours.

So far as I can tell, people have run a variety of proceedures over the
years in tests like the JAES one, and have used various items of equipment.
Indeed, the JAES paper was based on using various items, in various
locations, etc.

I can see that *some* blind/controlled tests might have a problem due to
the choice of a poor item of equipment, or for some other specific reason.
But there have been various blind/controlled tests using diverse protocols
and equipment, and they do seem to return results consistent with the
recent JAES one.

Given this, it seems to me not to be very plausible to try and dismiss the
results by nit-picking. If those who distrust the results want to challenge
them, then it seems to me that the appropriate - and to me most convincing
- method would be to run their own similar tests, using items they think
*would* allow them to detect any differences they feel should be audible.

I haven't managed to read all the comments on the above, though. So perhaps
some have made more substantive points that I've yet seen. TBH my
impression was that many of those debating hadn't seen or understood the
actual JAES report. Would be nice if it were openly published. But I don't
know what the JAES expect in terms of the authors having copyright to do
this after magazine publication. Fairly usual for academics to send out
reprints in PDF form these days, though.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.audiomisc.co.uk/index.html
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html

"Dave Plowman (News)" wrote in message
...
In article , David Looser
wrote:

It makes them all at the same potential. So touching two of them at
once can't electrocute you regardless of any fault condition.

But what happens when you only touch one???, a *far* more likely event
and one for which bonding makes things *worse*.

If you only touch one there is no return path so no current flows.

Pardon? you are standing in bare, wet feet on a wet conductive floor. You
touch live metalwork and NO CURRENT WILL FLOW??


I understand the principle all too well. More to the point I understand
that it simply isn't relevant in a *real* bathroom. Bathrooms aren't
Faraday cages - they are nothing like Faraday cages and no wishful
thinking on your part is going to make then anything like Faraday
cages. Unless you think that people float about in bathrooms a couple
of inches off the floor, never entering or leaving, and only ever touch
bits of bonded metal in pairs then all this "equipotential" stuff is so
much theoretical nonsense.

Fine. Then show examples of those injured by this principle. There aren't
any I know of.

Nor do I, but I can easily imagine situations in which someone would be. Can
you show examples of people being saved from injury by the use of bathroom
bonding?

The (electrically) safest metalwork in a
bathroom is metalwork that isn't connected to anything electrical, it's
simply impossible to get a shock from it. Bonding it to something else
creates the possibility of creating a shock hazard from it that
wouldn't have existed otherwise.

The far greater likelihood is that parts of it are connected via copper
pipes to other parts of the house where a fault may well occur making it
live. An immersion heater, for example. Boiler. Shower or shower pump. and
that's before a cable rubbing through and touching under the floor
somewhere. Add into this random lengths of plastic pipe and you could
easily have two bits of metalwork in the bathroom with 240 volts between
them. We are, after all, talking of what ifs.

The connection of 240V to plumbing is a highly dangerous situation as I
thought my example clearly demonstrated. Someone could come into contact
with it anywhe kitchens, utility rooms, bedroom washbasins (as in my
example), airing cupboards etc. Indeed if there is a hot-water based central
heating it could happen in any room. So the proper response is to ensure as
far as humanly possible that it never happens. Clearly as a minimum
requirement all such electrical items should be properly earthed via their
earth-continuity conductors and fed via a regularly tested RCD. The idea
that it doesn't matter because you've bonded the pipework to something else
in the bathroom is dangerous nonsense. What you are effectively creating is
a bathroom which is basically all at earth potential except for the taps etc
which are live. Doesn't that sound a tad dangerous even to you? Just because
ALL the taps are equally live doesn't make it safe! Unless you really do
turn the bathroom into a sort of Faraday cage (line floor and walls with a
conductive material and bond that too) all the bonding has done is to
increase the number of points of danger. And if you did that then what about
people entering or leaving the "cage"?, or touching bonded pipework
elswhere?


So the entire committee of qualified people thought it necessary - at the
time - but you know better? They're not a trade body with axes to grind -
like making work for their companies by unnecessary regulations.

Are you suggesting that committees of qualified people cannot make mistakes?
The paperwork that I was sent by way of justification for this rule was
related to industrial situations - not bathrooms. ISTM that a rule that was
created for one situation was simply transferred to another without adequate
thought.

AFAIK the committee is made up of qualified electrical engineers, not risk
analysists, so I do not see that they are actually any more qualified to
make judgements on this issue than I am. Risk analysis is a notoriously
subjective area anyway, the conclusions depending heavily on what weight is
given to various risk factors. My considered opinion (considered long and
hard and with some real experience to draw on) is that the committee got it
wrong.


David.