Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

(pointed out to me by a friend who frequents the forums there)

Darren

On 13/11/2011 21:36, D.M.Chapman wrote:
Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

(pointed out to me by a friend who frequents the forums there)

Darren


We thought kengreen was a troll, but his persistence is a bit worrying
(based on other rubbish he posts). Fortunately we're pretty sure he
doesn't actually fly (as per the main theme of the forums!).

JB.

"D.M.Chapman" dmc@puffin. wrote in message
...


Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

(pointed out to me by a friend who frequents the forums there)


Just to check that the post copied below is accurate:
*****
"Ken, I used to think you knew about electricity and electronics. I am
beginning to wonder.

To answer the questions I posed, briefly: inside a switch in the neutral or
in the live of a lighting circuit, the highest measurable voltage to be
found is 230 volts (assuming you're on 230 volt mains). This is why nobody
should work on a switch with the power on.

If the house is wired in accordance with the latest regulations, the highest
current available in a switch with a 100 watt bulb connected is a shade
below 400mA under either scenario. Touching live and earth will pass 30mA
before the RCD trips. Without an RCD, the current will be much higher -
certainly in the fatal range in both cases. Few houses, so far, are wired
with RCDs in the lighting circuits.

Fatal current is generally reckoned to be 50mA - not across the heart, but
across the body. The actual current that will pass will depend on skin
resistance; the generally accepted fatal voltage is anything over 50 volts.

So: a person standing on a metal ladder earthed in any way, and touching the
"live" wire in a bayonet light socket wired with neutral switching is in
grave danger of death.

If the person is not on an earthed surface but the bayonet holder is metal -
and therefore earthed in accordance with the regulations - then the shock
will be mostly to the hand, but there will be some residual shock to the
rest of the body. Still very unpleasant, and potentially fatal to someone
with a weak heart (for example). Touching the live pin with one hand while
holding the earthed lamp with the other would probably be fatal.

The same person with live switching, in the "off" position, will not be
shocked. (If in doubt, the main switch should always be off or the fuse
removed.)

It is for this reason that the wiring regulations prohibit neutral switching
(and fusing the neutral). It's a pity the kengreen regulations are not the
same as the legal ones.

I'm sure you will continue to argue, Ken, but the regulations are not likely
to change.

I would strongly recommend that anyone doing wiring in their houses (legally
or not) should follow the regulations and switch the live, not the neutral.
I feel very strongly about this, which is why I have kept on about it."
******

Just making sure I am adding to my education and not subtracting.
--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On 13/11/2011 22:52, David WE Roberts wrote:

"D.M.Chapman" dmc@puffin. wrote in message
...


Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

(pointed out to me by a friend who frequents the forums there)


Just to check that the post copied below is accurate:

Erm, no not really...

Might as well pick it apart:


*****
"Ken, I used to think you knew about electricity and electronics. I am
beginning to wonder.

To answer the questions I posed, briefly: inside a switch in the neutral
or in the live of a lighting circuit, the highest measurable voltage to
be found is 230 volts (assuming you're on 230 volt mains). This is why
nobody should work on a switch with the power on.

So far ok.

If the house is wired in accordance with the latest regulations, the
highest current available in a switch with a 100 watt bulb connected is
a shade below 400mA under either scenario. Touching live and earth will

Complete twaddle. The live wire in the switch will be directly fed from
the lighting circuit MCB (typically rated at 6A nominal, however one of
those would require a fault current of 30A to move into the "instant"
part of its trip curve[1]. Hence the MCB is going to offer no protection
from direct contact at all.

[1] http://wiki.diyfaq.org.uk/images/d/d...e-MCBTypeB.png

pass 30mA before the RCD trips. Without an RCD, the current will be much
higher - certainly in the fatal range in both cases. Few houses, so far,
are wired with RCDs in the lighting circuits.

This is also twaddle. He has failed to understand that the RCD has no
mechanism to limit the current passed. All it can do is limit the
duration of the shock, when the shock current exceeds the trip threshold
of the device (can be anything from 66% of the rated threshold upwards).
The speed of operation should be within two mains cycles (i.e. 40ms) for
appreciable shock currents (its allowed by the specs to be longer for
ones just over the threshold - but in reality I have never found one
that was not 40ms or faster at 30mA or more).

Limiting the shock duration will limit the total energy let through. Its
the total energy that counts, so the danger of a shock is closely
related to both the magnitude and the duration.

Fatal current is generally reckoned to be 50mA - not across the heart,

Only part of the story - see above...

but across the body. The actual current that will pass will depend on
skin resistance; the generally accepted fatal voltage is anything over
50 volts.

As a bold statement that again is not really supportable, but I suspect
he may be thinking about limiting touch voltage with EQ bonding etc.

(You can stick you hand on Van de Graaff generator and receive a 100Kv
shock and walk away unharmed).

50V and under is generally point at which low impedance (i.e. those that
can supply injurious levels of current are considered "touch safe". Its
the standard to which equipotential bonding needs to perform when
limiting touch voltage for example)

So: a person standing on a metal ladder earthed in any way, and touching
the "live" wire in a bayonet light socket wired with neutral switching
is in grave danger of death.

Neutral switching should never be used anyway.

Bayonet connectors do not actually pose as much risk as one might expect
since the contact area is very small, and its difficult to maintain
contact for any significant duration once shocked.

If the person is not on an earthed surface but the bayonet holder is
metal - and therefore earthed in accordance with the regulations - then
the shock will be mostly to the hand, but there will be some residual
shock to the rest of the body. Still very unpleasant, and potentially
fatal to someone with a weak heart (for example).

Possibly but unlikely as a direct result of the shock. Falling off the
ladder however is a far more likely way to suffer!

Touching the live pin
with one hand while holding the earthed lamp with the other would
probably be fatal.

Again, it can deliver the magnitude, but it would be hard to deliver the
duration. The bodies natural response will tend to yank the hand away
and break contact.

The same person with live switching, in the "off" position, will not be
shocked.

Agreed

(If in doubt, the main switch should always be off or the fuse
removed.)

Take care even with the fuse removed. Two way switched circuits with
borrowed neutrals can leave the neutral of an apparently isolated
circuit live and able to bite.

It is for this reason that the wiring regulations prohibit neutral
switching (and fusing the neutral). It's a pity the kengreen regulations
are not the same as the legal ones.

I'm sure you will continue to argue, Ken, but the regulations are not
likely to change.

I would strongly recommend that anyone doing wiring in their houses
(legally or not) should follow the regulations and switch the live, not
the neutral. I feel very strongly about this, which is why I have kept
on about it."

The remainder seems non contentious.

******

Just making sure I am adding to my education and not subtracting.

From what brief stuff I have read, the Kengreen posted stuff can be
disregarded out of hand as the rantings of a drooling retard. The Keef
responses generally are on the right track, but he appears to have
misunderstood a few quite key points.


--
Cheers,

John.

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

On Sun, 13 Nov 2011 21:36:30 +0000 (UTC), dmc@puffin. (D.M.Chapman)
wrote:

Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

Ken Green is an utter ****, is the impression I get.

"John Rumm" wrote in message
o.uk...
On 13/11/2011 22:52, David WE Roberts wrote:

"D.M.Chapman" dmc@puffin. wrote in message
...


Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

(pointed out to me by a friend who frequents the forums there)

snip useful stuff

I thought that the main risk with 240V a/c was that the current was not
enough to cause immediate major damage, but the flow of current across the
body could interrupt the electrical control of the heart.
So lower voltages might not hurt, higher voltagees would just cause the
muscles to contract and hurl you away but at 240V you just hang there
quivering whilst your heart gets reprogrammed.

Could be urban myth, of course.

Thought also that the risks with 110V were different, but Google is not
being my friend this morning.

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

On Mon, 14 Nov 2011 10:16:43 -0000, David WE Roberts wrote:

I thought that the main risk with 240V a/c was that the current was not
enough to cause immediate major damage, but the flow of current across
the body could interrupt the electrical control of the heart.
So lower voltages might not hurt, higher voltagees would just cause the
muscles to contract and hurl you away but at 240V you just hang there
quivering whilst your heart gets reprogrammed.

It's complex but the basic "volts that jolts, mills that kills" holds
trueish. The lower the voltage the "force" there is to make a current
flow. Under normal circumstances anything below 50v is not going to
cause a current high enough to kill to flow. But under the correct
conditions a 1.5v battery could kill...

--
Cheers
Dave.

David WE Roberts wrote:


"John Rumm" wrote in message
o.uk...
On 13/11/2011 22:52, David WE Roberts wrote:

"D.M.Chapman" dmc@puffin. wrote in message
...


Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

(pointed out to me by a friend who frequents the forums there)

snip useful stuff

I thought that the main risk with 240V a/c was that the current was not
enough to cause immediate major damage, but the flow of current across the
body could interrupt the electrical control of the heart.
So lower voltages might not hurt, higher voltagees would just cause the
muscles to contract and hurl you away but at 240V you just hang there
quivering whilst your heart gets reprogrammed.

Could be urban myth, of course.

Thought also that the risks with 110V were different, but Google is not
being my friend this morning.


If you mean site-tools 110V, then those are 55-0-55 (0 is earth) so you are
in ELV territory - but it would still zing a bit as you picked rain soaked
extension socket out of a muddy puddle whilst standing in the same.

--
Tim Watts

Tim Watts wrote:

If you mean site-tools 110V, then those are 55-0-55 (0 is earth) so you are
in ELV territory

ELV is under 25V RMS AC (or under 60V DC, not so useful for transformers!).

Andy Burns wrote:

Tim Watts wrote:

If you mean site-tools 110V, then those are 55-0-55 (0 is earth) so you
are in ELV territory

ELV is under 25V RMS AC (or under 60V DC, not so useful for
transformers!).

Quite right - I was thinking of DC when I wrote that. I'll get some more
coffee...

But - yes, 55V AC is not too bad all the same.
--
Tim Watts

On 14/11/2011 10:16, David WE Roberts wrote:

"John Rumm" wrote in message
o.uk...
On 13/11/2011 22:52, David WE Roberts wrote:

"D.M.Chapman" dmc@puffin. wrote in message
...


Sounds like a holiday let to avoid...

http://forums.flyer.co.uk/viewtopic.php?f=6&t=73604

(pointed out to me by a friend who frequents the forums there)

snip useful stuff

I thought that the main risk with 240V a/c was that the current was not
enough to cause immediate major damage, but the flow of current across
the body could interrupt the electrical control of the heart.

Its plenty high enough to cause (fairly) immediate damage.

So lower voltages might not hurt, higher voltagees would just cause the
muscles to contract and hurl you away but at 240V you just hang there
quivering whilst your heart gets reprogrammed.

Generally 240V will in many cases cause you to involuntarily retract you
hand etc. The danger of getting "locked onto" something is still there
if you can grasp round it though.

Could be urban myth, of course.

Thought also that the risks with 110V were different, but Google is not
being my friend this morning.

110V as in US mains will be similar in theory but more dangerous for
other practical reasons usually. 110 as in site transformers etc is
designed to be very much safer due to the 55-0-55 nature of the supply.


--
Cheers,

John.

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

On 14/11/2011 12:14, Tim Watts wrote:


Quite right - I was thinking of DC when I wrote that. I'll get some more
coffee...

Wrong, actually. In BS 7671 ELV is defined as "not exceeding 50 V AC or
120 V ripple-free DC, whether between conductors or to earth."

But - yes, 55V AC is not too bad all the same.

Depends on the circumstances. Electrocution had been known at 24 V, I
believe.

--
Andy

Andy Wade wrote:

On 14/11/2011 12:14, Tim Watts wrote:


Quite right - I was thinking of DC when I wrote that. I'll get some more
coffee...

Wrong, actually. In BS 7671 ELV is defined as "not exceeding 50 V AC or
120 V ripple-free DC, whether between conductors or to earth."

It's a bad day. I felt sure 50V AC was the limit, then I foolishly checked
Wonkypedia that mentions 25VAC and confused myself into thinking it was
50VDC! Presumaly that was what got the other Andy...

But - yes, 55V AC is not too bad all the same.

Depends on the circumstances. Electrocution had been known at 24 V, I
believe.




--
Tim Watts

Tim Watts wrote:

I felt sure 50V AC was the limit, then I foolishly checked
Wonkypedia that mentions 25VAC and confused myself into thinking it was
50VDC! Presumaly that was what got the other Andy...

Yes, when the proper standards are only available at a price, people who
can't justify the price will turn to whatever sources are free.

It seems the 25VAC/60VDC that wikip refers to are actually the limits
for SELV used in a damp environment.

On 14/11/11 10:33, Dave Liquorice wrote:
On Mon, 14 Nov 2011 10:16:43 -0000, David WE Roberts wrote:

I thought that the main risk with 240V a/c was that the current was not
enough to cause immediate major damage, but the flow of current across
the body could interrupt the electrical control of the heart.
So lower voltages might not hurt, higher voltagees would just cause the
muscles to contract and hurl you away but at 240V you just hang there
quivering whilst your heart gets reprogrammed.

It's complex but the basic "volts that jolts, mills that kills" holds
trueish. The lower the voltage the "force" there is to make a current
flow. Under normal circumstances anything below 50v is not going to
cause a current high enough to kill to flow. But under the correct
conditions a 1.5v battery could kill...


I had volts vs amps explained to me at primary school in science lessons as
being akin to water in a hosepipe.

The volts (Joules per Coulomb) is like the water pressure in a pipe. The
higher it is the harder the energy is pushing those electrons down the wire.
In the same way as water stored in a tank at the top of a hill has lots of
potential energy, volts is the potential energy of electricity (!) and also
called the potential difference.

The amps (Coulombs per second) is like the flow rate of water. The higher it
is, the more electricity flows at once. The narrower the pipe (wire) the
higher the resistance and the more volts (pressure) needed to overcome the
resistance and still maintain a satisfactory current (flow rate).

etc. etc.


The combination of volts x amps is the power and like with water, multiplying
the

Andy Burns wrote:

when the proper standards are only available at a price

I remembered my library card allows access to a subset of standards
online, just double-checked and BS7671 isn't one of them, but it seems
that BSi/IET may be allowing online access to it now.

https://bsol.bsigroup.com/en/BSOL-FAQs/#Custom+Collection+users+

I've asked the library if they anticipate adding 'GBM81' to their
subscription package ...

On 14/11/2011 14:13, Andy Burns wrote:
Tim Watts wrote:

I felt sure 50V AC was the limit, then I foolishly checked
Wonkypedia that mentions 25VAC and confused myself into thinking it was
50VDC! Presumaly that was what got the other Andy...

Yes, when the proper standards are only available at a price, people who
can't justify the price will turn to whatever sources are free.

Although some free sources are actually worth what you pay for them ;-)

http://wiki.diyfaq.org.uk/index.php?...ltage_or _ELV


--
Cheers,

John.

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

John Rumm wrote:

Although some free sources are actually worth what you pay for them ;-)

clearly they've squandered the tenner I gave them last year!

http://wiki.diyfaq.org.uk/index.php?...ltage_or _ELV

How do we juke the pagerank of the wiki?

In article ,
John Rumm writes:

110V as in US mains will be similar in theory but more dangerous for
other practical reasons usually. 110 as in site transformers etc is
designed to be very much safer due to the 55-0-55 nature of the supply.

BTW, US changed to 120V some time before we standardised on 240V ;-)
(although some states have since reduced to, e.g. 117V, as an energy
saving measure).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Nov 14, 12:56*pm, John Rumm wrote:
110V as in US mains will be similar in theory but more dangerous for
other practical reasons usually. 110 as in site transformers etc is
designed to be very much safer due to the 55-0-55 nature of the supply.

My understanding (and I would be delighted to be corrected), is that
110V causes fewer deaths/serious injuries by electrocution (because
the voltage is lower), but more by fire (because the current is twice
as high, and the heat generated by a slightly dodgy connector is four
times as high). Fires caused by electrical faults are a bigger
problem *in the UK* than electrocutions, this is not a good trade-
off.

However, the problem is not so bad as to justify moving to a different
electrical distribution system.

Martin Bonner wrote:
On Nov 14, 12:56 pm, John Rumm wrote:
110V as in US mains will be similar in theory but more dangerous for
other practical reasons usually. 110 as in site transformers etc is
designed to be very much safer due to the 55-0-55 nature of the supply.

My understanding (and I would be delighted to be corrected), is that
110V causes fewer deaths/serious injuries by electrocution (because
the voltage is lower), but more by fire (because the current is twice
as high, and the heat generated by a slightly dodgy connector is four
times as high). Fires caused by electrical faults are a bigger
problem *in the UK* than electrocutions, this is not a good trade-
off.


Its a very good one on a building site, where fires are pretty commin
anyway.. the plumber whose blowtorch gutted a 1000 year old house..


However, the problem is not so bad as to justify moving to a different
electrical distribution system.


definitely not. My gut feeling is that 240v around the home is about
optimal, and 55-0-55 is about right on a building site!

On 17/11/2011 13:50, Martin Bonner wrote:
On Nov 14, 12:56 pm, John wrote:
110V as in US mains will be similar in theory but more dangerous for
other practical reasons usually. 110 as in site transformers etc is
designed to be very much safer due to the 55-0-55 nature of the supply.

My understanding (and I would be delighted to be corrected), is that
110V causes fewer deaths/serious injuries by electrocution (because
the voltage is lower), but more by fire (because the current is twice

All else being equal that would probably be true. However the US suffers
far more electrocutions per capita than we do (by several orders of
magnitude). This is probably more a reflection on the quality of their
electrical accessories and installation methods, than the voltage however.

as high, and the heat generated by a slightly dodgy connector is four
times as high). Fires caused by electrical faults are a bigger
problem *in the UK* than electrocutions, this is not a good trade-
off.

What do you propose, 480V per phase and half the current?

However, the problem is not so bad as to justify moving to a different
electrical distribution system.


--
Cheers,

John.

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

On 17/11/2011 19:29, John Rumm wrote:
This is probably more a reflection on the quality of their electrical
accessories and installation methods, than the voltage however.

Or perhaps it's because as it's a low voltage they aren't as careful.

Like in this image.

http://tinyurl.com/chmxu5a

Andy