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Re: ABC Inventors - electrical safety device


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My point is that the current has to flow through your heart to have any
chance of killing you. Either from one arm to another or from one arm to a
leg, or through your brain somehow. That is why the old trick of working on
high voltage with one hand behind your back actually does work when working
with high voltage supplies that are not referenced to ground such as high
voltage secondary windings on a transformer etc.

Frilly fact time. Did you know that hospitals use isolated power supplies,
and therefore do not have an active or neutral? Touching either side of the
power points (one at a time) will not hurt you at all.


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Not that I have done the research but I bet most deaths caused in this way
occur when a parent goes to pull out the hair dryer while it is still in the
bath tub before turning it off at the power point.  -- without an RCD fitted
to the mains of course.



Re: ABC Inventors - electrical safety device



"Heywood Jablome" <reply to thread> wrote in message
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active
have
the
I agree. The group of people killed mostly these days by electricity is
electricians and that is due to the widespread deployment of RCD's. What's
the chance of having a hand basin full of water and dropping an electric
shaver into it. NIL. You wouldn't have a handbasin full of water if you are
using an electric shaver.  derrrrrrr!!!

There is more chance of this happening to you.
http://www.big-boys.com/articles/badcar.html

Cheers.



Re: ABC Inventors - electrical safety device



"Chris"
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** How come RCDs only kill electricians ???

    Vengeful little suckers are they  ???



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**  Very high.

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**  Rot  -  shaver isolation transformers are sold because of exactly this
risk .


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**  A.  What a limited knowledge of shaving you have.

B.   The shaver may fall in the basin when not in use but still live.




...........    Phil



Re: ABC Inventors - electrical safety device



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Well why don't you try it for yourself and post the results




Re: ABC Inventors - electrical safety device


On Thu, 5 May 2005 18:26:32 +1000, "Heywood Jablome" <reply to thread>
put finger to keyboard and composed:

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According to my reading of the info at the ABC website, Protex is
claimed to protect an individual should he simultaneously grab both A
and N conductors while being perfectly insulated from earth. Clearly
this is impossible.

The info is also contradictory:

"If a person comes into contact with the active and neutral conductors
while handling faulty plugs or appliances, the safety switch will not
detect this contact unless there is also an avenue for current to flow
to earth. The current flow to earth comes from 3-pinned appliances, or
what the industry refers to as class 1 appliances."

"If you use a 2 pin, non-earthed appliance you or your surroundings
have to become the connection to earth to make a safety switch
operate. The level of electricity that is likely to go through you
depends on your surroundings and the level of electricity flowing
through an appliance."


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

Re: ABC Inventors - electrical safety device


On Thu, 5 May 2005 13:45:48 +1000, "Phil Allison"

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Phil

That would seem to be a plausable explanation but what about if it was
built into a GPO ? There would be no way to sense the voltage on the
case or internal metal without an extra wire back to the GPO.

Perhaps this is why he claims that it 'could' be built into a GPO but
he hasn't done it yet - because it is impractical ?

BTW could you use a triac instead of a solenoid switch or would this
cause problems with some appliances ?

Dave Goldfinch

Re: ABC Inventors - electrical safety device



"Dave Goldfinch"
 "Phil Allison"

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**  AFAIK  that is a purely hypothetical product.  It would need to sense
voltage on the appliance earth wire -  so breaking the rules about earth
continuity.


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**  IMO,  100%  yes.


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**  The safety trip MUST break both the active and neutral conductors ( in
case of A-N reversal) and provide galvanic isolation  -  ie an air gap or
solid insulation.  A triac is just not on.




...........   Phil




Re: ABC Inventors - electrical safety device



"
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significant AC voltage means the person is well and truely shocked !!!

An electrocuted  person can be electrocuted by  leaks that dont cause such
signficant voltage.

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The case of a fridge or heater has to be connected to earth.



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I think he just means its impractical to put such a stupid device in there.

Mabye you could only tolerate the stupid thing in a hair dryer.

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triacs cant be used as a safety device  - they dont work well enough - not
reliable, and their reliable performance as as with isnt good enough for
safety.





Re: ABC Inventors - electrical safety device



"Brad Hogan"
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**  Not at all  -  the mere presence of water inside the appliance will
cause tripping, no need for a person to be the conductor.  Plus the AC power
is cut off very fast  -  faster than an RCD that takes 30mS.


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**   You have not understood the principle at all.

 A Class 2 appliance is not an electrocution risk unless wet or submerged  -
in either case the Protex will have isolated it before it could do any harm.





............    Phil




Re: ABC Inventors - electrical safety device


On Thu, 05 May 2005 08:51:11 GMT, Dave Goldfinch

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I dont  see how you could safely use a Triac to switch OFF the mains
in a safety product like this.  for one, triacs still tend to leak a
bif of voltage even when off, and when triacs (and many such SS
devices) fail, they tend to go short circuit rather than open circuit.
I have heard of people in swimming pools being electrocuted by very
low voltages such as 12 or 24v, so even small leakage occuring through
the bathwater (specially if its possibly made even more conductive
than normal tap water by "contaminants" like skin oils, dirt, soap,
shampoo, bath salts and such)

Also,  when used in things like hairdryers, toasters, kettles and such
domestic heating appliances (as shown in the "inventors" video) the
current being drawn could easily be the full 10 amps, and assuming
there is a 0.6v voltage drop across the triac, that would mean power
dissipation of around 6w !  

Triacs (used in typical cheap light dimmers) also tend to die (and
internally short) very easily with surges caused by incandescent bulbs
blowing and such.

Again, this is only my thought, but if you absolutely HAD TO have the
mains shut off at such a lightning speed, and you needed a triac or
such device to do it - the mains would have to be also then cut out by
a relay as a back up as well. (and/or some sort of "crow bar" circuit
as well)  At least then - even in worst case and the triac shorted and
didnt open the circuit - the relay backing it up  would do the job a
fraction of a second later when its contacts finally opened.


Re: ABC Inventors - electrical safety device


On Thu, 05 May 2005 08:51:11 GMT, Dave Goldfinch

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But the ABC URL claims that he has built it "into a homes electrical
power box or switch board", which amounts to the same thing. And if
you saw the demo you would have noticed that the device was external
to the appliance, so unless there was a third wire, there would have
been no way to sense the voltage on any metalwork ... as you have
said.

Here is some sketchy info:

http://www.ferret.com.au/articles/4c/0c02c74c.asp

"Protex is unique according to its manufacturer because it does not
rely on an earth to operate.

Protex is compatible with both ac and dc voltage from 12V dc to 415V
ac and works on all electrical equipment, whether Class 1, 2 or 3.
About the size of a matchbox and with minimal moving parts, the
switching technology can be readily incorporated into existing
electrical equipment."

There is a photo, but I'm not sure what it all means.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

Re: ABC Inventors - electrical safety device


On Thu, 05 May 2005 08:45:01 +1000, Franc Zabkar

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Go to this video (the link above in the OP's post )  - and take a look
^carefully^ at where he dunks the live light bulb/socket into the
tupperware container of water



If you look carefully - it appears to me to be a 3 pin moulded plug,
and the short length of cord its on also appears to be 3 core round
(about 7.5amp appliance cable)

(IE: it has an earth in it ? !!)



Is there a loose (earth) wire hanging out the end of that cord and
therefore making it work like an everyday earth leakage unit ???


Re: ABC Inventors - electrical safety device


to keyboard and composed:

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Maybe the secret to the device is in its configurability? Perhaps it
is configured as a normal RCD for earthed 3-wire appliances, but uses
an extra wire in the case of 2-pin appliances to sense the voltage on
the metal parts.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

Re: ABC Inventors - electrical safety device



"Franc Zabkar"
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 **  There is no evidence that the Protex device is an RCD  -  but IS  a
voltage sensing trip just as claimed.

The version that uses three wires merely senses voltage on the earth wire
( having interrupted that wire by inserting an impedance) and hence current
flow in the earth wire.  It likely trips at the usual 20 - 30 mA.

This, however, fails to work in situations where the current is flowing to
other than the AC supply earth wiring  - so does NOT perform the safety
function for human life or fire protection that an RCD does.

Safety devices ( ie circuit breakers) that sense current flow in the supply
earth have been around for decades but are ( AFAIK ) only used in industrial
situations.




...........    Phil



Re: ABC Inventors - electrical safety device


On Thu, 05 May 2005 08:45:01 +1000, Franc Zabkar

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Like yourself Franc, I was flabergasted when this so-called
:invention" came up on The New Inventors. The inventor sounded as
though he didn't have a clue about ac electricity or its mode of
operation in a domestic situation. Worse still, the panel were totally
clueless and seemed to respond purely from the point of "if it
promotes safety (apparently), then it must be good". And, if he really
wanted to demonstrate how safe the device was using his toaster
set-up, why didn't he actually poke a metal knife into the toaster
with his bare hand? Using a test switch to simulate such a case of
stupidity was a cop out as far as I was concerned.

Also, since the relevevant state electrical codes all require RCD's to
be fitted in the main distribution box of all new buildings on both
GPO and lighting circuits (have done for many years now), and there
are approved portable RCD devices and extension cords already on the
market, I can't see the rules changing to do away with them in favour
of Protex or even to add Protex in conjunction to an RCD. Frankly, I
can't see this device ever getting off the ground. I can't imagine the
inventor of ever convincing appliance manufacturers to actually
incorporate it into their products either and I can't see any
manufacturer agreeing to include it no matter how cheap it is. Just
imagine the situation where a toaster (for example) having one of
these devices in it, still managed to electrocute a user. The court
case would be interesting I think.

I tend to agree with Phil's assessment of the device's mode of
operation.


Re: ABC Inventors - electrical safety device



"Ross Herbert"

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**  Surely a hair dryer, shaver or heater that can boast complete safety
even when very wet or submerged has an edge marketers can use.

A phrase like " Bathroom and Kitchen Safe Appliance "  might be used.

Folk are already aware of the danger posed by the sort of water related
accidents being referred to.


BTW:

RCDs may be installed now in all  *new* premises  -  but so what ??

90 % of premises are old and do not have to have one !!!

In NSW one can fully renovate a premises, including rewiring and the
**NOT**  have to fit an RCD -  until this rule is changed a million older
houses, flats and units will NEVER get them.


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**  Just my "two cents"  worth of surmising  -  you know.




............   Phil



Re: ABC Inventors - electrical safety device


On Fri, 6 May 2005 12:37:03 +1000, "Phil Allison"

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But this claim would tend to convince people that they would be
totally protected from electrocution and it would be difficult to
prove in practice. A manufacturer would be afraid of the litigation if
someone was electrocuted and he had a label saying "Bathroom and
Kitchen Safe" on his product. How does he guarantee that an insulation
breakdown or moisture ingress on the input side of the device can not
occur such that this claim would be compromised? That's why a court
case would be interesting. They would far prefer not to be involved in
the safety device aspects of electricity.

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True, but that's why I referred to the "portable" RCD items already on
the market. I accept that the user must make a pro-active decision to
actually use one of these however, and they might simply forget to. A
permanently wired safety device is preferable of course, but I would
predict that Protex will produce so many false trippings that it will
be like the boy who cried wolf and people will probably disconnect
them.

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Different states have different rules. In WA any old house (pre RCD)
being renovated and having new electrical work performed has to have
the main switchboard upgraded to include RCD's. At least that's what
my electrician told me back in '95 when I did some major renovations.

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But you also have some valued technical knowledge which makes sense.

Re: ABC Inventors - electrical safety device



"Ross Herbert"
 Phil  Allison
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**  Optimists misconstrue all the time  -  but the law does not back them
up.


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**  All product makes have Liability Insurance  - long as the claim is not
false or misleading they are covered.


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**  The claim merely refers to the existence of the safety trip device.
There are recognised standards for water proofing and insulation that if
complied with protect a maker from blame.  Certainly the cable, its
anchoring and the device need to be waterproof  -  this is the product
maker's job to get right and get type approved.

The Protex apparently has no safety approvals at present  -  it is a non
starter until it has got them.  However, it would  be wrong to assume it is
not possible.



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**  But they are NOT  being widely used in homes and nor are ever likely to
be.

 One cannot claim that RCDs are already providing adequate protection to the
Australian public.



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 **  Huh  ??   Forget to  ??



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** But in millions of domestic premises it is simply NOT  there and will not
be in the foreseeable future.


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**   You need to explain this "prediction"  - it a brand new one.


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 **  In QLD, when premises change ownership an RCD must be fitted  -  at
least this ensures statewide RCD protection in the next 20 years or so.

But whatever the case -  there are still millions of unprotected premises.

One cannot claim that RCDs are already providing adequate protection to the
Australian public.




.............   Phil



Re: ABC Inventors - electrical safety device


On Fri, 6 May 2005 13:44:02 +1000, "Phil Allison"

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I can see where this is going so I don't intend to respond further.


SNIP


Re: ABC Inventors - electrical safety device



"Ross Herbert"
 "Phil Allison"

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**  When digging oneself into bottomless pit  -  it is wise to know when to
stop.




..............   Phil





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