hello

remember this one from the sssf??

martin smith was adamant that low voltages couldn’t cause injury regardless of all reason and explanation on a science forum i couldn’t convince anyone that low voltages can cause injury.

extra low voltage is 50VAC and less, just 7 Volts more caused injury

check this link out from aurora energy in tassie

Aurora Energy today urged Tasmanians to use their CablePI electrical safety sensors
following recent incidents that could have resulted in serious injury to householders.
Aurora Energy CEO Dr Peter Davis said two recent incidents had highlighted the
importance of the safety sensors, which were distributed free of charge to all
Tasmanian households last year.
“In the first full year since we distributed the safety sensors, we have discovered
2250 faults on our networks and in the homes of our customers,’’ Dr Davis said.
“While early results indicate that the frequency of serious faults have fallen
significantly since the rollout began, we remain concerned that some householders
are either not using the sensor or failing to contact Aurora when the alarm sounds.’’
Dr Davis said two close calls in September had prompted the public safety warning.
On one occasion a customer received an electric shock while washing up. The
home’s neutral wire faulty, causing the electricity in the house to take an alternative
path, which resulted in a 57 volt charge in the kitchen taps. A CablePI sensor was not
used but would have alerted the customer to the problem. This voltage was enough
to cause serious injury or even death to the occupants.
Eight days later a customer awoke to the sound of the CablePI alarm in the early

www.auroraenergy.com.au/media_centre/Download.aspx?view=90

>extra low voltage is 50VAC and less

Yes, very pertinent information.

Of course the CablePI detects faults on Low Voltage systems which range from >50 <1000 volts.

>just 7 Volts more caused injury

Causing tongues to twist?

How do those cable pi thingos work? i have one in a power point here, it seems to do noting…

(although i do know that tassie Aurora power ranges from 180V to 260V and aurora seem to be quick on replacing electrical items that die and you question them over it being dodgy power that killed it)

Stumpy, I’d imagine it is measuring the Earth-Neutral voltage and triggering an alarm once a certain threshold is exceeded.

sibeen said:

Stumpy, I’d imagine it is measuring the Earth-Neutral voltage and triggering an alarm once a certain threshold is exceeded.

thanks for that

http://tdworld.com/projects_in_progress/business_in_tech/aurora-energy-cable-pi-0309/

Boris, that article doesn’t state how it detects the broken neutral, and I’m still going with the Earth-Neutral voltage measurement.

One thing from the article did raise my eyebrows:

The device is considered so promising that Aurora Energy, has set up a subsidiary company EziKey Group Pty Ltd, licensed to commercialize the international patent for the product.

If my E-N voltage monitoring is correct, they’ve been given a patent for the bloody obvious.

it is also known as WireAlert. all one word.

Bugger, with this new fangled internet thingy you’d think I’d be able to find a summary of the bloody patent application for this device.

So far, no luck.

Bugger, with this new fangled internet thingy you’d think I’d be able to find a summary of the bloody patent application for this device.

annoying isn’t it?

i’d never heard of the device but it probably works like this….

the point of supply is where the electrical connection between the power company and the customer occurs, it would normally be a special connection that joins the power companies cables and customers cables together.

the cable that takes power from the point of supply to the main fuse and meter is called the consumers mains until it hits the main fuse.

after the main fuse sits the meter beyond the meter is the main switch board and all of the protective devices that supply power to the house.

you might install a device that looks at total current flowing into the house. for an example, in normal circumstances most of the current flows from the active cable – through a toaster – and back through the neutral (this isn’t actually what happens but further explain will confuse things). for example 1A in from the active flows through a toaster and 1A flows through the neutral back to the transformer in the street,

in a fault situation where the NEUTRAL at the point of supply is broken (quite common): current flows from the active through a toaster but CANNOT flow back through the neutral. the current must flow across a special connection between netral and the earth connection and back through the earth to the local transformer (again this isn’t exactly what happens but it will be better to understand this first before moving further). current is now flowing through “earths” to make its way home not neutral , this creates the potential for harm.

plumbers often kill themselves when they cut pipes in the ground and the neutral connection is broken because current is now flowing through the pipe not the neutral.

the loss of the neutral connection means that the only way home for the current now is via “earth” which means that you get potential between a tap and the kitchen floor as the current seeks many ways to go home to the transformer.

the device would monitor current flowing into the house (active) and current flowing from it (neutral) and maybe current flowing across the neutral and earth connection.

an significant imbalance between current flowing in and current flowing out would suggest that the neutral was broken

in some cases an installation might have an amazing earth which means that most curretn would be flowing through the earth (go figure)

martin smith was adamant that low voltages couldn’t cause injury regardless of all reason and explanation on a science forum i couldn’t convince anyone that low voltages can cause injury
————
Was Martin reffering to LV or ELV? Because all the dead people from LV incidents would be a bit of a giveaway.

an significant imbalance between current flowing in and current flowing out would suggest that the neutral was broken
———————-
No really. It would suggest that an easy path was found, usually Earth.

wookiemeister said:

the device would monitor current flowing into the house (active) and current flowing from it (neutral) and maybe current flowing across the neutral and earth connection.

an significant imbalance between current flowing in and current flowing out would suggest that the neutral was broken

in some cases an installation might have an amazing earth which means that most curretn would be flowing through the earth (go figure)

so would that be using electricity while it’s testing?

so would that be using electricity while it’s testing?

——————
Sorta, not really, but a very very little bit, kinda…

Stealth said:

martin smith was adamant that low voltages couldn’t cause injury regardless of all reason and explanation on a science forum i couldn’t convince anyone that low voltages can cause injury
————
Was Martin reffering to LV or ELV? Because all the dead people from LV incidents would be a bit of a giveaway.

it was the brooke hanson incident that enraged him

it was down to 14 VAV i think/ 15 VAC

voltage isn’t the thing that kills you, its the amps

brooke was dripping wet whilst stepping out of the spa

the aurora victim was washing up dishes

in hospitals the way that current flows in the circuits is taken seriously, the power being supplied to rooms where open heart surgery takes place is usually ISOLATED ie the supply has NO reference to earth. the reason being that stray currents in surgery could make a heart stop (micro amps for example as the heart is completely exposed).

10 milliamps will give you a serious bite and will kil some people

in a theatre situation microamps can kill

Stealth said:

an significant imbalance between current flowing in and current flowing out would suggest that the neutral was broken
———————-
No really. It would suggest that an easy path was found, usually Earth.

yes but in a normal situation, earth isn’t a return path.

earth cables aren;t considered something that current should flow in , on a regular basis

Stealth said:

so would that be using electricity while it’s testing?

——————
Sorta, not really, but a very very little bit, kinda…

i might turn it off when i’m out of the house then

(sorta alittle but x 24/7 = a significant amout eventually

i might turn it off when i’m out of the house then

(sorta alittle but x 24/7 = a significant amout eventually

——————
I don’t think you would notice either way. Most likely a few cents per decade.

the device might well be using current to operate in the same way an rcd might use it – miniscule

if the device has a brain (likely) then a small current draw would be expected

a power meter will use a small amount of power to operate

the old spinning disc types use a small amount of current to operate (they have their own neutral where current can flow home)

Stealth said:

i might turn it off when i’m out of the house then

(sorta alittle but x 24/7 = a significant amout eventually

——————
I don’t think you would notice either way. Most likely a few cents per decade.

oh ,ok..so not much out of my $20/ week then :)

newer types of RCDs actually have a wire that connects to the earth bar this might be something to do with getting an earth reference and helping power the device

i’ve got a funny feeling that it allows the RCD to actually work when the point of supply neutral has been knocked out (the thing being discussed)

in normal sutations the imbalance of current is measured by measuring neutral and active currents BUT this device relies on the neutral line side to be working properly

in the event of the neutral being knocked out at the POS (the broken neutral scenario), the brain of the rcd is no longer powered and cannot work. the earth connection from the RCD to the earth bar allows the brain to know when a fault has occurred because the RCDs return path of current through earth keeps power to the RCDs brain

i’ve not done much installation for the last few years so i’m not sure if this new type of rcd is prevalent.

Stealth said:

martin smith was adamant that low voltages couldn’t cause injury regardless of all reason and explanation on a science forum i couldn’t convince anyone that low voltages can cause injury
————
Was Martin reffering to LV or ELV? Because all the dead people from LV incidents would be a bit of a giveaway.

ELV

in normal sutations the imbalance of current is measured by measuring neutral and active currents BUT this device relies on the neutral line side to be working properly
——————
No, it measures that the L-N is balanced regardless of the neutral side working properly.

in the event of the neutral being knocked out at the POS (the broken neutral scenario), the brain of the rcd is no longer powered and cannot work. the earth connection from the RCD to the earth bar allows the brain to know when a fault has occurred because the RCDs return path of current through earth keeps power to the RCDs brain
——————
There is no ‘brain’ as such. The system works by an unbalanced L-N creating power to trip a relay.

No, it measures that the L-N is balanced regardless of the neutral side working properly

===

are you talking line side or load side?

are you talking line side or load side?
———————
Both.

There is no ‘brain’ as such. The system works by an unbalanced L-N creating power to trip a relay
===

in a normal RCD i guess but i’m led to believe they’ve changed the way some of these work??

it was mentioned that in this situation the broken neutral line side would mean that the rcd couldn’t operate

one day i’ll contact the manufacture as to exactly why the earth connection is needed

Combined with overcurrent devices

rcd/CBO
Residual current and overcurrent protection may be combined in one device for installation into the service panel; this device is known as a GFCI breaker (Ground Fault Circuit Interrupter) in USA/Canada and as an RCBO (Residual current circuit breaker with overload protection) in Europe. In the US, RCBOs are more expensive than RCD outlets.

As well as requiring both line and neutral (or 3-phase) input and output, GFCI/RCBO devices require a functional earth (FE) connection. For reasons of space some devices use flying leads rather than screw terminals, especially for the neutral input and FE connections
===

the earth cable must be afunctional earth according to wiki

which seems to back up my assumptions that the “ brain “ must be using the earth connection to help power the device

>newer types of RCDs actually have a wire that connects to the earth bar

No. They have a lead which is connected to the Neutral.

sibeen said:

>newer types of RCDs actually have a wire that connects to the earth bar

No. They have a lead which is connected to the Neutral.

i’ve seen them connected to the earth bar

its a white cable

must be a functional earth

No. They have a lead which is connected to the Neutral.
———-

i’ve seen them connected to the earth bar

———
I just cut the bugger off to avoid an argument :)

its a white cable

must be a functional earth

————————————————————————————————————-

White will never be used as the colour for an Earth cable…anywhere.

Of course, in single phase equipment in the USA, white is the colour that is used for the neutral wire, with black being the colour used for the active.

i’m trying to get back into it nowadays, i’ve spent a few years away from the trade and have buggered around with medical stuff

once i’ve got some strength (money) up after a few months i’ll start doing temp electrical jobs to get back into it, perhaps shut down work?

sibeen said:

its a white cable

must be a functional earth

————————————————————————————————————-

White will never be used as the colour for an Earth cable…anywhere.

Of course, in single phase equipment in the USA, white is the colour that is used for the neutral wire, with black being the colour used for the active.

FAQ 007/2009: AS/NZS 3000:2007—CLAUSE 3.8 & TABLE 3.4 & CLAUSE 5.2.2
3.8 IDENTIFICATION
TABLE 3.4 CONDUCTOR COLOURS FOR INSTALLATION WIRING
5.2.2 EARTHING FUNCTIONS—Functional earthing (FE)
Question 007/2009. If an RCD is provided with a functional earthing conductor (typically coloured white or
pink), may this conductor be connected to an earthing terminal/connection or bar?
Answer. Yes. The purpose of the conductor is to allow a return path for the electronic circuit, if the neutral is
disconnected, to ensure the RCD still operates correctly. The conductor does not perform a protective earth
function.
———————————————————————————————————————————————————————————————-

If you are trying to get back into the electrical field then perhaps I’d suggest a remedial course in the colours that are used for identifying cables in low voltage networks.

http://www.google.com.au/url?sa=t&rct=j&q=abb%20functional%20earth%20rcd&source=web&cd=1&ved=0CFEQFjAA&url=http%3A%2F%2Fwww.wiringrules.standards.org.au%2FLinkClick.aspx%3Ffileticket%3D0dh1qsn5NBA%253D%26tabid%3D380&ei=m5W3T_OXLIPAiQfM9sj9CA&usg=AFQjCNHbRyYLCXtcnhxWomj9MqneouMG6Q

sibeen said:

If you are trying to get back into the electrical field then perhaps I’d suggest a remedial course in the colours that are used for identifying cables in low voltage networks.

haven’t you read what i’ve just posted up

go and argue with australian standards

they’ve just said exactly what i’ve said

the earth connection is if the neutral line saide fails

great minds think alike i guess

if you devoted more time to thinking about the subject instead of being ascerbic everyone would get along fine

>haven’t you read what i’ve just posted up

Yes, and what you have just posted has to do with Functional Earthing systems (FE) rather than Protective Earthing Systems (PE). They are completely different kettles of fish.

sibeen said:

>haven’t you read what i’ve just posted up

Yes, and what you have just posted has to do with Functional Earthing systems (FE) rather than Protective Earthing Systems (PE). They are completely different kettles of fish.

the rcd has functional earthing to keep the thing workingin the event of a neutral break lineside

i’m fully aware of what functional and protective earths do

think before you attack, this isn’t the sssf

Wookie, perhaps you should have a look at figures 3.1 and 3.2 in AS3000.

sibeen said:

Wookie, perhaps you should have a look at figures 3.1 and 3.2 in AS3000.

i’m telling you the rcd was being used to supply normal circuits

the white cable was connected to the earth bar

the white cable is for functional earthing of the rcd

From AS3000:

5.2.2 Functional earthing (FE)
Equipment may be required, to be connected to the earthing system for
purposes of correct operation rather than the safety conditions associated
with protective earthing. In such cases functional earthing conductors are
not required to be selected and installed to withstand fault currents or to be
identified in the same manner as a protective earthing conductor.

Where required, for operational purposes, functional earth connections for
data and signalling purposes should be insulated from all protective
earthing connections and conductors and should only be connected
together at one point, normally at the connection to the main earthing
terminal/connection or bar. Care must be exercised to avoid unintentional
contact between the two earthing systems.
No conductor insulation colour for functional earth conductors has been
detailed in this standard. To ensure that functional earthing connections are
made to the correct earthing system a green or green/yellow conductor
identification should not be used.

A FE is not a PE.

sibeen said:

Wookie, perhaps you should have a look at figures 3.1 and 3.2 in AS3000.

figure 3.1 page 135 single phase flexible cords and cables

figure 3.2 page 135 multiphase flexible cords and cables

nothing to do with rcds

>nothing to do with rcds

But a fair bit to do with cable colour codes, which is what we are currently arguing.

Question 007/2009. If an RCD is provided with a functional earthing conductor (typically coloured white or
pink), may this conductor be connected to an earthing terminal/connection or bar?
Answer. Yes. The purpose of the conductor is to allow a return path for the electronic circuit, if the neutral is
disconnected, to ensure the RCD still operates correctly. The conductor does not perform a protective earth
function.
——————————-

the white cable is connected to the earth bar

sibeen said:

>nothing to do with rcds

But a fair bit to do with cable colour codes, which is what we are currently arguing.

you’ll find that earthing wires can also be purple when it comes to telecommunications – functional earthing

functional earthing wires don’t need to be green yellow

FAQ 008/2009: AS/NZS 3000:2007—CLAUSE 6.3.4 and CLAUSE 7.5
6.3.4 SWIMMING POOLS, PADDLING POOLS AND SPA POOLS OR TUBS – Selection and installation of
electrical equipment
7.5 EXTRA-LOW VOLTAGE ELECTRICAL INSTALLATIONS
Question 008/2009. May the power supply for electrical equipment, such as luminaires, intended for installation
in Zone 0 be designed for an output voltage above the nominal voltage to allow for a voltage drop in the cables
between the power supply and the equipment?
Answer. No. The power supply is to be designed for the nominal voltage of 12 V a.c. or 30 V ripple-free d.c.
———————————————————————————————————————————————————————————————-

i liked this in the FAQs

looks as if some bright spark wanted to run long cables from the transformer to the pool lights and suddenly realised that the lights weren’t as bright and wanted to bump up the voltage

>functional earthing wires don’t need to be green yellow

As my last post pointed out, they are not allowed to be yellow or green, as they are not a PE.

you’ve forced me to do this now

sibeen said:

>newer types of RCDs actually have a wire that connects to the earth bar

No. They have a lead which is connected to the Neutral.

yes they do this is a functional earth

Stealth said:

in normal sutations the imbalance of current is measured by measuring neutral and active currents BUT this device relies on the neutral line side to be working properly
——————
No, it measures that the L-N is balanced regardless of the neutral side working properly.

in the event of the neutral being knocked out at the POS (the broken neutral scenario), the brain of the rcd is no longer powered and cannot work. the earth connection from the RCD to the earth bar allows the brain to know when a fault has occurred because the RCDs return path of current through earth keeps power to the RCDs brain
——————
There is no ‘brain’ as such. The system works by an unbalanced L-N creating power to trip a relay.

not according to the AS FAQ

FAQ 007/2009: AS/NZS 3000:2007—CLAUSE 3.8 & TABLE 3.4 & CLAUSE 5.2.2
3.8 IDENTIFICATION
TABLE 3.4 CONDUCTOR COLOURS FOR INSTALLATION WIRING
5.2.2 EARTHING FUNCTIONS—Functional earthing (FE)
Question 007/2009. If an RCD is provided with a functional earthing conductor (typically coloured white or
pink), may this conductor be connected to an earthing terminal/connection or bar?
Answer. Yes. The purpose of the conductor is to allow a return path for the electronic circuit, if the neutral is
disconnected, to ensure the RCD still operates correctly. The conductor does not perform a protective earth
function.
———————————————————————————————————————————————————————————————-

i never like having to do this

Wookie, what you are talking about, an RCD with a FE connection, is rarely seen in Australia. I’ve never come across one in my life, and I do see quite a few installations.

In this case the RCD does require an earth connection to operate, hence the functional earth (FE) designation. The vast, vast, vast majority of RCDs used in Australia use an active and a neutral connection and no other.

I’m not surprised by the FAQ 007/2009 as I’d be fairly certain that the writers of AS300 hadn’t even thought about the scenario where a three wire RCD was used on a single phase system, hence the clarification that they needed to issue.

sibeen said:

Wookie, what you are talking about, an RCD with a FE connection, is rarely seen in Australia. I’ve never come across one in my life, and I do see quite a few installations.

In this case the RCD does require an earth connection to operate, hence the functional earth (FE) designation. The vast, vast, vast majority of RCDs used in Australia use an active and a neutral connection and no other.

I’m not surprised by the FAQ 007/2009 as I’d be fairly certain that the writers of AS300 hadn’t even thought about the scenario where a three wire RCD was used on a single phase system, hence the clarification that they needed to issue.

the only place i ever saw one was in some library near cairns

wookiemeister said:

sibeen said:

Wookie, what you are talking about, an RCD with a FE connection, is rarely seen in Australia. I’ve never come across one in my life, and I do see quite a few installations.

In this case the RCD does require an earth connection to operate, hence the functional earth (FE) designation. The vast, vast, vast majority of RCDs used in Australia use an active and a neutral connection and no other.

I’m not surprised by the FAQ 007/2009 as I’d be fairly certain that the writers of AS300 hadn’t even thought about the scenario where a three wire RCD was used on a single phase system, hence the clarification that they needed to issue.

the only place i ever saw one was in some library near cairns

and there was somehting weird going on with the testing of the rcd

what was happening was that if we tried to test the rcd at the mainswitchboard then the rcd wouldn’t trip (or wouldn’t trip in any reasonable time), if you then found a socket outlet away from the MSB and performed the test there the rcd would trip in the right time.

i felt that there was some problem being created by the new type of rcd, either way we just tested at the socket outlets and left.

It’s hard to say what is the safe upper limit of voltage to run through your body. It depends on the path of the current and how well you have connected yourself.

Around 20 mA can paralyse your respiratory muscles and stop breathing.

I found these quotes from a similar discussion -

“I heard somewhere that low DC voltages that you may not notice can do electrolysis damage to cells. Supposedly, a person was killed while working on a vehicle with a 24 volt battery and somehow managed to get pinned with part of his body in contact with one of the terminals and another to the body (ground) of the vehicle. He was trapped that way for a while (hours?) and died later due to the damage to his cells from the current.”

“In the electrical engineer safety discussions, a “nightmare” scenario was something like, “A technician is working on a piece of low voltage electronic equipment. The equipment has energized components with sharp edges, for instance voltage test pins. The technician slips and manages to spear a finger on each hand with a pin and pierce the skin. What’s a safe voltage level here?” The answer was that there probably was no safe level.”

http://www.candlepowerforums.com/vb/showthread.php?261353-When-does-DC-voltage-become-dangerous

Ian said:

It’s hard to say what is the safe upper limit of voltage to run through your body. It depends on the path of the current and how well you have connected yourself.

Around 20 mA can paralyse your respiratory muscles and stop breathing.

I found these quotes from a similar discussion -

“I heard somewhere that low DC voltages that you may not notice can do electrolysis damage to cells. Supposedly, a person was killed while working on a vehicle with a 24 volt battery and somehow managed to get pinned with part of his body in contact with one of the terminals and another to the body (ground) of the vehicle. He was trapped that way for a while (hours?) and died later due to the damage to his cells from the current.”

“In the electrical engineer safety discussions, a “nightmare” scenario was something like, “A technician is working on a piece of low voltage electronic equipment. The equipment has energized components with sharp edges, for instance voltage test pins. The technician slips and manages to spear a finger on each hand with a pin and pierce the skin. What’s a safe voltage level here?” The answer was that there probably was no safe level.”

http://www.candlepowerforums.com/vb/showthread.php?261353-When-does-DC-voltage-become-dangerous

i have had this argument with martin smith of sssf about this

if you are highly conductive then even extra low voltage (up to 50VAC) will do you damage, brooke hanson was knocked unconcious by 14v i think.

if the killing factor is amps not volts then even low voltage can do damage

you should regard all voltages as dangerous, if you do this then you’ll take precautions to minimise the risk

another problem with the know it all types is that they have the tendency to believe everything they have read from one source of information and then regard themselves as a guru on various matters.

for example, the resistance in a multimeter should “protect” you from getting a zap if you have one probe touching 240VAC and one probe touching your finger 9when the multimeter is set on volts). someone was telling me about how he was testing with one probe on a live contact and the other probe was floating around in his hand, he decided to scratch his head with the free probe and got zap to the head.

Ian said:

It’s hard to say what is the safe upper limit of voltage to run through your body

Should of course be: voltage across your body
.

wookiemeister said:

another problem with the know it all types is that they have the tendency to believe everything they have read from one source of information and then regard themselves as a guru on various matters.

Well, we could go on bagging out MS all night.. but he doesn’t come here..

Ian said:

Ian said:

It’s hard to say what is the safe upper limit of voltage to run through your body

Should of course be: voltage across your body
.

wookiemeister said:

another problem with the know it all types is that they have the tendency to believe everything they have read from one source of information and then regard themselves as a guru on various matters.

Well, we could go on bagging out MS all night.. but he doesn’t come here..

moi?

Well, we could go on bagging out MS all night.. but he doesn’t come here..

moi?

non

from memory anything beyond 9/10 mA will do you some damage

the other factor in damage to the body is time

the longer you are exposed the worse the damage

if you were exposed to 1 ma current flowing through you that is survivable, but what if you were hooked up for a while??

theres a table somewhere that explores this notion about exposure and time

wookiemeister said:

hello

remember this one from the sssf??

martin smith was adamant that low voltages couldn’t cause injury regardless of all reason and explanation on a science forum i couldn’t convince anyone that low voltages can cause injury.

Actually that is not what I said. Not even close. I said it would be extremely rare for very low voltages (around 12v) to cause death. I said V=Iz always holds. So the only way to get a high enough I with a low V is to have a low Z. I specifically said dry skin tends to have a high enough z to prevent shocks from low voltages. So it is fairly safe to touch your car battery with dry hands.

Being wet, having probes go through the skin etc, are all means by which the z can be reduced to get a high enough I for damage.

However in General low voltages well below 50v are rarely fatal.

The objection I have is when people say “volts don’t kill current does”. Well volts and current are proportional to each other, by z. So you need all three in the right combination to get damage.