Hardly warrants it’s own thread but if AC is working in both directions why is there still a positive and negative terminal?

There isn’t. There is a live and neutral terminal (or three lives and a neutral, or three lives and no neutral). The live is the source of the voltage/current both ositive and negative and the neytral is the return path.

Stealth said:

There isn’t. There is a live and neutral terminal (or three lives and a neutral, or three lives and no neutral). The live is the source of the voltage/current both ositive and negative and the neytral is the return path.

easy. ta

For the purposed of some consistency in the wiring, and importantly and not unrelated the earth and neutral system are connected together at the house or whatever and through the distribution sytem, essentially keeping the neutral “neutral” relative to the ground mass and other earthed/grounded bodies.

It’s nice to know when you go to replace a light fitting or whatever that the neutral is neutral, though for reasons demonstrated here it’s not a good idea to assume with great certainty it will be, so it pays to treat it as if it possibly may not be.

:) there you, brought down to earth and neutralized.

And again not unrelated, it’s nice to know the switched are in the active line, not in the neutral, as of the latter case the wiring with the switch off will be live right from the power source through the switched appliance and out the other side all the way to the switch, which still works just it’s in the wrong colour wire and more wiring and appliances have power going through them than required, even when turned off.

Yeah, wot ‘e said.

The MEN system we use in Australia requires one of the wires to be tied to earth potential. (So it has “Neutral” potential to earth)

transition said:

And again not unrelated, it’s nice to know the switched are in the active line, not in the neutral, as of the latter case the wiring with the switch off will be live right from the power source through the switched appliance and out the other side all the way to the switch, which still works just it’s in the wrong colour wire and more wiring and appliances have power going through them than required, even when turned off.

That’s why caravan and demountable switches often need to switch both lines.

>>That’s why caravan and demountable switches often need to switch both lines”

You never know what you’ve got at the end of an extension cord, the best you can hope for is the same mistake was made at both ends :)

transition said:

>>That’s why caravan and demountable switches often need to switch both lines”

You never know what you’ve got at the end of an extension cord, the best you can hope for is the same mistake was made at both ends :)

The best thing to happen to extension leads is cheap Chinese manufacturing making it cheaper to buy a new lead than to repair an old one.

Riff-in-Thyme said:

Hardly warrants it’s own thread but if AC is working in both directions why is there still a positive and negative terminal?

there is no positive BUT there is something called ACTIVE

there is no neutral BUT there is something called NEUTRAL

the main difference between them is this

the NEUTRAL is referenced to EARTH that is in practical terms – if you looked in your main switchboard in your house you would see a green/yellow wire going from the NEUTRAL bar to the EARTH bar.

the NEUTRAL wire is the wire connected to EARTH

the ACTIVE isn’t

if you then take a voltmeter and test the pins on your socket outlets you’ll discover something very interesting

the voltage between ACTIVE and NEUTRAL is 240V

the voltage between ACTIVE and EARTH is 240V

but the voltage between NEUTRAL and EARTH is 0V

this is because the NEUTRAL and EARTH are connected and because of this there is no potential difference / voltage difference/ electrical pressure difference between them – unlike the other two tests

wookiemeister said:

if you then take a voltmeter and test the pins on your socket outlets you’ll discover something very interesting

the voltage between ACTIVE and NEUTRAL is 240V

the voltage between ACTIVE and EARTH is 240V

but the voltage between NEUTRAL and EARTH is 0V

And for bonus points, measure the voltage between the active in your power point and the active in your neighbour’s power point. (You’ll need a long extension lead)

Carmen_Sandiego said:

transition said:

>>That’s why caravan and demountable switches often need to switch both lines”

You never know what you’ve got at the end of an extension cord, the best you can hope for is the same mistake was made at both ends :)

The best thing to happen to extension leads is cheap Chinese manufacturing making it cheaper to buy a new lead than to repair an old one.

assuming they got the connections the right way round

it has happened before

non electricians/ less competent people tampering with extension leads causes problems

the brook hanson incident where she was zapped by 15VAC when stepping from a spa onto the floor was caused because there was an insulation breakdown combined with the fact that the extension lead powering the thing had a faulty/ missing earth

Carmen_Sandiego said:

wookiemeister said:

if you then take a voltmeter and test the pins on your socket outlets you’ll discover something very interesting

the voltage between ACTIVE and NEUTRAL is 240V

the voltage between ACTIVE and EARTH is 240V

but the voltage between NEUTRAL and EARTH is 0V

And for bonus points, measure the voltage between the active in your power point and the active in your neighbour’s power point. (You’ll need a long extension lead)

it depends what phase you and your neighbour are connected to

assuming you are connected to single phase power

if you are connected to phase one/ red

he is connected to phase two/ white then you’ll measure 415VAC

if he is on the same phase 0VAC

if you are connected to 3 phase you can measure the 415VAC in your own house

in theory the power authority staggers the phase distribution but many times this isn’t done and you get more current flowing down A phase/ B phase or C phase

wookiemeister said:

Carmen_Sandiego said:

The best thing to happen to extension leads is cheap Chinese manufacturing making it cheaper to buy a new lead than to repair an old one.

assuming they got the connections the right way round

it has happened before

non electricians/ less competent people tampering with extension leads causes problems

the brook hanson incident where she was zapped by 15VAC when stepping from a spa onto the floor was caused because there was an insulation breakdown combined with the fact that the extension lead powering the thing had a faulty/ missing earth

I do not doubt cheap manufacturing has its problems, but nowadays incidents like that are isolated events rather than a weekly/monthly occurrence.

wookiemeister said:

Carmen_Sandiego said:

wookiemeister said:

if you then take a voltmeter and test the pins on your socket outlets you’ll discover something very interesting

the voltage between ACTIVE and NEUTRAL is 240V

the voltage between ACTIVE and EARTH is 240V

but the voltage between NEUTRAL and EARTH is 0V

And for bonus points, measure the voltage between the active in your power point and the active in your neighbour’s power point. (You’ll need a long extension lead)

it depends what phase you and your neighbour are connected to

assuming you are connected to single phase power

if you are connected to phase one/ red

he is connected to phase two/ white then you’ll measure 415VAC

if he is on the same phase 0VAC

if you are connected to 3 phase you can measure the 415VAC in your own house

in theory the power authority staggers the phase distribution but many times this isn’t done and you get more current flowing down A phase/ B phase or C phase

My father and his neighbour have a shared power point in the shed that runs the 3 phase welder

>>>but the voltage between NEUTRAL and EARTH is 0V

Nah, did that, and with the bar heater going there was a difference of a few volts.

Should I call my electrician?

stumpy_seahorse said:

wookiemeister said:

Carmen_Sandiego said:

And for bonus points, measure the voltage between the active in your power point and the active in your neighbour’s power point. (You’ll need a long extension lead)

it depends what phase you and your neighbour are connected to

assuming you are connected to single phase power

if you are connected to phase one/ red

he is connected to phase two/ white then you’ll measure 415VAC

if he is on the same phase 0VAC

if you are connected to 3 phase you can measure the 415VAC in your own house

in theory the power authority staggers the phase distribution but many times this isn’t done and you get more current flowing down A phase/ B phase or C phase

My father and his neighbour have a shared power point in the shed that runs the 3 phase welder

if they are both hooking up their 3 phase system to the same powerpoint that sounds illegal

that must be chewing through some serious power

transition said:

>>>but the voltage between NEUTRAL and EARTH is 0V

Nah, did that, and with the bar heater going there was a difference of a few volts.

Should I call my electrician?

you could call the power authority if you wanted

its common to see a few volts difference it could be a slightly high resistance earth/ neutral I think

I haven’t done any electrical stuff for a while now. they don’t teach these kinds of things at tafe anymore anyway. most electricians are cable pullers now.

i’d need to do the contractors course to pick over the brains of the teachers now

generally theres very few people that actually know how the power system is connected up. there is a tafe course that covers it but its not available unless you are in major cities and there wouldn’t be much point me doing it anyway – secret black magic knowledge tha no one must know about

wookiemeister said:

stumpy_seahorse said:

wookiemeister said:

it depends what phase you and your neighbour are connected to

assuming you are connected to single phase power

if you are connected to phase one/ red

he is connected to phase two/ white then you’ll measure 415VAC

if he is on the same phase 0VAC

if you are connected to 3 phase you can measure the 415VAC in your own house

in theory the power authority staggers the phase distribution but many times this isn’t done and you get more current flowing down A phase/ B phase or C phase

My father and his neighbour have a shared power point in the shed that runs the 3 phase welder

if they are both hooking up their 3 phase system to the same powerpoint that sounds illegal

that must be chewing through some serious power

each house is on a separate phase, so they have 1 power point wired up from both power sources to run the 3-phase.
(it’s been there for about 30 years.. just haven’t been caught :)

wookiemeister said:

it depends what phase you and your neighbour are connected to

They usually stagger the phase distribution up the street, so there is not a very big chance you are on the same phase.

For those playing at home:

There are three “Actives” running along your street. (That’s why there are so many wires on the power poles)

The generator has three windings spaced around it, and each gives a “peak” voltage at a diferent point of the generator’s rotation – like this:

The magic of electricity means that the voltage measured between any two different “actives” is 415v in Australia.

Carmen_Sandiego said:

wookiemeister said:

Carmen_Sandiego said:

The best thing to happen to extension leads is cheap Chinese manufacturing making it cheaper to buy a new lead than to repair an old one.

assuming they got the connections the right way round

it has happened before

non electricians/ less competent people tampering with extension leads causes problems

the brook hanson incident where she was zapped by 15VAC when stepping from a spa onto the floor was caused because there was an insulation breakdown combined with the fact that the extension lead powering the thing had a faulty/ missing earth

I do not doubt cheap manufacturing has its problems, but nowadays incidents like that are isolated events rather than a weekly/monthly occurrence.

I think it was someone who had used an extension lead without checking it

stumpy_seahorse said:

My father and his neighbour have a shared power point in the shed that runs the 3 phase welder

:O

That is really… um…

Runs away screaming

>>>its common to see a few volts difference it could be a slightly high resistance earth/ neutral I think”

It’s OK now, I fixed it by tieing the neutral and earth together in the bar heater, which gave me some volts back, the E and N have exactly zero volts between them, the heater is generating tiny bit of extra heat .

So all good.

Is the bar heater now less safe do you think?

transition said:

>>>but the voltage between NEUTRAL and EARTH is 0V

Nah, did that, and with the bar heater going there was a difference of a few volts.

Should I call my electrician?

That is not abnormal for high current items.

Carmen_Sandiego said:

wookiemeister said:

it depends what phase you and your neighbour are connected to

They usually stagger the phase distribution up the street, so there is not a very big chance you are on the same phase.

For those playing at home:

There are three “Actives” running along your street. (That’s why there are so many wires on the power poles)

The generator has three windings spaced around it, and each gives a “peak” voltage at a diferent point of the generator’s rotation – like this:

The magic of electricity means that the voltage measured between any two different “actives” is 415v in Australia.

my experience of working for a power authority is that there is a very good chance of not being staggered

old power systems mean that the red white blue set up isn’t always red white blue

some character a few years ago will have set it up red , blue, white or blue red white, this means its very important to make sure you put the phases back in the same way you found them or you’ll cause headaches with three phase motors going backwards in the neighbourhood

the first rule for working on any piece of equipment you don’t strictly know very well is to work slowly and methodically asking yourself what you are doing and why and what could have gone wrong down the line , it will save your life and someone else’s life too.

make sure you know what order the phases were in the first place before connection, it could be important

in the private sector you have to work on things you don’t know much about

Did you hear about the electrician who kept chewing on a piece of wire?

It was just a phase he was going through.

transition said:

>>>its common to see a few volts difference it could be a slightly high resistance earth/ neutral I think”

It’s OK now, I fixed it by tieing the neutral and earth together in the bar heater, which gave me some volts back, the E and N have exactly zero volts between them, the heater is generating tiny bit of extra heat .

So all good.

Is the bar heater now less safe do you think?

unless you know what you are doing I think that its a bad idea

its not solved the problem its simply made the problem less measureable at that point of testing I think

morrie said:

Did you hear about the electrician who kept chewing on a piece of wire?

It was just a phase he was going through.

(polite applause)

party_pants said:

morrie said:

Did you hear about the electrician who kept chewing on a piece of wire?

It was just a phase he was going through.

(polite applause)

golf clap

>>>its not solved the problem its simply made the problem less measureable at that point of testing I think”

I don’t have an RCD fitted, if I fit one will it trip it with the E and N connected in the appliaance?

this is why its so important to follow the standards

when you deviate from a agreed way of working and installation you’ll get problems

don’t adapt any machinery unless you know what you are doing

I condemned a pile of machinery that had been laying around at the powerstation – the didn’t like it

one section had all the power points connected with active and neutral transposed, I repaired this fault but was generally hated by the union boss because so much was wrong and I was finding it.

transition said:

>>>its not solved the problem its simply made the problem less measureable at that point of testing I think”

I don’t have an RCD fitted, if I fit one will it trip it with the E and N connected in the appliaance?

if there is an imbalance between active and neutral return currents then yes

some of that current that should be flowing back through the neutral is returning through earth

transition said:

Is the bar heater now less safe do you think?

Yes. Undo what you just did and put it back to normal.

at another place I discovered that the lock out tag out system didn’t work, the cabinet could accessed whilst you were working on it, it was only assumed that the cabinet was locked and the isolator/switch couldn’t be accessed.

they didn’t like that one either

the supervisor of that place didn’t like me so much because I was going through and discovering basic glaring errors that could kill people

I walked into this bathroom to discover after investigation that he had placed a socket outlet at the right height for normal circumstances but considering water normally sat a few cms from a surface when the hand basin was being used and the water pooled under the outlet it wasn’t appropriate.

stupid bastard, after he came after me once too many times I stuck it to him good. to my knowledge he no longer works in the electrical industry

>>>>if there is an imbalance between active and neutral return currents then yes..”

So, if my GPO circuit has just one appliance on it, being a 2.4KW heater, on the end of 10metres of 2.5mm power cable, and I connect the earth and neutral together in the appliance, and fit an RCD at the switchboard its running from, will it trip the RCD? All the wiring etc is in proper working condition.

i would imagine onty was having a lend.

transition said:

>>>its not solved the problem its simply made the problem less measureable at that point of testing I think”

I don’t have an RCD fitted, if I fit one will it trip it with the E and N connected in the appliaance?

Yes.

>>>Yes. Undo what you just did and put it back to normal.

Oh, and I was having so much fun ;).

no place in Australia is wired to the AS3000

in newer places the problems are designed into the installation

in older places degradation and new laws make most places problematic.

they are STILL laying cables over the roof beams in an accessible roof cavity in every new house

transition said:

>>>>if there is an imbalance between active and neutral return currents then yes..”

So, if my GPO circuit has just one appliance on it, being a 2.4KW heater, on the end of 10metres of 2.5mm power cable, and I connect the earth and neutral together in the appliance, and fit an RCD at the switchboard its running from, will it trip the RCD? All the wiring etc is in proper working condition.

yes

if your earth wire in your appliance and house wiring is working properly

the neutral and earth are now parallel paths for current to flow and will cause an rcd to trip

>>>the neutral and earth are now parallel paths for current to flow and will cause an rcd to trip.

What if the heater is not turned on, but E&N are connected together internally, with an RCD fitted to that circuit, and nothing else is turned on on any other circuit connected to that switchboard, when the HWS on that switchboard turns on which draws a similar load but doesn’t have an RCD on its circuit, will the HWS trip the RCD on the power circuit supplying the heater, even though the heater is turned off?

heater = bar heater.

HWS = hot water service.

transition said:

>>>the neutral and earth are now parallel paths for current to flow and will cause an rcd to trip.

What if the heater is not turned on, but E&N are connected together internally, with an RCD fitted to that circuit, and nothing else is turned on on any other circuit connected to that switchboard, when the HWS on that switchboard turns on which draws a similar load but doesn’t have an RCD on its circuit, will the HWS trip the RCD on the power circuit supplying the heater, even though the heater is turned off?

The heater will trip the RCD when it is turned on, but apart from that it should not affect the operation of anything else. I suspect, however, it will trip an ELCB even when off)

BTW, like a lot of things electrical, just because it works doesn’t mean it is safe. In this instance (E+N joined in heater, no ELCB/RCD) it will work, and probably won’t kill you. However, if the Neutral ever breaks or becomes open circuit (or the resistance increases) then the heater case could kill you if you touched it. (Similar has happened before)

>>>BTW, like a lot of things electrical, just because it works doesn’t mean it is safe. In this instance (E+N joined in heater, no ELCB/RCD) it will work, and probably won’t kill you. However, if the Neutral ever breaks or becomes open circuit (or the resistance increases) then the heater case could kill you if you touched it. (Similar has happened before)”

Worst I’ve heard, related by an x-utility chap, as I recall it, was a case of the a house earth-stake connection being broken and the neutral back to the SWER transformer also detaching.

transition said:

>>>BTW, like a lot of things electrical, just because it works doesn’t mean it is safe. In this instance (E+N joined in heater, no ELCB/RCD) it will work, and probably won’t kill you. However, if the Neutral ever breaks or becomes open circuit (or the resistance increases) then the heater case could kill you if you touched it. (Similar has happened before)”

Worst I’ve heard, related by an x-utility chap, as I recall it, was a case of the a house earth-stake connection being broken and the neutral back to the SWER transformer also detaching.

They overhauled the electrical licencing laws in QLD after a series of problems and coincidences resulted in a young girl getting electrocuted.. Plumbers replacing gal pipe with poly, corroded earth wiring + high resistance neutral connection + mum turning on stove as girl taking a drink from garden tap = dead girl.

The heater will trip the RCD when it is turned on,
—-
Yes

but apart from that it should not affect the operation of anything else. —- True I suspect, however, it will trip an ELCB even when off) —- It shouldn’t trip when off. The current is perfectly balanced between the active and neutral, 0A on both even with a parrallel 0A going down the earth wire.

Stealth said:

The heater will trip the RCD when it is turned on,
—-
Yes

but apart from that it should not affect the operation of anything else. —- True I suspect, however, it will trip an ELCB even when off) —- It shouldn’t trip when off. The current is perfectly balanced between the active and neutral, 0A on both even with a parrallel 0A going down the earth wire.

You can trip an ELCB by touching a neutral with no current flowing through it.

In the case of a 30mA RCD, for example, you don’t need much voltage into a short circuit to get that and trip. Meaning a small voltage between E&N , which in the case of no loading on the switchboard wouldn’t maybe happen, but enough loading anywhere can create a small PD. The loading of any circuit will tend to pull the neutral bus upward, which somewhere is linked via MEN to earth, but the building earthing system via earth stake or whatever adds and results in a lower combined parallel impedance, so as any load pulls the neutral bus upward some current starts to flow via the earthing system, which doesn’t ordinarily matter because the RCD is after that . It could be seen that in the case E&N were connected in an appliance, that this is an unwanted E-N link parallel to the MEN , so the unwanted E-N short starts to carry current as the N-bus is pulled up by loading anywhere. Something like that maybe.

It’s maybe important to distinguish between RCDs and ELCBs. The former operate on current difference between N&A, the latter I think simply breaks the circuit based on the current in some earth circuit, or bunch of circuits. The latter have been around for a long time, perhaps near a century.

An RCD measures, via a balanced toroidal transformer,the difference between the active and neutral currents. If this current difference exceeds 30 mA, in the case of a residential RCD, then it will trip. There doesn’t have to be a short circuit involved, and a PD has no influence on the device.

years ago in electronics today i think it was there were schematics to build your own rcd. this is back in the early 70s.

Boris said:

years ago in electronics today i think it was there were schematics to build your own rcd. this is back in the early 70s.

The electrics is easy. The mechanics to make it trip in a poofteenth of a second is the difficult bit.

Australia generally uses, although not always, what is known as a TN-S earthing system, although more correctly a TNC-S system.

T = Terra = Earth
N = neutral
C = Combined
S = Seperated.

So we have the TN combined ( the MEN point) the TNC component and then they are separated, the S component.

This requires that the Earth and Neutral are combined at one point only within infrastructure and thereafter need to be separated.

In industrial and large plant it does become a fair bit more complex and this is what keeps sibeen generally employed :)

Carmen_Sandiego said:

transition said:

>>>BTW, like a lot of things electrical, just because it works doesn’t mean it is safe. In this instance (E+N joined in heater, no ELCB/RCD) it will work, and probably won’t kill you. However, if the Neutral ever breaks or becomes open circuit (or the resistance increases) then the heater case could kill you if you touched it. (Similar has happened before)”

Worst I’ve heard, related by an x-utility chap, as I recall it, was a case of the a house earth-stake connection being broken and the neutral back to the SWER transformer also detaching.

They overhauled the electrical licencing laws in QLD after a series of problems and coincidences resulted in a young girl getting electrocuted.. Plumbers replacing gal pipe with poly, corroded earth wiring + high resistance neutral connection + mum turning on stove as girl taking a drink from garden tap = dead girl.

in theory equipotential bonding with an appropriate conductor should stop this

as far as i’m aware any changes to the electrical system of a house means that the electrical installation needs to conform to the as3000. they used to have an additions and changes clause in the old as3000. the new as3000 it seems to have disappeared..

they need a rule where the electrician can hand over a sheet signed by himself to the owner of a residence that problems have been discovered, the onus of repair should be placed on the informed owner, the electrician should need proof of handing it to the owner because they’d only refuse to accept it or claim they’d never seen it. a copy remains with the electrician only. people don’t like being grassed up to the power authority.

wookiemeister said:

in theory equipotential bonding with an appropriate conductor should stop this

as far as i’m aware any changes to the electrical system of a house means that the electrical installation needs to conform to the as3000. they used to have an additions and changes clause in the old as3000. the new as3000 it seems to have disappeared..

they need a rule where the electrician can hand over a sheet signed by himself to the owner of a residence that problems have been discovered, the onus of repair should be placed on the informed owner, the electrician should need proof of handing it to the owner because they’d only refuse to accept it or claim they’d never seen it. a copy remains with the electrician only. people don’t like being grassed up to the power authority.

In actuality, that only works for new houses. Older houses that have “equipotential bonding” with a suitable conductor such as the water mains that have sections of the older gal pipes replaced with poly pipes may have earthing issues. That is why an earth stake is required nowadays.

BTW, the new AS3000 is AS3001.

Carmen_Sandiego said:

wookiemeister said:

in theory equipotential bonding with an appropriate conductor should stop this

as far as i’m aware any changes to the electrical system of a house means that the electrical installation needs to conform to the as3000. they used to have an additions and changes clause in the old as3000. the new as3000 it seems to have disappeared..

they need a rule where the electrician can hand over a sheet signed by himself to the owner of a residence that problems have been discovered, the onus of repair should be placed on the informed owner, the electrician should need proof of handing it to the owner because they’d only refuse to accept it or claim they’d never seen it. a copy remains with the electrician only. people don’t like being grassed up to the power authority.

In actuality, that only works for new houses. Older houses that have “equipotential bonding” with a suitable conductor such as the water mains that have sections of the older gal pipes replaced with poly pipes may have earthing issues. That is why an earth stake is required nowadays.

BTW, the new AS3000 is AS3001.

in this thread its assumed that we are talking hardwiring in normal residence, the as3001 is about ….

Electrical installations – Transportable structures and vehicles including their site supplies

each type of installation would have its own ideosyncracies, its why you I suspect you can’t just merrily wire up a donga in the same way as a house, there would rules about how the electrical system in a donga is to be set out

the as3000 is THE book to start from and it then refers to other Australian standards in the as3000 (no doubt the as3001)
The as 3001 is NOT the new AS3000 – I’ve just googled it http://infostore.saiglobal.com/store/details.aspx?ProductID=1085701
I would find it very strange that they had changed the number (if not stupid).

older houses don’t have water pipes as the equipotential bonding they ARE the earth!!! I’ve argued this with a technician (who was quietly had a word with to tell him I was right)

equipotential bonding is a bit of cable to a bit of metal that is not part of the electrical system per se

you have equipotential bonding TO the water pipes

TO the reinforced steel of a swimming pool and to the metallic gate, fence of the pool area

the frame of the main switch board has to be earthed but I don’t think they define it as such (though I could be wrong) either way you must have a conductor appropriate to the size of the ACTIVE feeding the electrical installation.

>BTW, the new AS3000 is AS3001.

DO, different standards.

3001 is only for mobiles.

>>>In actuality, that only works for new houses. Older houses that have “equipotential bonding” with a suitable conductor such as the water mains that have sections of the older gal pipes replaced with poly pipes may have earthing issues. That is why an earth stake is required nowadays.”

Just guessing, but reckon in the early days the plumbing system was often the main local earthing system, probably not really what you’d call an ‘equi’-bonding system’, not sure when that term arrived, maybe it is an old term, I can’t say.

More would have thought the equi’-bonding the modern way was not intended to assist the main local earthing system, more it is to keep the plumbing tied down by the main earthing system? Reduces tingles and in the case of serious fault and inadequate say HWS earthing it reduces chances of plumbing being pulled up too much above ground/earth and the plumbing becoming a conductor between different parts of a building or from say one unit to the next, or one floor to the next. Half inch copper pipe makes for a nice uninsulated conductor, probably has equiv’ x-sectional area as, guessing maybe 10mm-16mm?

There’s certain requirements too of the earthing wires sizes etc and keeping them unbroken and to do with where they are places on plumbing.

transition said:

>>>In actuality, that only works for new houses. Older houses that have “equipotential bonding” with a suitable conductor such as the water mains that have sections of the older gal pipes replaced with poly pipes may have earthing issues. That is why an earth stake is required nowadays.”

Just guessing, but reckon in the early days the plumbing system was often the main local earthing system, probably not really what you’d call an ‘equi’-bonding system’, not sure when that term arrived, maybe it is an old term, I can’t say.

More would have thought the equi’-bonding the modern way was not intended to assist the main local earthing system, more it is to keep the plumbing tied down by the main earthing system? Reduces tingles and in the case of serious fault and inadequate say HWS earthing it reduces chances of plumbing being pulled up too much above ground/earth and the plumbing becoming a conductor between different parts of a building or from say one unit to the next, or one floor to the next. Half inch copper pipe makes for a nice uninsulated conductor, probably has equiv’ x-sectional area as, guessing maybe 10mm-16mm?

There’s certain requirements too of the earthing wires sizes etc and keeping them unbroken and to do with where they are places on plumbing.

the min size for equipotential bonding is 4mm cable BUT this will change based on the size of the incoming active ie it will get bigger

the other thing is this

it should be a connection that is appropriate and be protected from the elements to stop high resistance happening

normally you’ll have a special connector for outside that is then painted or protected in some appropriate way AND if need be protected by physical mechanical damage. you would certainly do this for the MEC connection

one pet hate of mine is seeing the earth electrode (earth stake) set into concrete – this is illegal, they all need to have earth around their base

its a shame they got rid of the installation inspectors, I did some time with them and loved it

nothing is more satisfying than opening a main switch board looking at it and then going through the problems

NO incoming cables not surrounded by fire protection

NO cable to main switchboard facing up into towards the direction of rain

NO screw to open board too close to edge and meter to allow access

NO board too high

NO 100 protective earth twizzled together and drizzled with a bit of solder

NO new circuit installed, no earth stake installed (old system relied on being connected to water pipes)

Ths explains it well.

http://wiki.diyfaq.org.uk/index.php?title=Earthing_and_Bonding

>>The best thing to happen to extension leads is cheap Chinese manufacturing making it cheaper to buy a new lead than to repair an old one.

Don’t entirely agree with that.

I’ve got 40+ year old heavy duty cords that are going fine.

I find the Chinese jobs end up getting twisted and bendy because of the internal cables moving wrt the outer cover… even if I’m careful and storing them in big coils.

>>>There doesn’t have to be a short circuit involved, and a PD has no influence on the device”

Off chance that is a correction of something I said.

My point was to do with placing a short between E&N. Like for example you go to terminate a GPO circuit fed from a load centre on a new upper apartment, the cable is wired in at the board but breaker off, the board is live though, you chomp through the power cable to shorten it before terminating into the GPO, and it throws the RCD.

Point being the voltage difference between E&N caused by loading elsewhere may be quite small, but being a dead short with only the resistance of the wires back to the RCD etc, it’s not difficult to get 30mA difference between A and N, there being no current in A.

Sound about right, guessing you’d have bumped into it.

transition said:

>>>There doesn’t have to be a short circuit involved, and a PD has no influence on the device”

Off chance that is a correction of something I said.

My point was to do with placing a short between E&N. Like for example you go to terminate a GPO circuit fed from a load centre on a new upper apartment, the cable is wired in at the board but breaker off, the board is live though, you chomp through the power cable to shorten it before terminating into the GPO, and it throws the RCD.

Point being the voltage difference between E&N caused by loading elsewhere may be quite small, but being a dead short with only the resistance of the wires back to the RCD etc, it’s not difficult to get 30mA difference between A and N, there being no current in A.

Sound about right, guessing you’d have bumped into it.

You wouldn’t get any current on the N. From where you cut it, it goes out to the load and then back along the active to nothing, as the CB is disconnected. Effectively you have a piece of wire that you are adding a voltage to one en

… To one end, but as it is open circuit no current will flow.

(Stupid iPad cut me off)

>>>… To one end, but as it is open circuit no current will flow.

Think of the pliers across the E&N on a circuit on the sub as being parallel to the MEN elsewhere in the main board. Consider the neutral bar on the sub is pulled up a bit above earth proper by typical loading on circuits somewhere. Loading results in active wire voltage drop takes active down, and neutral line voltage drop takes neutral up relative to ground earth for my purposes here. A&N move toward each other – voltage drop is shared on A and N wires.

So the neutral bar is being pulled up a bit relative to ground. The earth wire back to the earth bar and MEN though doesn’t have any current in it (until I put the pliers across E-N), so has no drop, it’s unloaded so is at the same potential as ground-earth proper.

So on the GPO line coming off the sub on the new upper floor apartment, as per example, when I cut the cable and short E&N, current flows between E&N. Reason being E&N aren’t at exactly same potential at the sub. Why would they be?

The pliers across E&N result in a closed circuit between E&N, parallel to the MEN in the main board some distance away. Current flows around via N-E courtesy of the pliers and causes an imbalance the RCD senses.

Not sure it is this simple, but if the round trip resistance of twenty metres of 2.5mm cable were .288 Ohms (assuming earth wire same circ’ mils), then you only need .00576Volts difference between N&E at the sub to trip the 20mA RCD when you short with the pliers.

Doubtful it’s quite that simple, seems like a very low voltage difference. Probably roughly right, depends on other things perhaps like how solid the supply is to the sub, and where and the nature of the loads on the arrangement. .

New question: I have a small rc car. It has 3*1.5v AAA’s in the car and 2 of the same in the handset. Would fitting both with 9v batteries be at all likely to run too much current through any vital parts?

Riff-in-Thyme said:

New question: I have a small rc car. It has 3*1.5v AAA’s in the car and 2 of the same in the handset. Would fitting both with 9v batteries be at all likely to run too much current through any vital parts?

Not advisable. 9V instead of 4.5V and 3.0V make electric smoke come out.

Geoff D said:

Riff-in-Thyme said:

New question: I have a small rc car. It has 3*1.5v AAA’s in the car and 2 of the same in the handset. Would fitting both with 9v batteries be at all likely to run too much current through any vital parts?

Not advisable. 9V instead of 4.5V and 3.0V make electric smoke come out.

:( no fun. I though it would just make it more responsive and give it longer battery life

how’s biz Geoff?

Riff-in-Thyme said:

Geoff D said:

Riff-in-Thyme said:

New question: I have a small rc car. It has 3*1.5v AAA’s in the car and 2 of the same in the handset. Would fitting both with 9v batteries be at all likely to run too much current through any vital parts?

Not advisable. 9V instead of 4.5V and 3.0V make electric smoke come out.

:( no fun. I though it would just make it more responsive and give it longer battery life

how’s biz Geoff?

Increasing the voltage won’t help, get some better batteries – ones that have at least 2000 mAHs (lithium type batteries from memory).

Careful though, that link is actually for AAs with some bonus AAAs…

poikilotherm said:

Careful though, that link is actually for AAs with some bonus AAAs…

cheers

Riff-in-Thyme said:

how’s biz Geoff?

Not too flash at the moment.

poikilotherm said:

Riff-in-Thyme said:

Geoff D said:

Not advisable. 9V instead of 4.5V and 3.0V make electric smoke come out.

:( no fun. I though it would just make it more responsive and give it longer battery life

how’s biz Geoff?

Increasing the voltage won’t help, get some better batteries – ones that have at least 2000 mAHs (lithium type batteries from memory).

What if I included a resistor when installing the 9v battery?

Riff-in-Thyme said:

poikilotherm said:

Riff-in-Thyme said:

:( no fun. I though it would just make it more responsive and give it longer battery life

how’s biz Geoff?

Increasing the voltage won’t help, get some better batteries – ones that have at least 2000 mAHs (lithium type batteries from memory).

What if I included a resistor when installing the 9v battery?

FIIK.

Heart foundation’s calculator says 58-78 for me. I was quite fit when I was 60 kg. At the current weight loss of about 0.5 kg/week, getting back to 60 will take nearly forever…

Fred Wong. Sorry.

>>>What if I included a resistor when installing the 9v battery?

Load varies, which is part of the voltage divider, so wont hold up a stable voltage.

transition said:

>>>What if I included a resistor when installing the 9v battery?

Load varies, which is part of the voltage divider, so wont hold up a stable voltage.

Maybe I will simply have to install upgraded components

>>>Maybe I will simply have to install upgraded components.

Any voltage above what is required adds further losses, often, and certainly so in the case any series resistance is used. Simple voltage dividers when loading on them or some part of them vary substantially have terrible voltage regulation.

If the equip has onboard linear reg and nine volts doesn’t exceed its max input voltage, then the added power losses across the reg will be IxVdrop across the reg plus a little bit. Basically it’d waste some power, possibly send the reg into shutdown. 9Volt batteries don’t have much grunt anyway.

If the equipment has any passive protection, like a zener, the nine volt battery may ride up to that which wouldn’t be what you’d want.

Generally equipment such is built around the maximum voltage expected to be seen on the batteries fitted, there maximum terminal voltage, which with a plug in charger is the max open circuit voltage of the charger with variations on mains or whatever in the case unregulated or dynamic regulation. In the case the charger does not connect to the batteries in-situ then the maximum voltage expected is the voltage fully charged fresh off the charger, and anything below that.

I think the open circuit voltage of a new 9Volt batteries may be above 10Volts or higher, can’t recall now, depends on type of battery anyway.

In some cases, you know like all the ICs and components etc are rated well above the voltage it generally runs at, it may not matter.

But it pays to consider V/R = I, and IxV = W when considering upping your voltage, even for the most simple things.

When whatever is connected with a simple series resistor to drop the voltage, the equipment itself is part of a voltage divider, so a very light loading by the equipment will see its voltage go up, possibly up too much, and with heavy loading it will go way down, droop, like be all over the shop.