normal wiring scheme these days.

lomb

whats the normal set up wrt wiring a house for sockets. is one 32 amp electrical ring used upstairs and one downstairs with 2x twin and core 2.5mm coming back to the fuseboard or is it prefered to do 16amp daisy chain? if so what has the average semi d have? how many of these would be in a house.
what are the rules these days for rcds, are these fitted across everything or are the lighting circuits and water heater excluded?
how many 10 amp lighting circuits are there. are all lights run off one circuit?
thanks for the help, i am in the UK and want to get an idea of normal specs for the electrics in ireland.

McFearless

a normal 3 bed 2 story house has: a seperate ring main circuit for the kitchen sockets only, wired in 2.5 t+e.A radial circuit for all other sockets downstairs,agian 2.5 t+e, they should both be supplied with 20 amp mcb's,although a ring may need a 32amp?upstairs an a radial ran in 2.5 running on a 20amp mcb.
lights seperate upstairs and downstairs.I think the new etci rules say that all circuits should now have an rcd?lights can go on a 10amp mcb,assuming you dont go crazy,maybe have a different circuit for outdoor lighting...thats how id wire a house anyway,im pretty sure most of the wiring rules are the same in ireland as the uk.

Stoner

In my opinion here is a rough stab at it, narrow your questions down a bit if you want to know more about what your electrician should install

Well a kitchen will require 2 number radial circuits each with 20Amp MCBs

A socket cct for upstairs and another for downstairs would be minumum

32 amp for the cooker in 6sq T+E(might want a 20 Amp for a hob too)

40 Amp RCBO for an electric pump shower cabled in 10sq T+E

Ring circuits are on the way out and are not allowed in kitchens.

Immersion on the RCD

Keep socket circuits like garages and computer rooms on their own 20Amp RCBOs IMO

Lighting circuits are not as strict now as they were, you need to watch the loadings now and not so much the amount of fittings.

You'd want at least 3 10 Amp lighting circuits, one upstairs, one downstairs and one for security lights

Remeber an MCB for the intruder alarm panel and the doorbell traffo

Cable for an intruder alarm, doorbell and heating controls

Earthing roughly , clean 10 sq earth to the hotpress, gas boiler and earth rod

Kitchen sink should have a clean earth, cross bonding in the hotpress and all taps

willbur

as above , but 6amp mcb for the smoke and heat detectors ,placed in as manny rooms as pos

fishdog

I would agree pretty much with Stoner, but would add:

a kitchen will require 2 number radial circuits each with 20Amp MCBs

Correct, this is a regulation.

A socket cct for upstairs and another for downstairs would be minumum

I would agree, but bear in mind that a radial socket is only allowed to supply a maximum of 2 rooms (a hall or landing is not counted as a room).

40 Amp RCBO for an electric pump shower cabled in 10sq T+E

A 10mm sq is only required for showers in excess of 9kW or for long runs. Generally a 6mm sq is OK and much cheaper.

Ring circuits are on the way out and are not allowed in kitchens.

I would agree with Stoner on this, but RECI dont!! I had a "disagreement" with them about this.

Lighting circuits are not as strict now as they were, you need to watch the loadings now and not so much the amount of fittings.

Exactly. Lights have become much more energy efficient, so they draw much smaller loads now than in the past.

You'd want at least 3 10 Amp lighting circuits, one upstairs, one downstairs and one for security lights

The regulation is 2 circuits minimum, but I would agree with Stoner here too.

Cable for an intruder alarm, doorbell and heating controls

Think about heating controls. Zone valves, stats and multi channel time clocks give far better heating control and save you a lot of money on heating bills.

Wire the alarm back to some where that is not too easy for an intruder to find! I have seen cases where the intruder has simply smashed the panel before the alarm has contacted keyholders/monitoring station. Intruders only need to be delayed for a few minutes.
Note: It is not permitted to install alarm panels in a hot press!

clean 10 sq earth to the hotpress

This is not required if the house is plumbed in plastic piping.

lomb

Stoner wrote: »

In my opinion here is a rough stab at it, narrow your questions down a bit if you want to know more about what your electrician should install

Well a kitchen will require 2 number radial circuits each with 20Amp MCBs

A socket cct for upstairs and another for downstairs would be minumum

32 amp for the cooker in 6sq T+E(might want a 20 Amp for a hob too)

40 Amp RCBO for an electric pump shower cabled in 10sq T+E

Ring circuits are on the way out and are not allowed in kitchens.

Immersion on the RCD

Keep socket circuits like garages and computer rooms on their own 20Amp RCBOs IMO

Lighting circuits are not as strict now as they were, you need to watch the loadings now and not so much the amount of fittings.

You'd want at least 3 10 Amp lighting circuits, one upstairs, one downstairs and one for security lights

Remeber an MCB for the intruder alarm panel and the doorbell traffo

Cable for an intruder alarm, doorbell and heating controls

Earthing roughly , clean 10 sq earth to the hotpress, gas boiler and earth rod

Kitchen sink should have a clean earth, cross bonding in the hotpress and all taps

Would you take a seperate mcb for the intruder alarm and a seperate one for the doorbell? why not get them off a spur off a radial circuit? is there a limit to the number of MCBs on a residential CU?
the other thing was i want a 100 amp supply as im upgrading for heat pumps etc. would this mean seperate single core input cables from the meter rather than 16mm2 twin/core?

davelerave

lomb wrote: »

Would you take a seperate mcb for the intruder alarm and a seperate one for the doorbell? why not get them off a spur off a radial circuit? is there a limit to the number of MCBs on a residential CU?
the other thing was i want a 100 amp supply as im upgrading for heat pumps etc. would this mean seperate single core input cables from the meter rather than 16mm2 twin/core?

25mm pvc/pvc singles and 16sq earth to meter
cabinet for the 80amp supply.i dont think there is a 100 in single-phase wholecurrent anyway

lomb

davelerave wrote: »

25mm pvc/pvc singles and 16sq earth to meter
cabinet for the 80amp supply.i dont think there is a 100 in single-phase wholecurrent anyway

yes im sure you are right, on the web some uk domestic fuseboards main switch is 100 amps so persumed that the cables need to be capable of supplying 100 amps. i will be getting a commercial 15kv supply however i am sure it may exceeed that at some odd times(i think they charge you if you exceed it but however).

davelerave

lomb wrote: »

yes im sure you are right, on the web some uk domestic fuseboards main switch is 100 amps so persumed that the cables need to be capable of supplying 100 amps. i will be getting a commercial 15kv supply however i am sure it may exceeed that at some odd times(i think they charge you if you exceed it but however).

theres a 16kva common now for small heat pumps .normally dual-tarriff as well
but you need to check the load first anyway.the company supplying or fitting the heat pump would have a fair idea of the supply needed but you need the specs anyway for the application.

lomb

the load would be 30 amps maximum which is 7200kva
which gives me another 7800 to play with. occasionally im sure it would overshoot the 15kv supply.

davelerave

lomb wrote: »

the load would be 30 amps maximum which is 7200kva
which gives me another 7800 to play with. occasionally im sure it would overshoot the 15kv supply.

there would be a max starting current for the pump with the 16kva supply current.i have the details somewhere i'll check it

lomb

i think the max starting /running current would be 30 amps as they are soft start. i think you may be referring to a ground source heat pump, i am putting in some air source air conditioners with heat pumps and luckily they are soft start with built in dc inverters.

davelerave

sorry ya with soft start it should be ok .but work out the total loading .i'd recommend gas hob and mixer showers anyway.you may need to consider ct metering if you're upgrading the single-phase supply depending on the loading but it depends whats available as well

fishdog

i dont think there is a 100 in single-phase wholecurrent anyway

There is, that is the ESB install a 100A fuse for their larger single phase supply (16kVA). This will require 25mm sq. T+E and an 80A main switch fuse on the customer side.

theres a 16kva common now for small heat pumps .normally dual-tarriff as well

Yes dual tarrif would be much better for a heat pump.

sorry ya with soft start it should be ok . i think you may be referring to a ground source heat pump, i am putting in some air source air conditioners with heat pumps and luckily they are soft start with built in dc inverters.

Are you sure this heat pump has soft start?? I have never seen VSDs form a mains single phase supply. It sounds like a good idea though. Would you have a link to this?

Would you take a seperate mcb for the intruder alarm and a seperate one for the doorbell? why not get them off a spur off a radial circuit?

Form a security point of view it would be better to have such a supply take from a circuit that does not pass through an RCD. There is less chance of the supply being lost. In general fixed appliences (apart from water heaters) are not protected by an RCD, although you would be permitted to do as you suggested.

you may need to consider ct metering if you're upgrading the single-phase supply depending on the loading but it depends whats available as well

CT metering only happens for 3 phase supplies. Even then there is a popular whole current metering for 3 phase supplies in the region of 40kVA. If you require CT metering your bills will be through the roof.

davelerave

fishdog wrote: »

There is, that is the ESB install a 100A fuse for their larger single phase supply (16kVA). This will require 25mm sq. T+E and an 80A main switch fuse on the customer side.


Yes dual tarrif would be much better for a heat pump.


Are you sure this heat pump has soft start?? I have never seen VSDs form a mains single phase supply. It sounds like a good idea though. Would you have a link to this?


Form a security point of view it would be better to have such a supply take from a circuit that does not pass through an RCD. There is less chance of the supply being lost. In general fixed appliences (apart from water heaters) are not protected by an RCD, although you would be permitted to do as you suggested.


CT metering only happens for 3 phase supplies. Even then there is a popular whole current metering for 3 phase supplies in the region of 40kVA. If you require CT metering your bills will be through the roof.

ct. metering is available for single-phase supplies i've installed it with dual-tariff for commercial premises which applies here (the book shows it available for commercial or domestic but that would depend on site survey anyway) .read the esb handout for more info fishdog !
also the size of the esb cut-out doesn't determine the rating of the enhanced supply .its still an 80amp 16kva supply not a 100amp supply!
a 3-phase supply would be simpler but the pump will need to be 3-phase for this!
i'm not saying he should get ct-metering or anything else just sort out the loading first and the costs and whats available!

fishdog

ct. metering is available for single-phase supplies

That is interesting, I never saw them. I assume you are talking about ESB meters? I had heard that new meters were being introduced alright.

read the esb handout for more info fishdog !

I did, the problem is that was a few years ago when I was an electrical contractor. I guess things have changed. Have you got a link??

also the size of the esb cut-out doesn't determine the rating of the enhanced supply .its still an 80amp 16kva supply not a 100amp supply!

I know it dosent. But I did connect one with a 100A fuse in the ESB cut out. At the time (about 5 years ago) I was told this was standard practice.

a 3-phase supply would be simpler but the pump will need to be 3-phase for this!

True, but a 3 pahse pump would be a better and cheaper and more efficient pump.

i'm not saying he should get ct-metering or anything else just sort out the loading first and the costs and whats available!

I know.

Davy

fishdog wrote: »

That is interesting, I never saw them. I assume you are talking about ESB meters?

Ct meters can handle 3ph or single phase, its the same meter. Either 2 manufacturers Abb or vision afaik.

davelerave wrote: »

also the size of the esb cut-out doesn't determine the rating of the enhanced supply .its still an 80amp 16kva supply not a 100amp supply!

You mean 80A 12kva,, or enhanced supply of 100A 16kva. Cut out still same the regardless.

fishdog

You mean 80A 12kva,, or enhanced supply of 100A 16kva. Cut out still same the regardless

I know, that is what I said same cut out different fuse!
I never said the cut out was different

Ct meters can handle 3ph or single phase, its the same meter. Either 2 manufacturers Abb or vision afaik.

I agree, I have installed plenty of them!

What I have said is that it is news to me that the ESB are using CT metering on single phase supplies as davelerave has suggested.

I have only seen the ESB using CT metering for 3 phase supplies over a certain size.

davelerave

davton wrote: »

Ct meters can handle 3ph or single phase, its the same meter. Either 2 manufacturers Abb or vision afaik.




You mean 80A 12kva,, or enhanced supply of 100A 16kva. Cut out still same the regardless.

i call the fuse and cut-out 'the cut-out' ,just a habit.
http://www.esb.ie/esbnetworks/downloads/standard_charges_quick_reference.pdf

Davy

fishdog wrote: »

What I have said is that it is news to me that the ESB are using CT metering on single phase supplies as davelerave has suggested.

I have only seen the ESB using CT metering for 3 phase supplies over a certain size.

I think most people would have 3ph if they had a load that size, i suppose certain cases where a 3ph cable wasn't easily connected to, would be to costly to install a new one. If they can get away with the single phase sure why not.

davelerave

the 20-29 kva single phase supply would be used if only the single-phase mv network is available,i've seen it used for commercial loads like 25kva.

fishdog

davelerave, I went looking for your single phase CT metered supply. In the "The National Code of Practice for Customer Interface – 4th edition, 2008"
It says:

Single phase whole current meters will be used to measure loads up to 80A per phase. In general, three phase whole current meters will be used to measure loads over three phases up to 80A per phase.

So I thought you were wrong, until on page 11 (link below) I found what you were talking about! Fair play

The National Code of Practice for Customer Interface – 4th edition, 2008

This is a handy link to have. It replaces the 3rd edition.

I think most people would have 3ph if they had a load that size, i suppose certain cases where a 3ph cable wasn't easily connected to, would be to costly to install a new one. If they can get away with the single phase sure why not.

Yes. But what I have seen is often houses with heat pumps are in rural areas, where the owner is a farmer that has or requires 3 phase anyway. Otherwise as you say it is uneconomical or impractical.

I have often seen people push single phase beyond what it should be supplying with predictable consequences.

mikejjp

fishdog wrote: »

I would agree pretty much with Stoner, but would add:
<snip>
This is not required if the house is plumbed in plastic piping.

The point of bonding metal items is to cause the safety device (fuse, rcb) to trip if the item becomes live, e.g. due to leakage from a local live circuit. This is still possible even when a metal sink is fed by plastic pipes, so I'd advise a 10mmsq bond to earth. I would have thought ETCI Regs would require equipotential bonding /PME as normal. I don't have a copy of the Regs so maybe a profesisonal could advise?

M cebee

mikejjp wrote: »

The point of bonding metal items is to cause the safety device (fuse, rcb) to trip if the item becomes live, e.g. due to leakage from a local live circuit. This is still possible even when a metal sink is fed by plastic pipes, so I'd advise a 10mmsq bond to earth. I would have thought ETCI Regs would require equipotential bonding /PME as normal. I don't have a copy of the Regs so maybe a profesisonal could advise?

don't think that's correct -bonding isn't designed to trip protective devices

all plastic piping there would be no need for main bond afaik

mikejjp

Imagine that all items, e.g. kettles, washing machiness, metal casings, sinks, metal pipes, tanks, etc, were not earthed, then if they accidentally became live (e.g. due to insulation failure) then quite possibly they would stay live because the return path would potentially of too high a resistance to permit a fault current large enough to trip the RCD or blow the fuse. Then if some unsuspecting person were to touch the live item, a small but nevertheless lethal current could/would take a (relatively) low resitance path to earth through their body. RIP :eek: or did I miss the point?

M cebee

mikejjp wrote: »

Imagine that all items, e.g. kettles, washing machiness, metal casings, sinks, metal pipes, tanks, etc, were not earthed, then if they accidentally became live (e.g. due to insulation failure) then quite possibly they would stay live because the return path would potentially of too high a resistance to permit a fault current large enough to trip the RCD or blow the fuse. Then if some unsuspecting person were to touch the live item, a small but nevertheless lethal current could/would take a (relatively) low resitance path to earth through their body. RIP :eek: or did I miss the point?

bonding of pipes,sinks etc. isn't designed to trip a protective device as the metalwork isn't part of the electrical system
http://sparksstudent.co.uk/experts-online/76-what-is-the-difference-between-earthing-and-bonding

i'll have to go back and read the damn thing myself now,i keep forgetting everything

the earthing of exposed metalwork is different (the earth in a lead etc),and is designed to trip a protective device



for instance in the uk-if the metalllic services in a premises were isolated from the met(earth bar),there would be no requirement to bond them at all

we seem to have a different slant on bonding here-metallic services are just bonded regardless

2011

+1

The idea of equipotential bonding is to keep simultaneously conductive parts at the same potential.

The CPC (circuit protective conductor) is designed to carry the fault current, and should be sized in such a way that it ensures that the protective device will operate within the correct time to comply with the regulations.

Bruthal

M cebee wrote: »

for instance in the uk-if the metalllic services in a premises were isolated from the met(earth bar),there would be no requirement to bond them at all

we seem to have a different slant on bonding here-metallic services are just bonded regardless

Mainly due to the neutralising practice we have. Neutral failure outside the neutralised point, and any earthed metal goes up toward 230v with anything but the smallest load on in the house. So bonding everything to the earth bar keeps it all at the same potential to minimise shock risk, even if that is all at 230v.

The now isolated earth rod at the meter will do little to keep the earth bar at earth potential with anything more than a cfl bulb on most likely.

If the earth rod was a perfect conductor to earth, the broken neutral would go un-noticed.

Bruthal

mikejjp wrote: »

Imagine that all items, e.g. kettles, washing machiness, metal casings, sinks, metal pipes, tanks, etc, were not earthed, then if they accidentally became live (e.g. due to insulation failure) then quite possibly they would stay live because the return path would potentially of too high a resistance to permit a fault current large enough to trip the RCD or blow the fuse. Then if some unsuspecting person were to touch the live item, a small but nevertheless lethal current could/would take a (relatively) low resitance path to earth through their body. RIP :eek: or did I miss the point?

The path through a persons body is a high enough resistance, and from one contact point like the hand down through the feet, in most cases would be too high to even percieve a shock, contrary to the likely popular belief that touching a 230v item and nothing else, means a certain shock.

Enough current can flow through a person from 230v to trip an RCD alright, but this shock would be very perceivable when at the level to trip one. Thats the idea of them. To protect persons from electrocution.

M cebee

robbie7730 wrote: »

Mainly due to the neutralising practice we have. Neutral failure outside the neutralised point, and any earthed metal goes up toward 230v with anything but the smallest load on in the house. So bonding everything to the earth bar keeps it all at the same potential to minimise shock risk, even if that is all at 230v.

The now isolated earth rod at the meter will do little to keep the earth bar at earth potential with anything more than a cfl bulb on most likely.

If the earth rod was a perfect conductor to earth, the broken neutral would go un-noticed.

i don't mean tt and tn-c-s

here afaik it's not normal to test metallic services, sinks and bathroom pipes to see if they are actually extraneous and need bonding
for example:
http://www.voltimum.ie/news/8332/cm/september-s-question-of-the-month---bathroom-bonding.html


whereas in the uk afaik,they do

mikejjp

M cebee wrote: »

http://www.voltimum.ie/news/8332/cm/september-s-question-of-the-month---bathroom-bonding.html
... an interesting quote.

How about ... http://en.wikipedia.org/wiki/Electric_shock ... Facts claimed:

> "The world population 95 percentile has 2125 Ohm body resistance at 220 V" - see Body Resistance Table

> "A domestic power supply voltage (110 or 230 V), 50 or 60 Hz alternating current (AC) through the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 60 mA."

Ohm's Law: I = V/R = 220/2125 = 103 mA

From this you'd think 103 mA is enough to kill most people - at least a very nasty experience. Looks like a vulnerable, old person or someone with a dicky ticker is going to be toast. Btw, how to get real-life experimental evidence unless you live under a Nazi regime! Maybe from experiments on apes?
Thanks for the mercy of earth bonding.

2011

My understanding is that 50mA has the potential to cause death at main voltage (230VAC in Ireland). This is why RCDs installed on socket circuits are no greater than 30mA (I Δ n).

Equipotential bonding is only part of the story. For it to make a difference something else will have to have failed, if not there would be no potential difference between the two points being bonded together.

There are number of ways to reduce the risk and severity of electric shock in a domestic installation.

This includes, but is not limited to:

1) Supplementry protection from an RCD

2) Protective devices such as MCBs and fuses

3) Equipotential bonding

4) Double insulation

5) Installing CPCs and verfiying the earth fault loop impedance is low enough to ensure that the protective device operates within the required time.

6) Mechanical protection.

7) Devices that automaticaly disconnect from the mains when the cover is removed.

Bruthal

mikejjp wrote: »

M cebee wrote: »

http://www.voltimum.ie/news/8332/cm/september-s-question-of-the-month---bathroom-bonding.html
... an interesting quote.

How about ... http://en.wikipedia.org/wiki/Electric_shock ... Facts claimed:

> "The world population 95 percentile has 2125 Ohm body resistance at 220 V" - see Body Resistance Table

> "A domestic power supply voltage (110 or 230 V), 50 or 60 Hz alternating current (AC) through the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 60 mA."

Ohm's Law: I = V/R = 220/2125 = 103 mA

From this you'd think 103 mA is enough to kill most people - at least a very nasty experience. Looks like a vulnerable, old person or someone with a dicky ticker is going to be toast. Btw, how to get real-life experimental evidence unless you live under a Nazi regime! Maybe from experiments on apes?
Thanks for the mercy of earth bonding.

A person touching only a live point, and nothing else except feet on the ground in shoes etc, will present a far higher resistance than 2k ohms, and in most cases, would perceive no shock. You were looking for real life experimental evidence. I did that test a few times. Perhaps a video is needed:eek:

And the skin contact resistance itself varies very widely, so the severity of shock received from 230v contact from one hand to the other can vary to a very high degree, depending on a number of factors such as sweaty hands, contact area in mm square etc. But 100ma is achievable easy enough. I tripped RCDs myself on a couple of occasions through unintended contact.

If you do your ohms calculation for 110v, it would show 50ma, but direct contact with 110v would be quite an achievement to result in electrocution. It would want very good contact area in both places and a sustained contact.

2011

robbie7730 wrote: »

A person touching only a live point, and nothing else except feet on the ground in shoes etc, will present a far higher resistance than 2k ohms, and in most cases, would perceive no shock. You were looking for real life experimental evidence. I did that test a few times. Perhaps a video is needed:eek:

I believe you, please don't post a video of this. Others may copy and then lean against a metal pipe :eek:

And the skin contact resistance itself varies very widely, so the severity of shock received from 230v contact from one hand to the other can vary to a very high degree

Very true. This is why bathrooms present increased risk.

Bruthal

2011 wrote: »

My understanding is that 50mA has the potential to cause death at main voltage (230VAC in Ireland). This is why RCDs installed on socket circuits are no greater than 30mA (I Δ n).

Mine would be that the 50 ma is 50 ma, and the level of voltage does not really matter. Obviously the voltage level affects the current, and 50ma wont be flowing from 12v ac. But if one person contacts 170v and 50ma flows, and another contacts 250v, and 50ma flows, they both perceive the same shock.

The person is like 3 resistors in series, 2 skin contact resistances which can widely vary, and internal resistance which is generally similar. So the 50ma will feel the same, regardless of the voltage of the item contacted.

Bruthal

2011 wrote: »

I believe you, please don't post a video of this. Others may copy and then lean against a metal pipe :eek:

I was going to lean against a pipe in the video:D

Interesting that you say you believe it. Would you not say its a fact? I know a fair few electricians that dont believe it, and assume you will perceive a current flow in that scenario.

Bruthal

2011 wrote: »

Very true. This is why bathrooms present increased risk.

True. Water is actually a poor conductor. But what it does is form a large mm square contact area on the fingers, but extremely short in length, as in the distance from finger tip to the contact point is through water only microns thick, but with a huge surface area compared to this conductor length, the resistance through this water is low, so it drastically reduces the skin contact resistance.

2011

Interesting that you say you believe it. Would you not say its a fact? I know a fair few electricians that dont believe it, and assume you will perceive a current flow in that scenario.

Just because something is a fact does not mean that it is university agreed

Current will only flow between 2 points if there is a potential difference between them. There would be so little potential difference across you due to your shoes almost no current would flow. Therefore no shock would be experienced.

2011

robbie7730 wrote: »

True. Water is actually a poor conductor.

Funny you should say that. I was working with an engineer recently who was installing an automatic system that would use deionized water to quench electrical fires in switchrooms. Water only conducts due to impurities, making deinonized water a good insulator.

Bruthal

2011 wrote: »

Funny you should say that. I was working with an engineer recently who was installing an automatic system that would use deionized water to quench electrical fires in switchrooms. Water only conducts due to impurities, making deinonized water a good insulator.

Yea its another assumption that it is a good conductor. If you can imagine a 10 meter square area of water in contact with 10 meter square copper plates connected to 10 square cable, but the layer of water is just 1mm thick between the large plates, that would conduct a fair current to power a shower etc no problem. But get a 10 meter column of water but 1cm square, and it wouldnt power a cfl.

The large surface area but very thin, is the way is works with wet hands in contact with a live item and earth or neutral. Sweat adds in salt as well, which greatly increases the conduction.

Bruthal

2011 wrote: »

Just because something is a fact does not mean that it is university agreed

And vice versa.

mikejjp

https://sites.google.com/site/4occasionaluse/shock ... diagrams.

Assumptions:
Rfloors = 1000 Ohm
Rfault = 0 Ohm
Rkichencupds = 10000 Ohm
Rbody = 5000 Ohm ... wet hands on the sink and bare feet on a wet kitchen floor
Calculations:
Rcct = Rfault + (Rkitchencupds x Rbody) / (Rkitchencupds + Rbody)
Rcct = 0 + (10000 x 5000) / (10000 + 5000)
Rcct = 3333 Ohm
Icct = 240/3333 = 0.072 A = 72 mA
Ibody = Icct x Rkitchencupds / (Rkitchencupds + Rbody)
Ibody = 72 x 10000 / (10000 + 5000)
Ibody = 48 mA
Conclusion:
In the appropriate place, enough to kill a fit person.
Bond their sinks, or rely on the RCB to save their life. :eek:

Mod Edit, comment removed, unrelated to the OP.

2011

mikejjp wrote: »

Mod Edit, comment removed, unrelated to the OP..

I don't think that these type of demonstrations are a good idea. A safer way to illustrate this is by disconnecting the neutral from a light bulb. It does not set a good example. Doing this where I work would guarantee permanent removal from site.

Apprentices often copy what they are shown. Before you know it one may attempt to touch 2 live wires while standing on an insulator, the only problem is they may be 2 different phases!

Bruthal

2011 wrote: »

A safer way to illustrate this is by disconnecting the neutral from a light bulb. Doing this where I work would guarantee permanent removal from site.

Well its fairly serious leaving everyone in the dark alright:pac: