The Importance Of Earth Wires

[chuchok]

, and remember to turn the gas off if you can smell it

cheers

<{POST_SNAPBACK}>

When I used to live in Hastings I used to turn my gas meter round so it ran in reverse, to make sure the gas was not leaking I would light a match and run it around the joint.

True story.

<{POST_SNAPBACK}>

I know a bloke in NZ who does EXACTLY the same. He used to be a gas fitter by trade.The day after the meter has been read, he does the same.

[astral]

Very few houses in Thailand have ANY earth system.

When I move in I have the house rewired and insisted on all sockets being earthed.

Well it is my house.

The alternative is to have an electrician fit a "safety cut".

Bascially this monitors the electricity in on one wire and makes sure it

all comes back on the other wire.

Any leakage and the breaker trips.

The cost is quite small and it goes on the input to the house, by the switch

box and protects the whole house.

[lopburi3]

Very few houses in Thailand have ANY earth system.

When I move in I have the house rewired and insisted on all sockets being earthed.

Well it is my house.

The alternative is to have an electrician fit a "safety cut".

Bascially this monitors the electricity in on one wire and makes sure it

all comes back on the other wire.

Any leakage and the breaker trips.

The cost is quite small and it goes on the input to the house, by the switch

box and protects the whole house.

<{POST_SNAPBACK}>

Actually you should have both the ground and ECLB for much more safety. The ground will only cut power if the current makes it to the ground material and at the breaker rating (10-20 amps or so) and slow (breakers are designed not to trip on surge current) and you may not survive that if across your body. The ECLB will trip fast if it sees 30 milliamps difference (or less if you so set). I strongly urge using both in homes where you are likely to be in bare feet on conductive surface and walls are also usually near ground potential. The cost is low for a great deal of safety.

[toastwars]

actually tuky, those safe t cut boxes are not really that good, well not for a farang house in thailand, actually lets get this straight b4 im attacked yet again, the safe t cuts are good but are not suitable for farangs houses the way they are set up, the most safety cut units i have seen in one building is one per building, now these have many differant current draw settings, generally with most farang houses they will have half a dozen aircons, now each aircon when the compressor kicks will draw from 10 amps upwards, if all 6 kick in at the same time that will be 60 amps, so straight away you need a really high setting for that safe t cut, that really defeats the object of a safe t cut having the setting so high, in a perfect world you would have differant safety cuts for differant areas of your house, but alas i have never seen that here

also even an old 12,000btu aircon unit can draw upto 16 amps as the compressor kicks in, lets say you have 6 of them, the smallest usable aircons available, yep that safety cut then gets turned off and is never used again

Six Aircon Units?????? I have two fans and a cold shower And I got my name from my plan to take over the world by having total control of all bread products and starvng the populus into submission; Thaths why I am in Thailand, promotion of crumpets and muffins as an alternative to Tom Yam. I will soon have them hooked and eating out of my hand....Bwahahahahaha!!!

[Rinrada]

Bit of a lowdown on RCDs.

Althought these apply and refer to standard IEE -NICEIC -ECA installation and testing procedures they are basically the same with respect all other codes (incl.Americian wiring regs and JSA standards)

RCD's

RCDs are often known by other names, eg., earth leakage circuit breakers (ELCB) or safety switches.

An RCD is an electrical safety device specially designed to immediately switch the electricity off when electricity "leaking" to earth is detected at a level harmful to a person using electrical equipment.

An RCD offers a high level of personal protection from electric shock.

Fuses or overcurrent circuit breakers do not offer the same level of personal protection against faults involving current flow to earth. Circuit breakers and fuses provide equipment and installation protection and operate only in response to an electrical overload or short circuit. Short circuit current flow to earth via an installation's earthing system causes the circuit breaker to trip, or fuse to blow, disconnecting the electricity from the faulty circuit.

However, if the electrical resistance in the earth fault current path is too high to allow a circuit breaker to trip (or fuse to blow), electricity can continue to flow to earth for an extended time. RCDs (with or without an overcurrent device) detect a very much lower level of electricity flowing to earth and immediately switch the electricity off.

RCDs have another important advantage - they reduce the risk of fire by detecting electrical leakage to earth in electrical wiring and accessories.

This is particularly significant in older installations.

How They Work

RCDs work on the principle "What goes in must come out". They operate by continuously comparing the current flow in both the Active (supply) and Neutral (return) conductors of an electrical circuit.

If the current flow becomes sufficiently unbalanced, some of the current in the Active conductor is not returning through the Neutral conductor and is leaking to earth.

RCDs are designed to operate within 10 to 50 milliseconds and to disconnect the electricity supply when they sense harmful leakage, typically 30 milliamps.

The sensitivity and speed of disconnection are such that any earth leakage will be detected and automatically switched off before it can cause injury or damage.

Analyses of electrical accidents show the greatest risk of electric shock results from contact between live parts and earth.

Contact with earth occurs through normal body contact with the ground or earthed metal parts. An RCD will significantly reduce the risk of electric shock, however, an RCD will not protect against all instances of electric shock. If a person comes into contact with both the Active and Neutral conductors while handling faulty plugs or appliances causing electric current to flow through the person's body, this contact will not be detected by the RCD unless there is also a current flow to earth.

On a circuit protected by an RCD, if a fault causes electricity to flow from the Active conductor to earth through a person's body, the RCD will automatically disconnect the electricity supply, avoiding the risk of a potentially fatal shock.

Examples of equipment recomended to be protected by a RCD

• Hand held electric power tools, such as drills, saws and similar equipment.

• Tools such as jack-hammers, electric lawn mowers.

• Equipment on construction sites.

• Equipment such as appliances which move while in operation, such as vacuum cleaners and floor polishers.

• Appliances in wet areas such as kitchens, including kettles, jugs, frying pans, portable urns, food mixers/blenders.

• Hand held appliances such as hair dryers, curling wands, electric knives etc.

• Cord extension leads.

and lots more...

http://www.pat-testing.info/index.htm

[paulfr]

As an electronics engineer, I find this discussion interesting.

But I still cannot understand why the lady was killed in the shower.

The article said she had burns on her neck, so that implies she took a fair amount of current and was thus part of a HV circuit.

I can see how a metal shower hose could become live due to strapping at the water heater. In fact since non purified or non deionized water is an excellent electrical conductor, she did not even have to touch the metal shower hose to touch the HV circuit. But how could the bathtub or tiled floor have significant leakage to earth to allow a live metal shower hose (or water flowing thru it) to make her part of/complete a 220V circuit and thus fry her ? How can tiles or a tub leak so badly ? Are they very poor electrical insulators ?

(Note; You have to touch two nodes of a circuit for current to flow thru your body. Touching only one node will just have you floating (electrically) at that node's potential (voltage) and will not harm you. )

Is there another way she could have died ?

Having an electrical appliance like a hair dryer in the shower could explain it, but there was no mention of this as I recall.

Edited February 22, 2005 by paulfr

[lopburi3]

As an electronics engineer, I find this discussion interesting.

But I still cannot understand why the lady was killed in the shower.

The article said she had burns on her neck, so that implies she took a fair amount of current and was thus part of a HV circuit. 

I can see how a metal shower hose could become live due to strapping at the water heater. In fact since non purified or non deionized water is an excellent electrical conductor, she did not even have to touch the metal shower hose to touch the HV circuit. But how could the bathtub or tiled floor have significant leakage to earth to allow a live metal shower hose (or water flowing thru it) to make her part of/complete a 220V circuit and thus fry her ? How can tiles or a tub leak so badly ? Are they very poor electrical insulators ?

(Note; You have to touch two nodes of a circuit for current to flow thru your body. Touching only one node will just have you floating (electrically) at that node's potential (voltage) and will not harm you. )

Is there another way she could have died ?

Having an electrical appliance like a hair dryer in the shower could explain it, but there was no mention of this as I recall.

<{POST_SNAPBACK}>

All you need is a path to the hot side wire and a path to ground. Tile floors are on cement and that makes a very, very good path to ground.

This is why I have been harping on ECLB so much here - tile floors are ground so when you have bare feet on them it is a very dangerous situation it you contact anything hot (as in electrical).

All heaters sold here have a built in ECLB so not sure what happened in this death - and the missing person make me wonder more. But they can fail, usually due to crud buildup preventing trip of breaker - that is why they must be tested on a regular basis. But this was a new unit so probably other reasons.

[Morgan]

Guys you never ever use your water pipes as your earth. This is crazy. The last thing you want if you have an electrical fault is to have the fault current passing through your water system. As the girl in the shower found to her cost.The earth straps you find on water pipes are there to ground the pipe work should it become live. They are not used to earth the fixed wiring system or any electrical appliance.

[buadhai]

Question: Is an ECLB the same device which is known as a Ground Fault Interrupter (GFI) in the US?

I built a house in the tropics some years ago and used GFI breakers in every circuit that was either outdoors or in a room that had plumbing of any sort. I found them to be a pain in butt because whenever the humidity got high the GFI would detect the minute leak and trip off. I ended up dumping the GFI circuit breakers and instead installing individual GFI protected outlets outdoors, in the kitchen, bathroom, etc.

I had a similar problem with smoke detectors. High humidity and the alarm goes off. I dumped them as well.

Do moden ECLB/GFI's avoid this problem with high humidity?

BTW, the tropical house is grounded (earthed) with a 1.5 meter copper strap buried in one of the wooden foundation pole holes. It seems to be quite effective.

[lopburi3]

Question: Is an ECLB the same device which is known as a Ground Fault Interrupter (GFI) in the US?

I built a house in the tropics some years ago and used GFI breakers in every circuit that was either outdoors or in a room that had plumbing of any sort. I found them to be a pain in butt because whenever the humidity got high the GFI would detect the minute leak and trip off. I ended up dumping the GFI circuit breakers and instead installing individual GFI protected outlets outdoors, in the kitchen, bathroom, etc.

I had a similar problem with smoke detectors. High humidity and the alarm goes off. I dumped them as well.

Do moden ECLB/GFI's avoid this problem with high humidity?

BTW, the tropical house is grounded (earthed) with a 1.5 meter copper strap buried in one of the wooden foundation pole holes. It seems to be quite effective.

<{POST_SNAPBACK}>

Yes. GFI used to be the name but it is confusing as you do not need a ground wire so ELCB is probably a better name.

If you have marginal wires humidity could cause a problem as it would make the path to ground easier. But if your wires are good it should not happen. But I gave up with the normal 220 run to door bell underground here as could never get to last more than a year or so and would be a real danger without ELCB protection - so now use battery/xmtr type. When you use one unit the total loss of all circuits can trip it where outlets would not be a problem so using the outlet method should be effective for anything plugged into that outlet - but not for anything before it. I have not found any outlet type available here in Thailand (220v). Although the US thinking is that they are needed for pool and bathrooms only having tile floors here rather than carpet makes them especially important for all the house.

[frequentatore]

What is usually the size of the wire connected to the copper rod?

[paulfr]

What is usually the size of the wire connected to the copper rod?

-------

I don't have my tables, but a paper clip should handle 5-10 amps. So scale up accordingly. Need 100 amps ? 10-20 paper clip crossections in parallel (or equivalent wire size) should do.

For another reference point;

Four aut cable (4/0) will handle 250 amps DC and it has a crossectional area of about a US quarter. And since fault currents are transient in nature, you need a much lower rating than that required for DC/steady state.

Then again, for fire protection, you'd want the full DC current rating or what can be delivered to the home from the power lines.

Note: more crossectional area => more current handling capability due to the lower resistance of the link/wire.

[paulfr]

All you need is a path to the hot side wire and a path to ground.  Tile floors are on cement and that makes a very, very good path to ground.

Tile floors (ceramic) and cement make good electrical conductors ??

You can make electrically and thermally conductive ceramics I know by adding conductive impurities. But I would think a tile floor on cement would be a superb insulator.

I know that cement is a porous material. You can see it draw up water from the ground on a rainy day by the floor wet spots that can occasionally be seen inside a building like a warehouse. So the water may be the conductor. But the tiles ??

Hmmmmm ...... mai khow chai !!

Edited February 23, 2005 by paulfr

[lopburi3]

All you need is a path to the hot side wire and a path to ground.  Tile floors are on cement and that makes a very, very good path to ground.

Tile floors (ceramic) and cement make good electrical conductors ??

You can make electrically and thermally conductive ceramics I know by adding conductive impurities. But I would think a tile floor on cement would be a superb insulator.

I know that cement is a porous material. You can see it draw up water from the ground on a rainy day by the floor wet spots that can occasionally be seen inside a building like a warehouse. So the water may be the conductor. But the tiles ??

Hmmmmm ...... mai khow chai !!

<{POST_SNAPBACK}>

Perhaps I should phrase that as less insulating than wood/carpet that most western homes have on floors when talking with technical persons.

What I want to stress is that a person on a tile floor is not insulated from harm they way they would be on other materials. If you add the sweat the direct contact with gout lines believe you will get what I am talking about. I have tile that shows no conductivity when dry to a wall in bathroom that reads around 100v between it and a hot wire when dry. In most cases the gout lines are good conductors, but as you say it is a function of moisture. I only takes a slight amount of water on a tile to make conditions very different.

[Mr_Happy]

I would use at least 6 AWG as this also could be conducting lightning surges which can be quite alot of current...

[andy50]

hi guys im an electrician (35 years)ive been to los 10 times now,

i always visit new build when there,and have a look around at the general build quality etc

regarding the earthing question ,its inperative to have an earth-rod installed, and a 6-10mm cable from the comsumer unit to it .

its no good earthing extranious pipework/sockets w/heater etc, in your home if you havent got a earth rod fitted, indeed it would be lethal ,as if a fault did occur,there wouldnt be anywhere for the fault current to go,(ie the rod) thus tripping the relavent faulty circuit trip/breaker in the consumer unit-- so the metalwork in the house would remain live !!

also as others have said , a 30ma safety trip is also essential as this would detect any fault current and trip off,(hopefully!)

,btw, when installing the earth rod ,the ground must be moist not bone dry,otherwise the resistance of the rod will be too high, rendering it not as good,or even useless!

remember if the metalwork in the house is earthed ,but no earth rod is fitted, the fault current will just remain in the pipes etc and if/when you come into contact with said metalwork especially on a tiled/wet floor with no thing on feet--and if the safety trip doesnt work properly--its curtains!

Edited February 23, 2005 by andy50

[lopburi3]

On difference here is that most home are built with cement that is filled with rebar and that rebar extends deep into the earth inside concrete support poles. The rebar is welded into one continuous loop so it does provide a very good path to ground.

If you are thinking of neutral to ground there is usually a connection at entry pole but that may be missing some places. But even with a few volts floating it is better to have that ground on the water heater than become the ground yourself. There should still be enough current flow to trip any reasonable breaker. But the ELCB will do it without the ground so that is even more important in situations as we find here.

[andy50]

On difference here is that most home are built with cement that is filled with rebar and that rebar extends deep into the earth inside concrete support poles.  The rebar is welded into one continuous loop so it does provide a very good path to ground. 

If you are thinking of neutral to ground there is usually a connection at entry pole but that may be missing some places.  But even with a few volts floating it is better to have that ground on the water heater than become the ground yourself.  There should still be enough current flow to trip any reasonable breaker.  But the ELCB will do it without the ground so that is even more important in situations as we find here.

<{POST_SNAPBACK}>

hi lopburi3 absolutely agree with you ,the rebar in the concrete would make an exellent grounding point as you say,instead of a rod, as its so vast in area-- cheers

[Crazy Dave]

hmmmm, i really dont think using the rebar as an earth is a real good idea.

a 2 storey house has footings of just over a meter, the rebar is steel, but is encased in concrete.

an earthing rod is copper and 2 meters long and goes into the dirt without concrete.

then again either is better than no earth at all, but using the rebar as an earth goes against all learnings of how to do electrics. but its still most defineately better than no earth at all..

[paulfr]

If your earthing rod does not hit the water table, what good is it at all ??

Where does the current go ??

[lopburi3]

I was not advocating using home rebar as your earth rather than an earth rod but for those in high rise it might be the only option (and they extend a lot more than one meter below ground level) - just giving an example of why it is often such a good ground and why you are likely to make ground when you touch wall or floor of a Thai home. Here in Bangkok the footers go down 6 meters or more in water filled mud so they indeed are well below the water line.

[david96]

Ref. AS/NZS3000:2000 Wiring Rules Section 5 Earthing arrangements and earthing conductors.If the TT system is used it is essential that RCDs or RCD/MCBs are installed on all final circuits.RCDs must disconnect the supply in less than 300ms.

[Pink Mist]

Ref. AS/NZS3000:2000 Wiring Rules Section 5  Earthing arrangements and earthing conductors.If the TT system is used it is essential that RCDs or RCD/MCBs are installed on all final circuits.RCDs must disconnect the supply in less than 300ms.

<{POST_SNAPBACK}>

thats the rules as they apply here in Oz and nz but in reality Los has no rules

[david96]

Ref. AS/NZS3000:2000 Wiring Rules Section 5  Earthing arrangements and earthing conductors.If the TT system is used it is essential that RCDs or RCD/MCBs are installed on all final circuits.RCDs must disconnect the supply in less than 300ms.

<{POST_SNAPBACK}>

thats the rules as they apply here in Oz and nz but in reality Los has no rules

<{POST_SNAPBACK}>

Quite correct I was looking at a standard reference as a guide. Thailand has been influenced by Japanese and US wiring codes in the past but chose to adopt the european 220/380/50Hz system. The US does not have the same attitude to electrical safetyas in UK and Aust/NZ. For all practical purposes earthing does not exist in residential electrical instalations in Thailand.

[toastwars]

If your earthing rod does not hit the water table, what good is it at all ??

Where does the current go ??

erm....what the hull are you talking about...water table????? whats a water table got to do with earthing electricity?

[paulfr]

If your earthing rod does not hit the water table, what good is it at all ??

Where does the current go ??

<{POST_SNAPBACK}>

erm....what the hull are you talking about...water table????? whats a water table got to do with earthing electricity?

<{POST_SNAPBACK}>

Well you don't have to get emotional about this. (hull = h*ell = a sign of distress)

First physics ....

All current flows in a loop.

Water with impurities is a good conductor of electricity.

Dry earth is a poor/non conductor of electricity

Now my point ....

As stated in my post .......... where does the current go if it does not hit the water table ?

If the earthing rod does conduct down to the water table then the current/electrons can get back to the source at the pole ...... IF the pole has been grounded to the water table too AND a "continuous" water table exists at that location.

As an electronics engineer with 30 years experience I can tell you that there is more mythology and misunderstanding of this area of electronics than any other subject you will encounter.

Edited February 26, 2005 by paulfr

[toastwars]

If your earthing rod does not hit the water table, what good is it at all ??

Where does the current go ??

erm....what the hull are you talking about...water table????? whats a water table got to do with earthing electricity?

Well you don't have to get emotional about this. (hull = h*ell = a sign of distress)

First physics ....

All current flows in a loop.

Water with impurities is a good conductor of electricity.

Dry earth is a poor/non conductor of electricity

Now my point ....

As stated in my post .......... where does the current go if it does not hit the water table ?

If the earthing rod does conduct down to the water table then the current/electrons can get back to the source at the pole ...... IF the pole has been grounded to the water table too AND a "continuous" water table exists at that location.

As an electronics engineer with 30 years experience I can tell you that there is more mythology and misunderstanding of this area of electronics than any other subject you will encounter.

you don't need to be in contact witht he water table to get electricity to earth, an earthing rod is 60cm in lenth well above the water table. this is why you are an electronics engineer and not an electrical engineer that is like me spouting off about sheep farming when I raise pigs.

Edited February 26, 2005 by toastwars

[Pink Mist]

without getting to excited and abusive guys, the electrode doesn't need to go to a water table, in south oz they have a distribution system called SWER used in country areas, it means 1 wire for the consumer and the return wire is earth, Single Wire Earth Return, no water table just a big stake at the power station, it works in the driest state in Oz

[JimGant]

The ECLB will trip fast if it sees 30 milliamps difference (or less if you so set)

Lop,

As usual, your electrical guidance is very instructive......but sometimes confusing to the layman (or at least, this layman).

First, is "ECLB" the generic of what a Safe-T-Cut is? I'm assuming it is, since we're talking about something that is safety related, but is not dependent on the system being grounded (earthed).

Also, you mention about setting the ECLB to something less than 30 milliamps. I've seen the Safe-T-Cuts in Home Pro with setting options -- but wouldn't have the slightest idea what my best option would be? What do the various options allow me? Probably a safety vs. too many trips option, I'm assuming....? If so, what is the "best", in your opinion, setting?

Lastly, that GFI plug on my US bought hair dryer -- is that just another variant of an ECLB?

How do you know so much about electricity? Are you a double E in a former life?

Thanks for your time.

Edited February 26, 2005 by JimGant

[lopburi3]

The ECLB will trip fast if it sees 30 milliamps difference (or less if you so set)

Lop,

As usual, your electrical guidance is very instructive......but sometimes confusing to the layman (or at least, this layman).

First, is "ECLB" the generic of what a Safe-T-Cut is? I'm assuming it is, since we're talking about something that is safety related, but is not dependent on the system being grounded (earthed).

Also, you mention about setting the ECLB to something less than 30 milliamps. I've seen the Safe-T-Cuts in Home Pro with setting options -- but wouldn't have the slightest idea what my best option would be? What do the various options allow me? Probably a safety vs. too many trips option, I'm assuming....? If so, what is the "best", in your opinion, setting?

Lastly, that GFI plug on my US bought hair dryer -- is that just another variant of an ECLB?

How do you know so much about electricity? Are you a double E in a former life?

Thanks for your time.

<{POST_SNAPBACK}>

Yes. Most of the world use the ELCB to indicate leakage rather than ground because a ground is not required for this devise to operate.

The Safe-T-Cut has several options and the lowest would be preferred if you do not get too many trips at that setting. If you use the higher 30 setting and are still getting trips then you really need to find the source (usually a compressor on a refrigerator or perhaps poor insulation in an outlet box). Method used would be to unplug everything and start putting back until trip (you can use lower ratings during this process to help pinpoint faster). Then you fix or replace. Or if you know unit is safe from touch you could bypass (for wall air conditioner and such - although it would still be a good option to use a ELCB breaker on that piece of equipment only; just as your bath hair drier).

I am not connected to Safe-T-Cut in any way but have used one of the first made, almost 30 years ago, and very pleased with it. There are other brands made here and I also use Clipsal imported from OZ. Am sure others are also imported.

My former employment required an understanding of many things but did not include the formal EE; most of which I have forgotten or are no longer a part of life.