Domestic Electrical Wiring

[elkangorito]

Thanks for your post Robin but there some things that you said that need to addressed. My comments are in red.

Electrical wiring is one of many pet hates in the los. thai wiring at the user level is completely incompetent and unsafe judged against europeean stands - i wont even beging to mention on how many accounts but its a national disgrace. I fully agree.

the flang can best protect his domestic residence by installing an RCD safety breaker (earlier called an ELCB and also named a GFI in the states. Its around 1500 baht in homepro and can be part of proper distribution board (as made by Square D, one of the better makes). This is not entirely true. The BEST & FOREMOST form of protection is a correctly earthed MEN system employed at the installation. Earth Leakage Protection devices are electronic & are therefore, apt to fail. To put your life TOTALLY in the hands of one of these devices is foolishness.

It is an invaluable ADDED protection for your family BUT

be aware

a) Much of thai electrical goods is very shoddy electrically which means that you will get earth leaks in time - a rice cooker is a typical example - sometimes lethal. so this may result in nuisance trips or intermittant trips. A proper earthing system & an MEN link will fix this provided the appliance is adequately earthed.

Most existing witring will be 2 wire and the RCD is an essential protection, but a 3 wire Euro pattern system is preferable (available in homepro and typically seen on PC peripherals. but this needs a proper earth rod installed in the ground. this may increase the number of nuisance trips. The addition of Earth rods do not cause nuisance trips...unless equipment is faulty. In such a case, the fault is easily detected & the device is repaired/replaced.

c) If you use an earth rod, dont put it anywhere near an aerail mast as a lightening strike may blow your safety breaker without you knowing. this happened to me on my shower heater and the safety trip no longer worked - and I DIDNT KNOW i was unprotected. There is absolutely no evidence to say that earth rods attract lightning. On the other hand, a lack of earth rods will increase the risk of death should lightning strike an installation. After a lightning strike (secondary or primary), the user is advised to have all electrical protection tested for correct operation. The safest option is to replace all protection devices. This is rarely done as it is not generally necessary unless a direct strike has destroyed equipment.

d) RCDS are essential for electric showers (usually built in to the unit) and also for any equipment to be used outside in the yard. To be really safe you should use a step down transformer 200/110 and 110 volts machinery but its diifficlt to find here. If you indicate the use of a 'stepdown transformer', be sure to know what you are talking about. The technically safe 'low' voltage is any voltage less than 32 volts RMS. Contrary to popular belief, 110v is as dangerous as 220v.

e) PC power supplies are notoriously leaky and shocking so you may not be able to use this via you RCD cisrcuit. You will have to provide a separate supply and its own earth rod - as i do. Many appliances are 'leaky & shocking' because an appropriate earthing system is not used together with an appropriate MEN link. Again, the installation of an appropriate earthing system & an MEN link will resolve these problems. There is no such thing as a 'non leaky' appliance. For this reason, the MEN system together with appropriate earthing was introduced.

Still alive but I know of some who are not. If you continually trust your RCD's, you may not be alive much longer.

Hello again from Barry

The surge protection system you enquired about is:

Tesco - http://www.tesco-online.com/products/se/TES240R.htm - 240 VAC Surge Arrester for residential and light industrial usage. Installed at wattmeter, service entry, or weatherhead, safety clamps and dissipates lightning induced safely AC line high voltage current impulses going to a residence.

In the discussion above keep in mind - if you increase voltage you lower current - and voltage doesn't kill you - its the current.

Barry

Sorry Barry but tell that to the victims of 11 000 volts+. By saying that "if you increase voltage you lower current", you assume a constant load/impedance. Human impedance is not able to be calculated, thus the human load can vary. In the instance of a human being electrocuted, the amount of current that flows through a human, will totally depend upon the resistance (impedance) of the human. Of course, if the human impedance is low, a maximum current (which is limited by the supply source) will flow through the human. The higher potential difference tends to 'ionise' particles, which therefore creates a low resistance current path. Thus it is the combination of voltage & current that causes the damage. But please bear in mind that the higher voltages facilitate the flow of current (Ohm's Law) & consequently, it is not only current that kills.

[Crossy]

BTW Since our document will be 'dynamic' in nature we should have a fixed reference to the latest version. I have tons of web space available where we can host the file then provide a fixed link from the thread posts.

Edited May 1, 2006 by Crossy

[Crossy]

Back to disagreement. The color code that has been used here is black/hot, grey/neutral, green/ground and that is the only type of wire you are likely to find for sale in my experience. Just being able to obtain three conductor wire was a real problem up until very recently. When we start saying black is neutral it becomes a real danger as in just about every house in Thailand it is hot.

Yep, that's what I thought. I've not seen (but not looked for) other codes being used.

[elkangorito]

Back to disagreement. The color code that has been used here is black/hot, grey/neutral, green/ground and that is the only type of wire you are likely to find for sale in my experience. Just being able to obtain three conductor wire was a real problem up until very recently. When we start saying black is neutral it becomes a real danger as in just about every house in Thailand it is hot.

6 months ago, I managed to purchase (after much insisting) 2 core & earth cable. This cable arrived as red, black & green. Because I am not looking at what exists in Thailkand (who wants to? It is wrong & faulty but nonetheless exists), the colour coding of the cables represents the universal norm which WILL be the case in Thailand. The old colour codes are based upon outdated American standards. The 'future' colour codes will be that of the IEC/ISO system. The idea of the 'US gallon/ounce' etc & 'it's' colour codes are almost gone (thank god).

I don't believe that anyone can competently comment upon current Thai electrical colour codes. Even so, the future of electrical systems in Thailand will rely upon universal conformity & not old, dangerous & out dated' adopted standards'.

The lesson here is to not trust colours but instead to trust electrical equipment. Trust the voltmeter & not the wire colour.

What's that? Don't know how to use a voltmeter? Then get an electrician. What's that? Can't trust a Thai electrician? (I don't blame you). Then the only recourse is to BEGIN implementing the appropriate system. Also, there are many capable farangs of qualified electrical capability (albeit illegal for them to do work as such).

The sooner everyone starts to reject the faulty Thai electrical system & outdated colour coding system, the sooner Thailand will become a safer place.

If you can't tell which wire is active, you should not venture any further. You should consult an electrically qualified person.

[elkangorito]

BTW Since our document will be 'dynamic' in nature we should have a fixed reference to the latest version. I have tons of web space available where we can host the file then provide a fixed link from the thread posts.

Bloody fine idea Dave. Let me know of the webspace link etc.

I love how the word D a_m.N is censored from the posts but 'bloody' is not:)

Edited May 1, 2006 by elkangorito

[kerrs69]

Just stick to these regulations and everybody will be ok.

These should apply to thailand as well as the same supply voltages

and supply type's are used .

iee regs

Rab

[backflip]

"There is absolutely no evidence to say that earth rods attract lightning."

Lightning rods are not meant to attract lightning. Why would anyone want to have a multi-million volt, multi-million amp charge of electricity attracted to their home/barn/outbuilding? There's no way to safely handle that amount of electricity. The purpose of a lightning rod is to drain the atmospheric electrical charge BEFORE the potential reaches the point of atmospheric discharge.

[Crossy]

Just stick to these regulations and everybody will be ok.

iee regs

Rab

Hi Rab. I'd love to apply the IEE regs here, since they are common sense.

The Thai 'rules' that I've seen (unfortunately an unofficial document in Thai) are actually nearer to the Oz standards, particularly the non-use of ring mains for outlets and the widespread (supposedly, in Thailand) use of PME / MEN systems (which are only just gaining acceptance in the UK).

There are at least 3 (you would be 4) qualified electricians regularly posting on these forums, the only problem is that we are from different countries with (slightly?) differing regulations.

I am 100% certain that we can come up with a sensible set of rules that are :-

a. Safe (most important)

b. Broadly compliant with what rules Thailand has.

c. Agreed between us all

d. Easy for the layman to at least verify what he's got.

Just talked to our office electrician (he actually designs Rail Traction Power substations, a bit heavier than we are really interested in). He reckons (get out the salt) that the US black-white-green and the Oz black-red-green and the Euro brown-blue-green/yellow colour schemes are all OK (never seen brown-blue-green/yellow cable here). Interestingly he's never come across the 2 core twin+earth with a naked ground conductor that is in widespread use in the UK.

At least green is always ground. I think the key has to be consistancy through your installation

[elkangorito]

I think that the colour codes will present a major problem...particularly with those who cannot change easily & others who will be confused by the current 'non-existant' colour code. Nonetheless, the fact that I was able to purchase 3 core cable in 2005 (I did not request wire colours) that was of a logical colour code (red, black & green), proves to me that Thailand will sooner than later, adopt a sensible system.

The colour Grey is quite often used in control wiring in Australia but never as an Active or a Neutral in Domestic installations.

I think it may be sensible to realise the European Standards. Also, it may be a good idea to TRY to understand the Thai colour codes but I feel that they will never be substantiated due to the lack of Thai electrical continuity.

Consequently, a Voltmeter is the only real way of substantiating what is Active & what is Neutral in Thailand. 'Guessing' & info from other folks is obviously dangerous & unreliable.

In the meantime Red will be Active, Black will be Neutral & Green will be Earth for all new installations.

Make sure you insist upon this type of cable.

[thailand_property_search]

Electrons are colour blind.

They don't care what colour the cables are. First priority is safety. 3 core is a must (and correct size!) if you can get the international colours...so much the better (at least other farang will know what is what) if you can't - use whats available. If your a purist then you can always tag the cables for future tennents or in case you forget.

[thailand_property_search]

Oh.

As an after thought.

Most electricity offices have earthed mains schematics and how to wire instructions on noticeboards (Thai and English).

Take your sparky down there and say I WANT!

[Crossy]

Electrons are colour blind.

They don't care what colour the cables are. First priority is safety. 3 core is a must (and correct size!) if you can get the international colours...so much the better (at least other farang will know what is what) if you can't - use whats available. If your a purist then you can always tag the cables for future tennents or in case you forget.

You obviously never met Mr Bentley our Machines and Control lecturer at Bath Uni. If he EVER saw a red and blue wire connected together in a lab exercise he would leap around disconnecting every wire in sight. Occasionally done deliberately to see the reaction

Meanwhile, it would be sensible to stick to one of the major recognised standards, US (black, white, green), IEC (red, black, green), Euro (brown, blue, green/yellow) and maintain consistency throughout your installation.

[elkangorito]

Here are the latest documents available for download.

Another site for Electrical advice is http://www.crossy.co.uk/wiring/

[JimmyGreaves]

Good stuff Guys.

Keep it going as this will be invaluable to all. Nice to be able to soon get the docs on Crossy's site as it is really easy reading for someone like me who knows nothing about electrics and am soom to start house building. Just wondering if it's worth buying any of the main kit in the UK.

[elkangorito]

Earth Leakage Protection devices will be the next installment.

[Pink Mist]

Well guys this topic is pinned, fyi I am a contractor in Adelaide, South Australia and have kept current with the AS 3000/ 2000 rules ( was NZ meant to be there)

anyway guys a good place to have a chat and should provide a wealth of information.

all information posted here will be in good faith, but Thai Visa will accept no liability

[elkangorito]

Well guys this topic is pinned, fyi I am a contractor in Adelaide, South Australia and have kept current with the AS 3000/ 2000 rules ( was NZ meant to be there)

anyway guys a good place to have a chat and should provide a wealth of information.

all information posted here will be in good faith, but Thai Visa will accept no liability

Thanks Bronco...good on ya mate

[elkangorito]

Here are the latest documents available for download.

Another site for Electrical advice is http://www.crossy.co.uk/wiring/

Edited May 5, 2006 by elkangorito

[Crossy]

Here are the latest documents available for download.

Another site for Electrical advice is http://www.crossy.co.uk/wiring/

Just for information, the site mentioned by Elkangorito contains all the information in his papers together with additional material from myself.

Please read and digest the material, it should answer most queries

Edited May 6, 2006 by Crossy

[Crossy]

Good stuff Guys.

Keep it going as this will be invaluable to all. Nice to be able to soon get the docs on Crossy's site as it is really easy reading for someone like me who knows nothing about electrics and am soom to start house building. Just wondering if it's worth buying any of the main kit in the UK.

Cheers for the positive feedback

Don't forget that a lot of the material came from Elkangorito who's initial posting of 'useful information' prompted me to actually get of my ar$e and do something.

Meanwhile, it may be an idea to get your ELCB and breakers (prbably get the consumer unit case as well) from the UK, not too heavy and you KNOW they will be to recognised standards.

Well known brands (Panasonic) ARE available here but there is always the doubt that they may no quite be up to spec.

[Crossy]

Well guys this topic is pinned, fyi I am a contractor in Adelaide, South Australia and have kept current with the AS 3000/ 2000 rules ( was NZ meant to be there)

anyway guys a good place to have a chat and should provide a wealth of information.

all information posted here will be in good faith, but Thai Visa will accept no liability

Well done that man :)

Your input will be more than welcome, particularly if we've missed something vital.

Like I've said before, if we save one person from a "shocking experience" it will be worth the effort.

[elkangorito]

Good stuff Guys.

Keep it going as this will be invaluable to all. Nice to be able to soon get the docs on Crossy's site as it is really easy reading for someone like me who knows nothing about electrics and am soom to start house building. Just wondering if it's worth buying any of the main kit in the UK.

Thanks for the positive feedback jflundy.

I think that many people will find Crossy's site very helpful. He has managed to make some of my content a bit more 'user friendly', which is something that I'm not used to doing when it comes to technical documentation.

When I started this topic, I did not anticipate Crossy's support (or anyone elses). His objectivity & technical 'know how' has proven to be more than invaluable.

Anybody is free to contribute but I must insist that all information posted as 'gospel', must be as technically correct as possible & not 'guestimations' or 'beliefs'. This ultimately is a 'life & death' topic with little room for 'guestimations' or 'beliefs'.

As far as purchasing electrical gear, Schneider Electric have many outlets throughout Thailand. Their products are Scneider/Square D...considered to be good gear in Oz. I've been using a lot of their stuff for many years in much larger industrial applications.

Edited May 6, 2006 by elkangorito

[Crossy]

As far as purchasing electrical gear, Schneider Electric have many outlets throughout Thailand. Their products are Scneider/Square D...considered to be good gear in Oz. I've been using a lot of their stuff for many years in much larger industrial applications.

Schneider looks promising They have an English website here :-

http://www.schneider-electric.co.th/

Products from Square D, Merlin Gerin and Telemecanique are amongst the best you can get (not cheap though). The site has a list of distributors, worth a visit.

[Crossy]

Website updated to include discussions on Earth Leakage Protection

http://www.crossy.co.uk/wiring/

Thanks to Elkangorito for the material

[elkangorito]

Website updated to include discussions on Earth Leakage Protection

http://www.crossy.co.uk/wiring/

Thanks to Elkangorito for the material

No probs Crossy. BTW, did you draw the diagram? I think it's a great addition. I think you're better at diags than me. It takes me ages to produce one.

Hopefully, people will begin asking questions soon since the material provided is not 'all encompassing'.

Thanks again mate

Edited May 6, 2006 by elkangorito

[elkangorito]

The latest attachment on Earth Leakage Protection as follows;

This is the same info that can also be seen on http://www.crossy.co.uk/wiring/. The information presented on this link is enhanced & therefore a little easier to digest.

[elkangorito]

Well guys this topic is pinned, fyi I am a contractor in Adelaide, South Australia and have kept current with the AS 3000/ 2000 rules ( was NZ meant to be there)

anyway guys a good place to have a chat and should provide a wealth of information.

all information posted here will be in good faith, but Thai Visa will accept no liability

Hi Bronco,

Just wondering if you'd be willing to produce a simplified paper on Circuit Breaker selection for the MEN system? It relates to the tripping of such devices by an earth loop fault. I do not have ready access to the latest AS/NZ 3000 regs. It would mainly speak of Class C or D breakers etc. Can you help?

Cheers.

Edited May 6, 2006 by elkangorito

[robint]

Thanks for your post Robin but there some things that you said that need to addressed. My comments are in red.

HI elk. your input is most valued but I think you misunderstand me is some areas, for clarification I comment in blue

Electrical wiring is one of many pet hates in the los. thai wiring at the user level is completely incompetent and unsafe judged against europeean stands - i wont even beging to mention on how many accounts but its a national disgrace. I fully agree.

the flang can best protect his domestic residence by installing an RCD safety breaker (earlier called an ELCB and also named a GFI in the states. Its around 1500 baht in homepro and can be part of proper distribution board (as made by Square D, one of the better makes). This is not entirely true. The BEST & FOREMOST form of protection is a correctly earthed MEN system employed at the installation. Earth Leakage Protection devices are electronic & are therefore, apt to fail. To put your life TOTALLY in the hands of one of these devices is foolishness.

I do not wish to imply that earth rods are unnecessary. Of course they should be employed and an RCD added as a supplement. The real problem is that many domestice appliances are only 2 wire. They have no convenient earth connection. A rice cooker is a typical and sometimes fatal example. So its not generally earthed in Thai practice - my wife was electrocuted by one of these that developed a leak after many years. An RCD will give a valuable additional protection although I suggest a plastic flooring covering as a first line, in the kitchen.

It is an invaluable ADDED protection for your family BUT

be aware

a) Much of thai electrical goods is very shoddy electrically which means that you will get earth leaks in time - a rice cooker is a typical example - sometimes lethal. so this may result in nuisance trips or intermittant trips. A proper earthing system & an MEN link will fix this provided the appliance is adequately earthed.

Most existing witring will be 2 wire and the RCD is an essential protection, but a 3 wire Euro pattern system is preferable (available in homepro and typically seen on PC peripherals. but this needs a proper earth rod installed in the ground. this may increase the number of nuisance trips. The addition of Earth rods do not cause nuisance trips...unless equipment is faulty. In such a case, the fault is easily detected & the device is repaired/replaced.

Well I'm afraid we are talking thailand here and reality, Im sure we would all like to have euro/US standards of safety but thats not the real world out here and I am talking basic survival. If you put and RCD and a 3 wire circuit together on kitchen appliances then you are likely to get nuisance trips because of the poor quality - I had a fridge that would do that by itself intermittently. I would come back to a stinking mess after it had tripped out, so you need to choose your circuits selectively. Similarly lighting circuits can be leaky and you end up sitting in the dark, but lighting circuits used solel;y for that purpose should no normally be in contact with humans, so dont need an RCD.

c) If you use an earth rod, dont put it anywhere near an aerail mast as a lightening strike may blow your safety breaker without you knowing. this happened to me on my shower heater and the safety trip no longer worked - and I DIDNT KNOW i was unprotected. There is absolutely no evidence to say that earth rods attract lightning. On the other hand, a lack of earth rods will increase the risk of death should lightning strike an installation. After a lightning strike (secondary or primary), the user is advised to have all electrical protection tested for correct operation. The safest option is to replace all protection devices. This is rarely done as it is not generally necessary unless a direct strike has destroyed equipment.

Im afraid you have misunderstood my point here, its the TV aerial mast that attracts the lightning spurs not the earth rods, please read again. I am quoting a real life experience here BTW. Lightening can destroy an RCD and you wouldnt know. Fortunately all RCDs are supplied with a test button, so its as well to test whenever there has been a thunderstorm. My wife always wants to cut the main breaker and pull out the aerail from the tv. She is probably right.

d) RCDS are essential for electric showers (usually built in to the unit) and also for any equipment to be used outside in the yard. To be really safe you should use a step down transformer 200/110 and 110 volts machinery but its diifficlt to find here. If you indicate the use of a 'stepdown transformer', be sure to know what you are talking about. The technically safe 'low' voltage is any voltage less than 32 volts RMS. Contrary to popular belief, 110v is as dangerous as 220v.

Well I am quoting from industrial practice here and what happens on construction sites. A transformer will isolate the main power from earth. That means that if you touch either of the leads from the 100v side you will not get a shock against earth (of course if you touch both leads you are asking for trouble as you point out but that is an unlikely scenario for the use of power tools).

Incidentally original US practice was to supply houses via their own 110v transformers which were centre tapped to earth. This gave a maximum line voltage of 55vac which was considered relatively safe

Isolating transforers are only as good as the insulation but modern construction should be extremely reliable

e) PC power supplies are notoriously leaky and shocking so you may not be able to use this via you RCD cisrcuit. You will have to provide a separate supply and its own earth rod - as i do. Many appliances are 'leaky & shocking' because an appropriate earthing system is not used together with an appropriate MEN link. Again, the installation of an appropriate earthing system & an MEN link will resolve these problems. There is no such thing as a 'non leaky' appliance. For this reason, the MEN system together with appropriate earthing was introduced.

Still alive but I know of some who are not. If you continually trust your RCD's, you may not be alive much longer.

I dont quite know what your point is but certainly you will have confused the layman completely

I will restate my case

a) Yes you should have a earth rod system (preferably several in case one fails or dries up) but what can you do in a tall appartment block with no such modern electrical installation? It migh5t be quite difficult to run a wire 10 floors down to earth assuming the owner will let you.

An RCD is an essentail back up to a basic earth rod system but you cant always use an RCD and you cant always earth an appliance conveniently

c) its inconvenient to use an RCD on a fridge (which is normally all plastic and not hazardous) or a PC which is often very leaky and must be earthed somehow or dont have bare feet - be aware its dangerous - what about kids!!!

d) electrical surges can disable an RCD so test them often

e) electric showers must be earthed and have a built in RCD - I know of a case where a mamasan was electricuted by a cheap shower heater

I support the use of RCDs and so does the Thai electric authority in my area. One old ladies house burn down because of leaky wiring that got wet. An RCD would have saved her, wherase a standard fuse will not. The authority kindly installed an RCD in her rebuilt house.

[elkangorito]

Thanks for your post Robin but there some things that you said that need to addressed. My comments are in red.

HI elk. your input is most valued but I think you misunderstand me is some areas, for clarification I comment in blue

Electrical wiring is one of many pet hates in the los. thai wiring at the user level is completely incompetent and unsafe judged against europeean stands - i wont even beging to mention on how many accounts but its a national disgrace. I fully agree.

the flang can best protect his domestic residence by installing an RCD safety breaker (earlier called an ELCB and also named a GFI in the states. Its around 1500 baht in homepro and can be part of proper distribution board (as made by Square D, one of the better makes). This is not entirely true. The BEST & FOREMOST form of protection is a correctly earthed MEN system employed at the installation. Earth Leakage Protection devices are electronic & are therefore, apt to fail. To put your life TOTALLY in the hands of one of these devices is foolishness.

I do not wish to imply that earth rods are unnecessary. Of course they should be employed and an RCD added as a supplement. The real problem is that many domestice appliances are only 2 wire. They have no convenient earth connection. A rice cooker is a typical and sometimes fatal example. So its not generally earthed in Thai practice - my wife was electrocuted by one of these that developed a leak after many years. An RCD will give a valuable additional protection although I suggest a plastic flooring covering as a first line, in the kitchen.

It is an invaluable ADDED protection for your family BUT

be aware

a) Much of thai electrical goods is very shoddy electrically which means that you will get earth leaks in time - a rice cooker is a typical example - sometimes lethal. so this may result in nuisance trips or intermittant trips. A proper earthing system & an MEN link will fix this provided the appliance is adequately earthed.

Most existing witring will be 2 wire and the RCD is an essential protection, but a 3 wire Euro pattern system is preferable (available in homepro and typically seen on PC peripherals. but this needs a proper earth rod installed in the ground. this may increase the number of nuisance trips. The addition of Earth rods do not cause nuisance trips...unless equipment is faulty. In such a case, the fault is easily detected & the device is repaired/replaced.

Well I'm afraid we are talking thailand here and reality, Im sure we would all like to have euro/US standards of safety but thats not the real world out here and I am talking basic survival. If you put and RCD and a 3 wire circuit together on kitchen appliances then you are likely to get nuisance trips because of the poor quality - I had a fridge that would do that by itself intermittently. I would come back to a stinking mess after it had tripped out, so you need to choose your circuits selectively. Similarly lighting circuits can be leaky and you end up sitting in the dark, but lighting circuits used solel;y for that purpose should no normally be in contact with humans, so dont need an RCD.

c) If you use an earth rod, dont put it anywhere near an aerail mast as a lightening strike may blow your safety breaker without you knowing. this happened to me on my shower heater and the safety trip no longer worked - and I DIDNT KNOW i was unprotected. There is absolutely no evidence to say that earth rods attract lightning. On the other hand, a lack of earth rods will increase the risk of death should lightning strike an installation. After a lightning strike (secondary or primary), the user is advised to have all electrical protection tested for correct operation. The safest option is to replace all protection devices. This is rarely done as it is not generally necessary unless a direct strike has destroyed equipment.

Im afraid you have misunderstood my point here, its the TV aerial mast that attracts the lightning spurs not the earth rods, please read again. I am quoting a real life experience here BTW. Lightening can destroy an RCD and you wouldnt know. Fortunately all RCDs are supplied with a test button, so its as well to test whenever there has been a thunderstorm. My wife always wants to cut the main breaker and pull out the aerail from the tv. She is probably right.

d) RCDS are essential for electric showers (usually built in to the unit) and also for any equipment to be used outside in the yard. To be really safe you should use a step down transformer 200/110 and 110 volts machinery but its diifficlt to find here. If you indicate the use of a 'stepdown transformer', be sure to know what you are talking about. The technically safe 'low' voltage is any voltage less than 32 volts RMS. Contrary to popular belief, 110v is as dangerous as 220v.

Well I am quoting from industrial practice here and what happens on construction sites. A transformer will isolate the main power from earth. That means that if you touch either of the leads from the 100v side you will not get a shock against earth (of course if you touch both leads you are asking for trouble as you point out but that is an unlikely scenario for the use of power tools).

Incidentally original US practice was to supply houses via their own 110v transformers which were centre tapped to earth. This gave a maximum line voltage of 55vac which was considered relatively safe

Isolating transforers are only as good as the insulation but modern construction should be extremely reliable

e) PC power supplies are notoriously leaky and shocking so you may not be able to use this via you RCD cisrcuit. You will have to provide a separate supply and its own earth rod - as i do. Many appliances are 'leaky & shocking' because an appropriate earthing system is not used together with an appropriate MEN link. Again, the installation of an appropriate earthing system & an MEN link will resolve these problems. There is no such thing as a 'non leaky' appliance. For this reason, the MEN system together with appropriate earthing was introduced.

Still alive but I know of some who are not. If you continually trust your RCD's, you may not be alive much longer.

I dont quite know what your point is but certainly you will have confused the layman completely

I will restate my case

a) Yes you should have a earth rod system (preferably several in case one fails or dries up) but what can you do in a tall appartment block with no such modern electrical installation? It migh5t be quite difficult to run a wire 10 floors down to earth assuming the owner will let you.

An RCD is an essentail back up to a basic earth rod system but you cant always use an RCD and you cant always earth an appliance conveniently

c) its inconvenient to use an RCD on a fridge (which is normally all plastic and not hazardous) or a PC which is often very leaky and must be earthed somehow or dont have bare feet - be aware its dangerous - what about kids!!!

d) electrical surges can disable an RCD so test them often

e) electric showers must be earthed and have a built in RCD - I know of a case where a mamasan was electricuted by a cheap shower heater

I support the use of RCDs and so does the Thai electric authority in my area. One old ladies house burn down because of leaky wiring that got wet. An RCD would have saved her, wherase a standard fuse will not. The authority kindly installed an RCD in her rebuilt house.

Hi Robin.

Sorry for any misunderstandings but I would suggest you see this this link. It will explain in more detail about many of the things you speak of.

http://www.crossy.co.uk/wiring/

In the meantime, there is a simple choice...CORRECTLY install an MEN system (& I don't mean installing earth rods everywhere as this can be hazardous if not done correctly). If you can't afford it now, TEMPORARILY rely upon the RCD's until the PRIMARY defense system (MEN system) is installed. There are no other other alternatives...no short cuts.

Edited May 6, 2006 by elkangorito

[robint]

Fine Elk, have looked at that Crossy site, very nice presentation indeed and a basic description for laypersons. I presume the section on shower heaters will be forthcoming. I always view these installation with extreme suspicion - if they fail you have no chance. Indeed the IEE regs was remarkably superficial about these devices and did not insist that they be fitted with an RCD - very strange.