Breaker Box Wiring

[stevehaigh]

Again, it is imperative that the Main Earth Bar in your distribution board, to be directly connected to the earth stake via a minimum 4mm squared cable (greater than this size is better). Then, it ia also imperative that the Main Earth Bar be connected to the Main Neutral Bar (an MEN link) to provide the necessary 2 paths to earth. If any of the above is not done, then you are at risk of electrocution, should an appliance become faulty & the metal chassis of the appliance become live. This means that YOU will become the current's path to earth.

how sure are you about this? When I short the neutral in my box to ground, the main breaker trips. I have a sefety-cut box with build in GFCI.

I remember my box the US has a MEN link but the instructions in the safety-cut box do not specify a MEN link. could there be a diference in Thai and US electrical supply?

just for giggles, i tried shorting the live to ground to see if the chang fai guys wied it up backwards, but that gives a nice big arc just as you would expect.

any ideas what's going on?

steve

[astral]

Even in the UK I would expect a few volts difference between Neutral and Earth.

In Thailand it can be a lot higher.

The whole system seems to float.

In the UK, if one phase goes the main breaker at the substation will trip due to the imbalance.

That is not true in Thailand. On several ocassions I have seen one phase go

but the others remain, either on full of half power.

It took a lot of explaining to convince my wife that it was not a problem in the house

wiring, when the light and applicances in the kitchen went off, but the rest were on.

[Crossy]

Astral is 100% correct. The neutral is nominally grounded at the transformer on your pole, but judging by the bit of damp string they seem to use (certainly on ours) any load imbalance will give a not insignificant earth-neutral potential

It is this potential which is sufficient to cause your RCD / ELCB / RCCB (or whatever we are calling it this week) to trip when you short earth-neutral. Rest assured all is working correctly

Your electrician will know whether you require a MEN link in your dizzy board. I've not come across a MEN system in Thailand as yet (doesn't mean they don't exist though). It is important that you don't fit a MEN link on a non-MEN system, interesting things will happen in the event of an open-circuit neutral. Depending upon where the break occurs your MEN link could end up carrying all the neutral current for your entire moo baan, fizzzzz!!

[elkangorito]

Crossy said;

<Astral is 100% correct. The neutral is nominally grounded at the transformer on your pole, but judging by the bit of damp string they seem to use (certainly on ours) any load imbalance will give a not insignificant earth-neutral potential ermm.gif

It is this potential which is sufficient to cause your RCD / ELCB / RCCB (or whatever we are calling it this week) to trip when you short earth-neutral. Rest assured all is working correctly smile.gif

Your electrician will know whether you require a MEN link in your dizzy board. I've not come across a MEN system in Thailand as yet (doesn't mean they don't exist though). It is important that you don't fit a MEN link on a non-MEN system, interesting things will happen in the event of an open-circuit neutral. Depending upon where the break occurs your MEN link could end up carrying all the neutral current for your entire moo baan, fizzzzz!!>

Let's just iron a few things out here.

The "star point" of the distribution transformer MUST be earthed (on the substation transformer or on the pole transformer). The 'star point' is also connected to the neutral conductor. An MEN link MUST be installed only into the Main Distribution Board of the installation . Multiple MEN links (links in other downstream boards) are not permitted. This is not a matter of countries or rules, this is a matter of physics & safety. Star-delta transformers, voltage & current are the same all over the world. I do know for a fact that Thailand is supposed to be using the MEN system of earthing. Out-of-balance currents are normal & expected in every multiphase power system & only cause problems if they are extreme. Earth-neutral potentials are eliminated when the neutral is earthed, thus eliminating a dangerous & annoying problem.

Stevehaigh, if you shorted the earth to the neutral & your RCD tripped, it is because of a floating neutral voltage that was on the neutral or a faulty appliance connected in circuit. If you install an MEN link CORRECTLY (by somebody who knows how) & then turned on your power, the RCD would not trip providing there are no electrical faults, & providing the tripping current is set to no less than 30 mA. If your RCD is protecting the complete power to your house (a bad idea), something like the fridge can trip the RCD. Fridges & other inductive equipment usually have a residual leakage current, which is normal & gets worse as the equipment becomes older. It can be anything up to the order of hundreds of milliamps. Therefore, this equipment should be properly earthed & not connected into a circuit that is protected by an RCD.

A WARNING!!! It is a complete falacy that RCD's, ELCB's & the like do not require an earth to function correctly. It is true that these devices detect out-of-balance current but there has to be significant current to flow in order to allow the device to work properly. A fully earthed system gives 2 current paths in which adequate fault current can flow, thus ensuring the correct operation of all protection equipment. This is called having a low "earth fault current loop" impedance. A poor or broken neutral connection is VERY dangerous. If you are in the rare situation of becoming the neutral conductor yourself, without proper earthing or an MEN link, the RCD will not trip & you will be electrocuted.

MEN links are sized the same as that of your main neutral conductor & is therefore capable of handling the design fault current, providing that the protective (circuit breakers etc) equipment is adequate & functioning correctly.

To my knowledge, the SWER (Single Wire Earth Return) is not used in Thailand rural areas.

[lopburi3]

A WARNING!!! It is a complete falacy that RCD's, ELCB's & the like do not require an earth to function correctly. It is true that these devices detect out-of-balance current but there has to be significant current to flow in order to allow the device to work properly

And that is exactly how they work without a ground and do indeed function correctly. The tripping current flow is set to a level below that which would normally be fatal.

Advise to keep faulty appliances (and remove from RCCB) is also unwise (to an extreme) in my opinion (any failure of that ground wire and you are dead). There should not be leakage period. I have run a house will full protection for 29 years and that includes 5 refrigerators.

[chownah]

Crossy said;

<Astral is 100% correct. The neutral is nominally grounded at the transformer on your pole, but judging by the bit of damp string they seem to use (certainly on ours) any load imbalance will give a not insignificant earth-neutral potential ermm.gif

It is this potential which is sufficient to cause your RCD / ELCB / RCCB (or whatever we are calling it this week) to trip when you short earth-neutral. Rest assured all is working correctly smile.gif

Your electrician will know whether you require a MEN link in your dizzy board. I've not come across a MEN system in Thailand as yet (doesn't mean they don't exist though). It is important that you don't fit a MEN link on a non-MEN system, interesting things will happen in the event of an open-circuit neutral. Depending upon where the break occurs your MEN link could end up carrying all the neutral current for your entire moo baan, fizzzzz!!>

Let's just iron a few things out here.

The "star point" of the distribution transformer MUST be earthed (on the substation transformer or on the pole transformer). The 'star point' is also connected to the neutral conductor. An MEN link MUST be installed only into the Main Distribution Board of the installation . Multiple MEN links (links in other downstream boards) are not permitted. This is not a matter of countries or rules, this is a matter of physics & safety. Star-delta transformers, voltage & current are the same all over the world. I do know for a fact that Thailand is supposed to be using the MEN system of earthing. Out-of-balance currents are normal & expected in every multiphase power system & only cause problems if they are extreme. Earth-neutral potentials are eliminated when the neutral is earthed, thus eliminating a dangerous & annoying problem.

Stevehaigh, if you shorted the earth to the neutral & your RCD tripped, it is because of a floating neutral voltage that was on the neutral or a faulty appliance connected in circuit. If you install an MEN link CORRECTLY (by somebody who knows how) & then turned on your power, the RCD would not trip providing there are no electrical faults, & providing the tripping current is set to no less than 30 mA. If your RCD is protecting the complete power to your house (a bad idea), something like the fridge can trip the RCD. Fridges & other inductive equipment usually have a residual leakage current, which is normal & gets worse as the equipment becomes older. It can be anything up to the order of hundreds of milliamps. Therefore, this equipment should be properly earthed & not connected into a circuit that is protected by an RCD.

A WARNING!!! It is a complete falacy that RCD's, ELCB's & the like do not require an earth to function correctly. It is true that these devices detect out-of-balance current but there has to be significant current to flow in order to allow the device to work properly. A fully earthed system gives 2 current paths in which adequate fault current can flow, thus ensuring the correct operation of all protection equipment. This is called having a low "earth fault current loop" impedance. A poor or broken neutral connection is VERY dangerous. If you are in the rare situation of becoming the neutral conductor yourself, without proper earthing or an MEN link, the RCD will not trip & you will be electrocuted.

MEN links are sized the same as that of your main neutral conductor & is therefore capable of handling the design fault current, providing that the protective (circuit breakers etc) equipment is adequate & functioning correctly.

To my knowledge, the SWER (Single Wire Earth Return) is not used in Thailand rural areas.

I've been considering installing a Single Wire Earth Return service to a remote part of my property. I'll be doing some irrigation pumping so I will need to service a heavy load....I figure I can cut my expense for wire in half. Along with the irrigation pumping I want to have a panel and perhaps all the things for a small house...hot water, lights, fridge, etc..... Can you give me advice on the safest way to do this, any internet links on information, etc?

[david96]

RESIDUAL CURRENT DEVICES RCD/RCBO/GFCI.

How do safety switches work?

Are safety switches failsafe?

Test your safety switch

Why did it ‘trip’?

Safety switches monitor the flow of electricity through a circuit. They automatically shut off the electricity supply when current is detected leaking from faulty switches, wiring or electrical appliances. This stops the chance of current flowing to earth, through a person, electrocuting them.

Are safety switches failsafe?

Nothing is failsafe. You should regularly check your safety switch. Just like a smoke detector or other safety device, if it is not working properly, it cannot protect you.

It is also important to make sure your electrical appliances, electrical wiring, extension leads and other electrical equipment are regularly checked and kept in good working order.

Test your safety switch

To test a safety switch, simply press the TEST button.

This should automatically trip the switch to the ‘off’ position.

Reset by pushing the switch back to ‘on’.

If it doesn’t work, contact your electrical contractor immediately.

Carry out safety switch test every three months.

Why did it ‘trip’?

If a safety switch turns off your power, you could be using a faulty appliance or your electrical wiring may have become faulty.

Reset the safety switch. If it trips again, unplug the last appliance used. If everything works okay, take that appliance to a licensed electrical contractor to be checked.

If the safety switch keeps tripping, disconnect all appliances and plug them in, one at a time, until you locate the faulty one.

Avoid touching appliances while carrying out this process.

Contact your electrical contractor if problems persist.

Last updated July 17, 2005

[david96]

Which switch is which?

Safety switches are often confused with circuit breakers and surge protectors. Here is a quick guide to help understand the differences.

Surge protectors

Circuit breakers

Safety switches

Portable safety switch

Surge protectors

Surge protectors safeguard your appliances and wiring from voltage surges such as those resulting from a lightning strike.

Safety switches and surge protectors play entirely different roles – surge protectors protect electrical appliances, safety switches protect people.

Circuit breakers

Circuit breakers cut the power off when electrical wiring in a building has too much current flowing through it. Too much current flowing through a circuit would heat an electrical appliance's wires or the building wiring to unsafe levels. This could result in an electrical fire.

Fuses work in the same way as circuit breakers. Both fuses and circuit breakers do not provide personal protection against electrical shock.Safety switches

Safety switches monitor the flow of electricity through a circuit. They automatically shut off the electricity supply when current is detected leaking from faulty switches, wiring or electrical appliances. This stops the chance of currents flowing to earth, through a person, electrocuting them.

Portable safety switch

A portable safety switch unit is ideal when using plug-in electrical equipment used indoors or outdoors. They are convenient to use where permanent safety switch protection is not available.

However the portability of these devices means they can be subject to damage and should be inspected regularly.

Safety switches are not the same as circuit breakers or fuses. They are an additional form of protection to be used with circuit breakers and fuses. A RCBO is a combination protective device MCB/RCD ie 20A/30ma.Last updated July 17, 2005

[Tywais]

For those who like detailed descriptions of GFCI:

http://www.codecheck.com/gfci_principal.htm

http://electronics.howstuffworks.com/question117.htm

http://www.epanorama.net/documents/wiring/gfci.html

[elkangorito]

It is evident that some people do not understand the technical detail about earth leakage & protective devices etc.

I say again, RCD's may not work properly if an effective earthing system is not implemented. The reason for this is to ensure that the maximum amount of current can flow in the shortest amount of time. Those who question this are simply looking at 1 function of an RCD & do not understand the other function, which is to break the circuit safely & in time. The "circuit breaker" part of an RCD must be able to safely interrupt the "fault current", which can be in the order of thousands of amps as well as react quickly as an overload device. The "core balance" part of the RCD will operate the circuit breaker and, if good quality, will open in less than 10 milliseconds from time of trip. The speed at which it operates (governed by the internal mechanics of the circuit breaker) is critical. So, there are 2 sides to an RCD...the "core balance" part, which should be set at a sensitivity of no less than 30 mA, & the circuit breaker part, which must be able to quickly & safely open the circuit under fault conditions.

It is foolish to assume that an RCD used in an installation that is not properly earthed, will save your skin. The earth is needed as a second current path, should the neutral fail (which can be common in devices that vibrate or generate heat). The whole idea is that the earth/neutral current path has the lowest resistance possible so as to allow the protective devices to act in the appropriate amount of time. Also, RCD's are electronic devices that can readilly fail without your knowledge. What if it fails just after to do your periodical "test trip"? You will not know & you will think it is working properly.

This is why the MEN system MUST be implemented. It must be considered as the primary method of protection. Earth Leakage devices should be considered as secondary protection. Failure to acknowledge these things will be putting yourself in the "hot seat"...literally.

BTW, if you have 5 fridges going through an RCD, and the RCD is not tripping, it will be because that your appliances are not eathed at all or not earthed properly or the earthed is highly resistive. If this is the case, one day when the fridge is old, you may very well get a zap from it & you may be dead.

More on SWER & MEN systems can be found here;

http://www.dir.qld.gov.au/electricalsafety...t/index.htm#men

MEN info can be found here;

http://www.eng.newcastle.edu.au/eecs/ect/o...essQuizTut.html

I have also attached a very simple PDF about how the MEN system works.

[lopburi3]

No it is not foolish. What is foolish in my opinion is to talk down the only safety device that will work on the normal Thai non grounded home electrical system.

My house is properly grounded and if I have leakage they will trip and be fixed. I will not depend on only the ground wire to protect me.

[Gary A]

Since the house was already wired I ground my appliances separately. There is no third wire. I have an earth stake for my computer, another for my hot water shower and the third for the work shop. Lately I noticed the wife pulling the plug on the microwave. She told me it was shocking her so that means I need at least one more. If I were to build a house here I WOULD have grounded circuits for every box.

[chownah]

Elkangorito,

Thanks for the links. I read the code stuff for the swer system and understand most of it. I have single phase 220V to my house and I want to establish another service some 200 metres away. If I understand what the code is saying, I can forget about the high voltage stuff and follow the low voltage information which is mostly that for the return circuit earthing system I should have three earth ground electrodes seperated the proper distance and connecte so that if two of the wires between electrodes were to break there would still be one electrode functioning....and each electrode should be able to carry the full panel load without undue voltage drop. Of course added precautions should be made to protect the earthing system's components to avoid tampering or deterioration. In addition, I'm thinking that if I want to install a safety breaker at this installation then its earth electrode system must be well seperated from the return circuit earthing system.

I'd appreciate it if you would comment on what I have written and if you have any other links that might describe how to actually make the return circuit earthing system....description of electrodes, better to be near a pond or better to stay away form ponds for safety?...the ground water level here is never more than 3 metres below surface, should I place electrodes in the ground water and if so should they be galvanized iron, solder coated copper, or what..... sizing of wires, etc.

I guess since I now know that this system is officially called a swer system I guess I can go google and find for myself....thanks for your help.

Chownah

[david96]

The attachment shows a typical earthing arrangement

[Crossy]

More information on EUROPEAN grounding systems here:-

http://www.epanorama.net/documents/groundl...rangements.html

Note that MEN systems are NOT the norm in the UK (where I trained, long expired cert, I remember voltage operated ELCBs being the latest thing) although they are becoming more common as the are far safer when correctly implemented.

IMPORTANT (I'm sure Elkangorito will agree with me here) If you have an MEN link do not interfere with it, if you DON'T have an MEN link do NOT install one unless advised by your electrician (and let him install it, then it's all his fault )

Edited February 12, 2006 by Crossy

[elkangorito]

No it is not foolish. What is foolish in my opinion is to talk down the only safety device that will work on the normal Thai non grounded home electrical system.

My house is properly grounded and if I have leakage they will trip and be fixed. I will not depend on only the ground wire to protect me.

Lop,

It was not my intention to "talk down' RCD's. I suppose, in a long winded way, I was trying to say that it is not wise to totally rely on 1 device that can readily & unknowingly fail without notice. A proper earthing system is considered to be much more important, above & beyond all other things.

I will re-state what I said before;

"It is foolish to assume that an RCD used in an installation that is not properly earthed, will save your skin. The earth is needed as a second current path, should the neutral fail (which can be common in devices that vibrate or generate heat). The whole idea is that the earth/neutral current path has the lowest resistance possible so as to allow the protective devices to act in the appropriate amount of time. Also, RCD's are electronic devices that can readilly fail without your knowledge. What if it fails just after to do your periodical "test trip"? You will not know & you will think it is working properly."

You can do what you like & believe what you like but at the end of the day, it could cost someone's life for not having a proper earthing system...as it seeems to happen frequently in Thailand.

[lopburi3]

The fact is the most home systems are not properly grounded and a tenet has little control over that. But in most cases they can install RCCB for about 4,000 baht without the landlord having a heart attack. As I say and advise - have both. But if you do not have the ability to have a grounded electrical system use RCCB and attach grounds to those units that are likely to have leakage, refrigerator, air conditioner, microwave. toaster oven. dishwasher, dryer, washer, water heater etc.

I do have a grounded system and fully support that concept. My objection was the comment on RCCB not working without a ground and that many readers will take that to mean forget it because it will not work. Any protection is better than none and in my experience GFI has worked well during the 20 years that my house did not have a proper ground system and probably saved my butt.

Another warning here is that very few electricians (outside of EGAT) have a clue in my experience. They (EGAT) seem to be willing to check home supply (at least here in Bangkok) and advise what needs to be done. At least the electrician can't laugh them off like they often do to others.

This is kind of a crusade with me so admit I came down hard as have some one post wonders who will say most authoritatively that GFI will not work so forget it and I feel a persons life may be lost because of that misinformation. I have lost friends so am very sensitive on the subject. Am most happy that you have brought up grounding and electric safety and hope that some reading may take actions that can save them or someone they love.

[david96]

The attachment shows a typical earthing arrangement

save this image to my pictures (xp) and open there it will be clearer to read.

[elkangorito]

Hi chownah,

Firstly, I'd like to point out the various parts of a SWER system. Essentially, it is divided into 2 parts - the high voltage side (HV) & the low voltage side (LV). You have no control over, & should not be concerned with, the HV side. You will be directly connected to the LV side.

The HV side.

The supply normally originates from a suburban or metropolitan substation & is delivered at normally 19kV (19 000 volts) or higher, depending upon the distance it must travel to the remote LV transformer. In plain English, 1 or more phases of HV is sent to the remote transformer & returns to the metro/urban substation via earth - there is no neutral conductor for the HV side.

The LV side.

The HV is transformed into LV at the transformer, which is located somewhere near you (can be many kms away). You have no control over the connections at this transformer, however, since Thailand uses an MEN system, the neutral on the LV side of the transformer should be connected to an earth stake at the transformer. From this transformer, you should receive an Active conductor & a Neutral conductor. At your Main Distribution Board in your house, you should install an MEN link as prescribed by the drawing that david96 posted. Minimum cable size of 16mm squared cross sectional area.

NOTE 1: this drawing shows the same MEN wiring in 2 different ways.

NOTE 2: cable sizes are not indicated in these drawings & will be determined by the Maximum Demand of the load (your house). These cables sizes can be found in AS/NZ 3000:2000 & AS/NZ 3008. These standards are Australian but can apply to Thailand. The standards can be purchased through the Standards Australia website http://www.standards.com.au/

These Australian standards are normative (legislated & therefore mandatory) throughout Australia.

Remember, you only have control over the wiring at your end of the electrical system although you may be able to persuade the Thai electrical folks to follow these guidelines as discussed.

I further recommend, since the Thai authorities probably won't do things properly, to install your Main Earth stake as follows;

1) In your situation, the stake should be at least 2 metres long & be of the 'steel core copper sheathed' type (this is easier to belt into the ground). If not, a pure copper stake is ok but the further it needs to be driven into the ground, the thicker it should be as copper is easily bent. If you can't get a steel core copper sheathed stake, ensure that the pure copper stake is at least 20mm diameter so it won't bend as you drive it down deep, otherwise about 12.5mm (half inch for those not into the SI system) diameter will suffice. Ensure that there is at least 200mm of stake exposed after driving it into the ground. The Main Earth stake should be placed as close as possible to your Main Distribution Board. The Main Earth connection to this stake is critical. The connection point on the stake should be cleaned & polished with steel wool (or similar) prior to bonding the Main Earth cable to the stake, with an appropriate clamp. After the Earth connection to this stake has been done, it should then be painted with acrylic paint (do not use oil based paint) to prevent oxidisation. The Main Earth point of connection should always be accessible at all times. The cable to this connection must be mechanically protected against disconnection ie mowing grass, building works etc. This is normally achieved by running the Main Earth cable in PVC conduit along the exposed area.

If this is done & all of your 'metal cased' appliances are properly earthed, you have just completed the most critical life saving thing. Please take note - you will probably have to supply your own earth & 3 pin plug with most Thai appliances. Eg I did an MEN system on my mates house in Amphur Klaeng. I made sure that all GPO's (general purpose outlets or power points) were 3 pin & were connected to the Main Earth bar in the Main Distribution Board. This is ok but I did advise him that all of this is useless unless all metal clad appliances are effectively earthed via the GPO's. After getting several shocks from his fridge (old fridge - high residual earth leakage, which is why you should not not put your whole house through an RCD), he had to run a separate earth wire to a 3 pin plug. All shocks have stopped. BTW, it appears that 2 core & earth cable is difficult to get but not impossible to get in Thailand. Same as '3 core flex' (extension cord).

It's fine that I tell you all of this but there are details that cannot be explained like the method of terminating cables/wires etc. This comes from years of practice & know how, & is also very important.

Prior to energisation of the installation, an insulation test should be conducted with the use of a 'Megger' (minimum 1000 volt). The outcome should be infinite resistance from any phase to earth (all appliances unplugged from the GPO's & power NOT turned on at the Main Distribution Board). If you get otherwise, you have a problem & the installation should not be energised until it is sorted.

Also, if you are thinking of installing another downstream DB (distribution board) for the purposes of irrigation, this should come from your Main Distribution Board (as a 'sub mains'). You do not require a SWER system for this. The only problem I can see with this is that you may exceed your Maximum Demand & therefore need to upgrade your cable sizes & protection equipment at your Main Distribution Board.

Hope this helps.

To Crossy...I fully agree. DO NOT INTERFERE WITH AN MEN LINK. Further, only one MEN link is permitted per residential installation. This link is always at the Main Distribution Board.

Edited February 12, 2006 by elkangorito

[david96]

Thailand uses the TT system also known as the direct earthing system, ie when an earthing system is employed.

The TN-C-S is the MEN system as known in Australia/NZ.

One cannot see any reason why the MEN system cannot be used in an electrical installation in Thailand. The supply authority benefits as it earths their supply neutral as well.

[phibunmike]

Your electrician will know whether you require a MEN link in your dizzy board. I've not come across a MEN system in Thailand as yet (doesn't mean they don't exist though). It is important that you don't fit a MEN link on a non-MEN system, interesting things will happen in the event of an open-circuit neutral. Depending upon where the break occurs your MEN link could end up carrying all the neutral current for your entire moo baan, fizzzzz!!

Interesting info from you all. However I have now read apparently contradictary advice about MEN links.

How do I know whether to fit a link between my Neutral and Earth in my distribution box ?

If I measure voltage difference across N-E first, and it is less than a certain amount, is this a good test ?

Thanks.

[phibunmike]

Further to my last post...

My house is new, I installed L-N-E wiring throughout with 3 pin sockets. I instaleld a distribution box by "Green" purchased from the big hardware store in town. It is ready fitted with RCD (on all circuits - I intend modifying that so that my fridge can go on a non-RCD circuit). But it has no MEN link.

I am in the process of installing an earth rod (copper, about 1.5 m x 1cm) which will be a in the permanently wet soil where my kitchen sink waste water runs out, about as close to the distribution box as I can get - maybe 7m as the wire runs. I could make it a couple of metres closer with an awkward cable run. I have a metal strap to run from the ground stake back to my distribution box.

My house plumbing is PVC, except for a couple of metres from the water heater to the shower. It is my intention to wire a ground wire from the heater socket to a clamp on those steel shower pipes.

Any comments welcome

Thanks, Mike.

[Crossy]

This information is from a UK point of view, from a UK trained and certified (expired) sparks.

If you are not sure whether you are on an MEN system do NOT install a link.

If your house is the only one on the local transformer, you can install a link and improve your system safety.

If there are other houses on the same transformer, beg a look at their breaker boxes (look at a couple if possible), if they have MEN links, install one, if they don't have links do NOT install one.

The whole point of MEN is that it is MULTIPLE earth. A single link between earth and neutral could present a hazard in the event of a neutral failure as all the neutral current will flow through your ground stake. In a properly implemented MEN the neutral current will be shared between all the earth stakes (in the event of a neutral failure) making it inherently safe. This is the main reason that MEN systems were slow to catch on in the UK.

Personally, I would install TWO ground stakes with separate wires back to your earth bar in the breaker box.

Your water heater should have a ground connection on its metalwork, connect that to ground and supplement with a pipe clamp ground as well.

[phibunmike]

This information is from a UK point of view, from a UK trained and certified (expired) sparks.

If you are not sure whether you are on an MEN system do NOT install a link.

If your house is the only one on the local transformer, you can install a link and improve your system safety.

If there are other houses on the same transformer, beg a look at their breaker boxes (look at a couple if possible), if they have MEN links, install one, if they don't have links do NOT install one.

The whole point of MEN is that it is MULTIPLE earth. A single link between earth and neutral could present a hazard in the event of a neutral failure as all the neutral current will flow through your ground stake. In a properly implemented MEN the neutral current will be shared between all the earth stakes (in the event of a neutral failure) making it inherently safe. This is the main reason that MEN systems were slow to catch on in the UK.

Personally, I would install TWO ground stakes with separate wires back to your earth bar in the breaker box.

Your water heater should have a ground connection on its metalwork, connect that to ground and supplement with a pipe clamp ground as well.

Thanks a lot Crossy. I had to laugh when you said "beg a look at their breaker boxes" as no-one else for miles has one - they all have a single double-pole porcelain knife switch and a ceramic 5A fuse !!! No-one has an earth of any sort.

I am on the same side of the transformer as several other houses. Probably my set-up is familiar to most other Isaan dwellers in the forum.

I guess from what you say I should NOT install the MEN link.

I will follow you advice a propos the second ground stake. I have a second distribution box slaved off the first in a separate building for my garage, spare toilet, well pump and garden lights. Would it be a good idea to provide a separate ground stake for this, or better to keep to a "star" arrangement of grounds ?

Thanks again for your valuable advice .

[chownah]

By far the appliance with the greatest possibility of electrical danger is the hot shower. Why not get a gas shower and eliminate the problem altogether and get a bigger volume of hotter water to boot? Any room with good ventilation can have a gas shower in it and every village bathroom I've seen has enough ventillation....or if you're worried about this then get a gas on demand heater and install the unit outside. You will also avoid voltage drops everytime someone showers!!!

I've got a gas shower and I don't have any cutout switches anywhere in my house and I feel perfectly safe like all of humanity did before the invention of these devices which was only a few decades ago afterall....its great to be safe and all and I certainly think that if you can not feel safe without one of these safety devices then by all means get one or many if you like but please do consider that they are not necessary...just like motorcycle helmets are not necessary.

Edited February 13, 2006 by chownah

[elkangorito]

phibunmike, it is a dangerous idea to use water/gas/any other metal pipes as an earth. Only use 1 main earth. If you choose to use 2 main earths, as crossy suggests, ensure that both main earth cables are run to the Main Earth Bar in the Main Distribution Board. Generally, only 1 main earthing conductor is prescribed under residential conditions. The reason for this is that residential installations do not (generally) suffer the mechanical trauma that a commercial/industrial installation would.

Crossy, I must disagree with you about the installation of MEN links in this regard - Thailand uses an MEN system. If an MEN link is not installed in a residential Main Distribution Board, it does not mean that an MEN link should not be fitted. If the 'star point' of an upstream distribution transformer is not earthed, then the earth return will come from a transformer further upstream. Obviously, this transformer will be of higher voltage but will be so far away from the residential load so as not to cause any problems with any high voltages being accidentally presented onto the residential system. Therefore, my advice is to install an MEN anyway. Your feedback on this would be appreciated.

When I installed an MEN system to my mates house, I did not notice an earth from the 'star point' of the local distribution transformer (on a pole about a kilometre away). Nonetheless, the installation tested ok for earth return voltage, which proved to me that there was an earth return connection. This is obviously much safer than relying on a neutral, which can be broken.

Edited February 13, 2006 by elkangorito

[phibunmike]

phibunmike, it is a dangerous idea to use water/gas/any other metal pipes as an earth. Only use 1 main earth. If you choose to use 2 main earths, as crossy suggests, ensure that both main earth cables are run to the Main Earth Bar in the Main Distribution Board. Generally, only 1 main earthing conductor is prescribed under residential conditions. The reason for this is that residential installations do not (generally) suffer the mechanical trauma that a commercial/industrial installation would.

Crossy, I must disagree with you about the installation of MEN links in this regard - Thailand uses an MEN system. If an MEN link is not installed in a residential Main Distribution Board, it does not mean that an MEN link should not be fitted. If the 'star point' of an upstream distribution transformer is not earthed, then the earth return will come from a transformer further upstream. Obviously, this transformer will be of higher voltage but will be so far away from the residential load so as not to cause any problems with any high voltages being accidentally presented onto the residential system. Therefore, my advice is to install an MEN anyway. Your feedback on this would be appreciated.

When I installed an MEN system to my mates house, I did not notice an earth from the 'star point' of the local distribution transformer (on a pole about a kilometre away). Nonetheless, the installation tested ok for earth return voltage, which proved to me that there was an earth return connection. This is obviously much safer than relying on a neutral, which can be broken.

Thanks Elkangorito. It is not my intention to use the water pipe connection as an earth for the house, only to provide additional safety for anyone using the shower - so that I can be sure the stream of water they are standing under, and the tap they grab, are earthed. I am using a copper stake for the house earth, which I might double up following crossy's suggestion. From your post I guess a separate ground stake for the slave consumer unit (in the garage block) is NOT a good idea.

When you say "Thailand uses an MEN system", what does that mean ? Does it simply mean E-N link at every transformer ? It surely can't mean at every house as (in my area anyway) very few houses have earths.

The supply from the pole to my house is only two blue wires - presumably Live and Neutral - with no separate earth (although I assume the Neutral is earthed at the transformer, but I don't know).

I await with interest while you two elecy's discuss the issue of the MEN link... (thanks for your time and input guys).

Chownah, I have a (probably illogical) distrust of gas, although I do use it in the kitchen. My bathroom is not well ventilated, so could put one outside and build a little room for it, but will probably stick to the electric one - although I must admit the lights do dim when someone is in the shower !!!

My next project with respect to hot water is to run some pipes on the roof with a small storage tank as a home-grown solar system, just to get the initial chill off the well water. That would mean that often a cold shower would be refreshing instead of unpleasant, and the electric heater has less work to do...

Edited February 13, 2006 by phibunmike

[elkangorito]

phibunmike, under no circumstances should you use metal piping as an earth...even as a secondary earth. Earth 'potentials' can be dangerous, so only use the one earth...the main earth. Having more than one earth, especially at distances greater than 3 metres apart, can lead to 'earth potentials'. ONLY USE THE MAIN EARTH VIA A GPO OR VIA AN EARTH WIRE DIRECTLY CONNECTED TO THE MAIN EARTH BAR IN YOUR MAIN DISTRIBUTION BOARD. This only applies if you choose to use an earth that is NOT a stake driven into the ground. Residential earthing should always be via an earth stake driven into the ground.

Cheers,

Rob.

Edited February 13, 2006 by elkangorito

[Crossy]

From Mike's description he has a TT system, overhead lines, neutral grounded at the transformer but WITHOUT a MEN link in the breaker box. Each installation has it's own earth rod / plate (if it has anything). This is a UK standard for remote locations fed by overhead line (probably Oz as well).

The TT arrangement is allowed by IEC 364 (1995) and IEC 60364 (2005) and is noted as being as safe as TN-C (MEN), TN-S (separate ground provided by supplier) and TN-C-S (a combination of the two which is becoming popular as the UK incarnation of MEN) when used in conjunction with a suitable RCD (ELCB).

Interestingly, TT is actually noted as being preferable to TN-C by IEC 60364 in locations where IT equipment is installed because of the smaller transient ground currents that will flow due to a line-earth fault.

There is some very interesting (but technical) reading here for the sparks amongst us :-

http://www.electrical-installation.merling...nstallation.htm

I do stand by my assertion that Mike does NOT use a MEN link as we now know that no-one else has one, unless of course, the other houses install links (and grounds of course).

phibunmike, under no circumstances should you use metal piping as an earth...even as a secondary earth. Earth 'potentials' can be dangerous, so only use the one earth...the main earth. Having more than one earth, especially at distances greater than 3 metres apart, can lead to 'earth potentials'. ONLY USE THE MAIN EARTH VIA A GPO OR VIA AN EARTH WIRE DIRECTLY CONNECTED TO THE MAIN EARTH BAR IN YOUR MAIN DISTRIBUTION BOARD. This only applies if you choose to use an earth that is NOT a stake driven into the ground. Residential earthing should always be via an earth stake driven into the ground.

Cheers,

Rob.

ABSOLUTELY 100% !!!!!!

[chownah]

In the US I owned a house and I replaced the main panel. I used two earth rods and for some reason I was required to connect a ground wire to the galvanized steel pipe supplying the hot water heater...this was the steel pipe came from the street underground....so...I guess sometimes havinga ground link to a pipe is required....can't remember just exactly what this was called or why it was necessary.