electau

In answer to post # 35 by doglover.

Only the metering requirements are required to be accessible at all times so they are located on the outside wall of a domestic electrical installation. Provision is made for 2 meters and a time switch usually but the main switchboard can be mounted inside the building subject to the requirements of AS3000. The metering enclosure is fitted with a hinged panel for the mounting of the meters and circuit protection devices (MCBs RCDs) etc. In multi tenanted installations metering is at one location only and units are all separately metered, with sub mains and load centre (CU) for each individual living unit.

I prefer a copper clad steel earthing rod.

A galvanized water pipe will eventually rust away to nothing.

In reply to post # 15.

In Australia it is the supply authority who decides the location of the metering position and in domestic electrical installations the metering and switchboard are combined in a metal weatherproof enclosure on the property. In Australia it is an offence to carry out electrical work unless you are licenced under the legislative requirements.The main earth connection must be visible for inspection and exposed to the weather and the last 300mm of the electrode is usually saddled to the outside wall of the structure for mechanical protection.

In Thailand metering is not on the consumers property so there is no requirement to have the main switchboard in an external enclosure on an outside wall.

The USA is the only country to have an oddball political system, the Westminster system or variants off it have been proven to work effectively.

The European system is still better than the US one.

All updated processing times are on the Australian Embassy website.

http://www.thailand.embassy.gov.au/bkok/DIAC_Lodging_visa.html

A galvanised star picket or a length of 20mm ID galvanised water pipe min. can be used as an earth electrode. It is an option that can be used.

Here is a good site for those interested in nuclear power.

http://www.world-nuclear.org/info/inf08.html

The AUD is in demand and one reason is our trade with China (PRC) and their demand for coal, iron ore and LNG. China is now our largest trading partner.

Australian defence ties are with the USA. Australias future rests on demand from China.

Australia has an official unemployment rate of 5% and the Bank MLR is 4.75%. Inflation is just below 3%. But Australia is a 2 speed economy, it is the mining and energy sectors that are doing well. Our financial sector is strong.

One should remember that the AUD was worth 1.25USD in the 1970s. It was then floated in 1983 by the then Keating government.

The high dollar affects exporters.

PP.......2 hours NE of BKK

Electi......how to fix to make safe and sure ?? ...rented house, not mine...

If you have no earthing system or none of your electrical equipment is bonded to earth touch voltages like this will always be a problem. The voltages themselves are at safe levels, ie less than 50VAC. You need to get your earthing fixed first.

Not enough to throw you against the wall....have had that before.....just unpleasant low level electric fence type shocks.

Had them from computer, electric small oven, TV if you touch the rear where the screws are and the DVD thus far.

The SafetyCut is not working and waiting on owner to have it replaced....been promising to do it over last few weeks.....there is an issue of distance between him and us...but regardless.

Your installation has poor earthing or no earthing also.Have you tested the RCD at the test button? this will test the operation of the device. If this does not work replace the unit.

How many beers would it cost to get this info in English ??.....preferably Aussie english....and even better outback aussie lingo ??

We are getting shocks from severalmitems in the house currently....waiting on <deleted> owner to do something..

How severe are the electric shocks that you are receiving? From what you say it would appear that you have no earthing or poor earthing.

Ask yourself this question,

How many persons have died since 1955 as a result of radiation fron a commercial nuclear reactor?

How many persons have died as a result of UV radiation from the normal rays of the sun in everyday exposure?

Both cause cancer. Cancer within the normal population are normally between 22 and 25%.

One would agree with you Crossy.

1. The black wire which you seem to think may be the main earth should be green or green /yellow as black is a phase colour.

2. The neutral should be clearly identified by white sleeving at each end.

From the PEA drawing the earths are connected to the main neutral link which makes polarity testing and all testing very difficult as the earths and neutrals must be electrically separated. A separate earth bar could easily be fitted.

What made me doubt than there was a main earth was the fact that a subcircuit neutral was found to be used as a protective earth, in other words the electrician may have understood that bonding only was required.

Solar power grid connected are interlocked so when the grid supply fails or is isolated for maintainance the solar inverter shuts down. It is a mandatory safety feature.

From your photographs of the main switchboard it would appear that the main neutral terminates on the earth bar instead of the main neutral link and the neutral then goes to the main switch (MCB).

The neutral link appears to be adjacent to the main switch.

There appears to be no main earth conductor (which should terminate at an earth electrode external to the building). It should be green or green /yellow, minimum 4sqmm.

You have a neutral - earth link but no main earth.(?) If you had an open circuit neutral your earthing system would rise to full line voltage. Earthing the neutral means to connect to an electrode. If you can not verify the main earth install a new one to an electrode.

The main earthing conductor runs from the main earth bar.

If you have sensitive electronic equipment it would be advisable to install a surge protection device.

The correct way to install an MEN is

1. Neutral to the main neutral link.

2. Main earth from the main earth bar to electrode.

3. MEN link from the neutral link to the earth bar.

The MEN link can then be removed for test purposes.

You should have an PE at every point of utilisation, eg socket outlets, aircon,etc and they should run back to the earth bar in the switchboard.

It should be noted that this post is not Thailand related.

It is an Australian problem. The current Gillard government has made a mess of the refugee problem as it has with everything else. Off shore processing is the best way at present.

Australia has legal obligations under international law. Thailand is one of the countries that people transit through to use to get to Australia, along with Malaysia and Indonesia, the last country before voyaging to Christmas Is.

Providing a satisfactory ground requires someone with the proper training and equipment. Having a rod stuck into the soil outside (or inside) your home doesn't mean you have an effective Earth. For example if the surrounding soil is sand it will be completely useless. If it is a floculent soil e.g. a clay type, its resistivity will change with the seasons. Wet= excellent Dry= poor. The soil resistivity needs first to be tested with a galvanometer connected to three rods, spaced apart according to the depth the tester wishes to check the soil resistance. The resistance tested could indicate that you need more than one rod attached to each other either vertically or horizontal. Horizontal in the ground where rocky soils are found. With regard to earthing standards this country is not Robinson Crusoe. Even in Western countries most electricians have little or no knowledge of proper Earthing methods. Many tradesman just piss on the earth surrounding the ER before leaving the scene hoping things will work out. But in the field of telecommunications and power where proper earthing is critical then you can guarantee the soil resistivity is tested and appropriate action taken to design and maintain the wanted (constant) resistance. Home earthing resistance is usually acceptable at 10 ohms or less.

A satisfactory earthing system is one that complies with a recognised standard. Example. AS/NZ,BS or IEC.

The minimum is regarded as a 12.7mm copperclad steel electrode driven at least 1.2 metres along with a ME conductor 4sqmm minimum, including earth bonding and PE conductors.

For example. Under AS3000 the resistance of the electrode to the surrounding soil is not required to be tested as the area in contact with the soil is regarded as sufficient and MEN system is mandatory. (However if the TT system is used earth resistance measurements may be required. A typical value for a single electrode is in the order of 70 to 100 ohms). With a TT system RCDs must be used for earth fault protection.

To state that electricians in Western countries do not understand earthing is not true. It is you that does not understand the training and licencing, mandatory testing and the legal obligation requirements for electricians.

First you should consider obtaining the services of an competent electrical contractor.

They will or should carry out tests on the earthing system

1. Visual check of main earth and connections.

2. Visual check MEN or TT at main neutral link.

3. Main Earth continuity check using a continuity tester. ( max 0.5ohms)

4. Continuity check of all final sub circuit PE conductors

5. Check earth bonding ( continuous metallic water piping that enters the ground).

Other tests.

1. Insulation tests

2. Correct connection tests

3 Polarity tests.

4. Verification of impedance (earth fault loop impedance) on socket outlets not protected by an RCD (MEN system only) This can be carried out using an ohmmeter or by a suitable instrument designed to measure low impedance values.

5. Operation of all RCDs (time/current--ms/30mA.) This test is done last of all.

The max resistance from any part of the earthing system to the main earth connection in practice should not exceed 1.0 ohm.

(Based on the requirements of AS3000).

If you could measure the voltage between the earthing system and the neutral of the transformer ( hypothetical) it would be at full line voltage when there is a O/C neutral.

The touch voltage is between the earthing system and the general mass of earth where a person is standing. This is limited to less than 50VAC.

If the main earth and earth bonding was to be disconnected the touch voltage would rise to full line voltage and a hazardous situation would be created.

Voltages up to 50VAC are regarded as non hazardous under normal conditions. Voltages over 50VAC are regarded as hazardous and automatic disconnection must occur.(AS3000).

Touch voltages only exist under fault conditions. It is the earthing system that minimises the effects of a open circuit neutral and reversed polarity with the MEN system.

Equipotential bonding is intended to minimise the risks associated with the occurrence of voltage differences between exposed conductive parts of electrical equipment and extraneous conductive parts.(AS3000). It is not quite the same as protective earthing.

Normally the voltage between the earthing system ( eg a washing mahine) and the general mass of earth will be minimal and close to 0 volts AC. Up to 1 to 2 volts AC as a guide.

Under AS3000 one can run an earthing conductor to a switchboard in an outbuilding, the MEN is at the main switchboard.( 1 earth electrode)

Alternatively one can MEN each switch board. This is often used on farms etc where there are aerial submains to other buildings. (1 earth electrode for each switchboard).

With reference to Crossys post #1.

If you have any any earth on the load side of an RCD the RCD will trip. In this case the earth is on the neutral.

The only known method is to monitor the neutral to earth voltage and the protective device set to operate at a set value below 50VAC, perhaps 10 to 12 volts. The device would require a functional testing requirement. It would have to protect against high resistance connections in the neutral also.

A compliant earthing system minimises the touch voltage to safe levels.

However, where the neutral integrity ( and for that matter the earthing system) can not be guaranteed the MEN system should not be used. This is the most logical reason to use the TT system and RCDs.

Faulty neutrals are a supply authority problem (PEA/MEA) which they should address.

If one is using the MEN system and a compliant earthing system that conforms with (for example) AS3000.

If the neutral conductor is broken the potential of the earthing system rises to full line voltage.

The touch voltage to earth by a person in contact with the earthing system will not exceed 50VAC. A mild tingling effect may be experienced.

If the touch voltage to earth does not exceed 50VAC, then how can the potential of the earthing system rise to full line voltage?

Equipotential bonding. The actual touch voltage is difficult to calculate but the main earth and equipotential bonding minimise the voltage rise to less than 50VAC.

The earthing system is at line voltage relative to the neutral at the source of supply, the transformer.

The touch voltage is the voltage between the earthing system and the general mass of earth.

If one is using the MEN system and a compliant earthing system that conforms with (for example) AS3000.

If the neutral conductor is broken the potential of the earthing system rises to full line voltage.

The touch voltage to earth by a person in contact with the earthing system will not exceed 50VAC. A mild tingling effect may be experienced.

If this should occur isolate the power at the main switch and the have the problem rectified.

This is the same as having reversed polarity but in this case the power cannot be isolated at the main switch. Reversed polarity should never occur if correct testing procedures are carried out.

With the TT and IT systems if the neutral is broken there will not be a rise of potential within the earthing system.

The main earth or MEN bond must never be disconnected (except for testing purposes).

The first signs of a faulty neutral developing are flickering lights when additional load is switched on. A faulty neutral develops over time.

This is why the main earth is an important feature of the MEN system and affords protection.

Ground rods in Thailand,you must be having a joke (that's other than ex-pat's houses and probably some up-market residences and industrial installations)

In Australia the earth wire is usually clamped to an external water-pipe somewhere convenient (no plastic used, normally copper or galvanised steel) and given a good coat of paint.

An electrode had been made mandatory under AS3000 since 1976. the metallic water pipe is equipotentially bonded to the main earth.