david96

If you have the full load current in amps on can calculate the voltage drop and hence the correct cable size in copper in sqmm.

The switch should be able to carry the full load of the motor continuously. You should replace the switch if possible and fit an MCB in place of the knife switch, 20Amp may be sufficient.

Also, a word of warning, although I doubt Jetstar would ask, but most airlines will not allow a passenger to fly on a ticket purchased with a creditcard in someone elses name unless that person is present at checkin to produce the card. I know Air Asia dont ask because I have done it many times using my Dads creditcard.

Not too sure about this one......my wife travelled on Thai with a ticket purchased on my credit card.....more than once.....was never questioned and I was here in Oz.

Cathay Pacific Airlines required one to be able to produce the credit card at initial check in at the airport.

That was according to their website about 12 months ago. Whether they check at an Australian airport

or not is another matter. On-line website bookings only.

An RCD will minimise the effects of electric shock and automatically disconnect the supply from the following.

A broken PE conductor in the cord of a defective appliance (indirect contact).

A damaged appliance cord with an exposed live conductor (direct contact).

A broken active pin of a 3 pin plug top exposed in a socket outlet (direct contact).

Damage to a 2 core and earth cable, damage will generally involve the earth with the line or neutral conductor.

An incorrectly wired 2 core and earth extension lead or appliance (line or neutral to earth).

Most electrical fatalities are caused by indirect contact.

Earthing will not protect a person from the effects of electric shock from direct contact. ( Unless the circuit is protected by an RCD.)

A 10mA RCD will disconnect in less than 0.04secs, a 30mA RCD will disconnect in less than 0.2/0.3secs. An RCD must operate between 50% and 100% of its rated current in mA. In practice the sensitivity is about 70% of rated mA.

An RCD must be used where the earth impedance is not sufficiently low enough to trip an overcurrent protective device within the required disconnection times ( 0.4secs).

RCDs should be used on final subcircuits where the integrity of the earthing system cannot be guaranteed.

All your socket outlets should be RCD protected not just some of them.

A socket outlet in a Thai style bathroom is not advised. There is no reason to have a socket outlet in a bathroom at all.

Once you have your max demand calculated you would be advised to contact the PEA/MEA first for your energy metering requirements. Then see if they require a MCB as a main switch along with any requirement to instigate an MEN on your main switchboard.

They also use 220/440V 60Hz this is a 3 phase system.

220/440 is not a 3-phase voltage. 208Y/120 and 480Y/277 are examples of common US 3-phase systems. 120/240 is the prevailing single phase voltage for residential use in the US and the transformer has a center tapped grounded neutral.

One was refering to multi voltage motors 3 phase 60HZ 208/220/440V in this case

Sorry for being the skeptic here but I cannot imagine a normal, household residential type of clock used in the USA that uses 240 volts for power. You would not normally have a wall socket in a room wired for 220 volts in the US and if so it does not look like other 120 volt sockets and is not wired the same. Is this some specialized kind of clock? If so the power requirements would be similar to a electric dryer or electric cooking appliance and the plug/sockets required are different.

and even if this was the case US 240v and Thai 240v are two different animals. US 240v is two phases each 110/120v, Thai is single phase 220/240.

Thai voltage is 220V 50Hz 2 wire for single phase applications, the Americans use single phase 3 wire supply with a centre tapped neutral, 115-0-115V 60Hz. 230V on the two outer wires. It is single phase in operation.

They also use 220/440V 60Hz this is a 3 phase system.

The timer motor would most likely overheat and burn out one can run a 50Hz motor on 60Hz but not the other way round.

Have the same problems, today 31/3 it is can be used only with dificulty a lot of info is blanked out or has an "X".

Running IE8, no problems with other websites, just Thaivisa.

MCBs and fault current ratings.

MCBs up to 100A are generally of a common frame size, examples are the Terasaki SAF-T, the Heinmann CF, and the Eaton QC range. They all have a common fault current rating of 6kA. This is based at 380/440V 50Hz. They are the standard MCB used in electrical installations. Fixed overcurrent and earth fault tripping, Curves B, C and D. Curve C is the most widely used for lighting and power circuits. Standard curve is C.

The other standard is the European pattern known as DIN. They are smaller physically and are manufactured up to 100A in 3kA, 4.5kA, 6kA and 10kA. but will fit in a common panel board or loadcentre. They also have fixed overcurrent and earth tripping features. Available in curves B,C, and D.

Over 100A and the fault level of these devices increases and they are kown as MCCBs.

These may have adjustable tripping characteristics and earth leakage modules may also be fitted, 0.3ma to 10A with time delays 0 /0.5/1.0 sec. These MCCBs are used on large main switchboards etc. They are used on subcircuits that have a high fault current at the switchboard. They are expensive. HRC fuse switches are the alternative.

Circuit breaker manufacturers will type test their products with a recognised testing authority and the kA ratings will be given for different voltages and frequencies.

A MCB may be rated at 6kA for 380V and could be 10kA for 220V. In othe words if one uses a 6kA MCB it would comply.

Those Square D MCBs available in Thailand are almost identical to the Eaton QC range. The QC range originated from Westinghouse in the USA.

......

The neutral is bonded to earth along the distribution network by a single copper conductor to an individual earth electrode at regular intervals. This bonding enables the PD between the neutral and earth at close to zero volts as possible.

...

Interesting thread. Just a minor observation: in my PEA area, the neutral is bonded to earth (I think every 200 metres) by aluminium cable to a galvanised earth rod - I've never seen copper being used here.

It was in Australia one was refering to as a typical well implemented MEN system. Copper is used and the minimum MEN conductor on the distribution system is generally 16sqmm to a copper clad steel electrode.

On the point of earth electrodes, no mention is made to prove one has achieved the minimum

of 5/25ohms. This requires specialist equipment.

On RCDs, very vague about their implementation and only recomended. If they are genuine

regarding protection they should spend less time on the onerous earthing requirements of a consumers installation and concentrate on the mandatory installation of RCDs instead.

HRC fuses will clear a short circuit fault of high magnitude much faster than a MCB/MCCB.

This is why most DSBs in many large electrical installations are specified with 6kA MCBs. The sub mains supplying them may be 250A or 160A but they are protected by CFS units with HRC fuses on the main switch board which may have a rating of 50kA.

With an HRC fuse protecting the consumers mains one can use MCBs with far lower short circuit ratings. Means lower costs for an electrical installation, and protection is not compromised.

The most logical place to install HRC fuses to protect consumers mains in Thailand would be on the line side of the PEA/MEA metering point.

Ref to post #19 by Elk.

Costs being born by the consumer not the PEA/MEA regarding implementation of their version of the MEN system. To try and obtain a contact resistance (5 ohms/25ohms) between the earth electrode and the soil surrounding it can be an expensive exercise.

But the electricity distributor carries this out on the distribution system neutral at the transformer earthing may be vertical rods in a trench bonded with a bare copper conductor or alternative means such as horizontal strip electrodes buried at the required depth.

The neutral is bonded to earth along the distribution network by a single copper conductor to an individual earth electrode at regular intervals. This bonding enables the PD between the neutral and earth at close to zero volts as possible.

This is why under AS3000 a depth of 1.2/1.8M with one 12mm copper clad steel electrode is regarded as complying. It in effect just bonds the main neutral to the general mass of earth.

Fault current limiters: These are in effect the service protective device which in most cases is a cartridge type HRC fuse. These fuses may be mounted on a pole, or in a distribution box with underground reticulation. Essentially they protect the consumers mains. They are not for overload protection. They also provide a point to disconnect the electrical installation. This is why one can use 3kA MCBs. and previously before MCBs, rewirable porcelain fuses which had a lower kA rating again.

Short circuit levels are far less on a single phase 220V supply than a 380V bolted 3 phase fault.

"No differing potentials between any two points on the surface of the earth" One might interpret that to mean equipotential bonding in some form. Or do they refer to "touch voltages"?

One would agree with your comments in the last paragraph. Also there is no mention of mandatory testing.

(One used soil resistivity and contact resistance as meaning the same , they are not it is contact resistance with the electrode was what was being refered to and one of the reasons an earth electrode must be exposed to the weather and not be encased in concrete.)

It would appear that the earthing arrangements costs are being born by the consumer not by the PEA/MEA in their implementation of the MEN system. These figures of soil resistivity (contact resistance) of 5 ohms and 25 ohms is what might be expected when earthing the neutral of the distribution network. It is not stated if the neutral of the distribution system is actually earthed and at what points.

The 10kA fault levels for MCBs seem very high for a residential installation. Have they not heard of fault current limiting?

What "Standard" are they refering to?

What do they mean by "no earth (ground) potentials permitted"? No mention of insulation values which should be a minimum of 1.0 Megohm.

Compare this with AS3000.

Service protective device

MCBs generally a minimum of 3kA.

Main Earth 4.0 sqmm minimum.

Earth electrode 12.7 copper clad steel 1.2M. minimum.

No soil conductivity tests to main earth electrode required.

While some may find Thai electrical installations confusing, with 2 pin and 3 pin socket outlets, 3 types of plug top, Euro and the American pattern, no earthing etc.

Australia never had the problems of 2 pin socket outlets unlike The UK, Europe and the Americas. We specified 3 pin socket outlets and 3 pin plug tops from the very beginning. And our socket outlets were standardised and foreign outlets were prohibited. This meant that every earth connection of a socket outlet was earthed and there would be a neutral link and main earth at every main switchboard and a neutral link at every sub board in an electrical installation. Supply Authorities installed rewirable service fuses on the phase conductors on all consumers mains. The main earth was generally the mains water supply pipe or a 3/4inch galvanised pipe electrode. We also adopted the MEN system from the beginning, although some small supply authorities used Direct Earthing and Voltage operated ELCBs, these had mostly been changed over to MEN by the end of the 1950s.

Australia had the safest electrical installations in the world and was ahead of most countries in the 1960s including the UK.

Thailand suffered because they compromised between America, Japan and European standards and different installation methods.Thailand is trying to do now that what should have been done in the first place and it will be very difficult if not impossible.

Here are some points for discussion regarding Earthing.

1. Why is earthing carried out ?

2. The function of the PE conductor.

3. The function of the main earth and main earth electrode in an MEN system

4. The function of the main earth and main earth electrode in a TT or IT system.

5. Why must the main earth connection never be disconnected while supply is connected to an electrical installation?

6.When and why must auto disconnection of a protective device occur in the event of an earth fault?

7.Touch voltage and its effects.

8.Equipotential bonding.

It is normal practice with an MEN system to connect the incoming neutral directly to the neutral link. The incoming neutral must not be switched. All sub circuit neutrals teminate at the neutral link. The Main earth is connected directly to the earth bar and all protective earths are connected to this earth bar.

The MEN link is connected between the neutral link and the earth bar. It is removed only for testing purposes.

Source: AS/NZ3000.

Australian Standards, AS/NZ3000/2007 Permanent fixed wiring, Colour codes.

Red. phase or active conductor.

White. phase or active conductor.

Blue. phase or active conductor.

Black. neutral conductor.

Green/yellow trace. earthing conductor.

Brown and Grey. control wiring.

Any colour with a black trace. control wiring.

Any colour with a colour trace. control wiring.

Flexibles, Single phase. Brown. Active. Light Blue. Neutral. G/Y earth.

Multi phase Red. phase

White. phase

Dark blue. phase

Black. neutral

Green. earth.

European, Flexibles.

Brown. phase

Black. phase

Grey. phase

Light blue. neutral

G/Y. earth.

In Thailand one has only seen the IT system utilised and some areas may be TT on installations, and they have to be visually verified.

Transformer earthing an electrode 6 meters? I think that can be interpreted as a trench with multiple earth electrodes bonded together. Equal to or better than.

The minimum earthing resistance is generally regarded on LV distribution network at the tranformer as 10 ohms. (Visual check to see if earthing has been implemented).

Drawing 1 appears to show a MEN link. Drawing 2 shows a MEN link but only a 2 pin socket outlet, no PE. Protection is by RCD only. Main earth electrode indicates 2.4M in the ground.

Earth fault loop impedance or verification of impedance. AS3000.2007 Clause 8.3.9 ( as a guide)

Where an installation includes circuits containing socket outlets not protected by an RCD the impedance required for automatic disconnection of supply shall be verified on each such circuit by:

1. Verification of the total resistance of the active and protective conductors ( using a continuity tester); or

2. Where supply is available verification of the earth fault loop impedance. (With a suitable instrument designed to measure low values of impedance).

If you install RCDs loop impedance testing is not required.

Crossy, did you get the drawing translated? If not, I'll take it to work & have one of the electrical guys translate it. It may shed more light on this subject.

The drawing is clear but a translation would be more informative.

It would appear that 10sqmm is the minimum for the main earth. It would appear that their implementation of the MEN system relies on the main earth at each electrical installation and at least one earth on the distribution system. By definition it is TN-C-S.

One wonders why a separate earth link is not used in the drawing. A 2 pole MCB is used as the main switch but a single pole device in the phase conductor is all that is required. The neutral link is before the main switch because perhaps a 2 pole device is used in this case. 10kA fault level has been selected as consumers service protective devices are rarely used.

The document in itself would seem to legitimise and justify the use in practice of the MEN system on new electrical installations from the start of 2547/2005.

It is a drawing that can be expanded upon for electrical installations in general.

Thanks, Crossy.

Now it all becomes clearer.

Thai system of implementation of the MEN would seem to be.

Install the neutral link on the line side of the main switch (MCB).

Use of the neutral link and earth bar, no separate earth bar.

10 sqmm for the main earth.

2 x 10 sqmm for the consumers mains minimum.

All circuits on a 30ma RCD.

I would agree with you on the location of the neutral link.

Actually Crossy, if one carries out a risk assessment there is a potential electrical hazard that may be introduced by the use of the MEN system in Thailand.

The hazard is electric shock from the earthing system from reversal of polarity on the consumers mains. In Australia/NZ/UK that hazard is minimal and in practice may never happen.

In Thailand it is different, reversal of polarity is far more common and it seems to be picked up when the MEN system is implemented at an individual electrical installation. Therefore the chances of this hazard occurring is high and there is a likely event that it could occur. With this in mind one would try to minimise the hazard and the only way to do this is to not use a MEN link.

One wonders how may electrical installations in Thailand have incorrect polarity and have been like that for perhaps years. And no one notices it because the MEN system is not implemented.

Some of the older installations eg 20 years use double pole MCBs no neutral link or 2 pole fused switches.

The ones I have seen were of the "MEM" brand and a recent one used Square D MCBs in Bangkok in a new residence, all MCBs were 2 pole and no neutral link.

What Thai government website did you obtain the information on the MEN connection? How is it that the PEA/MEA cannot advise on its use? It has to be enshrined in legislation before it can be implemented.

Evidence shows that no one has any knowledge of its official or mandatory use. It would be interesting to locate that document.

p.s. what is a "unit"?

1 kWh Naam, as I'm sure you well know

I agree with the others, something seems well adrift here (or are you keeping polar bears?). You should be able to get the supply authority to check your meter if nothing is apparent from the isolation tests others have suggested.

How many units (kwh) did you use as per the account in the month?

Your account should indicate the date read, the meter number, the previous reading and the current reading with the daily average consumption. You can then work out the average cost per kwh.

Take a reading of the meter and note the time and date for your information.

1900B for the month might be nearer the mark. They may have counted the last digit on the meter as a unit, it is actually one tenth of a unit.

Have you a legal will? If not you should arrange to have one for your assets in Thailand and a separate one for your UK assets. If you were to divorce you then rewrite your will.

A lot of Thais think that as a divorcee of their previous husband they can claim on the death of their previous spouses estate. That is why it is important to have a valid will.

When you divorce she has no claim on your estate on your death, unless she is provided for in a legal will.

If you die interstate there is a fixed formula for distribution of assets, and your estate has to go for probate first anyway, but this may not be the case in Thailand, eg bank accounts etc.

Double pole (2 pole) MCBs are readily available in Thailand, one brand is Square D. Often a 2 pole is used as a main switch and single pole on sub circuits in a metal distribution board (load centre)

I have never seen a MEN installation in Thailand, all have utilised the direct earthing system, if earthing is implemented at all.

No one has produced as yet a document in Thailand (in English) stating that the MEN system is mandatory.

either in a regulation or conditions of supply by the PEA/MEA. Until that time and the fact that correct circuit connections and polarity testing is not carried out on connection to supply it would be advisable NOT to connect a MEN link at the consumers main switchboard.

The wide use of 2 pin sockets and appliances connected by a 2pin plug top and twin flex, along with 2 core extension leads would be a problem as there is no PE (protective earth) so in the event of an earth fault the protective device would not operate, and the person could receive a severe electric shock. However RCDs would

disconnect the circuit in less than 0.2 secs, affording protection. In practice about 0.02secs.

RCBOs are available in 1 pole + fixed neutral and 2 pole, 10ma and 30ma.