electau

So Crossy the TT system of earthing is still used in the UK for an overhead supply with the PME (MEN) system used for an underground supply to an electrical installation.

Indeed, UK supplies on LV overheads are invariably TT.

Underground may be TNC-S (with or without PME) or TNS. The supply authorities often convert TNS systems to TNC-S when the armouring of the underground cable (which is used as the ground conductor) becomes degraded and no longer provides a functional earth.

Just to throw confusion into the mix your local supply company may not be able to tell you which earthing arrangement you have. TT is fairly obvious, but TNS and TNC-S look the same at the service head (any N-E link is sealed within and not accessible).

Would agree there Crossy.

With the UK PME system the MEN link is the responsibilty of the supply authority and does not form part of the consumers electrical installation. For test purposes the incoming earthing conductor can be disconnected at the main switch board. TN-S.

With the Australian system under AS3000 the consumers main neutral, the MEN link and the main earth and electrode form part of the consumers electrical installation. TN-C-S.

The TT system was never used in Australia although a hybid version combining a V-ELCB and was used in the 1930s as an option it was discontinued by the 1940s and was last mentioned in th 1961 Ed of the now AS3000. There were considerable practical problems with its use.

All were converted back to a conventional MEN connection at the main switchboard. The TT system itself was never seriously cosidered. Leaving out the MEN link is regarded as a serious offence under current electrical legislation.

If you have more than one floor and have outbuildings one can have the main switchboard at the main building and a distribution board at the upper floor of the house, and a distribution board at each outbuilding.

An earth conductor should be run to each distribution board from the main switchboard with the sub mains.

On each board a minimum of 2 light circuits, and 2 power (socket outlets) other circuits as required.

If the TT system of earthing is used RCD protection will be required on all final sub circuits.

Main earth and electrode from the main switchboard.

In general, a typical residence only requires 2 lighting and 2 power(socket outlets) with other indivual circuits as required , eg, HW, Aircons etc.

(Based on Australian wiring and installation practice, and AS3000). With exception to the reference to the TT system).

It is mainly a question of cost which way one goes, 1 main switch board and sub circuits or 1 main switchboard with distribution boards and sub mains.

Circuit requirements. mininum.

1 lighting circuit 10A 1.0sqmm

2 power, socket outlets 16 or 20A, 2.5sqmm.

1 HWS 20A, 2.5 sqmm.

Aircons 1 per circuit min 16A 1.5sqmm,actual protective device size and cable size dependant on actual load current. Same with any other permanently connected equipment over 10A.

Mains size minimum 10sqmm Cu PVC/PVC. Protection 50A MCB for 16sqmm 63A.

All circuits protected by 30mA RCDs or RCBOs. All socket outlets earthed and all permanenly connected equipment earthed, eg, aircons, hws, etc.

Main earth and earth electrode to required standard.

TT earthing ( no MEN bonding at main earth bar and main neutral link).

There is minimal risk of a hazard of an open circuited neutral if there is a compliant main earth and electrode. The MEN system has been used in Australia under AS3000 since 1931 and is mandatory.

However.using it in Thailand is not advised because of the following.eg.

1. The integrity of the main supply neutral can not be guaranteed.

2. The integrity of the MEN link can not be guaranteed.

3. There is no regime of testing of electrical installations.

4. Polarity tests may not be carried out prior to connection of supply.

5. The earthing of the distribution network neutral may be non compliant.

Therefore the TT or Direct system of earthing should be used and all circuits protected by 30mA RCDs.

So Crossy the TT system of earthing is still used in the UK for an overhead supply with the PME (MEN) system used for an underground supply to an electrical installation.

Malaysia uses the TT system with RCDs.

"Bond your roof metalwork to the lightning rod, but whether you also bond to your power ground is open to debate. In Oz they do in Europe they don't.." What does this mean exactly?

Equipotential bonding, all conductive metal which may enter the ground are all at the same potential. (AS 3000). There is a separate AS1768 standard for lightning protection systems.

A distance of 1.5 kilometres is to far for a LV supply to your property.

You will require a HV supply to a transformer located as close as practicable to your property, so the LV supply is as short as possible to your main switchboard.

You will need to know your max demand in amps per phase and whether you require single or 3 phase LV supply.

You will also need to know the route length of the LV so as to compute voltage drop.

A cable with a route length of eg. 30metres, 20 metres of this in thermal insulation, partly or completly would require derating. ie. a protective device with a lower current rating. 20A to 16A for 2.5sqmm cable. Derating is based on the circuit carrying full rated current.

One should avoid running cables in thermal insulation, run above in free air above the thermal insulation itself.

Cables lain on thermal insulation are regarded as partly enclosed, the same as in conduit or duct. Cables within layers of thermal insulation are completely surrounded and must be further derated.

Testing of electrical installations before connection to supply.

1. Visual checks

2. Earthing tests.( Continuity tests). Main earth and all protective earthing conductors.

3. Insulation tests 500V DC with an insulation tester. L to E, N to E.

4. Correct circuit connections

5. Polarity tests. L to N and L to E.

6. Functional test of all RCDs using test button ( power connected).

With the TT system of earthing a voltage to earth is normal 2 to 4 volts.

The installation was connected as a MEN system, there is nothing wrong with this as long as it is compliant with PEA/MEA requirements.

You should check the earthing you will most probably have not compliant earthing system and the earthing system will remove any small voltages that may appear due to leakage.

You should also check to see if you have 30mA RCD protection on all final sub circuits.

The main earth electrode should be 13mm copper clad steel 1.2/1.8metres into the soil.

You seem to have poor earthing or no earthing.

Fibreglass pink batts are available in plastic sleeves.Do not place insulation over recessed light fittings to prevent overheating and fire. cables should be over 50% of their length in insulation to be derated. Short lengths of cable do not require derating.

Best I continue this thread, with so much great stuff in it already from Electau and Crossy. Thanks guys by the way.

I have a few, possible concerns and questions. I am a bit clueless on this I admit.

The biggest meter we could get was 15(45)Amp 3 Phase running 4 X 50mm Alloy cables.

It is a small house by western standards, 4 bedrooms, 2 bathrooms, western kitchen.

I have been looking a little bit at Aircons, each bedroom with have air, and later I expect the lounge room to have some units installed, but not yet, so working on 4.

It appears that inverter systems are a bit more economical, but from what I have read, it appears a big bonus is as they are running constantly, you avoid the initial draw down. How do I know if I am at risk of getting brown outs at the initial draw down when the compressor kicks in? Currently in a rental with 5 Amp meter, when the 2nd AC kicks in, lights dim and if the shower is on (water pump and little hot water heater), my UPS will kick in and beep away and the fridge will make werriod noises for about 20 seconds, really good brown out material !!!! ( I have since bought UPS for the fridge and TV, trying to avoid them dying while my name is on the rental).

I just looked at a AC in my room, says it is 1100W, any idea what would be the initial draw down when the compressor kicks in when starting?

Next, much to my surprise, the little shower hot water heater is 6500 Watts.

In the house we are building, it will need 3 of these, --- 2X bathroom and 1 X kitchen.

I can put gas hot water in, do you think these electric hot water heaters will cause issues?

There are clearly going to be several circuits in the house,

Lastly, the builder wants to lay the insulation in the ceiling (3 inch chopped strand fiber stuff in silver bags) before the wiring is done, this sound arse about face to me, any comments? Any concerns rearing a metal framed roof, and silver lined insulation?

Lastly, I want each room to have 1 light, the water pump and some low wattage lights out side to come on during a power failure and a couple of independ plug sockets and security alarm . ( Water pump is fine to be manually switched over ).

I presume that a generator that automatically kicks in is going to be expensive. I have a little gen set, max rated out put 2.0kW, I am happy with that for the short term. What is the easiest way of running a big UPS that automatically switches on in a power failure, we get allot of them them here.

In general, the cost of this bloody house has grossly blown out....... but I am not trying to be pathetic with foundations, roofing, security and electrical. With electrical, I don't want to go overboard, but it must be as decent as I can get it with a little redundancy.

Also, does it cause any problem having 3 or 4 safety switches, I presume on different circuits, to help redundancy and trouble shooting easier, trying to find the

offending device?

Does the below mean, the hot water heaters are a non issue?

Crossy Said:

Thailand uses 3-phase 4-wire so you need four identical cables.<br style="font-size: 13px; line-height: 19px; background-color: rgb(250, 251, 252); ">Your installation will probably be mostly single-phase appliances, these are connected between the neutral (the fourth wire) and one or other of the phases.<br style="font-size: 13px; line-height: 19px; background-color: rgb(250, 251, 252); ">Assuming your '15 Amp' meter is a 15/45 3-phase supply it will be capable of providing nearly 30kW of power!

Sorry for the messy post, kind of thinking out loud, any help will be awesome.

We are going to pay for materials and pay per socket and switch and an agreed amount to put the circuit boards in, hoping to avoid cable and breakers being to small and all off 1 non earthed circuit.

15/45 amp meter 3 phase 4 wire supply with 4 x 50sqmm aluminium cables will be ample.

Balance load over 3 phases. 45A will be your max demand per phase.

One really needs to know the actual connected load to calculate max demand accurately.

ie. Number of lighting points, no of socket outlets, aircon size in amps (each) etc.

,

I find 15/45 supply OK and could have sometimes 3 out of 4 air-cons all going at the time.

1100 watts will draw 5amps

6500 watts shower !! 3 on at the same time whow !

Mines a 4500W as well as ELB on the shower there's a 30amp safety breaker switch before the 20amp MCB in the dist box.

Lastly, the builder wants to lay the insulation in the ceiling (3 inch chopped strand fiber stuff in silver bags) before the wiring is done, this sound arse about face to me, any comments?

Yes a bit back to front but as long as he maintain it's lay when installing the wiring.

Any concerns rearing a metal framed roof, and silver lined insulation?

No.

Yes there is. You should not use metallic foil over electrical wiring the risk is that a fixing may penetrate a cable. You may also have to derate the current rating of cables because wiring is partly or completly enclosed in thermal insulation. Metallic foil must be earthed if you intend to use it.

One would advise against the use and use thermal fibreglass batts instead. of foil. Earth the steelwork.

good news , for the people of burma .

now the race is on between ,

russia, china and america

to gain favour in burma.

i wonder why?.

:jap:

Balance of power in the region. Political, Military and Economic. All can be used to influence a nation.

Electau, you need to translate that into 'Average Joe', sadly AS3000 suffers from the same issues as BS7671, they talk in ways that are very open to interpretation. Those paragraphs you quote are difficult for me to interpret and I know what they mean at least in a UK context.

Havaniceday, don't forget, there are metal cased appliances that are also double-insulated and do not require a ground wire. My Toshiba fridge has a 2 pin lead, a metal case and the double-insulated symbol hidden round the back.

Looks like this:-

The interpretation is very clear, earthing of electrical equipment is required, as if one does a risk assessment and asks the question "is it in an earthed situation" the answer must be "yes" Class 2 double insulated equipment is not earthed. Class 1 must be earthed. AS3000 is written so that it avoids different interpretations.

If your house has conductive floors and walls you have an earthed situation.

However in Thailand RCDs are regarded as sufficient protection where there is no earthing.

Lightning protection.

Most buildings do not require lightning protection as such.

Most damage is caused by surge voltages entering the system through the distribution system.

1. Make sure you have a compliant earthing system and main earth/ electrode.

2. Equipotentially bond all structural steel work.

3. Install SPDs on the main switch board on the line side of any RCD protection. Protect with a 32A MCB. Connect with 6.0 sqmm earthing conductor to the earth bar.

TT systems are more risk than a compliant MEN system and require SPDs on the Line and Neutral conductors.

If you do have lightning rod(s) the earth electrode of the lightning protection system should be equipotentially bonded to the main electrical installation earth.

Earthing of equipment.

Exposed conductive parts.

The exposed conductive parts of electrical equipment shall be earthed where the electrical equipment is:-

Installed or could operate in an earthed situation; or not installed in an earthed situation but any exposed conductive parts of the electrical equipment is electrically continuous with an extraneous conductive part that is located in an earthed situation.

Earthed situation.

A situation where there is a reasonable chance of a person touching exposed conductive parts and, at the same time, coming into contact with earth or any conducting medium that may be in electrical contact with the earth or through a circuit may be completed to earth.

Within 2.5metres in any direction from a conductive floor (such as an earthen, concrete, tile or brickwork flooring) permanently damp surface, metallic conduit or pipe, metal cable sheath or armour or any other material or which a person may stand.

Ref AS3000.

The above should explain where earthing is required in normal wiring practice within an electrical installation.

If you use any electrical equipment in relation to swimming pools electrical safety comes first.

1. All reinforcing used in its construction to be equipotentially bonded to the main earth.

2. All electrical equipment to be protected by 10mA RCDs All electrical equipment to be earthed.

3. All in-pool lighting to be ELV.

It will be interesting to see what countries in the region come under Communist Chinese influence. Where is Russia and the CIF in the equation?

Afganistan has a narrow border with China, and the US wants a presence there.

Points of possible confict, Korea, the Spratley islands in the South China Sea. There is the Indian Ocean and this is where Burma (Myanmar) comes in.

China is seen a a future enemy as far as the US and its allies are concerned but they will not publically admit it. Remember China is Communist it is not a Western style democracy.

Forget all the humanrights and humanitarian talk. perhaps a new "cold war"is in the air. China is interested in many areas of the world ie African countries and South America including Australia. China will have a large naval force which will rival the US in the West Pacific.

Remember Japan 1931, 1941. History has a habit of repeating inself only the script and the players change.

And Indonesia may not remain democratic in the future.

And there is India and China.

You should run an earth conductor to all points of utilisation , eg socket outlets, light fittings hotplate unit . HWs, airconditioners etc If possible use flat twin and earth enclosed cable.

Install RCD protection on all final sub circuits.

Minimum number of circuits, Lighting 2 x 10A, Socket outlets 2 x 20A all other equipment on their own circuit.

Minimum size of submains 4.0 sqmm.

Current rating of cable ( enclosed in conduit or duct ).

1.0 sqmm 10A, 1.5sqmm 16A, 2.5 sqmm 20A. 4.0sqmm 25A. 6.0 sqmm 32A.10sqmm 50A.

Unenclosed in free air ratings are.

1.0sqmm 16A, 1.5sqmm 20A 2.5sqmm 25A. 4sqmm 32A 6sqmm 40A 10sqmm 63A.

Voltage drop from the point of supply to any point of utilisation within the electrical installation should not exceed 5%.

With cable current ratings the enclosed ratings are to be preferred for residential installations.

All you need to do is earth the steelwork in the building, then equipotentially bond any extraneous conductive parts to the main earth. You will need a main earth conductor and electrode.

Fit SPDs on the main switch board and connect these to the main earth.

Earthing for electrical safety should be your first consideration.

An RCD will not prevent you from receiving an electric shock if there is an earth fault, however a 30mA RCD will disconnect the supply before fillabration of the heart occurs and in the case of 10mA units muscular contraction occurs. mA x time in mS.

One should point out that these extension leads with RCDs available in Thailand do not comply with IEC, BS or AS/NZ standards.

They appear to comply with Thai Industrial Standards (TIS). Most socket outlets are 2 pin not 3 pin.

Wago connectors are available for wire sizes from 1.0sqmm to 4sqmm. the smaller connectors are a "use once" type while others can be reused.

Further insulation is no required as they are fully insulated but the terminations must be enclosed in an approved manner, eg, a J box or within a fitting or behind an outlet or switch plate etc.

A VOM test voltage is 300mV. An insulation tester is 250/500V. One does not use a VOM to check insulation resistance.

50sqmm SDI (PVC) sheathed cable for a 3% voltage drop. Buried at a minimum of 500mm and protect from damage or run in conduit.

Or you could use XPLE insulated PVC sheathed cable.

This is one of the reasons why people pull large amounts of cash out and drive it to another province.

A totally retarded fee.

So you would take out 100,000 and burn 500-1500 baht in gas round trip to move some money around and save a little on fees? If you were going in that direction, I suppose it might be justified. But solely to save a few baht in fees?

Or pay 10baht per 10,000 baht (maybe online transfers there is a cap on fees on some circumstances?), and not have to walk around with cash, and have it credited to the account receiving account instantly?

Banking is surprisingly efficient in thailand.

You are forgetting that most people who complain about this fee probably live here on the smell of an oily rag. They also probably don't understand the concept of 'opportunity cost' which you've effectively explained in your previous post.

My guess is that the majority of the complainers are from the UK. While I'd like to use the 'whinging Pom' tag here , it would be unfair. During my time living in the UK (coming from Australia) I was rather surprised by the lack of banking charges for day to day transactions. On the other hand, I did have to put up with a relatively archaic and somewhat sluggish banking system (especially when it comes to internet banking). The point is though, they are rather unused to fee's, so any they see in Thailand would strike them as unfair.

Again, coming from Australia where you are generally charged $2 to $2.50 (ie GBP 1.3 to 1.8) to use a ATM outside of your network, or how bank charge fees on top of fees, the Thai banking system is rather refreshing with low fee's and a level of technology and convenience (ATM's EVERYWHERE) that would be hard pressed to find in Australia. So 10 baht for an intra-province transaction? Dead cheap if you ask me.

Very well written, some people just do not understand that there is no such thing as a "free lunch". In other words the end user pays for the service.

Australia has one of the best banking systems in the world, with excellent internet banking. Our banking and ATMs are on a national basis.

In Australia EFTPOS is widely used when paying for products and services.

If you use your own bank ATM the $2 is not charged.

Yes, by registered mail if you live in Qld. Takes 5 working days in total.

Return registered mail envelope with your address.

Passport.

Visa application form correctly filled in with the flight number and airline.

$45 money order made out to the Royal Thai Consulate, Brisbane.

2 current passport photos.