electau

The load centre should be 1 x 2 pole MCB 63A C frame 10kA @ 220V

Each final circuit connected to its own MCB one module 18mm wide.

Min. number of circuits.

2 lighting and fans, 2 socket outlets, one circuit for each permanently connected item of equipment over 10A, eg aircons, hws, etc. Final circuit protection devices rated to the current carrying capacity of the cable to be protected. (3kA minimum)

The existing MCBs may be replaced with RCBOs, 10mA or 30mA. or an RCBO/RCD unit may be installed between the main switch and the line side of the final circuit protective devices. the RCBO can be installed above the load centre.

Cable colours for to Thai Industrial standards are black/line, white/neutral, and green or green/yellow for earth. You should not change these.

There is no problem with installing 25sqmm cable it is easier to work with as it has 19 strands instead of 7. Make sure it is PVC insulated and PVC sheathed.

Current ratings for circuits.

Lighting and fans, 10 A or 16A. Socket outlets 20A. Cable sizes, 1.0sqmm 10A, 1.5sqmm 16A, 2.5sqmm socket outlets. Aircons HWS etc as per full load current.

Max number of points per circuit lighting 0.25A each unlimited number not to exceed current rating of cable. Socket outlets 10A, max 20 per circuit, 1 amp per outlet. A twin outlet is 2 sockets.

You actually answered your own question, you state that your peak load will rarely go over 30A.

Install a 63A MCB as the main switch and you have maximum demand by limitation.

With additional loading above 32A use one or two items of equipment at a time.

Load management is the answer to your problem. ie. Diversity.

If the transformer cannot supply the peak load of your installation and other installations connected to it low voltage problems on the distribution network may be encountered. 50sqmm mains will not solve that problem. A larger transformer will.

The max demand in amps for an electrical installation is for design purposes. Your actual demand in amps is what you consume at any point and will vary depending on your load at the time.

This peak demand may only exist for a short time. It will be in most cases be considerably less than the calculated max demand.

The PEA supply a transformer to supply this load and to other consumers in many cases.

The diversity of most LV residential loads from a single transformer is between 3 and 5 kW each residence. so a 100kVA transformer could supply up to 20 normal residences.

What is the size of transformer that will supply you?

The fact that the PEA wil supply you with a 30/100A meter does not mean that they can supply 100A you should look at peak loads of 30A in practice.

It should be pointed out that for most electrical installations ( not special purpose installations) all that is required irrespective of whether it is a MEN ( TN-C-S) or TT is one copper clad steel electrode with equipotential bonding with a compliant main earth conductor and PE conductors. It must be exposed to the weather and be accesible for the purposes of testing and inspection.

The main purpose of an earthing system is to provide a path for fault currents and auto disconnection in the event of an earth fault and to minimise the touch voltage to less than 50VAC.

The temperature of the cable insulation must not exceed (for most general purpose PVC cables) 70C ( TIS) under fault conditions.

The protective device if an MCB must trip within 0.4secs and if this can not be achieved RCD/RCBOs must be used.

Just to highlight a potential new problem it looks like the 2 pole breaker on the left is the incomer from the supply. If this is the case the size of the link wire between the breaker and the neutral bar does not look to be very large. From the photo appears to be 2.5 or maybe 4mm2 which I think is either to small or right on the limit, though for some reason I thought the link was supposed to be 10mm2, where is that dammed book of Thai electrical specs

Maybe Crossy or Electau can chime in on this one, my experience is industrial rather than domestic and all our switchboards had pre-wired link bars.

Cheers

The link from the neutral bar to the terminal of the MCB should be the same size in sqmm as the incoming neutral.

Here is a method (by calculation) to calculate max demand. This method is based on AS3000.

This information should be used as a guide only. This method is the most economical as far as costs and with general usage ( diversity) within an installation.

A. Lighting. 3A for up to 20 points. 2 A for the next 20.

B. Socket outlets (10A). 10 A for the first 20 and 5A for the next 20.

C. Hotplates. Clothes dryers over 10A 50% of connected load.

D. Airconditioning. 75% of connected load for units over 10A.

E. HWS storage type. Full connected load. Instantaneous type 33.3% of full connected load.

Thus for a residence with the following.

20 lighting points = 3A

20 socket outlets = 10A

Hotplate unit 7000W = 3500W = 16A.

Airconditioning 5000W input.= 3750W =17A

Instantaneous HWS. 6000W = 2000W= 9A.

Total max demand 55A.

This is for a single phase installation. for a three phase installation the load is balanced over the 3 phases. Most residential installations do not require a 3 phase supply.

The above is the calculation method. The other is by limitation of max demand by the use of an MCB.

The MCB used as a main switch effectively limits the max demand to the continuous rating of the device.

Number of circuits to an installation. Minimum.

Lighting 2.

Socket outlets 2.

Hotplates,Clothes dryers 1 individual circuit for each.

Airconditioners 1 individual circuit for each.

HWS 1 individual circuit for each.

Main switch. 1 x 2 pole MCB.

Calculate the max demand first, before purchasing any electrical equipment over 10A. Then approach the PEA to see if they can service that load in accordance with their conditions of supply.

The main neutral to an electrical installation should be terminated under a tunnel type connector terminal with 2 screws or by a bolted lug to the neutral bar. Copper to copper or copper to brass. With Aluminium conductors (16sqmm and over) use the correct termination lugs. Metering screws should also be 2 screw type.

With an MEN installation this can cause a potentially hazardous situation, the main earth and electrode ( with earth bonding ) maintain the touch voltage to less than 50VAC.

With a TT system this problem does not occur one justs loses supply.

No, an RCBO/RCD will not disconnect the consumers mains.

The problem is that many neutral links and earth bars (on DSBs) have only single screw terminals.

With one RCBO protecting the whole electrical installation you may experience nuisance tripping due to excessive leakage current. An RCD device is designed to trip at between 50% and 100% of the rated current ( or the current setting in mA if a selectivity switch is fitted). 10ma and 30mA are the IEC ratings.

The Main switch (MCB) isolates the whole installation for the purposes of safety.

In Thailand there is NO provision for service protective devices eg HRC fuse to protect the consumers mains and metering. This is for fault currect limiting ( short circuit protection) and an isolation point to disconnect the electrical installation. They are not for overload protection.

Two way switches are often used as the standard switch. they have three terminals 1- C- 2.

C, the common terminal switches between 1 or 2.

To wire a 2 way switched fitting the usual method is to run a twin between the 2 switches on terminals 1 and 2. the common C connects to the L for one switch and the other C terminal on the second switch is run to the SL terminal of the fitting. SL switched line or active.

The switching must NEVER be on the neutral conductor.

For a third or further switch in the circuit an intermediate switch is used it has 4 terminals and is connected in the twin pair between the other 2 switches. Intermediate 1-2 and 3-4. switches to 1-3 and 2-4.

Source. HPM, Clipsal. Clipsal fittings are available in Thailand.

MCBs. C. frame (standard) current rating in amps (16). 6000 short circuit capacity in amps.

These are the IEC ratings for a protective device.

RCBOs have as above but with the residual current for earth faults, 10mA and 30mA.

Main switch 50A C frame 10000A short circuit capacity.

Do not replace the main switch (MCB).

At less than 4 Bt per kWh for residential electric power there is no incentive to install solar panels.

It might if your nearest low voltage electric supply is more than 2km away ?

Yes, that is where RAPS may be used, solar PV array with diesel generation and batteries. However they are expensive. You would need to have the capital cost of a transformer and HV line extension to your property against the cost of a RAPS system and fuel running costs of about 0.3 litres/kW/Hour and on going maintainance costs.

First you should contact the PEA in your area and advise them of you proposed requirements.

You will need to calculate your max demand first. In Thailand 63A for a residential installation is ample. This is the setting of a fixed setting MCB for the main switch.

The standard metering is 45A and is the responsibility of the PEA.

The consumers mains should be a mimimum of 16sqmm and may be required to be larger to take into consideration voltage drop depending on the route length of the circuit. Also the PEA may stipulate a minimum size. One would suggest limiting voltage drop in mains to about 3%.

Minimum cable size for 3% drop for a 80 meter run would be 25sqmm for single phase connection. to the main switch board.

As you live in a village your options are limited. You should design your requirements around a 45 to 63 amp max demand. You do not need 10kW water heaters, use solar thermal or a 3 to 4 kW heater. Consider using LPG for cooking.

An MCB will carry short term overloads 1.2 x rated current of device continously and must trip at 1.45 x rated curent within the conventional tripping time ( 1 hour).

MCBs are available 40A and 50A.

You do not earth a switch, you earth the enclosure if metallic. The light fitting should be earthed but in Thailand if the fitting is out of arms reach from where it may be reasonably accessed ( eg from floor level) earthing is not required.However the circuit should have RCD/RCBO protection.

Loop in loop out at each fitting and use J -boxes where and as required. J boxes should have insulated screw type tunnel connectors or similiar. J -boxes are to be accessable.

Circuit for socket outlets should be 2.5sqmm with a PE conductor to each earth contact of the 3 pin socket outlet.

Protective device should be a 20A RCBO for the circuit. Max number of points on a circuit 20. A twin outlet is 2 socket outlets.

The structural steel of a building may be used in lieu of an electrode.

The conection must be accessible for testing purposes and this generally requires an electrode with the structural steel bonded to it.

The connection must be at ground level and exposed to the weather. The main earth conductor runs from the main switchboard to this connection.

With any earthing method the requirements of auto disconection by a protective device in the event of an earth fault must be maintained.

Surface wire in white PVC ducting with surface mounting blocks. Each outlet 8x8 RJ45 on a mounting plate. If you have T -Bar ceiling cabling can be run in this area. Maintain clearance from power cables. Cabling 4 pair Cat5, 5E or Cat 6 data cable. terminate using a 110 displacement tool ( Krone). Test using a low cost cable tester to make sure all connections are correct and there are no shorts or opens. Flex patch leads should be same Cat. rating as cabling for best performance.

Use screws to affix ducting and blocks to wall using 6mm wall plugs.

Where permitted by the PEA/MEA structural steel of the building may be used in lieu of an electrode. The earth conductor should be 10sqmm copper. The point of connection to the structural steel work should be accessible for the purposes of inspection and testing.

The incoming neutral should NOT be bonded to the earth bar, ie the TT system should be used.

RCD/RCBO protection should be provided on ALL circuits. PE conductors to all equipment including the earth contact of socket outlets.

16sqmm copper for the incoming mains with a 63A 2 pole MCB as a main switch.

From the Australian DFAT website.

Thailand.

Foreigners are required to carry identification at all times.

In other words an original document which states who you are. eg. Passport , drivers licence, ID card with a photograph of holder etc.

A Passport is the property of your government and penalties may be applied if it is lost or stolen.

Here is the actual breaker box as installed by builder. Size of meter? no idea- whatever is put in for the average housing development.

Not sure if this photo is correct size....What I am thinking is removing the two unused 20a breakers and inserting 2 x 25amp then using that to feed second box.

The switchboard appears to be a Square D ( Schneider) load center. The Main Switch (MCB)will be 2 pole and the individual MCBs single pole.

There appears that no provision has been made for RCDs/RCBOs. This is normal for most electrical installations in Thailand unless you specify them.

You should check to see if a main earth and electrode is installed and any protective earth conductors. You should check this with the electrician.

As you have 2 spare 25A MCBs you could replace one of them with a 32A MCB for the additional load centre adjacent to the existing one.

It is assumed that your supply is single phase L and N.

The main switch should be a 2 pole MCB 63A for 16sqmm consumers mains and 50A for 10sqmm mains minimum. (Your metering will generally be 45A)

ONE main switch should control ALL the electrical installation. It would be advised that all circuits be protected by RCBOs. This MCB provides short circuit protection on the load side of the device. Service protection on the line side of the metering is not used in Thailand.

A 50A protective device for a sub board if installed on 10sqmm cable but if load is not large a 32A on 6 sqmm would suffice.

To install a compliant earthing system you will require a 10sqmm main earth and earth electrode to PEA requirements, 16sqmm HD copper or copper clad steel 2.4 metres in the ground, and PE ( protective earth) conductors to all equipment including the earth terminal of 3 pin socket outlets. Earth conductors terminate on the earth bar of the switchboard.

It would be recomended that the earthing system complies with the current requirements of the PEA, ie TT or TN-N-S (MEN)

You should contact them before commencing upgrading your electrical installation.

Welding can be done off site at a workshop and the steel framework and roof trusses transported to site and then erected and bolted together. Your concrete slab is poured first with the footings. There is real reason to use a welder on-site with a residential type structure.

As the photo shows, the welder circuit has no protective device or earthing.

I'd like to install a joint box, to fix the unconventional wiring above the ceiling in my office. I've bought this box and a terminal block.

What is the best way (easy and safe) to install this onto a wall? I was thinking of putting the box on the wall with screws and just have the block suspended by the connecting the wires inside the box.

Affix the box onto the wall. For each individual circuit connect all L conductors to one terminal, all N conductors to a second terminal and all E conductors to a third terminal.

If you only have one circuit you will use 3 terminals only. otherwise 3 terminals per circuit.

The terminals must be enclosed within the box, so you will have to replace the lid (no exposed live terminals or connections).

You can install a additional load centre unit adjacent to the existing one. There should be one main switch (MCB) to isolate the whole electrical installation.

You should check the size of your incoming consumers mains size ( in sqmm) to make sure it can carry the extra load.

All equipment should be permanently connected to their own final subcircuits, each circuit protected by an MCB or RCBO.

The size of protective device (MCB/RCBO) depends on the current rating of the cable it protects.

You will require the rating in amps of each of the items you wish to connect.

All equipment should be earthed with a PE conductor to the earth bar of your switchboard.

A switch board should be installed in a readily accessible position from floor level eg no more than 2 metres to the top of the switchboard.

Thank you again

But to test the earth continuity where do I put the two probes on the multi meter?

If I have to put one end in the CU earth and the other on the earth connection in the plug/switch I will need a lead of at least 20 meters to test the furthest plug! forgive my ignorance on this I have only ever used a multimeter to test voltage!

Mike

Yes. you will require a long trailing lead attach one end to the earth bar at the switchboard and the other to one probe. The other probe to all points where there is an earth. this will prove earth continuity. You should do the same with the main earth with the probe on the electrode.