Can Somebody Explain How The Electrics Work In Thailand

[sotsira]

A laptop is something like 6 volts DC. How you could get a shock off it I don't know.

Suspect something else is wrong.

the shock he is getting is a 'floating' voltage of around 120 volts(rms,or 160 peak)

an earth or ground would eliminate this .however the shock won't be of anyharm,since as soon as you touch the casing of the equipment,you are doing the earthing thru yr body.

under no load,the voltage could measure thousands of volts,(maybe you can hear a spark also when you touch the offending unit)however the current is extremely small.

I find this hard to believe as the transformer that feeds the laptop has an input of 240v and an output of approx 18v, also the input lead that is connected to the mains socket is of thick gauge to accomodate 240v the output lead is a lot thinner as it only carries 18v.

If what you say did happen then the 120v (floating voltage?) would melt the output lead completely,and probably the laptop too.

The only part of a laptop configuration that can be earthed is the transformer input lead that connects to the mains socket and this would only earth the transformer NOT the laptop, as it runs on 18v DC.

My suggestion is that the laptop needs to be checked for insulation by an electronics engineer.

[paul1970]

A laptop is something like 6 volts DC. How you could get a shock off it I don't know.

Suspect something else is wrong.

the shock he is getting is a 'floating' voltage of around 120 volts(rms,or 160 peak)

an earth or ground would eliminate this .however the shock won't be of anyharm,since as soon as you touch the casing of the equipment,you are doing the earthing thru yr body.

under no load,the voltage could measure thousands of volts,(maybe you can hear a spark also when you touch the offending unit)however the current is extremely small.

I find this hard to believe as the transformer that feeds the laptop has an input of 240v and an output of approx 18v, also the input lead that is connected to the mains socket is of thick gauge to accomodate 240v the output lead is a lot thinner as it only carries 18v.

If what you say did happen then the 120v (floating voltage?) would melt the output lead completely,and probably the laptop too.

The only part of a laptop configuration that can be earthed is the transformer input lead that connects to the mains socket and this would only earth the transformer NOT the laptop, as it runs on 18v DC.

My suggestion is that the laptop needs to be checked for insulation by an electronics engineer.

High voltage would not melt a lead, it is excessive current that causes leads to melt or burn. That is why fuses are rated at the breaking current and not breaking voltage, excess current causes excess heat disapation which cause the fuse to melt or wiring if not properly fused.

If the laptop power adaptor has a 2 pin input plug from the mains lead then there should be a logo that shows a small square inside a larger square to indicate that the adaptor is double insulated and does not require an earth (ground for the US) connection. If you are getting a shock of this type of adaptor then it's likely that there is a fault with the adaptor.

A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth (US: ground).

The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation.

In Europe, a double insulated appliance must be labelled "Class II", "double insulated" or bear the double insulation symbol (a square inside another square).

Alternatively if there is no square within a square logo and the input connector has 3 pins then the adaptor needs an earth connection as there will be an EMI filter on the input that connects the live and neutral to earth via some capacitors, this will cause a small leakage current that would normally go to earth through the earth lead in the mains cord but if this lead is not connected to earth then this small leakage current may go through the negative output of the adaptor, which is probably what you are feeling. This current is small enough not to cause you any damage, though if the EMI filter capicitors where to short circuit with no earth connection then you could possibly get a nasty shock.

[JetsetBkk]

I actually visited a farang home here with a full-on three phase system. He didn't have anything in the house that would require three phase, but that's what he got. He had a huge panel that had volt and ammeters for each of the three phases. He could have run a small factory with all that capacity.

Or 17 air-cons. Didn't realise you knew Naam.

[djc45]

The 2 pin plugs that are used in Thailand obviously do not have an earth connection like the UK. So how is the electrical supply earthed ?

If i touch the metal part of my laptop plug i get a small shock, also if i touch the metal casing around my PC i also get a shock. So these appliances are not earthed if this is happening.

Of everything in Thailand, i am scared most of the electrical setup here. Am i alone ?

Most buildings in Thailand do not use an earth circuit in the wiring, therefore the only way is to make your own earth and run the wires in yourself or get an electrician that understands the principle of earthing as i've come across a few that don't. If you own your own property it's well worth doing as it makes it much safer.

I have asked the way the wiring works in Thailand and have it explained by highly educated electrical technician working in the uk the following

In Thailand its is not the same as the uk it would appear from the information I gave him about the electrical supply to my house in Issarn.

From the supply substation they only send a live feed and the second feed that you see over head is NOT a neutral supply feed but an earth a neutral is not needed to power up anything,

You can test this in the uk by wiring a light bulb up with the live wire to a live in a 3 pin plug and the neutral to the earth terminal in the plug and the bulb will light

The way it has been explained to me is that in the uk you would get a live feed and a neutral feed from the substation and the earth would be taken from a local source such as an incoming lead pipe or copper pipe or earth spike

Here in Thailand it would seem that the (neutral) is in fact a cable that just goes into the earth this is connected to the neutral terminal giving you the false idea that you have a neutral feed

If you then try to introduce an earth feed by way of a earth spike you could in fact cause more problems as any short to earth through the earth feed could return via the neutral wire

Most electric showers if not all that are sold in Thailand have a built in ELB with an earth wire connected to an earth spike un like the electric showers you see in the uk this is so that the power is switched of at the shower and the live cannot continue to the earth spike and back to the false neutral feed

If you look close at your incoming over head wires that supplies the incoming electricity you can see that the neutral wire when traced back to the joint has an UN insinuated wire running down the concrete pole into a conduit that goes into the earth

I hope this will shed some light on the subject

Edited November 8, 2008 by djc45