Mini TT system

[La Poste]

Greetings.

I've got a friend who lives in Thailand in a house with no earthing.
It's a two wire system with a RCD/ELCB at the point of entry to the house.
They seem to do this in Thailand, put an RCD at the main incomer even though they have no earth circuit.
I guess something is better than nothing and the logic is if there is an earth fault to the frame of an electric heater for instance and you then touch
the frame of the electric heater and get an electric shock the main RCD will switch off the supply as long as more than 30ma flows through you to earth.

My friend is getting electric shocks off of his computer equipment, the metal frame of his PC.
Without going into the earthing system of the whole house would it be safe just to earth the PC chassis by means of an earth rod without involving anything else in the house?

I'm thinking if just the PC is earthed with a local rod this should take care of any leakage current that is building up.
My friend has no test equipment and we don't know anything about the local transformer or whether the transformer is earthed itself.

Is this a safe thing to do and what would you recommend in these circumstances?

Thanks.

 

[La Poste]

And here's the life saving RCD/ELCB positioned at the electrical point of entry of the house:

 

[Engineer54]

Are you saying there are no CPC's for any of the circuits throughout the house??

 

[Richard Burns]

If you have a voltage already present on the case of the PC and provide a good low impedance path to earth then that should ensure that the RCD trips and wont reset.
The leakage current from a PC should not be enough to sense as it should only be a couple of mA and sensation is at about 5mA.
I would say that there are other problems here not just leakage current. Need to sort those rather than sending fault current to earth.
Get your friend to sit on an insulating chair and use rubber shoes, no path to earth then!

It also looks like the RCD is set to 15mA.

 

[Taylortwocities]

Can I get one of those RCDs here?

Looks like there's an over-ride position (the RED bit). That would stop all that niusance tripping!:49:

 

[La Poste]

There is no earth circuit in the house at all.

From what I can gather, and I will ask more questions later, the PC is not earthed and is supplied with two wires line and neutral.

My friend says he gets a mild shock when he connects his I phone and other appliances to his PC.

 

[La Poste]

I guess the question I'm really asking is whether it is safe to individually earth separate appliances with a rod to take care of leakage currents.

Rather than have a complete house re-wire which this place obviously needs would it be acceptable to install a rod just to take care of one or two pieces of equipment?

I'm not sure of the leakage current rate of IT equipment but it does sound quite a common problem for people living out that way IE they get mild shocks of from their computers.

 

[Strima]

You could try a temporary earth to see if it cures the problem but then any earth faults on the whole system may decided to transmit themselves through the PC depending on how the whole lot is wired.

 

[timbobelfast]

I had a similar problem when I had a house built in Thailand a few years ago. I foolishly let the locals wire it and there wasn't a cpc to be seen!
I was able to sorce some T&E type cable in Bangkok and re-wired the place. Got some BS material shipped over from the UK aswell.
My place like most is TT so installed a ground rod aswell.
Electrics in most of Thailand is shocking to say the least.
Best thing to do is to get your friend to get his wiring done properly and ship over some BS materials.
And when he's done, put that RCD in the trash!

 

[Engineer54]

I guess the question I'm really asking is whether it is safe to individually earth separate appliances with a rod to take care of leakage currents.

Rather than have a complete house re-wire which this place obviously needs would it be acceptable to install a rod just to take care of one or two pieces of equipment?

I'm not sure of the leakage current rate of IT equipment but it does sound quite a common problem for people living out that way IE they get mild shocks of from their computers.

Normally in the summer months when the heat combined with a humidity in these South East Asian countries that can easily be from the low 90 to 100%+. Making floors and other surfaces damp or even wet to the touch, including hands, if not the whole body!! ...lol!!!

Personally, if your friend intends to stay at this house for any length of time, it would be prudent to give the place a rewire, or at the very least pull in CPC's for the existing circuits. Coupled with a decent TT system that goes down at least 3 metres. An electricians rates in Thailand are not at all expensive. Either that, or you go out and have a free holiday with a couple of day's or so, spent doing the necessary, to get your mates house up to a decent safe standard... lol!!!

 

[timbobelfast]

I have found a picture of the original fake RCD that was installed in my place.

 

[La Poste]

Thanks for the comments.

Apparently you have to be a bit artful if you want to do your own wiring in Thailand, foreigners are not allowed and only local Thai electricians are authorised.

The problem is most local Thai electricians out in the sticks don't even understand earthing.

 

[trev]

Just do it and get one of them to cert and notify it

 

[Engineer54]

Thanks for the comments.

Apparently you have to be a bit artful if you want to do your own wiring in Thailand, foreigners are not allowed and only local Thai electricians are authorised.

The problem is most local Thai electricians out in the sticks don't even understand earthing.

Things must have changed a hell of a lot out in Thailand then, since i was last there!!!

 

[La Poste]

I'm not sure how it is in the big cities with large projects but this information comes from another friend of mine who has lived in the north of the country for many years.

I will double check this fact though.