I need to install a grounding-earthing system for a new washing machine at the back of the house.
I went to Homepro and Global house, both sell thin copper rods, either 1.85 m or 40 cm long.. I feel that 1.85 m is too long while 40 cm is too short... I wil add a 1 x 2.5 mm2 wire to the existing plug...
What would be the the appropriate length of the ground-earthing rod ?
Would a re-bar do the same or must it be copper ?

Both Homepro and Global offer minimal choice. Is there a better Electrical Supplies shop in Udon ?

Looking for your experience and expertise.

Thanks to all..

Ground rod ..
Re-bar

As long as possible will give the best results, it is very defendant on the soil type, at my house I have 3 rods of about 3.5 metres linked together. must be the proper copper plated rods for best results.

Was at Thaiwatsado recently and happen to notice a better supply of earthing materials than other two stores offer (HP/GH).

I think the longer the better as there is more chance of getting to damp ground. I have 4 mtr rods at 2 corners of the house plus 4 mtr rods at the corners of the outhouses. Have UK plugs and sockets fitted throughout and earth tested and have no problems. It's worth going onto ebay and getting the proper gear sent over.

Earth rods are usually copper plated steel, about 10mm dia and 4ft long. If you get the proper items they have threaded ends so can be stacked.
Earth impedance will depends on soil moisture levels, but really what you should be aiming for is low enough impedance that the RCD will detect the leakage and cut the power. In practice a few 10's of Ohms will be low enough. Its important to test the earth by pushing some current through it (use a 24V autotransformer and take some measurements with a multimeter then apply good old Ohm's Law)

I think someone needs a lesson in the theory and operation of modern day Earth Leakage devices.

For a start, measuring earth impedence requires the use of a 4 probe meter with current injection to assess the values which would mean nothing to the average man in the street anyhow.

Then there is earth loop impedence (yes, another specialised instrument) which is more important in any selection of breakers.

Safety switches, earth leakage units (same thing) work on a core balance arrangement.

i.e. The active and neutral conductor pass through a torroid transformer which detects any imbalance.
Standard domestic level is 30mA.
When this imbalance is reached, the circuit breaker switches off, usually in around 10 to 40 milliseconds.

There is no requirement for any earthing conductor for this to operate safely and effectively.

Earth electrodes in MEN are there for an entirely different reason.

I did some checks and it turns out the majority of Thailand is indeed MEN.

The lack of correct earthing methods is the reason why many tradespeople recommend installing the units in Thailand.

I would invite any responses to include a diagram of how they believe any earth fault current actually flows.
It would be nice if you do some checking before hand to avoid making any embarrassing mistakes.
Please include the supply authority distribution arrangement as this is paramount in the overall understanding.

bluejets wrote:
There is no requirement for any earthing conductor for this to operate safely and effectively.
.

Please note that in some instances this quote may be taken out of context.
It refers to the operation of the torroid core alone and not the installation as a whole.

Would not disagree with anything you have said. However when an earthed appliance develops a fault which might cause e.g. leakage to body of appliance then you want sufficient current to flow to earth an rcd to trip. Also, of course rcds don't work where there is transformer isolation.
TT earthing impedance can be verified using temporary voltage sensing and current injection electrodes and voltmeter and ammeter. Sure to be a cct diagram on the web somewhere.

The -Monk

Good to see that you are thinking safety.
I'll assume a lot here.
if I read your post correctly you have an electrical outlet for the washing machine which does not have an earth?
And therefore you are trying to individually earth the socket by installing a 2.5 earth into the socket and then take that new cable to be connected to a new earth rod?

Your reason for wanting the ground rod, and I am assuming here, is that you cannot take the new proposed 2.5 earth cable all the way back to the circuit board?
You can do what you propose, but the earth system on that socket will be completely independent of any ground system at the main board and therefore any protection device that requires an earth. Remember there are generally 2 types of earth leakage protection, USA Ground fault Trip and the Aust ELCB. Both work but are slightly different. But with your proposal the circuit breaker for the socket at the mainboard will still trip on overcurrent or short circuit.
The issue of the earth rod can get technical and confusing to non electrical people as posters have already correctly indicated but it doesn't need to be, a 3 meter rod would suffice your needs. An electrician can test the earth resistance for you with the correct measuring device.
My advice and to negate all the above and if at all possible is to get the 2.5 earth cable back to the main board and connect to the existing house main earth. If you do not have earth fault protection at the main panel then consider having it retro fitted to the panel.

Barney wrote:The -Monk

Good to see that you are thinking safety.
I'll assume a lot here.
if I read your post correctly you have an electrical outlet for the washing machine which does not have an earth?
And therefore you are trying to individually earth the socket by installing a 2.5 earth into the socket and then take that new cable to be connected to a new earth rod?

Your reason for wanting the ground rod, and I am assuming here, is that you cannot take the new proposed 2.5 earth cable all the way back to the circuit board?
You can do what you propose, but the earth system on that socket will be completely independent of any ground system at the main board and therefore any protection device that requires an earth. Remember there are generally 2 types of earth leakage protection, USA Ground fault Trip and the Aust ELCB. Both work but are slightly different. But with your proposal the circuit breaker for the socket at the mainboard will still trip on overcurrent or short circuit.
The issue of the earth rod can get technical and confusing to non electrical people as posters have already correctly indicated but it doesn't need to be, a 3 meter rod would suffice your needs. An electrician can test the earth resistance for you with the correct measuring device.
My advice and to negate all the above and if at all possible is to get the 2.5 earth cable back to the main board and connect to the existing house main earth. If you do not have earth fault protection at the main panel then consider having it retro fitted to the panel.

Thanks Barney and all others. Yes Barney ... You got the picture .. Yes there is no << house main earth >> not a single circuit has ground in this house.
There are 2 water heaters , and old one which has a ground wire connected to a re-bar, the other water heater has no ground, both have RCCB breakers outside the bathrooms..

Few montha ago, while i was not here, they purchased a new washing machine which has a streel frame..
They just pluged in to the same ac outlet outdoor as the one before... except that the old washing machine
was all plastic ( not metal ).. As you probably know the washing machine empties from under creating large wet areas.

Metal, electricity, water i don t like that cocktail, so it got me thinking of adding
a new ground rod and a wire back to the ground prong on the ac outlet. The other ground rod being far
and in not easily accessible.

Of course i understand that this approach would only protect this circuit.
After reading your post i think that i should consider adding a ground fault breaker RCCD (GFI) ( wall mounted on
the outside wall of the house ) to the washing machine circuit.

The retrofit of the main panel would have to wait..

I would advise you to install the ELCB at the washing machine outlet & also install the ground rod. I would doubt if you can find a local electrician who has the correct equipment to fully test your ground rod installation. A simple basic test which only needs a multimeter to see if your ground rod is working is on this link.
http://www.diyable.net/forum/viewtopic.php?f=13&t=49

One of the best electrical supply stores in Udon is Siritham. http://www.udonmap.com/udonthaniforum/p ... 20393.html