About earthing..yet again.

[jack2964]

Folks, I have gone through several threads here on TV about household electrics but still not 100% certain I understand what I read.

My question is; am I adequately earthed if I drive a copper rod about 1.5m length into the ground and connect said rod to chassis of say my fridge or washing machine.

Please view photos attached of my distribution box and a typical wall outlet.

That green wire from my distribution box (shown in photo) runs outside and then disappears into concrete and hopefully 'properly connected' to a similar ground rod.

The wall outlets although 3-pinned are I believe not wired to earth as the wires that run to the outlets are two-wires only.

Does this mean every appliance I use will need a loose wire from the chassis to a ground rod which of course is impractical for things like table fan or iron.

Finally how can I be sure that the green wire from the distribution box is making good ground connection, any quick tests?

Thanks in advance.

[FACTOR]

Great questions, Jack. I have similar questions and look forward to the answers from some of the folks on TV who are pretty expert at this stuff.

[bankruatsteve]

Yes, a ground rod connected to chassis is adequate earth bond.

Your CU does not appear to have a ground bus so if the green wire (connected to neutral bus) does go to a ground rod that would mean they have implemented MEN for some reason. There is no apparent grounding to any of your circuits so you would need to independently ground appliances, etc.

You should consider replacing the main 50a breaker with a RCBO which would give protection in case of fault.

[Crossy]

As usual +1 Steve.

Instead of replacing the incomer with an RCBO (may not be available) you could use an external RCBO, commonly called a Safe-T-Cut.

Since you have 3-pin outlets you could make a neater job of earthing kit that needs it by running the green wire from the earth pin inside the outlet box to your ground rod.

Things like fans are inherently 2-pin and don't require a ground, but your iron almost certainly does.

Is this home a rental?

[jack2964]

Yes, a ground rod connected to chassis is adequate earth bond.

Your CU does not appear to have a ground bus so if the green wire (connected to neutral bus) does go to a ground rod that would mean they have implemented MEN for some reason. There is no apparent grounding to any of your circuits so you would need to independently ground appliances, etc.

You should consider replacing the main 50a breaker with a RCBO which would give protection in case of fault.

Great...I can easily attach wires to large appliances like fridge and washing machine that stay put pretty much. Can several appliances share a single ground rod?

For items like fans, blender, iron, electric kettle would it be safe to continue using them without earth as they get used in different parts of the house?

I don't know what "MEN" is. For my purpose here I hope I can get by without this bit of knowledge.

Your last statement if I understand it correctly sounds like just what I need. So if I install that RCBO I am safe from death by electrocution?

Thanks!

[Crossy]

Anything with a 3-pin plug will, by convention, require a ground even if you have an RCBO.

An RCBO will significantly reduce the possibility of your dying from electrocution, but the very young, very old, or those with a weak heart may still be killed.

An RCBO is classed as a secondary protection device, primary protection is your ground connection.

Also, the RCBO is an electronic device, they can and do fail, you need to test it regularly.

[Chao Lao Beach]

Also, nearly every earthing rod I have seen in Thailand is steel that has a very pretty but exteamly thin copper coating. These rust up very quickly. Leave it outside in the rain and 4-6 months the entire copper coating is gone and it is rusting. After 2 years in the ground they rust up and are cancerous.

I have only seen real copper ones in a few places, 1 common place is the GLOBAL House shop that carry both, the real ones are about 1500B.

Edited December 13, 2013 by Chao Lao Beach

[jack2964]

As usual +1 Steve.

Instead of replacing the incomer with an RCBO (may not be available) you could use an external RCBO, commonly called a Safe-T-Cut.

Since you have 3-pin outlets you could make a neater job of earthing kit that needs it by running the green wire from the earth pin inside the outlet box to your ground rod.

Things like fans are inherently 2-pin and don't require a ground, but your iron almost certainly does.

Is this home a rental?

Please bear with me while I try and understand your post Crossy.

I've got a slightly better pic of my CU and everything on it is Safe-T-Cut so I guess this is just a brand name and that leftmost chunky block isn't an RCBO.

I'll pay a visit to the electrical store in town and see if I can find an RCBO for the 'incomer' position. I'll try to avoid fitting and external one.

This isn't a rental home, it's my missus's house. Thanks Chrossy.

[jack2964]

Great questions, Jack. I have similar questions and look forward to the answers from some of the folks on TV who are pretty expert at this stuff.

Fire away Factor, you are welcomed to share this thread, I am sure I will gain too.

[jack2964]

Also, nearly every earthing rod I have seen in Thailand is steel that has a very pretty but exteamly thin copper coating. These rust up very quickly. Leave it outside in the rain and 4-6 months the entire copper coating is gone and it is rusting. After 2 years in the ground they rust up and are cancerous.

I have only seen real copper ones in a few places, 1 common place is the GLOBAL House shop that carry both, the real ones are about 1500B.

Bugger! Just when I thought I got it sorted out. This means I'll need to buy new 'real ones' no point digging out the old ones, some are buried under concrete.

[bankruatsteve]

Yeah, I don't know how Safe-T-Cut gets by selling units that are without RCD but obviously they do. (If it was a RCBO, it would have a "Test" button.) And yes, the main 50a breaker is the one you would want to replace with RCBO - BUT you should check if it can be replaced. (?) If not, or if there is no replacement available (you can't just get any RCBO - it has to fit this CU) then you need to do as Crossy advised and front-end it with a RCD. RCD is the fault protection without the overcurrent breaker <- which you already have.

Also, you should be OK with the copper clad rods.

[jack2964]

Yeah, I don't know how Safe-T-Cut gets by selling units that are without RCD but obviously they do. (If it was a RCBO, it would have a "Test" button.) And yes, the main 50a breaker is the one you would want to replace with RCBO - BUT you should check if it can be replaced. (?) If not, or if there is no replacement available (you can't just get any RCBO - it has to fit this CU) then you need to do as Crossy advised and front-end it with a RCD. RCD is the fault protection without the overcurrent breaker <- which you already have.

Also, you should be OK with the copper clad rods.

Thanks Steve for your input I'll look around the local electrical stores first.

[Crossy]

Multiple rods can create a hazard in lightning prone areas, they are banned in Australia.

If you have multiple rods more than a metre or so apart run the cable linking them outside the building.

In the event of a local lightning strike differential ground potentials can lead to a very large current flowing between the rods via that cable, we don't want it starting a fire.

Rods less than a metre apart behave as a single longer rod and are close enough together that large differentials don't build up in the event of a strike.

[Forkinhades]

Guys you do realise that you need to measure your earth and get an ohmic reading? The resistivity of your soil can vary vastly, anything over 200 ohms is considered unstable. You should be looking for readings of below 10 ohms. If you do not have that, then you should seriously consider putting more rods in as Crossy has suggested at less than 1 metre apart. The lower your readings means your protective device opens quicker, which will save your life.

Unfortunately this test equipment is quite expensive (50,000 baht) and not many thai sparkies will have them.

Simply put. Just banging in some earth rods can cause more problems than benefits if not done correctly.

RCD protection is a must on TT systems. Ideally you should have a main one set at 100mA, with secondary individual ones set at 30mA. Both should be tested every 3 months.

[jpinx]

The quality of earthing in the ground also depends on the moisture content of the soil. You can earth in wet sand but as soon as it dries out you have no earth.

In a previous life I used old-fashioned thick-walled copper piping driven into the ground to about a metre depth to ensure that the bottom was always in the damp. I used a length of rebar to make the hole and made sure the copper was backfilled tightly. Also, be aware of the old jubilee clip trick to connect the earthing wire to the earth-rod. The clip will quickly corrode and leave you exposed. Better to not bury/cover your earthing system with concrete - you do need to check on it occasionally.

[jack2964]

Guys you do realise that you need to measure your earth and get an ohmic reading? The resistivity of your soil can vary vastly, anything over 200 ohms is considered unstable. You should be looking for readings of below 10 ohms. If you do not have that, then you should seriously consider putting more rods in as Crossy has suggested at less than 1 metre apart. The lower your readings means your protective device opens quicker, which will save your life.

Unfortunately this test equipment is quite expensive (50,000 baht) and not many thai sparkies will have them.

Simply put. Just banging in some earth rods can cause more problems than benefits if not done correctly.

RCD protection is a must on TT systems. Ideally you should have a main one set at 100mA, with secondary individual ones set at 30mA. Both should be tested every 3 months.

I understand the need for a good ground installation that falls within the acceptable limits but how does the typical home owner verify the ground's integrity and how often should that be?

Given the average sparkie here won't have this test gadget in his tool kit is there any alternative method? Can a simple digital multimeter be used to give at least a 'rough' reading to go on?

If so, how would one use it-my guess is; stick one probe of meter at my CU's green wire busbar and other probe of meter at a ground rod that I stuck in for the washing machine and fridge.

A crude method perhaps but I ought to get some resistive reading. Just my thought; could be total nonsense.

[jack2964]

I found this on ebay. I know it is for the Oz market but can be easily adapted to suit local plugs.

Big question is-will this still work if I ignore the earth wire(s) at both the inlet plug and outlet sockets?

Features/Benefits 4 OULTET 10 AMP PORTABLE POWER DEVICE WITH MCB AND RCD PROTECTION, IP33 RATED WITH 1.0MM FLEXIBLE HEAVY DUTY LEAD.ORANGE. 30mA SENSITIVITY. PROTECTION FROM ELECTROCUTION FROM ACTIVE TO EARTH

Edited December 14, 2013 by jack2964

[Crossy]

I found this on ebay. I know it is for the Oz market but can be easily adapted to suit local plugs.

Big question is-will this still work if I ignore the earth wire(s) at both the inlet plug and outlet sockets?

Features/Benefits

4 OULTET 10 AMP PORTABLE POWER DEVICE WITH MCB AND RCD PROTECTION, IP33 RATED WITH 1.0MM FLEXIBLE HEAVY DUTY LEAD.ORANGE. 30mA SENSITIVITY.

PROTECTION FROM ELECTROCUTION FROM ACTIVE TO EARTH

Yes, the RCD will still function without a ground, but by ignoring the ground you are reducing your protection by more than 50%.

Don't be so sure you can easily modify for Thai outlets, the back box size and screw spacing is different.

Outlets with built-in RCD protection are readily available, look on the Safe-T-Cut stall in Tesco or Big-C.

[jack2964]

Yes, the RCD will still function without a ground, but by ignoring the ground you are reducing your protection by more than 50%.

Don't be so sure you can easily modify for Thai outlets, the back box size and screw spacing is different.

Outlets with built-in RCD protection are readily available, look on the Safe-T-Cut stall in Tesco or Big-C.

I didn't make it clear when I said I can adapt this for local use; I meant to change the inlet plug and outlet sockets to Thai ones. I'd then plug this unit into an existing wall outlet and plug the fridge/washing machine ...etc..in. I didn't mean to fit it onto my CU. This way I could buy a few of these and use them around the house and leave the CU alone. Practical?

[Crossy]

Thai outlets won't fit in an Aussie box, size and screw spacings are wrong.

By all means bash it about to fit Thai outlets, just seems a rather expensive exercise.

But, as I noted, you can buy RCD outlets here which are a straight swap for your existing outlets. Put them where you are worried about shocks, replace the original outlets when you move.

[Forkinhades]

Guys you do realise that you need to measure your earth and get an ohmic reading? The resistivity of your soil can vary vastly, anything over 200 ohms is considered unstable. You should be looking for readings of below 10 ohms. If you do not have that, then you should seriously consider putting more rods in as Crossy has suggested at less than 1 metre apart. The lower your readings means your protective device opens quicker, which will save your life.

Unfortunately this test equipment is quite expensive (50,000 baht) and not many thai sparkies will have them.

Simply put. Just banging in some earth rods can cause more problems than benefits if not done correctly.

RCD protection is a must on TT systems. Ideally you should have a main one set at 100mA, with secondary individual ones set at 30mA. Both should be tested every 3 months.

I understand the need for a good ground installation that falls within the acceptable limits but how does the typical home owner verify the ground's integrity and how often should that be?

Given the average sparkie here won't have this test gadget in his tool kit is there any alternative method? Can a simple digital multimeter be used to give at least a 'rough' reading to go on?

If so, how would one use it-my guess is; stick one probe of meter at my CU's green wire busbar and other probe of meter at a ground rod that I stuck in for the washing machine and fridge.

A crude method perhaps but I ought to get some resistive reading. Just my thought; could be total nonsense.

You need to measure the external earth. One can calculate the resistance of cable, as a 16mm cable has resistance of 1.15m ohms per metre, so 10 metres would give us 0.01 ohms. That then needs to be added to the external earth which is what we dont know. There are a few different methods one can use to find this. A basic multimeter will not help. If the rod was to measured then the meter used has 3 or 4 leads (depending on make) which are staked in the ground at given distances apart (depending on meter), and one attached to the rod.

You can also do a live test to obtain the earth fault loop impedance. Which is the total resistance.

One should also be testing the TIME at which the protective device opens. This is the most important test of all.

[jack2964]

Thai outlets won't fit in an Aussie box, size and screw spacings are wrong.

By all means bash it about to fit Thai outlets, just seems a rather expensive exercise.

But, as I noted, you can buy RCD outlets here which are a straight swap for your existing outlets. Put them where you are worried about shocks, replace the original outlets when you move.

Sorry I must have misunderstood an earlier post of yours. Your option of replacing existing standard wall outlets with RCD integrated outlets sound like a good compromise if I cannot find a suitable RCD for the CU. Saves messing around with that ebay unit I posted about earlier.

Thanks for your patience Crossy.

[jack2964]

You need to measure the external earth. One can calculate the resistance of cable, as a 16mm cable has resistance of 1.15m ohms per metre, so 10 metres would give us 0.01 ohms. That then needs to be added to the external earth which is what we dont know. There are a few different methods one can use to find this. A basic multimeter will not help. If the rod was to measured then the meter used has 3 or 4 leads (depending on make) which are staked in the ground at given distances apart (depending on meter), and one attached to the rod.

You can also do a live test to obtain the earth fault loop impedance. Which is the total resistance.

One should also be testing the TIME at which the protective device opens. This is the most important test of all.

Thanks Forkinhades, I doubt if anything like this gets done here in Thailand. You'd think this should be made mandatory and carried out on a regular basis.

[Forkinhades]

It is mandatory

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[Crossy]

It is mandatory

In the UK.

Sadly nothing like that exists in any Thai regulations for domestic installations that I've found

Unless you've found something Forky.

It's also important to note that the Thai regs (such as they are) are prescriptive (much like the US) i.e. "Do it like this and it's to code" (bash in a 2.5m rod).

The UK regs are proscriptive, they describe the results you need to achieve, how you get there is (within reason) up to you (earth loop impedance must be less than x [x is determined by the protective device]).

[Forkinhades]

It is mandatory

In the UK.

Sadly nothing like that exists in any Thai regulations for domestic installations that I've found

Unless you've found something Forky.

It's also important to note that the Thai regs (such as they are) are prescriptive (much like the US) i.e. "Do it like this and it's to code" (bash in a 2.5m rod).

The UK regs are proscriptive, they describe the results you need to achieve, how you get there is (within reason) up to you (earth loop impedance must be less than x [x is determined by the protective device]).

I will have to research that, as I may have been misinformed.

In regards to figures you can work it out, you don't need any books.

Consider this : A 10A type C MCB, the C just means 10, you will just have to accept that for the moment. So 10x10=100. From ohms law we get 230/100=2.3 ohms. So in order for the MCB to open in time the earth loop impedance must be lower than 2.3 in order for the 100A fault current to flow. Anything higher than that and it will not open in the time stated in the regs.

So with a 32A mcb which requires 320A to open. The maximum Zs (earth loop impedance) allowable is 0.71 ohms. You are just not going to achieve these figures on a TT system.

With an RCD in place you only need 30mA of fault current.

With TN systems where the earth is supplied by the Elecric company. The external earth is 0.08 at most.

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[Crossy]

I will have to research that, as I may have been misinformed.

Please do mate, we've been trying to locate a cohesive set of Thai domestic installation regulations for years.

It's a bit like the 'must carry your passport' rule, everybody knows about it, nobody can quote a law which states it

[Forkinhades]

Hopefully people can get their head around my last post, and realise how important it is to have an RCD on TT systems. Whether or not it forms part of the thai code. Which I was informed was in fact more stringent than BS7671.

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[Crossy]

As far as I'm aware (and I've not seen it in any form of standard other than the PEA "Groundwire" document) all new domestic installations must have:-

1. A front end 30mA RCD/RCBO
2. All grounded outlets
3. Grounds to Class-1 fixed appliances
4. A 2.4m ground rod
5. MEN connected in line with the US NEC system

OR

1. A suitable amount of tea money

The above will get you on a permanent supply (4 Baht / unit) after that nobody gives a flying fart

[bankruatsteve]

So with a 32A mcb which requires 320A to open. The maximum Zs (earth loop impedance) allowable is 0.71 ohms. You are just not going to achieve these figures on a TT system.

??? How do you get that? And why would the "system" in use be that much different?

ie: what is the case that it requires 320A to open a 32A mcb on C?