Installing Earth Into Existing 2-wire System

[Frotting]

Hi Guys. I was wondering if Crossy or any of the others could help with a bit of onfo. The wife and I have just bought a new house, as she was getting a bit pi**ed off with me taking more than 3 years to complete the building of our place (we're out the country most of the time working - no opportunity). Anyway, we bought this place, a typical Thai build, not too bad but the usual problems - inadequate plumbing and dangerous wiring.

I get shocks from my computer, the iron and just about everything else we imported into Thailand from Malaysia. As you know Malaysia uses British style 3-pin plugs and an earthed system (only good thing about the place by the way).

So we're both getting tired of being fried all the time and I want to do something about it that doesn't require ripping everything out or any kind of rebuild. So the prospect of installing a ground spike and earth wire throughout, seems a good one. Additionally, I would like to change all power points to 3-pin. I have seen multi-style 3-pin sockets (they take just about all types of plug) that can be fitted to surface-mounted boxes. The ones I've seen are not cheap and nasty things but really look the business. I saw them in an industrial building in Thailand, so I imagine the supplier must be not on your normal 'Home Pro and Tesco' list of shops.

Prior to this I've identified the polarity on the existing 2-pin sockets and marked the live with a red marker pen. I still get a small shock. I measured 4 volts from my computer case to me (ground). I can feel this too, so must be a high current flow?

I've read Crossy's site on earthing and cable sizes. A great site by the way, very helpful. So a brief description of what I have to do should be something like this?:

1. Make hole in concrete over-site out side home. Hammer in ground spike (>1.5m long) run cable (minimum 10 mm sq area) to earthing bus bar in consumer unit (if it's got one).

2. Run earth wires (min 7 mm sq area) to each socket and water heater in bathroom from the bus bar in consumer unit.

3. Replace and connect new 3-pin sockets (multi style) making sure that all live wires are tested for and connected to the correct pin.

4. Fit ELCB's in consumer unit.

Crossy. Where does the MEN link come in (if required in this upgrade). Finally, do you know a supplier of the sockets I spoke about? These would be okay for the 2-pin monkeymetal plugs as well, so we could run everything we have.

Thanks in anticipation.

[Crossy]

1. Make hole in concrete over-site out side home. Hammer in ground spike (>1.5m long) run cable (minimum 10 mm sq area) to earthing bus bar in consumer unit (if it's got one).

2. Run earth wires (min 7 mm sq area) to each socket and water heater in bathroom from the bus bar in consumer unit.

3. Replace and connect new 3-pin sockets (multi style) making sure that all live wires are tested for and connected to the correct pin.

4. Fit ELCB's in consumer unit.

Crossy. Where does the MEN link come in (if required in this upgrade). Finally, do you know a supplier of the sockets I spoke about? These would be okay for the 2-pin monkeymetal plugs as well, so we could run everything we have.

1. Yup

2. You don't need such fat wire for your outlet grounds, 2.5mm² will be just fine, in fact the 2.5mm² twin+earth now sold in the UK has a 1.5mm² ground core. For your water heaters use a ground that is the same size as the supply to the heater.

3. I have issues with the 'shove anything in' outlets:-

a. They are invariably unshuttered and the holes are necessarily bigger than regular outlets, not good if there are small fingers around.

b. The L and N are the wrong way round if a UK plug is inserted putting the plugtop fuse in the N leg.

c. The local plugs (particularly the round pin ones) can tend to rattle around in these outlets.

IMHO You should either, replace your BS1363 plugs with local ones or install some proper BS1363 outlets. Unfortunately the BS outlets don't fit the local boxes, you can certainly get Shuko outlets here that do fit, I've not seen UK outlets that fit Thai boxes but they may be available.

4. Yup Consider installing a split-service CU so you can keep your freezer on an unprotected supply.

The MEN link goes between the ground bar and the incoming neutral, it MUST connect to the neutral on the incoming side of any earth leakage protection for proper operation and should be the same size as the incoming active conductors. BUT do not install one unless you are certain that the local system is implementing it as there are potential hazards if yours is the only MEN in the area as well as a potentially lethal situation if the incoming L & N get transposed (been reported as happening by several posters here) With ELCBs your system will be safe without the MEN i.e. a TT system as defined in the IEE regs 17th edition.

Edited September 15, 2008 by Crossy

[dotcom]

IMHO 1.5 mm2 is big enough from ground rod to CU & from CU to wall outlets.

If I were retrofitting I would drill a hole through my existing wall boxes to the outside of the house & strap ground wire onto the house.

I have done that in the past. My hot water pipes are run the same way.

[Crossy]

IMHO 1.5 mm2 is big enough from ground rod to CU & from CU to wall outlets.

If I were retrofitting I would drill a hole through my existing wall boxes to the outside of the house & strap ground wire onto the house.

I have done that in the past. My hot water pipes are run the same way.

I agree with most of the above, EXCEPT CU to stake wire size. Conventional thinking has always been that the main earth should be no smaller than the incoming active conductor. In order to save money and with the advent of reliable ground fault detection devices that requirement is now less important however, I would not use less than 4 or 6mm for a main ground (or bigger if there is a long run to the stake), generally, the bigger the better

In belt-and-braces UK, most main grounds are at least 10mm with many domestic installations having 16mm.

There are fault conditions where a large ground current could flow without tripping the ELCB such as a L - N reversal or an open supply neutral in a MEN system, it is vital that the ground connection is able to handle this current and keep the touch voltages within reasonable limits in these circumstances.

Edited September 15, 2008 by Crossy

[dotcom]

What size mains are used in residential wiring in LoS? What's the largest for a single phase system?

[Crossy]

What size mains are used in residential wiring in LoS? What's the largest for a single phase system?

Sorry mate, are you asking about incoming cable sizes or supply (meter) currents?

[Frotting]

1. Yup

2. You don't need such fat wire for your outlet grounds, 2.5mm² will be just fine, in fact the 2.5mm² twin+earth now sold in the UK has a 1.5mm² ground core. For your water heaters use a ground that is the same size as the supply to the heater.

3. I have issues with the 'shove anything in' outlets:-

a. They are invariably unshuttered and the holes are necessarily bigger than regular outlets, not good if there are small fingers around.

b. The L and N are the wrong way round if a UK plug is inserted putting the plugtop fuse in the N leg.

c. The local plugs (particularly the round pin ones) can tend to rattle around in these outlets.

IMHO You should either, replace your BS1363 plugs with local ones or install some proper BS1363 outlets. Unfortunately the BS outlets don't fit the local boxes, you can certainly get Shuko outlets here that do fit, I've not seen UK outlets that fit Thai boxes but they may be available.

4. Yup Consider installing a split-service CU so you can keep your freezer on an unprotected supply.

The MEN link goes between the ground bar and the incoming neutral, it MUST connect to the neutral on the incoming side of any earth leakage protection for proper operation and should be the same size as the incoming active conductors. BUT do not install one unless you are certain that the local system is implementing it as there are potential hazards if yours is the only MEN in the area as well as a potentially lethal situation if the incoming L & N get transposed (been reported as happening by several posters here) With ELCBs your system will be safe without the MEN i.e. a TT system as defined in the IEE regs 17th edition.

Hi Crossy

And Thanks very much matey, for the advice

I'll take your point about the multi-style 'plug anything in' sockets. The ones I saw were good, probably came from Singapore anyway. If I can actually get these I'll post here details about them. The ones I saw were based on the UK model and appeared primarily for UK plugs - but could take 2-pin types also. Maybe Crabtree make them, but have to check. If I can only get s*ite, then I'll do as you say with a difference. I'm currently (no pun intended) in Malaysia, where we can get surface mount boxes and sockets to UK standards. I'll buy a few and install a combination of these and 2-pin sockets for the Thai plugs. If I'm careful about polarity, do you think this would be safe?

Regarding the MEN link, all the houses on the estate (about 250) were built and wired by the same group of people, so the chances are that none of them have a MEN system. I will check the transformer our house comes off (if I can find it) and see if the star point is grounded (as per your instructions long ago). If so, then I'll assume that it is safe to install the MEN link.

Again, thanks for the advice. Just as an afterthought, when we eventually do get round to finishing our own place, I'm taking a trip to the UK to buy consumer unit, sockets, boxes, etc. Or maybe Singapore is an option.

[dotcom]

Crossy. From the meter to the Load Center.

[Crossy]

Crossy. From the meter to the Load Center.

Standard sizes, copper:-

CSA mm² ......... diameter (mm)

16 .......................... 4.5

25 .......................... 5.6

35 .......................... 6.7

50 .......................... 8.0

70 .......................... 9.4

95 .......................... 11.0

120 ........................ 12.4

The usual Thai installation with the meter on the pole means that you can end up with a long run from the meter to the loadcentre. Invariably this means that the cable size is determined by volt-drop requirements rather than the ultimate current capacity of the cable.

Edited September 16, 2008 by Crossy

[Crossy]

I'll take your point about the multi-style 'plug anything in' sockets. The ones I saw were good, probably came from Singapore anyway. If I can actually get these I'll post here details about them. The ones I saw were based on the UK model and appeared primarily for UK plugs - but could take 2-pin types also. Maybe Crabtree make them, but have to check. If I can only get s*ite, then I'll do as you say with a difference. I'm currently (no pun intended) in Malaysia, where we can get surface mount boxes and sockets to UK standards. I'll buy a few and install a combination of these and 2-pin sockets for the Thai plugs. If I'm careful about polarity, do you think this would be safe?

Regarding the MEN link, all the houses on the estate (about 250) were built and wired by the same group of people, so the chances are that none of them have a MEN system. I will check the transformer our house comes off (if I can find it) and see if the star point is grounded (as per your instructions long ago). If so, then I'll assume that it is safe to install the MEN link.

I remember we had BS outlets in Malaysia whose shutter arrangement allowed the 2 pin plugs on the telly, hi-fi etc to fit without poking your screwdriver into the ground hole. There were also 'adaptors' which tripped the shutter with a plastic earth pin.

Putting BS outlets on the same radials as Thai outlets will be just fine so long as you don't use an MCB bigger than 20A (not the UK 32A used on ring mains), do NOT wire a ring main and put Thai outlets on it!!!

Be careful with your MEN. The key word is MULTIPLE, if you are the only place with a N-E link and the neutral goes open between you and the transformer a (very) large current will flow in your ground system. Much better to leave the link out if no other houses have it.

Edited September 16, 2008 by Crossy

[Frotting]

I remember we had BS outlets in Malaysia whose shutter arrangement allowed the 2 pin plugs on the telly, hi-fi etc to fit without poking your screwdriver into the ground hole. There were also 'adaptors' which tripped the shutter with a plastic earth pin.

Putting BS outlets on the same radials as Thai outlets will be just fine so long as you don't use an MCB bigger than 20A (not the UK 32A used on ring mains), do NOT wire a ring main and put Thai outlets on it!!!

Be careful with your MEN. The key word is MULTIPLE, if you are the only place with a N-E link and the neutral goes open between you and the transformer a (very) large current will flow in your ground system. Much better to leave the link out if no other houses have it.

Thanks again Crossy.

Yes, the adapters you speak about are flat plastic shims the shape of a BS plug that have a square pin to open the socket, with two holes that allow the 2-pin plug to enter the socket through the aforesaid adapter. We used them all the time to plug our Thai things into the Malaysian sockets.

Yes, I'll put the BS outlets in place of the Thai ones, so they'll be on the same radials. I'll use 15A breakers. I don't intend a rewire, so I'll keep the same radials and just run earth cables to each outlet from the ground bus in the consumer unit, as you said. No ring-main therefore.

I take your point about the MEN link and will leave it out. I'll track down a source of electrical components whist still here in Malaysia, and post any details I uncover in this forum, should any of you wish to use BS fittings in their new home instead of Thai ones.

Cheers.

[xylophone]

Just a point about endeavouring to run an earth from your distribution board to every socket outlet..... being an ex electrician from many years ago (completed my apprenticeship in 1969 in the UK but have not worked on the "tools" since 1977).

Recently renovated the house I bought here and have found similar things, getting shocks off of just about everything, different coloured wiring throughout the house and even an air conditioner connected directly from the feed into the house, bypassing the distribution board!

Anyway, regarding your point about running an earth from the distribution board to every socket outlet -- -- you may find this is very difficult to do (as I found) as in my case the plastic conduit was embedded in the walls, and inside of which there were numerous twisted wires and some debris from the building which made it impossible to run any new cables, add to that the fact that they were often many elbows in the conduit. Even the tried and trusted method of adjoining new wires to an existing one and pulling this through did not work.

I ended up adopting a combination of the suggestions, ripping out some of the conduit (luckily not too deeply embedded in the concrete) and rewiring that way, and also drilling holes through the wall, earthing things like the cooker and microwave onto a 2 m copper earth rod. As it happens I checked the earth connection on the pole outside of the house and found it was a six inch nail pushed into some earth, which in itself was just a miniature garden resting on concrete! Obviously re-did this with a 2 m spike.

Only a couple of other things to do, but hopefully am getting on top of it now.

[dotcom]

Excellent approach. Now you know it is done right.

[mdechgan]

What really helps is ground the neutral of your main ciruit breakers.

Usually 2 wire systems don't ground the neutral at the mains.

Buy a grounding rod, atleast 1.5 - 2 M, run a 10 sqmm cable to the neutral bus bar of your breaker box.

It really helps. Most electricians especially the smaller budget contractors don't do this. Also make sure teh wires are correct. Sometimes they get the wires mixed. Correct colors are black (hot), gray (neutral). Some people use black and neutral thinking it is ground or negative like speaker wires and gray for hot or positive.

The smaller socket (usually on the left of the socket) is hot while the larger socket (usually on the right) is supposed to be neutral.

Other than that there's not much else you can do other than re-wire the house for 3 wire outlets. Depending if you run your cables inside the concrete walls, gypsum boards, or conduits.

[Crossy]

What really helps is ground the neutral of your main ciruit breakers.

Usually 2 wire systems don't ground the neutral at the mains.

Buy a grounding rod, atleast 1.5 - 2 M, run a 10 sqmm cable to the neutral bus bar of your breaker box.

It really helps. Most electricians especially the smaller budget contractors don't do this. Also make sure teh wires are correct. Sometimes they get the wires mixed. Correct colors are black (hot), gray (neutral). Some people use black and neutral thinking it is ground or negative like speaker wires and gray for hot or positive.

The smaller socket (usually on the left of the socket) is hot while the larger socket (usually on the right) is supposed to be neutral.

Other than that there's not much else you can do other than re-wire the house for 3 wire outlets. Depending if you run your cables inside the concrete walls, gypsum boards, or conduits.

WARNING, WARNING, WILL ROBINSON!!!!!

DO NOT under any circumstances connect your ground and neutral unless you KNOW that the MEN or PME system is implemented in your area, there is a serious danger of hazard in the event of an open neutral between you and the transformer (everybody elses neutral current goes though your ground rod).

Please explain how grounding your neutral will 'help' if you don't have 3 pole outlets (it's already grounded at the transofrmer).

Additionally it's not unknown for the incoming live and neutral to get transposed which could also have interesting effects. I used to be a great advocate of PME/MEN, and indeed, when correctly implemented and maintained it is THE safest system. BUT, this is Thailand and I'm moving towards being more happy with using high-sensitivity ELCBs rather than joining my ground (and thus all the exposed metalwork in my home) to a potentially live conductor.

[mdechgan]

What really helps is ground the neutral of your main ciruit breakers.

Usually 2 wire systems don't ground the neutral at the mains.

Buy a grounding rod, atleast 1.5 - 2 M, run a 10 sqmm cable to the neutral bus bar of your breaker box.

It really helps. Most electricians especially the smaller budget contractors don't do this. Also make sure teh wires are correct. Sometimes they get the wires mixed. Correct colors are black (hot), gray (neutral). Some people use black and neutral thinking it is ground or negative like speaker wires and gray for hot or positive.

The smaller socket (usually on the left of the socket) is hot while the larger socket (usually on the right) is supposed to be neutral.

Other than that there's not much else you can do other than re-wire the house for 3 wire outlets. Depending if you run your cables inside the concrete walls, gypsum boards, or conduits.

WARNING, WARNING, WILL ROBINSON!!!!!

DO NOT under any circumstances connect your ground and neutral unless you KNOW that the MEN or PME system is implemented in your area, there is a serious danger of hazard in the event of an open neutral between you and the transformer (everybody elses neutral current goes though your ground rod).

Please explain how grounding your neutral will 'help' if you don't have 3 pole outlets (it's already grounded at the transofrmer).

Additionally it's not unknown for the incoming live and neutral to get transposed which could also have interesting effects. I used to be a great advocate of PME/MEN, and indeed, when correctly implemented and maintained it is THE safest system. BUT, this is Thailand and I'm moving towards being more happy with using high-sensitivity ELCBs rather than joining my ground (and thus all the exposed metalwork in my home) to a potentially live conductor.

It has been clearly demonstrated that the MEN system removes the hazardous conditions imposed on someone by a broken neutral in the PME system. The multiple earth connections of the neutral in an MEN system provide integrity to the neutral return path. This provides not only continuity of supply, but ensures operation of earth leakage devices which require this supply.

In simple terms:

1) New regulations require all systems in the MEA to be neutral grounded. So all transformers should be.

2) Yes PME systems are grounded at the transformer.

3) MEN systems ensure that if their is a fault on the premises your appliance will ground in someway.

4) If the house next door does have a break or short it will ground at the nearest tee point. That means transformer. If you have a break or short your neutral will ground at the nearest tee point. Meaning either the transformer or your local ground. If the transformer ground is broken it will ground at the next ground point, your local ground. If no ground does exist then any surge or short will go into your house through your neutral. If you have a short it is better to ground nearest than having to go all the way to your transformer sometimes up to 50M away.

I've tried it my self and it does help and work. I don't think your neighbor's fault will short out your house. However if their is a short it is better to have it short out at your ground than no ground at all up to your plasma screen.

If their is no ground or 3 prong outlet grounding your neutral is better than having no ground at all. Another point is to ground as close as possible.

There is an exception though. Is this a house or flat, condo? Remember better to have some ground than no ground at all.

One flaw is that the MEN system is a bit inefficient, but safe. The neutral gains about 0.2 - 0.5 ohms resitance.

ELCB:

I prefer to use a ground system than depend my life on these things.

They only protect cable damage not current faults downline. They do not detect faults that don't pass current through to the earth rod.

They do not allow a single building system to be easily split into multiple sections with independent fault protection.

ELCBs introduce additional resistance and an additional point of failure into the earthing system.

You want a lowest grounding resistance as possible.

It is not unusual for ELCB protected installation to have a second unintentional connection to earth somewhere, via metal pipework in contact with the ground, structural framework, etc..

[Crossy]

I'm not going to argue with the above (mostly) ^^^

BUT the key word in MEN is MULTIPLE. If you are the only one with a ground-neutral link as can easily happen in Thailand as many areas have not yet implemented MEN, then, in the event of a broken neutral between you and the transformer there is a serious risk of all your metalwork heading in the direction of phase voltage as everyone elses neutral current is attempting to flow down your (fairly high impedence) ground stake.

Yes, grounded systems with ELCBs are the minimum I would recommend with MEN/PME if correctly implemented. The 17th Edition of the IEE Regs. now requires ALL circuits to be ELCB protected.

Not sure how you infer that MEN increases the neutral impedence by 0.2-0.5 Ohm (which is a LOT in power distribution), please explain

Modern ELCBs detect a difference in the L and N currents, they do not measure ground current directly or require an actual ground to operate. Since they don't measure ground current itself any additional parasitic earths have zero effect on their operation.

Ever heard of split-service consumer units or RCBOs? Handy to give independent fault protection to zones or even individual circuits

Edited October 3, 2008 by Crossy