Quick And Dirty Grounding/Earthing Installation

[Gary A]

A friend of mine is building a new house. The rafters and roof beams are steel and they are tied to the re-bar in the support posts. Another friend is a Brit sparky. He wired the house and uses the steel rafters for a ground. He is a pretty careful guy and if it is good enough for him, I'd have to say that it is a good way to come up with a reliable ground.

[Crossy]

Buildings all over the world use the structural steel as the grounding system. Even if it's not intended to act as the supply ground the Ufer effect will provide a ground easily good enough if an RCD is installed.

Even the plant-pot ground is using the structural steel as the path to earth, it just uses an unusual way to connect to it.

Nothing can replace a properly designed and implemented grounding system, but if your building does not have one, or you don't have access to it, then creativity and an RCD is required.

[dhrobertson]

Relying upon local ground alone is type TT. It is notoriously difficult to get good enough ground performance in this way.

Ponder this: to get a 20A type C minature circuit breaker to trip quickly (in less than 0.5s) we need 20 x 10 = 200A. If there is solid ground fault such that an air conditioning CDU case becomes live, then if the circuit has a 20A breaker, we need 200A to flow to ground. That means the total resistance of the phase wire, ground wire, ground conductor wire and ground rod must have a resistance not exceeding 220/200 = 1.1 ohms. This VERY unlikely.

This why you are much better off with TN-C-S where we use the main incoming neutral as a neutral conductor and ground wire combined (PEN). (A phase/ground fault automatically becomes a phase / neutral fault.). This achieved by bonding neutral and ground together at the main load panel / consumer unit (and adding local ground rods as a safety measure in case the main incoming neutral gets damaged or cut). With TN-C-S ground fault loop impedance is usually a fraction of an ohm.

TN-S (separate incoming main ground wire) is better when the property to be protected is VERY close to the transformer and/or MDB. Otherwise distance is such that resistance is too great.

Without appropriate test gear, you will not know how good or bad ground performace is.

Therefore, as Crossy says, fit an RCD/RCBO/ELCB. Either a single main one or protect individual circuits such as those supplying water heaters and those supplying socket outlets.

For the record, structural steel, telecoms grounds, lightning ground systems and your power system ground should all be bonded together.

[Crossy]

Yup ^^^, 100% agreement there DH

TN-C-S with MEN (Multiple Earthed Neutral) and a local ground stake is supposed to be the standard for new installations in Thailand, unfortunately many 'electricians' still don't wire homes with 3-pin outlets, and a lot of older properties are still TT.

i can never say too often, 'install an RCD', for the price it's cheap insurance against getting in the news for the wrong reasons.

[tim73]

Good info here, I never thought grounding could be quite complex issue. So more metal (copper plates?) to the ground, the more deep, the better? Single rods not very good?

Edited March 27, 2012 by tim73

[dhrobertson]

Yes, this is NOT a trivial issue.

Adequate ground performance depends on many variables including soil conditions, depth of ground rods, length and diameter (surface area of ground rods), number of ground rods, ground conductor size etc etc.

Take care. Please.

[electau]

Conditions. No compliant earth conductor from main switch board to condo distribution board.

Do NOT bond the neutral to earth. Bond the earth(s) at the earth bar to a metallic connection that goes directly or indirectly to the general mass of earth( ground). Minimum size 2.5sqmm.

The other option is to install a 32 x 6mm dynabolt into the wall ( a conductive material) below the distribution board and connect the earth at this point. Minimum size 2.5sqmm.

Install 30mA RCD protection.

This is not a compliant earthing system but it will ensure that the RCDs/RCBOs trip on earth fault and any minor leakage current is diverted to earth.

The readings given by Crossy indicate that there may be indirect connection between the building structural steel work and water pipes and the transformer neutral earthing . It does not indicate a compliant Neutral - Earth connection. Only verification by visual checking can confirm that.

Electrically it operates as a TT earthing system.

An electrical installation must be safe from electrical risk as far as practicable.

Edited March 28, 2012 by electau

[electau]

Never presume that an electrical installation in Thailand is TN-C-S (MEN) always visually verify the type of earthing before carrying out any electrical alterations, additions or repairs.

Most existing electrical installations (in Thailand) do not earth the neutral or have a complant earthing system.

Edited March 28, 2012 by electau

[electau]

Yup ^^^, 100% agreement there DH

TN-C-S with MEN (Multiple Earthed Neutral) and a local ground stake is supposed to be the standard for new installations in Thailand, unfortunately many 'electricians' still don't wire homes with 3-pin outlets, and a lot of older properties are still TT.

i can never say too often, 'install an RCD', for the price it's cheap insurance against getting in the news for the wrong reasons.

If you use a TT system you must use an RCD to protect the circuit from earth faults. The earth impedance is too high to trip a MCB. But it will trip an RCD.

If you use TN-C-S system an MCB must operate on a earth fault ( zero ohms) in less than 0.4secs. the fault path in back to the transformer neutral via the neutral-earth bond. The main earth and electrode carry negligible fault current and this current may be disregarded. In the event of a broken neutral the main earth will hold the touch voltage down to less than 50VAC.

　

[sparebox2]

I have to replace the capacitor of my air-con unit. Out of curiosity I test the brown and blue wire going into my air-con. Blue wire light up my current detector while brown did not.

I though it was the other way round? I don't think the electrican that wire my air-con knew the difference.

[wpcoe]

Questions from an obviously uneducated novice about RCDs:

Are they installed in individual circuits or individual outlets or can they be installed at the main circuit board (whatever the PC name is for "fuse box" is today) to protect the entire house? Reading on Wiki, I see that GCFI is a form of RCD, but I've only seen GCFI applied to individual outlets: you press a little red button to check if it's working on the outlet, implying that it only protects things plugged into that single outlet.

[BB1950]

Questions from an obviously uneducated novice about RCDs:

Are they installed in individual circuits or individual outlets or can they be installed at the main circuit board (whatever the PC name is for "fuse box" is today) to protect the entire house? Reading on Wiki, I see that GCFI is a form of RCD, but I've only seen GCFI applied to individual outlets: you press a little red button to check if it's working on the outlet, implying that it only protects things plugged into that single outlet.

There are two different kinds for home use, electrical outlets and circuit breakers. A GCFI circuit breaker also has a little red button to test if it's working properly.

[dhrobertson]

These devices go by various names such as RCDs, RCBOs, ELCBs, GCFIs. In Thailand, ELCB is the term most used. These all work on the same principle. They monitor the current in the phase wire and the neutral wire which should be approximately the same. If they're not, it could be because some current is leaking away, possibly through you!

In Thailand they are required on all water heaters and to protect equipment in wet areas. IEC 60364 (and therefore BS7671, AS/NZS 3000, FN1, DIN etc etc) also require these to protect all socket outlets and circuits supplying equipment in rooms containing a bath or shower.

They come in various trip ratings: 10mA, 30mA, 100mA, 300mA, 500mA. As it takes 50mA to kill you, 30mA is the maximum rating to protect against fatal shock.

You can install a single unit to protect an entire residence or you can protect individual circuits. The former is cheaper, but you lose all power if it trips. The latter invoves exchanging standard miniature circuit breakers in your fuse box (load panel or consumer unit) with units which combine residual current detection with over current detection. This solution is more expensive but gives much better control.

One good solution is to fit a main RCD with a trip rating of, say, 300mA and also protect key individual circuits with RCBOs/ELCBs rated at 30mA. This will protect against poor grounding, will avoid nuisance tripping but will provide adequate protection where it is required.

They all have test buttons by the way! Push to test every 3 months.

[wpcoe]

It makes sense that you might not want the electricity for the whole house to be shut down, although hopefully it's an uncommon occurrence so not TOO much of a nuisance? If I understand this correctly there are RCDs small enough to fit into my current circuit breaker box to replace the individual circuit breakers. If I take a photo of my circuit breaker box and make note of the individual ratings of each breaker and show it to the folks at Home Pro, will they know (and have) what I want? No way will I try to install them myself, but I'd feel better buying in advance, and if necessary getting reconfirmation here on the forum, and then hire an electrician to swap out the circuit breakers for RCDs.

Here's a photo of the circuit breaker box at my current home (a rented townhouse):

Nice and tidy, I must say! Is there any rhyme or reason for the yellow, black and red wires coming out of the bottom of each breaker?

If I've understood past pictures and discussions, that bar at top center is for ground/earth wires, no? The four smaller white wires toward the center are not connected to the circuit breakers but head immediately out of the box, and I think are attached to:

- two bathroom water heaters,

- the outdoors water pump, and

- 3-prong outlet where the washing machine is plugged in.

I only have one water heater now, and it has a an earth wire connection in it. The wires dangling from the wall in the other bathroom includes a third, small white-sheathed wire which I assume is earth. The outdoor water pump and the washing machine outlet have a small white-sheathed wire running adjacent to the main 2-wire power wire.

My computer is currently attached to a power strip that has a three-prong plug, but since all the outlets are two-prong, I use a three-to-two adapter:

Would it be okay to run a ground wire from the tab on that adapter to the ground bar in my circuit breaker box? They are not too distant from each other. Ideally, I'd like to make that outlet a true earthed three-prong outlet, but in the interim would it be okay to run a wire by myself?

What are the first three wires attached to that bar? The first two are black-sheathed multi-stranded copper wires, and the third is a white-sheathed multi-stranded copper wire. My guess is that the big white-sheathed one leads to an earth rod someplace? But, what are the first two black-sheathed wires?

Thanks for your patience in helping me learn!

Edited March 29, 2012 by wpcoe

[dhrobertson]

It makes sense that you might not want the electricity for the whole house to be shut down, although hopefully it's an uncommon occurrence so not TOO much of a nuisance? If I understand this correctly there are RCDs small enough to fit into my current circuit breaker box to replace the individual circuit breakers. If I take a photo of my circuit breaker box and make note of the individual ratings of each breaker and show it to the folks at Home Pro, will they know (and have) what I want? No way will I try to install them myself, but I'd feel better buying in advance, and if necessary getting reconfirmation here on the forum, and then hire an electrician to swap out the circuit breakers for RCDs.

Here's a photo of the circuit breaker box at my current home (a rented townhouse):

Nice and tidy, I must say! Is there any rhyme or reason for the yellow, black and red wires coming out of the bottom of each breaker?

If I've understood past pictures and discussions, that bar at top center is for ground/earth wires, no? The four smaller white wires toward the center are not connected to the circuit breakers but head immediately out of the box, and I think are attached to:

- two bathroom water heaters,

- the outdoors water pump, and

- 3-prong outlet where the washing machine is plugged in.

I only have one water heater now, and it has a an earth wire connection in it. The wires dangling from the wall in the other bathroom includes a third, small white-sheathed wire which I assume is earth. The outdoor water pump and the washing machine outlet have a small white-sheathed wire running adjacent to the main 2-wire power wire.

My computer is currently attached to a power strip that has a three-prong plug, but since all the outlets are two-prong, I use a three-to-two adapter:

Would it be okay to run a ground wire from the tab on that adapter to the ground bar in my circuit breaker box? They are not too distant from each other. Ideally, I'd like to make that outlet a true earthed three-prong outlet, but in the interim would it be okay to run a wire by myself?

What are the first three wires attached to that bar? The first two are black-sheathed multi-stranded copper wires, and the third is a white-sheathed multi-stranded copper wire. My guess is that the big white-sheathed one leads to an earth rod someplace? But, what are the first two black-sheathed wires?

Thanks for your patience in helping me learn!

Just got in. Do Nothing until I reply in full!

[Crossy]

WP, you seem to have a standard Thai wired CU with the incoming neutral passing via the ground bar (so it's MEN).

I don't see a lead to a ground stake, so please verify you have one.

No reason whatever that you should not connect your 2-3 pin adaptor to your ground bar (the one at the top of the CU).

This thread will get more hits in DIY now the Tech forum have had their fun Moving it there.

[wpcoe]

Crossy, I don't know if there is a ground stake. The rear of my townhouse is (a) difficult to access and ( highly overrun with tall weeds and snakes. In the year I've lived here I've had 6 or 7 (I lost count) tree snakes in my kitchen. I'm not keen on trespassing nor stirring up the snakes, but... The owner did a fairly extensive renovation of the place before I moved in, including the electrical work. Lots of added outlets in the downstairs and, as you can see, the nice circuit breaker box. I tend to think the electrician wouldn't have taken the time to add a wire from the outdoors water pump, showers and kitchen outlet to the ground bar if he didn't actually ground the ground bar. I know it's dangerous to assume, but odds are there is one some place.

I just looked at the expressway of wires leading up out the top of the box, and there is a wide (about 1cm) flat wire leading up through the ceiling, up the upstairs bedroom wall and through the upstairs ceiling into the open roof area (attic) space. I wonder if they earthed it to the metal roof framing? I don't have a ladder tall enough to allow me to squeeze through the access hole in the bathroom ceiling to the attic space.

I found the instruction sheet for the box. I assume L = Live and N = Neutral?:

So, yes, indeed they did route the neutral via the ground bar.

Do you think that the thick (1cm), flat wire I see leading up into the attic could be the thick, multi-stranded white-sheathed wire on the ground bar? If not, what *is* that wire attached to the ground bar?

[Crossy]

That fat wire could indeed be a ground to the roof steelwork, it's actually likely quite a good ground, and you have a MEN connection anyway.

I don't see any RCD protection, do you have a water heater? As a minimum you should replace the MCB feeding it with an RCBO.

[wpcoe]

Crossy, my entire involvement in this thread started with me asking what an RCD was. I appear to not have any RCDs, and I'm still trying to piece together a strategy. I will know in about a month if I'm planning to stay here, or move back to my condo, in which case I have an entirely different electrical mess to deal with. But, slowly I'm learning, thanks to you folks here.

FYI, there is only a water heater installed in the upstairs bathroom now. Based of the fear of all-that-is-holy that you all placed in me several months ago when I was asking about water heaters, I've been showering in the downstairs bathroom with no heater. Yeah, it was a bit breathtaking a few days in December, but I survived.

[Pacificperson]

I have to admit to being a bit confused. I thought that for using a concrete building as a ground, the grounding wire had to be bound to the rebar in the concrete and not just to the concrete itself.

[Crossy]

I have to admit to being a bit confused. I thought that for using a concrete building as a ground, the grounding wire had to be bound to the rebar in the concrete and not just to the concrete itself.

It does indeed. But concrete is not a perfect insulator, and when it's damp it's a pretty good conductor which is why using the steel works at all, the rebar itself is never in contact with the ground, Google Ufer ground.

All this messing around with plant pots etc is just a (poor) way of making the connection to the building steel.

[dhrobertson]

With a TN-C-S ground (ground and neutral bus bars linked, aka MEN ) you are essentially using the main neutral feeder as ground. The local connection to ground rods (and/or structural steel) is an additional safety measure in case the main neutral is lost.

Relying on a ground connection through concrete is better than nothing (just) but will not give adequate ground performance. We need to ensure that sufficient current flow to ground (or ground via neutral) in the case of a ground fault that the associated circuit breaker trips quickly (200A in the case of 20A C type breaker).

As Crossy says, you must (in Thailand) have an RCD (RCBO, ELCB) on circuits supplying a water heater.

[electau]

The result one must obtain to to have an electrical installation free as far as practical from electrical risk. the hazards are, electric shock and fire.

To enable this the protective devices ie MCBs and RCDs must operate in less than 0.4secs in the event of an earth fault.

RCDs obtain this result as they operate at less than 30mA and in practice around 0.02 secs.

They also do not require an earth conductor/ connection to operate unlike an MCB.

Edited April 2, 2012 by electau

[Crossy]

The result one must obtain to to have an electrical installation free as far as practical from electrical risk. the hazards are, electric shock and fire.

A wise mantra.

Slavishly quoting regulations from other regions where conditions are often very different, and, possibly worse, combining regs from different regions is unwise and counter-productive.

Pragmatism and practicality are the name of the game here, do the best you can with the resources available.

[electau]

That statement is a legal requirement.

AS/NZ3000 has for a minimum 13mm copper clad electrode 1.2/1.8 metres in the ground , minimum main earth conductor size 4 sqmm in practice this is is usually now 6sqmm, soil resistance tests are not required to be carried out, the minimum resistance of a main earthing conductor must not exceed 0.5 ohms, and fault clearance times on an earth fault must be less than 0.4secs for an MCB and 0.2secs for an RCD device.Where the touch voltage exceeds 50VAC automatic disconnection must occur.

The MEN system is mandatory under AS3000. Other systems are permitted in certain circumstances. AS3003, AS3007 TN, TT and IT. All electrical installations must comply with the minimum requirements of AS3000 in the first instance.

　

Soil resistance is uncontrolled. The contact area of the surface of the electrode to the soil meets a minimum value in sqmm.

Other standards have different values and requirements. Eg the National Electrical Code is one of them and here it is impossible to harmonise this standard with IEC, and must be regarded as a standard completely different to the IEC and treated on its own merits.

In Thailand there has to be a certain amount of compromise to get the intended result.

[tim73]

Well, actually there is a twist to this story. How they do grounding inside the International Space Station or similar space vehicles? They do it by having that earth wire connected to same point or point connecting to same area of outer surface with near zero resistance pathway.

The "earth" itself up there could be anything from zero to millions of volts, compared to some other point in the atmosphere. So by that flower pot I suggested, the point of earth of that flower pot is basically making is the same thing as in a space ship. High in the condo you are basically a "spaceship". You are in a isolated environment. As long as the ground is less resistant than yourself or any other path to yourself, you are safe.

[TimeMachine]

Hammer a 50 metre length copper rod into the earth that leads up the wall to your condo. Earth sorted.

 

Otherwise Hunt down where metal to earth exists and tie into it. 

 

Otherwise just do RCBO and forget earth.

[Crossy]

People. This thread dates from 2012, much has happened since then.

 

To avoid confusion, I'm going to lock this, there's another grounding thread running.