Can The Metal Conduit In The Walls Carry The Ground?

[Valjean]

I’m having my electrical upgraded in my home in Bangkok. The existing power that runs to the outlets goes through metal conduit within the walls. About 20%-30% of the outlets have grounds; the rest don’t. I am trying to minimize the amount of wires or conduit running over the surface of the interior or exterior walls.

I was wondering if it’s possible to use the conduit as a ground connection. If in all the outlets with ground I had a clamped connection from the green ground to the conduit and do the same with the non-grounded outlets would this work? I’d of course want to test each outlet to ensure that the conduit was in fact continuous but is this an acceptable way to get a ground to an outlet without running a new ground wire to it?

[david96]

I’m having my electrical upgraded in my home in Bangkok. The existing power that runs to the outlets goes through metal conduit within the walls. About 20%-30% of the outlets have grounds; the rest don’t. I am trying to minimize the amount of wires or conduit running over the surface of the interior or exterior walls.

I was wondering if it’s possible to use the conduit as a ground connection. If in all the outlets with ground I had a clamped connection from the green ground to the conduit and do the same with the non-grounded outlets would this work? I’d of course want to test each outlet to ensure that the conduit was in fact continuous but is this an acceptable way to get a ground to an outlet without running a new ground wire to it?

There is no reason why you cannot install PE earthing in this way, bond the conduits to the earth bar.It was pemitted up to the 1960s under the old NZ wiring rules. Now not permitted since 1970s. Instal RCDs on all socket outlets. Min earth size 2.5sq mm G/Y colour.

Certainly better than no earthing or earth bonding.

[lopburi3]

This also was used in the US in the 50's but the bonding required tight fit to metal outlet box and from outlet to box and these were subject to corrosion (steel) and not reliable so direct wire grounds were introduced. Agree much better than nothing and expect conduit used here is probably aluminum if metal (I have only seen plastic used myself).

[Crossy]

Measure the resistance between your outlet ground and the ground bar in the distribution box, if it's less than an ohm or so then OK.

I'd really like to see a proper ground wire but in an emergency using the conduit is far, far better than nothing. It is most definately now not to code in any western country.

You must use an RCD/ELCB etc if you use this grounding method.

[longball53098]

I have not seen the US NEC and the changes in the last several years but it was perfectly acceptable to use conduit as the grounding conductor. For many years. If this is changed please inform me.

As another poster said it must conform to the standards written in the code book. Requires strict adhearance to connections and tightness of all connections and fitting of the conduit. One loose connection or lock nut and you have issues. Also when the socket is fitted into the box if all is not metal and designed to be earthed than a wire would need to be fitted from the earth terminal of the socket to the box. In thailand can you find the proper sockets? The ones in the US were made to ground to the metal boxes.

Agree that a wire is much more positive

[Valjean]

Thanks everyone. It's good to know we should do the extra effort to run the wires where ever possible but also good if there are a few places where it's less practical this is a better than nothing alternative. Of course it needs to be tested but that's my other thread today.

Thanks again

[Cuban]

I use a pen, pencil or from time to time the arm of my glasses to stir a cup of coffee - neither impliment is designed for the task but it works. The metal conduit will might function as an electrical connection from point to point within your house; however you need to remember that it was not designed for that purpose. When the conduit was installed was every junction made with the intention that the joint itself would be suitable for passing an electrical current? I doubt it. I would suggest that simple corrosion will impact the resistance of each conduit joint and that would worry me if I was reliant on a system not designed for such an important fucntion. The strength of any system is dependant on it's weakest link, if the length of conduit that runs the final link to your real earth point has a bad electrical connection junction the whole system downstream of that point would fail.

There would be some path to earth via the structure of the building in contact with the conduit - but unless you have some serious damp problems I would expect this to be too high resistance to be of any practical use.

From what I understand of your situation what you propose is better than nothing, but I offer this thought. I was once helping a friend install an alarm system in his old large house, we did not want to drill through walls to wire each remote room to the central panel, but luckly found disused water pipes that although not direct ran through the different rooms we needed to connect. With the aid of a vaccum cleaner and a tuft of cotton wool we managed to suck a thread through the pipes, the thread pulled through a length of string and the string was strong enough to pull through the alarm cables. A very neat soluton.

With conduits that already have electrical wires running through them such a technique might not be practical, but worth a go for some sockets with shorter runs perhaps?

HTH.

Edited June 12, 2008 by Cuban

[PhilHarries]

I was wondering if it’s possible to use the conduit as a ground connection. If in all the outlets with ground I had a clamped connection from the green ground to the conduit and do the same with the non-grounded outlets would this work? I’d of course want to test each outlet to ensure that the conduit was in fact continuous but is this an acceptable way to get a ground to an outlet without running a new ground wire to it?

Not being an electrical engineer, a fact well proven in another thread , I'll ask a cautious question.

If the earthing is done as highlighted above it may introduce a long and torturous earth path for some, if not all, the current non-earthed connections. Obviously, as stated, this is better than no earth but is there any danger from the longer earth path and the inherent large number of joints?

[Crossy]

Any joint is a potential failure point. Using the conduit would be illegal in most modern countries.

If you cannot run a new cable (and to be honest, if there's conduit, there is the possibility of getting a real ground wire in) then measure the resistance between each ground pin and the ground bar in the distribution board. Use your multimeter with a long extension, (remember to zero the meter or subtract the resistance of the long lead), if the resistance is more than one ohm then you have a poor ground with its associated dangers (put 2 pin outlets back in).

Edited June 12, 2008 by Crossy

[Valjean]

One more question.

I'm back to running ground wires to most outlets based on this advice. In some cases the ground wire will be outside the house and we'll drill a hole from the outlet box to the outside. Outside the house does the ground wire need to be in conduit? If yes can it be in the flat style that affix to the wall? If I want to cut some channels in the exterior wall for the wire should that be in conduit within the wall? I was thinking of just a thin cut maybe 1-2 cm deep and just lay the wire in there to make it a little less unsightly.

[Crossy]

If I want to cut some channels in the exterior wall for the wire should that be in conduit within the wall? I was thinking of just a thin cut maybe 1-2 cm deep and just lay the wire in there to make it a little less unsightly.

The ground is not a current carrying conductor (except when there's a fault), nobody will get a shock if they bang a nail through it so don't worry about protecting it in conduit. I reckon the option of a narrow slot with the wire buried an inch or so down would be a neat solution, you may be able to cut the slot with a tungsten-carbide tipped blade in a regular circular saw (don't use a solid carbide blade, they tend to shatter with nasty consequences)

It's worth considering just which outlets actually NEED grounding. It would be a waste of effort to ground any outlet which only ever gets two pin double-insulated appliances plugged in, grounding these will not make anything any safer (obviously leave two pin sockets installed here).

Looking around my place I see that, apart from my AV and computer equipment, 99% of ground-needing appliances are in the kitchen. Just a thought

Edited June 13, 2008 by Crossy

[lopburi3]

Rodents do chew on wire and I have had them chew through double 2.5mm power wire (but perhaps the heat attracted them?). But I suspect the chance of rat failure is really slight. But overall it might look better to use something. If you use the flat stick-on type be sure to attach with some screws as the tape will not hold up.

[elkangorito]

If I want to cut some channels in the exterior wall for the wire should that be in conduit within the wall? I was thinking of just a thin cut maybe 1-2 cm deep and just lay the wire in there to make it a little less unsightly.

The ground is not a current carrying conductor (except when there's a fault), nobody will get a shock if they bang a nail through it so don't worry about protecting it in conduit. I reckon the option of a narrow slot with the wire buried an inch or so down would be a neat solution, you may be able to cut the slot with a tungsten-carbide tipped blade in a regular circular saw (don't use a solid carbide blade, they tend to shatter with nasty consequences)

It's worth considering just which outlets actually NEED grounding. It would be a waste of effort to ground any outlet which only ever gets two pin double-insulated appliances plugged in, grounding these will not make anything any safer (obviously leave two pin sockets installed here).

Looking around my place I see that, apart from my AV and computer equipment, 99% of ground-needing appliances are in the kitchen. Just a thought

Crossy, are you kidding!!!!!! Were you drunk when you posted this nonsense?

"Nobody will get a shock if they bang a nail through it so don't worry about protecting it in conduit."

Famous last words. What about the integrity of the earthing conductor?

Australian Standards basically say that insulated, unsheathed cables shall be enclosed in a wiring enclosure

throughout their entire length. The earth conductor is the most important conductor of all. The exceptions to this rule do not apply in this post.

...or is this now "two or more flashes & you might be ash"? What happened to "one flash & you are ash"?

"It's worth considering just which outlets actually NEED grounding. It would be a waste of effort to ground any outlet which only ever gets two pin double-insulated appliances plugged in, grounding these will not make anything any safer (obviously leave two pin sockets installed here)."

Let's just hope the installer of this faulty electrical system does not sell the house to some unsuspecting buyer. And what about visitors? Must one post a guard on these outlets to ensure that nobody uses them incorrectly according to the lack of earthing?

Is this not why electrical rules were created?

[david96]

Under AS3000 all cables have to be protected against mechanical damage where required. Earthing conductors can be run adjacent to the cables they protect without enclosure, eg cable tray, or on a wall providing they are not subject to mechanical damage.

[Crossy]

Crossy, are you kidding!!!!!! Were you drunk when you posted this nonsense?

"Nobody will get a shock if they bang a nail through it so don't worry about protecting it in conduit."

Famous last words. What about the integrity of the earthing conductor?

Australian Standards basically say that insulated, unsheathed cables shall be enclosed in a wiring enclosure

throughout their entire length. The earth conductor is the most important conductor of all. The exceptions to this rule do not apply in this post.

...or is this now "two or more flashes & you might be ash"? What happened to "one flash & you are ash"?

"It's worth considering just which outlets actually NEED grounding. It would be a waste of effort to ground any outlet which only ever gets two pin double-insulated appliances plugged in, grounding these will not make anything any safer (obviously leave two pin sockets installed here)."

Let's just hope the installer of this faulty electrical system does not sell the house to some unsuspecting buyer. And what about visitors? Must one post a guard on these outlets to ensure that nobody uses them incorrectly according to the lack of earthing?

Is this not why electrical rules were created?

Nope not drunk, just having a practical view.

With all due respect we are not in Australia (or the UK) so a pragmatic view of implementing the spirit of our regulations rather than blindly following them is an option open to us. This is an upgrade to an existing system, the problem of adding a ground would not occur back home as we don't have 2 pin outlets at all, for NEW installations there is no argument that we should follow the Oz/UK regs as closely as practical.

The OP was originally proposing a highly dubious grounding technique which he has now decided against. It is impractical to run the ground wire in the existing conduit so running it along the outside is a reasonable alternative, OK yes it should be protected and a surface run must be in a conduit of some sort, but being buried in the outside rendering is pretty good protection. Obviously this route should be avoided if at all possible and would be a total non-starter for current carrying conductors. Buried, unprotected, cables are still permitted in the UK although there are 'designated areas' where these may run (in the outside render is NOT one of them).

As the 'leave some outlets ungrounded', why not? Assuming that 2 pin outlets are installed where is the hazard? The vast majority of small appliances these days have two pin plugs and are should be double insulated (and if they're not a grounded outlet won't help if there is only a 2 pin plug fitted). We have a total of six appliances that are plugged in using grounded plugs (OK I've counted 4 PC's off one outlet and UPS as one appliance), apart from the sandwich grill and kettle none of these would be counted as 'portable'.

As noted previously, installation of an ELCB is non negotialble

Edited June 14, 2008 by Crossy

[elkangorito]

Under AS3000 all cables have to be protected against mechanical damage where required. Earthing conductors can be run adjacent to the cables they protect without enclosure, eg cable tray, or on a wall providing they are not subject to mechanical damage.

David, I strongly urge you to look at AS3000:2007;

1.5.14,

3.10.1.1,

3.10.2,

5.5.5.2.

Crossy, are you kidding!!!!!! Were you drunk when you posted this nonsense?

"Nobody will get a shock if they bang a nail through it so don't worry about protecting it in conduit."

Famous last words. What about the integrity of the earthing conductor?

Australian Standards basically say that insulated, unsheathed cables shall be enclosed in a wiring enclosure

throughout their entire length. The earth conductor is the most important conductor of all. The exceptions to this rule do not apply in this post.

...or is this now "two or more flashes & you might be ash"? What happened to "one flash & you are ash"?

"It's worth considering just which outlets actually NEED grounding. It would be a waste of effort to ground any outlet which only ever gets two pin double-insulated appliances plugged in, grounding these will not make anything any safer (obviously leave two pin sockets installed here)."

Let's just hope the installer of this faulty electrical system does not sell the house to some unsuspecting buyer. And what about visitors? Must one post a guard on these outlets to ensure that nobody uses them incorrectly according to the lack of earthing?

Is this not why electrical rules were created?

Nope not drunk, just having a practical view.

With all due respect we are not in Australia (or the UK) so a pragmatic view of implementing the spirit of our regulations rather than blindly following them is an option open to us. This is an upgrade to an existing system, the problem of adding a ground would not occur back home as we don't have 2 pin outlets at all, for NEW installations there is no argument that we should follow the Oz/UK regs as closely as practical.

The problem WOULD occur "back home". I think you will find that in "most" situations, the "regulatory authority" will insist that earthing be carried out in the strictest of ways. This not only means following the "rules to the letter" but also following the additional regulatory requirements.

The OP was originally proposing a highly dubious grounding technique which he has now decided against. It is impractical to run the ground wire in the existing conduit so running it along the outside is a reasonable alternative, OK yes it should be protected and a surface run must be in a conduit of some sort, but being buried in the outside rendering is pretty good protection. Obviously this route should be avoided if at all possible and would be a total non-starter for current carrying conductors. Buried, unprotected, cables are still permitted in the UK although there are 'designated areas' where these may run (in the outside render is NOT one of them).

What has not been discussed is the type of cable that could be used for this dubious "additional" earthing. In this case, it MUST be double insulated cable at the very least.

As the 'leave some outlets ungrounded', why not? Assuming that 2 pin outlets are installed where is the hazard? The vast majority of small appliances these days have two pin plugs and are should be double insulated (and if they're not a grounded outlet won't help if there is only a 2 pin plug fitted). We have a total of six appliances that are plugged in using grounded plugs (OK I've counted 4 PC's off one outlet and UPS as one appliance), apart from the sandwich grill and kettle none of these would be counted as 'portable'.

Crossy, you obviously know that you/we are in Thailand. You therefore know that the number of "shocking experiences" here are extraordinary compared to "back home". If a home (in Thailand) is fitted with both 2 & 3 pin power outlets, it is dangerous.

How many times have you & I told people NOT to cut off the earth pin of their appliance? How often have WE advised people about the importance of EARTHING? Have we not advised them to use a 3 pin plug in a 3 pin socket? To suddenly relax on the issue of earthing is asking for trouble.

This is not about any electrical conductor. This is about the most important conductor...the earthing conductor.

I believe that any relaxation about this matter is dangerous...particularly in Thailand where GOOD electricians are almost impossible to find. As far as you, I & some other electrically adept people are concerned, we don't have a problem because we know what is going on. We know what to look for. As for others, they are relying upon the opinions of knowledgable people.

If these knowledgable people begin to "relax" their advice, particularly about earthing, where will things end up? Who will decide the limit of "relaxed"? This is where I suggest the "rules" step in.

Again, "one flash & you're ash".

As noted previously, installation of an ELCB is non negotialble

Fully agreed

[Crossy]

The problem WOULD occur "back home". I think you will find that in "most" situations, the "regulatory authority" will insist that earthing be carried out in the strictest of ways. This not only means following the "rules to the letter" but also following the additional regulatory requirements. Absolutely, I was referring to the fact that an additional earth wire would likely not require installation in the first place as it would already be in place from original implementation.

What has not been discussed is the type of cable that could be used for this dubious "additional" earthing. In this case, it MUST be double insulated cable at the very least. Good point

Crossy, you obviously know that you/we are in Thailand. You therefore know that the number of "shocking experiences" here are extraordinary compared to "back home". If a home (in Thailand) is fitted with both 2 & 3 pin power outlets, it is dangerous. I would use the word 'hazardous' it's not going to kill you unless you do something silly. Of course people tend to do silly things.

How many times have you & I told people NOT to cut off the earth pin of their appliance? How often have WE advised people about the importance of EARTHING? Have we not advised them to use a 3 pin plug in a 3 pin socket? To suddenly relax on the issue of earthing is asking for trouble.

I believe that any relaxation about this matter is dangerous...particularly in Thailand where GOOD electricians are almost impossible to find. As far as you, I & some other electrically adept people are concerned, we don't have a problem because we know what is going on. We know what to look for. As for others, they are relying upon the opinions of knowledgable people.

If these knowledgable people begin to "relax" their advice, particularly about earthing, where will things end up? Who will decide the limit of "relaxed"? This is where I suggest the "rules" step in. This I can't argue with, you cannot totally protect people against their own ignorance/stupidity. Two pin systems are not inherently unsafe, they are made so by unsafe usage.

Ticking off accepted Humble pie purchased

At least our OP is not going to use his conduit as a ground

Edited June 14, 2008 by Crossy

[david96]

Under AS3000 all cables have to be protected against mechanical damage where required. Earthing conductors can be run adjacent to the cables they protect without enclosure, eg cable tray, or on a wall providing they are not subject to mechanical damage.

This post refers to protection in general not enclosure of cables.

In this case it refers to earthing conductors. AS3000/2007. Clause 3.10.1.1(d) and clause 5.5.5.2 protection against mechanical damage.

In this case the installation is in Thailand and a certain amount of compromise is required to obtain an earthing system that is safe and functional and provides protection against fire and shock.

[Valjean]

OK let me see if I have this right - and a few more questions...

Using Conduit as Ground

OK think I understand this and to assume that in a world of lesser evils in the case where I can’t for cosmetic or economic reasons get a ground to an outlet the preference is a 2 pin outlet versus a 3 pin with tested via conduit ground? For instance if I test the outlet to the metal screw to the outlet box it shows a good 240v Live to Ground. I could also test resistance. Not belaboring just want to get the best for the situation. I also assume that all 2 pin plugs come from internal grounded devices and are safe and that the dangerous scenario is adapters that allow a 3 pin plug to use the 2 pin outlet. Is that correct?

Ground Wire Protection

Right now my handyman is digging a trench around the house and putting the ground wire in plastic conduit. Then he’s running the conduit up the exterior of the wall to a hole that goes into the interior outlet – which I don’t like the looks of. If I don’t want the pipes on the exterior I could just have a larger channel cut and put them in the wall. I’ll still unclear from this thread if a small channel with just the wire perhaps 1 inch below the service and covered with cement is acceptable. It’s a considerably smaller channel and would just cut clean with one blade and leave less of a blemish and a lot less work.

One House = One Ground or Grounding Zones?

Do all the grounds in the house need to connect to each other and the power panel? Or could there be a zone where a proper grounding rod was put in the ground, the grounding wire that went to a series of outlets connected to that but that grounding never connected with other parts of the house or panel?

Big thanks as always!

[Pink Mist]

testing 240 volts to earth isn't the way to test, you have to test the impedance of the earth system to all points in the house to the main earth and as Crossy says it must be less than 1 ohm.

I like his idea of 2 pin outlets as most appliances these days are double insulated and have no earth pin, but diversity allways rules and what happens if an appliance that isn't earthed is used at that outlet, then we have a potential problem.

In reality we create the problem by earthing things in the first place

[Crossy]

OK let me see if I have this right - and a few more questions...

Using Conduit as Ground

OK think I understand this and to assume that in a world of lesser evils in the case where I can’t for cosmetic or economic reasons get a ground to an outlet the preference is a 2 pin outlet versus a 3 pin with tested via conduit ground? For instance if I test the outlet to the metal screw to the outlet box it shows a good 240v Live to Ground. I could also test resistance. Not belaboring just want to get the best for the situation. I also assume that all 2 pin plugs come from internal grounded devices and are safe and that the dangerous scenario is adapters that allow a 3 pin plug to use the 2 pin outlet. Is that correct?

IF you decide to use the conduit (definately NOT advisable or to UK or Oz code) you MUST check the resistance to the ground bar, merely checking the voltage will NOT do.

Personally I'd do all I could to get a proper wired ground and if not possible use only 2 pin outlets rather than risk having an iffy ground and thinking you're safe. Mixing 2 and 3 pin outlets is not dangerous per-se, it's only when someone uses an adaptor to put a 3 pin plug into a 2 pin outlet that danger comes into the equation. Obviously this can't happen if you have no 2 pin outlets.

Items with 2 pin plugs should be double-insulated and therefore not require a ground.

Install an ELCB/RCD/Saf-T-Cut if you don't already have one.

Ground Wire Protection

Right now my handyman is digging a trench around the house and putting the ground wire in plastic conduit. Then he’s running the conduit up the exterior of the wall to a hole that goes into the interior outlet – which I don’t like the looks of. If I don’t want the pipes on the exterior I could just have a larger channel cut and put them in the wall. I’ll still unclear from this thread if a small channel with just the wire perhaps 1 inch below the service and covered with cement is acceptable. It’s a considerably smaller channel and would just cut clean with one blade and leave less of a blemish and a lot less work.

In my opinion a narrow channel would be acceptable provided it wasn't in an area where the wire could get mechanically damaged, however to be strictly to Oz and UK code the conduit must extend up to the hole in the wall (deeper channel).

One House = One Ground or Grounding Zones?

Do all the grounds in the house need to connect to each other and the power panel? Or could there be a zone where a proper grounding rod was put in the ground, the grounding wire that went to a series of outlets connected to that but that grounding never connected with other parts of the house or panel?

ALL grounds MUST go to the ground bar in the distribution board and then to one or more ground spikes, it is vital to avoid having several grounds that are not connected to one another (Google "equipotential bonding"), ground potential is not a constant. There are documented examples of animals being killed by having different potentials between front and back legs.

Edited June 15, 2008 by Crossy

[Pink Mist]

earthing is a potentially bonding conversation

[Valjean]

Thanks all...

Off to Home Pro to get some 2 prong outlets. It's not so hard to get all the outlets on exterior walls to have a ground, it's some of the ones on interior walls that are problematice. Every room will end up with one or more grounded outlets so that should do the trick for now. Along with tossing all adapters out the door. As I remodel here and there I can always be on the lookout for opportunties to upgrade.

Thanks for the other info as well. One thing that is very clear to me is that my handyman friend of the family knows just enough to be dangerous. But that's why I've promoted myself from DYI to Stupidvisor to oversee the project.

Thanks!

[Pink Mist]

the trouble is dangerous does have dire consequenses with electricity unfortunately

[Valjean]

Just for a little shocking humor here's the set up in one bathroom. I figured having an ungrounded outlet between the faucet and soap dish was was good a place as any to put it

[Crossy]

Just for a little shocking humor here's the set up in one bathroom. I figured having an ungrounded outlet between the faucet and soap dish was was good a place as any to put it

I wonder sometimes what people are thinking when they install this sort of thing, at least it has a cover

Remove it and install a blanking plate, if practical isolate the feed at the other end.

Edited June 15, 2008 by Crossy