Earth Cable/Grounding

[UWEB]

Will built a Terrace on my 3 meter high pool house, it will become a 2.5 meter high metal Frame with Handrail and Sun Shade. Do I have to run an earth Cable for grounding of the Frame?

[carlyai]

I think a picture would help visualize the setup.

I don't think you would normally tie a metal pool fence to the mains earth.

If the metal hand rail goes into the pool that could be different, and how close power outlets are to the pool.

 

[sometimewoodworker]

It is quite likely that the metal frame will be tied into the foundations rebar, if so then it’s probable that they are already grounded. However the only way to know for sure is to get them tested and you have little chance of finding someone with the test equipment.

[bluejets]

Pool fencing or any metalic structure within the "pool zone" (including the reo) should have a 6 sq mm bonding earth run back to the main switchboard and connected to the main earth at that point.

"pool zone" is normally considered as being within 1.5m horizontally from the edge of the water in the pool.

 

Whether or not the rest of the installation meets the requirements would be questionable in Thailand.

 

As for "touching the ground already" , whether or not the reo or anything else for that matter actually touches ground is completely irrelevant as the requirement here is for "equipotential bonding".

[carlyai]

Please correct me if I'm wrong, but the thing I see against bonding the pool to the main earth is that if you get an open circuit supply neutral (which we have had, created by PEA), current returning to the PEA transformer is via earth returns which could make the pool live. 

[bluejets]

22 hours ago, carlyai said:

but the thing I see against bonding the pool to the main earth

Not a reason NOT to bond, more an excuse.

The occurance of open circuit neutral in an MEN system will cause any fault current to flow in the earthing system back to the transformer but the occurance of such is rather rare to say the least.

Many domestic installations in Thailand are not up to any standard to begin with so perhaps the least of your worries.

One would normally tend to notice the installation failing miserably due to low voltage and perhaps for most, the next thought would not be, oh <deleted> it, lets go for a swim.

Open circuit neutral occurance pretty much the same ratio of an overhead aerial line breaking and dropping into your pool or an aircraft loosing and engine and hitting your lounge room while watching tv.

Nothing is 100% guarantee, just manage to reduce the risks seems to work for most.

Any of the above not covered under dilutie attack or twist and tape application. ????

[carlyai]

56 minutes ago, bluejets said:

Not a reason NOT to bond, more an excuse.

The occurance of open circuit neutral in an MEN system will cause any fault current to flow in the earthing system back to the transformer but the occurance of such is rather rare to say the least.

Many domestic installations in Thailand are not up to any standard to begin with so perhaps the least of your worries.

One would normally tend to notice the installation failing miserably due to low voltage and perhaps for most, the next thought would not be, oh <deleted> it, lets go for a swim.

Open circuit neutral occurance pretty much the same ratio of an overhead aerial line breaking and dropping into your pool or an aircraft loosing and engine and hitting your lounge room while watching tv.

Nothing is 100% guarantee, just manage to reduce the risks seems to work for most.

Any of the above not covered under dilutie attack or twist and tape application. ????

Thank you.

As I have said, it did happen here.

Why not just isolate the pool from active, neutral and earth?

So 12 v pool lights are supplied from a double insulated fused robus pool transformer and RCBO connected pool pump and chlorinator are more than 2 meters from PVC pipe water inlets.

The concrete and dual rebar pool shell is completely interlocked and acts as a Faraday's Cage.

How is that ever going to become live?

If I introduce an earth tied to the mains earth then it could become live.

Anyway I am not an electrician but these are just my ignorant thoughts. ????

[sometimewoodworker]

1 hour ago, bluejets said:

The occurance of open circuit neutral in an MEN system will cause any fault current to flow in the earthing system back to the transformer but the occurance of such is rather rare to say the least.

While it is a rather less than usual fault and in countries with a better maintained system it maybe very rare, it is hardly unknown. The problem is that it can & does happen with zero warning to you as it is usually out of your sight, and if it happens and you have the luck to be the household that has someone who becomes however briefly part of the wiring the result can be fatal. That is why you reduce the possibility of the fault causing injury.

 

In Thailand with the conditions that prevail the chances are orders of magnitude greater, consequently it is more important to reduce the risk. So your suggestion is cavalier to say the least. 
 

The suggestion that you will notice because the voltage drops is suspect for various reasons, a couple being that in the daytime you may well not be using much that you immediately notice, another is that voltage drops of anything from 10v to 60v are not in the slightest rare in Thailand.

 

So from a professional that kind of justification is terrible.

[sometimewoodworker]

21 minutes ago, carlyai said:

Anyway I am not an electrician but these are just my ignorant thoughts.

Neither am I but you seem to be more knowledgeable than the supposed professional 

[carlyai]

To the OP, I am sorry I hijacked your thread and my New Year's Resolution is to change my ways. ????

[bluejets]

On 12/24/2022 at 9:59 AM, carlyai said:

How is that ever going to become live?

It can become live from a fault in the pumping/filtration system, or from a breakdown/misuse of non-isolated low voltage components in LV lighting.

 

The latter are everwhere in Thailand.

 

And, yes, I am a qualified electrical contractor, have been for 50 years.

 

[SomchaiDIY]

On 12/23/2022 at 7:14 AM, carlyai said:

Please correct me if I'm wrong, but the thing I see against bonding the pool to the main earth is that if you get an open circuit supply neutral (which we have had, created by PEA), current returning to the PEA transformer is via earth returns which could make the pool live. 

loss of line neutral is very common happening around thailand

wind and tree branch are the big problem for line break in thailand

 

 

many paper available about subject for pool safety in TN-C-S power system

i give sample here from europe please read pages for multiple protection earth

 

swimming-pools-bonding.pdf

 

 

 

thailand problem with tree and power pole breaking of power line

 

sample photo from internet

 

 

 

 

[sometimewoodworker]

5 hours ago, SomchaiDIY said:

loss of line neutral is very common happening around thailand

wind and tree branch are the big problem for line break in thailand

 

 

many paper available about subject for pool safety in TN-C-S power system

i give sample here from europe please read pages for multiple protection earth

 

swimming-pools-bonding.pdf 690.76 kB · 2 downloads

 

 

 

thailand problem with tree and power pole breaking of power line

 

sample photo from internet

 

 

 

 

So it seems from my reading of the paper that in general swimming pools SHOULD NOT be linked to the house earth and should be treated as a TT system. Do please clarify if I have misinterpreted the information. 

[SomchaiDIY]

4 hours ago, sometimewoodworker said:

So it seems from my reading of the paper that in general swimming pools SHOULD NOT be linked to the house earth and should be treated as a TT system. Do please clarify if I have misinterpreted the information. 

i read the paper this way also but translation not so perfect

[Crossy]

9 hours ago, SomchaiDIY said:

i read the paper this way also but translation not so perfect

 

Yes, this is exactly what I would do too. It's also how the UK regs treat pools, hot tubs and EV charge points.

 

The risk involved with bonding exposed metalwork to the main earth in a Thai TNC-S system is just too great.

 

It's not just open neutrals, we had a poster a little while back who was complaining his kitchen floor was getting hot, coincidentally just where his ground rod was buried! Turned out that the PEA had managed to swap L&N at the meter so his rod was actually connected to the hot side of the supply (we never did find out how much his power bill decreased by when it was fixed). Of course, turning off the main switch doesn't break that connection so if you happen to be holding on to that fence you still die!

 

As has been noted, electrical regulations vary around the world, some are highly prescriptive "do it like this and it is to code" (the US NEC is like this), others are more proscriptive "this is what you have to achieve, it's up to the designer how they achieve it" (the UK BS7671 IEE Regs follows this route), and many are somewhere in between.

 

There is a real risk in cherry-picking regs from one country and applying them randomly to another. One could actually introduce a hazard where there wasn't one before.

 

For example, a country may have very strict requirements for pool construction meaning that all the re-bar is interconnected, there are ground mats under the pool perimeter and any metallic fencing is also bonded to this, making an equipotential zone where there is no risk of getting between two "grounded" items that are actually at different potentials. There is no issue at all in connecting this zone to the main TNC-S earth.

 

Do the same here where your fence may not be bonded to the re-bar and the re-bar may not be solidly interconnected and a world of hurt can open up ????  

 

Generally, don't earth it just because it's metal. A stainless-steel sink in a granite worktop with plastic plumbing is probably not earthed at all, touch it and your faulty electric kettle and you probably won't die. If that sink was solidly bonded to deck ... let's hope your RCBO is up to scratch!

 

EDIT The "hot rod" thread https://aseannow.com/topic/1250930-earth-rod-is-hot/

 

 

[bluejets]

Please yourselves.

I quoted Aus electrical standards which are recognised as being one of the highest standards worldwide.

If you choose some "personal preference" over proven engineering design, so be it.

Thailand is full of dodgy electrical so adding one more will make no difference.

 

Although, with the number of those who have been electrocuted in Thailand pools, it should certainly raise a question or two.

Just guessing mind you, that none would have been related to the fitting of equipotential bonding whereas all relate to non-existent.

 

Perhaps a list of countries which recommend NOT to equipotential bond , and the reasons , should be forthcoming.

Certainly plenty for the compulsory installation of.

[Crossy]

Well, the UK is one.

 

The UK regs don't say "do not bond", they allow the designer to do a risk assessment and determine just how to address the issue.

 

The major point is whether you connect your equipotential zone to the TNC-S earth or have it with a local TT ground (and appropriate earth leakage protection of course).

 

IF you build your pool and surroundings to Aussie standards then bonding back to the MET is absolutely fine. As I said, you shouldn't cherry-pick requirements, do everything to your chosen standard.

 

Ideally, avoid having any mains powered equipment in the pool zone anyway. No amount of bonding will protect you from getting hold of a live wire or faulty electric barbie (hopefully the RCBO will).

 

[sometimewoodworker]

12 hours ago, bluejets said:

 

I quoted Aus electrical standards which are recognised as being one of the highest standards worldwide.

They are certainly recognised by you as such many others will have a different opinion.

 

You must support them to bolster the fact that with Ranking of the countries with the highest quality of electricity supply in 2019 Australia isn’t even in the top 20, even being beaten out by Kazakhsian

 

To give good advice you have to be careful of the fact that cherry picking certain sections is actually going to make things more dangerous not less so thus while your statements are true in Australia they can be deadly in Thailand where Australian building regulations aren’t in effect and the audience you are speaking to may think that because you have been an electrical contractor for years you actually know what you are talking about and your advice should be followed when that’s only true for colonial cousins in Australia or for a building built to strict Australian building regs.

[sometimewoodworker]

1 hour ago, sometimewoodworker said:

the audience you are speaking to may think that because you have been an electrical contractor for years you actually know what you are talking about

That was rather less qualified than it should have been. I don’t actually have any idea of your actual knowledge and should not have impugned it in that way. I should have said that you do not convey the knowledge you have in a safe way and seem to assume far more background knowledge in the audience than exists. So as an electrical contractor you may well have been superb but as a communicator that knowledge certainly doesn’t come across