Pool water stings open skin

[Costas > DownUnder]

And is bonding water a non-issue for concrete pools? Does bonding the rebar cover that?

Yes...!

With gunite/concrete the material itself is conductive especially if wet/damp - so the water is inherently making contact with the concrete whereas in a fibreglass pool the fibreglass is a very good insulator so the water is electrically insulated from everything.

This is why a gunite/concrete pool has a higher risk of electrocution if the external bonding is not present and an electrical fault exists outside the pool.

Does everybody with an SWG have this potential problem?

Not necessarily - It will depend on how the power supply circuitry is designed within the SWCG.




I did some further testing with the Astralpool chlorinator and while the plates are submerged in water, it produces (approx.) 4V AC potential difference between 'Earth' and any of its leads that connect to the cell - even while the cell is not being activated.

Below is a pic where I connected my multimeter across a GPO earth and the flow sensor connection.

Result - Approx. 4V AC

It did not matter which lead I was measuring on the cell - all would result in 4V AC.

 

[Costas > DownUnder]

So when I measure the voltage between my pool water [my pool water is not bonded] and "Earth' It should result in slightly less voltage allowing for any losses.

...and sure enough I can measure around 2.5V AC - However voltage is not telling us the full picture.

What is more important is current flow. It is the current flow that we feel when you receive a tingle or shock and NOT the voltage.

So let us see how much current is actually being drawn when I measure current flow between my water and 'earth'.



For the 'earth/ground' connection I used a metal stake which was being used to hold up some string line for my coping.

This was driven into moist soil which gave me a reasonably low conductivity path to ground.


One probe in the water and the other making good contact with the metal stake driven into moist soil.

The result is around 380uA which is 0.380mA.

Now touching the metal rod with a wet hand while placing my other hand in the pool water I could not detect any sensation.

However if my skin was cut I may have been able to perceive a tingle etc as open skin has much lower resistance and would allow more current to flow. I was to chicken to cut my skin today - Maybe a test for another day...

380uA is a very low current and not dangerous in any way - With my undamaged skin, the current through my body would have been much less as my skin resistance would prevent the same amount of current flow as the multimeter test simply due to the resistance of my unbroken skin.


Another test I performed today was to measure the current flow with the multimeter but through the wet granite coping.

Even while wet - the coping added another layer of resistance and I could only achieve around 10 to 20uA maximum - a bit like standing on an insulator while the concrete bond beam surrounding the pool gave me something in the region of 120uA when wet - Compare that to the metal stake in the soil which I could achieve around 380uA worst case.

 

[Dirk]

As I am trying to understand this myself, a few thoughts for... someone...

I thought it was explained that bonding is not grounding, though it includes a connection to ground. And that it is serving a slightly different purpose than a ground rod would. The purpose of bonding was to eliminate, through direct electrical connection via a pretty darn heavy duty wire (8 gauge), any difference in electrical potential between any two things that could conduct electricity within reach of a human in or around a pool and/or its connected equipment. How'd I do?

How I interpret this is: if an electrical potential comes into existence at any item at a pool, that potential would then exist equally across all the items (via the bond wire) such that touching any two items by a person could not cause a current to pass through that person (not shock them). Which is what I think is different about bonding than grounding. Grounding would send that stray voltage to ground and theoretically cause a breaker or ground-fault-interupter to shut down the circuit powering the stray, thereby protecting the person. But bonding would do its thing regardless if the stray was powered down or not, because there would be no difference in voltage (or is it potential?) between any two objects at a pool, because in essence, there are no two objects at a pool (electrically speaking) because they are all connected together as one. Now how'd I do?

Which, in my mind, is why I would not trust myself to troubleshoot bonding. And why i would question Costas' methods. Not in terms of the information you gathered about your pool and bonding, but in terms of you declaring yours safe. By that I mean: yes, you determined that there is a difference in electrical potential between two items at your pool. And yes, their current difference in potential is safe for a human to touch (both voltage and amperage). But what I got from your testing is (1) that you discovered a fault in your bonding, because it is allowing any difference in electrical potential between two items to exist, and (2) that you currently have a difference of potential (however harmless), which means (3) should a more serious difference of potential develop (like from a defective electrical pool component, or downed power line, or faulty house wiring, whatever) that that difference could be passed along to one item in your pool in such a way that it would not be matched in the other items, which could then cause someone some harm. Now how'd I do?

So if my understanding of this is in whole or part true, then just measuring your pool and looking for differences in potential is not necessarily a proper way to determine if your bonding is doing its job. Or, more importantly, ready to do its job should something else go wrong.

Thoughts?

 

[Costas > DownUnder]

I thought it was explained that bonding is not grounding, though it includes a connection to ground.

Bonding is simply the process of commoning the electrical earths of all the items together via a dedicated lead.

Pumps/heaters etc are all normally earthed via your GPO. Bonding just ensures that all the equipment is at the same common earth/ground which ensures no potential difference can exist between these items as they are all tied together.

So far so good.

Now to our pools - Pools are not an electrical appliance which is plugged into a GPO so pools natively do not have any direct connection to the electrical earth of your GPO which is where your electrical items get their earthing from.

So there exists the common situation that the pool will be at a different earth potential (voltage) than the GPO earth. Now since all our pumps etc are plugged into the GPO we can normally always measure a difference in potential between the GPO's earth and the pool itself which is a form of electrical ground from an electrical circuit perspective. The reason for this is that ground or earth is only at earth potential at the point where say a ground rod is driven into earth itself - Moving away from this rod will always see a potential difference increase simply because of natural and non natural earth currents and lots of free electrons....!

The pool itself (Gunite only) is a form of ground as it is connected directly to ground via conductive construction components - The concrete, the rebar etc all are actually slightly conductive especially if wet/moist and this is carried right through to the water itself.

From an electrical circuit perspective a fibreglass pool is a slightly different proposition as the fibreglass is an electrical insulator so the water in the pool is totally insulated from any earth (providing there are no other conductive items connecting the water to any outside components).

Current cannot flow to or from the water in a fibreglass pool unless a conductive device is attached to the pool's water which completes the circuit to outside of the pool.

With a gunite pool current can always flow as the pool itself is electrically conductive to the outside world due to its construction materials which are electrically conductive. So in this instance an electrical pathway is always present for current to flow via the water to and from the outer ground.

This is why it is very important to ensure that the external rebar etc is correctly bonded in a gunite installation as the water is always electrically making contact to the outer shell whereas on fibreglass it is not - it is normally insulated from the external material.



The OP's issue is slightly different again as it is to do with the way the chlorinator operates with it's internal switched mode power supply.

My testing above just verified the OP's issue as I have the same chlorinator.

Switchmode supplies normally have protection and noise suppression capacitors on the incoming active/hot and neutral lines, these allow a small amount of leakage current through and I fairly certain this is what we are seeing.

When the OP and myself unplug the chlorinator there is no voltage between the pool water and earth as it is the chlorinator which is introducing the minor current path via its circuitry.

You will actually receive a much larger shock simply by placing your tongue across a standard 9v battery...


Have you ever used one of those small electrical testing screwdrivers which you place a finger over the end and touch the screw driver tip on the mains and if hot the small neon lamp lights up inside the body of the screwdriver?

If you stand barefoot on concrete or a tiled surface you will feel a tingle at the end of the screwdriver when the neon lamp lights up as current is flowing through your body and through the neon lamp and a resistor. Only a small current flow but you can actually feel it. This current is way higher than what the OP experienced as you can feel the current as the neon lights up through unbroken skin whereas the OP's issue was with broken skin which has way lower resistance.


The chlorinator's power supply will more than likely have a slight leakage current through the capacitors I mentioned - this is normal for these types of power supplies. The capacitors limit the AC current due to their impeadance at 50/60Hz and therefore the current cannot get any larger etc. This does not mean that the pool is electrically un-safe or that the chlorinator is faulty.

 

[Poolzzz]

Pool bonding is the process of electrically tying EVERYTHING in and around a pool together so there can be no voltage difference between any of the objects. Basically any two objects that you can touch with any part of your body must be guaranteed to be the same potential. This prevents electrocution.

Measuring a voltage difference between any such objects indicates a failure in the bonding system.

The previous discussing conflates grounding with bonding which makes it overly confusing IMO.

 

[Dirk]

Pool bonding is the process of electrically tying EVERYTHING in and around a pool together so there can be no voltage difference between any of the objects. Basically any two objects that you can touch with any part of your body must be guaranteed to be the same potential. This prevents electrocution.

Measuring a voltage difference between any such objects indicates a failure in the bonding system.

The previous discussing conflates grounding with bonding which makes it overly confusing IMO.

Thanks Poolzzz. I think I'm getting the hang of it. Costas lost me because I don't know what GPO means and "earthing" or "commoning the electrical earths" doesn't speak to me. Not as wells as "electrically tying EVERYTHING in and around a pool together" does. And, in my head anyway, bonding isn't grounding. The ground (literally the dirt) just happens to be one of the things that gets bonded together with everything else.

The creepier issue is why this SWG is on the market, and not recalled. Is it a down-under-only product? I can't imagine it could survive in the litigious USA. I suppose the manufacturer can site, or prove, its fault is harmless. Still creepy though...

And just to keep hammering this home. Whether the thing is defective or not, or dangerous or not, it revealed the problem with the bonding, it didn't cause it.

 

[Costas > DownUnder]

Thanks Poolzzz. I think I'm getting the hang of it. Costas lost me because I don't know what GPO means and "earthing" or "commoning the electrical earths" doesn't speak to me.

I forgot that some of our terms Downunder don't quite carry over to our US based folk - Our GPO stands for general Purpose Outlet - ie a standard wall power outlet.

Easier to understand via a proper circuit diagram depicting the various elements but not much good for non electrical people.

The creepier issue is why this SWG is on the market, and not recalled.

It is actually not as creepy as you may think.

It is quite common for various electrical items to specify a maximum leakage current which is considered safe.

One of the tests many electrical items go through is to ensure that their leakage current falls below a minimum value. While many electrical devices do have zero leakage many have some.

This is why GFCI's usually trip at around 20 to 30mA and are not designed to detect even lower currents as it would cause nuisance tripping if a number of devices with a certain amount of 'safe' leakage current are all connected via the same GFCI.

And just to keep hammering this home. Whether the thing is defective or not, or dangerous or not, it revealed the problem with the bonding, it didn't cause it.

Well, the chlorinator's are not defective and the bonding standards for fibreglass pools here in Australia only specifies bonding of the outer elements (eg: concrete, rebar) as well as any conductive objects that are within 1.5m of the pool.

I suspect that the OP's issue is quite common here but most people would be unaware of it.

Here is a White paper on the topic which covers off some typical safe values: https://378m1o49xyfcl4may47q66uc-wpengine.netdna-ssl.com/App-slpower/images/whitepapers/An113%20Leakage%20Current.pdf

 

[Dirk]

Interesting. Thanks! Especially about the "nuisance buffer" built in to GFCIs. Makes sense.

 

[Poolzzz]

This is why GFCI's usually trip at around 20 to 30mA and are not designed to detect even lower currents as it would cause nuisance tripping if a number of devices with a certain amount of 'safe' leakage current are all connected via the same GFCI.

In Canada (and probably the USA) they trip at 5mA. I don't think 20mA devices are allowed for personnel protection here (equipment only).

the bonding standards for fibreglass pools here in Australia only specifies bonding of the outer elements (eg: concrete, rebar) as well as any conductive objects that are within 1.5m of the pool.

I suspect that the OP's issue is quite common here but most people would be unaware of it.

Do the bonding standards there require the pool water to be bonded? It's required here regardless of shell type.

 

[Costas > DownUnder]

In Canada (and probably the USA) they trip at 5mA. I don't think 20mA devices are allowed for personnel protection here (equipment only).

I have a copy of the latest (current 2018) Australian wiring rules document which specifies 30mA trip current unless used for medical applications (and in educational institutions where young kids are cared for or schooled) where 10mA is used.

Do the bonding standards there require the pool water to be bonded? It's required here regardless of shell type.

I looked carefully at the current standard and no where does it mention bonding of the water for either concrete or fibreglass pools.

All it refers to is the electrical equipment, all the outer conductive elements and any conductive fixtures/fittings that are installed within the pool that make contact with the outside such as metal hand rails, ladders etc.

There is a paragraph specific to "conductive pool structures" which defines the general bonding requirements for the rebar/mesh etc - but again no mention of the water.



For those that are interested - I stumbled on a short pdf that goes into some light detail on issues such as leakage current etc wrt GFCI/RCD installations. Note that it is Aust. based so RCD = GFCI

Good read for many as it is does not get overly technical...!

http://www.masterelectricians.com.a...es MEA march 2014 v1 [Compatibility Mode].pdf

 

[jgb75]

Here's another data point, new concrete pool in Australia with the Astral EQ25 Chlorinator. Readings taken with the Chlorinator plugged in but not running.

This is measured between the water and steel fence stirrup, the stirrups are electrically bonded to the rebar and the rebar is electrically connected to the house main earth (as is the standard practice in Australia).

AC voltage 269mV



Current 695uA



The bluestone coping and paving seems to be a good insulator, can't measure anything there even when wet.

Presumably this issue can be "fixed" by bonding the pool water as well, but that doesn't seem to be standard practice in Australia, kind of surprising as we are normally something of a nanny state for electrical regulations.

 

[Costas > DownUnder]

Presumably this issue can be "fixed" by bonding the pool water as well

Yes - Having a conductive path between the water and the outer conductive elements will sort that out.

Do you know if your spigots for the fencing are bonded?

 

[jgb75]

Do you know if your spigots for the fencing are bonded?

Yes, they are bonded.

 

[Costas > DownUnder]

Yes, they are bonded.

Good...!

If you bond your water the current will flow through your bond connection and not through anything else.

 

[jgb75]

I'm wondering why my pool water AC voltage is lower than your reading, also with the Astral EQ SWG. Would that be because my pool surface is conductive (but quite a high resistance conductor) and bonded which is pulling the voltage down somewhat, compared to your fibreglass pool.

 

[Costas > DownUnder]

Would that be because my pool surface is conductive (but quite a high resistance conductor) and bonded which is pulling the voltage down somewhat, compared to your fibreglass pool.

Yes I would say so.

The voltage is not all that important as the current is what you will feel.

Note that your current reading was higher than my example - More than likely due to the fact that you have a better connection to ground via your bonded spigot.

In my case I was just using a metal stake driven lightly into the soil (not very deep) so not making as good a contact to ground as compared to your bonded setup.

 

[jgb75]

Yes, makes sense. Thanks Costas.

 

[Hails]

Yes I would say so.

The voltage is not all that important as the current is what you will feel.

Note that your current reading was higher than my example - More than likely due to the fact that you have a better connection to ground via your bonded spigot.

In my case I was just using a metal stake driven lightly into the soil (not very deep) so not making as good a contact to ground as compared to your bonded setup.

Thanks so much for all your input in this costas I think you have cleared up alot for many people reading along.
I still have a concern though as to what would happen say if someone was swimming with this chlorinator plugged in and it somehow electrically malfunctioned causing a higher current in the water. Would you say it would just trip the switch at the metre box and the person will be fine? At this point, even though we now have bonded everything, I feel like I want to unplug it from its power source before swimming just to be safe. Am I being a bit paranoid there or cautious lol.

 

[Costas > DownUnder]

I still have a concern though as to what would happen say if someone was swimming with this chlorinator plugged in and it somehow electrically malfunctioned causing a higher current in the water.

It would entirely be dependent on the mode of failure.

Just remember that the SWG cell is only ever powered by low voltage and not any form of mains voltage - so you have an inherent safety barrier there.

Also the fact that your pool is bonded would mean that any large current would be drawn to the bond wire connection and would therefore prevent any current flowing through a persons body. A bit like how birds can sit on power lines but not feel a thing - while there are large currents flowing through the powerline the birds don't get zapped.

Would you say it would just trip the switch at the metre box and the person will be fine?

If some form of catastrophic failure occurred whereby somehow either the active or neutral line from your mains came into contact with the SWG plates, then your RCD (residual current device/Earth leakage breaker (GFCI for US folk)) should trip straight away provided everything is wired correctly ie all the electrical items are plugged into an earthed outlet etc.