Equipotential Bonding

[pool250]

I have tracked down the relevant regulations for equipotential bonding in Australia and to my laymans reading of it, there seem to be some important differences between Australia and the US. I have spoken to an electrician and told him about this and he said if I wanted to do it the American way (slipped a bit of Billy Joel in there whilst no one was looking) in addition to local regs then I should collate the info and let him know what I want, which is fair enough.

I would be grateful if anyone could let me know where there are differences and if the standard is higher in the US for any particular aspect and if I should incorporate it. Thanks
From what I can see they only require the deck to be bonded if it is reinforced, not if pavers are used.
The bonding needs to be earthed?: I am not sure this is the case in the US?
Only one point of contact is required for pool reinforcement.
Bonding conductor is not required to be bare


Here are the Australian wiring rules for equipotential bonding in swimming pools as of 19/01/2011:

5.6.2.6 Swimming and spa pools
The following items shall be equipotentially bonded: (a)The exposed conductive part of any electrical equipment in the classified pool zones. (b)Any exposed conductive parts of electrical equipment that are not separated from live parts by double insulation and that are in contact with the pool water, including water in the circulation or filtering system. Where any of the items described in Item (a) or Item (b) exist, the bonding shall be extended to the following additional items: (i)Any fixed extraneous conductive parts of the pool structure, including the reinforcing metal of the pool shell and deck. (ii)Any conductive fittings within or attached to the pool structure, such as pool ladders and diving boards
iii)Any fixed conductive material within arm’s reach of the pool edge, such as conductive fences, lamp standards and pipework. The bonding conductor shall be terminated or connected by any of the means permitted by Clause 3.7. In addition, where the connection may be subjected to the deteriorating effect of the pool water, it shall be covered with, or encapsulated in, a suitable compound. An equipotential bonding conductor, in accordance with Clause 5.6.3, shall be connected between the bonded parts and the earthing conductor associated with each circuit supplying the pool or spa, or the earthing bar at the switchboard at which the circuit originates.

NOTES: 1 Connections to the conductive reinforcement of the pool will generally be subject to the effects of water during the construction phase and to subsequent dampness. 2Where electrical appliances and luminaires are supplied as a separated circuit in accordance with Clause 7.4, all conductive parts of such electrical equipment are deemed to be separated from live parts by double insulation. 3 Conductive tie-wires used during construction of reinforced concrete pools are considered to be an adequate electrical bond between the conductive reinforcing components. Provided that the reinforcement is satisfactorily electrically connected together, one point of connection of the bonding conductor to the reinforcement is satisfactory where bonding is required by Item (i). 4 Fixed conductive parts and fittings that are not part of electrical equipment and that are not more than 100 mm in any dimension need not be bonded. 5 Underwater luminaire bezels should be made of plastics and any associated fixing screws be insulated or of insulating material

5.6.3 Bonding conductors
5.6.3.1 General The selection and installation requirements for equipotential bonding conductors shall be in accordance with this Standard for protective earthing conductors. Exception: The size of an equipotential bonding conductor shall be determined in accordance with Clause 5.6.3.2. 5.6.3.2Size The size of equipotential bonding conductors shall be determined from the requirements of this Clause 5.6.3.2 appropriate to the particular bonding conductor application. The equipotential bonding conductor need not be larger than these sizes provided that the installation conditions are such that mechanical damage is unlikely to occur and, in accordance with Clause 5.7.5, a larger size is not required to reduce the earth fault-loop impedance.

(a) Conductive piping, cable sheaths and wiring enclosures The equipotential bonding conductor required in accordance with Clauses 5.6.2.2 to 5.6.2.4 shall have a cross-sectional area not less than 4 mm2.
(b)Showers, bathrooms, swimming and spa pools The equipotential bonding conductors required to connect conductive parts of a shower, bathroom, swimming or spa pool in accordance with Clauses 5.6.2.5 and 5.6.2.6 shall have a cross-sectional area not less than 4 mm2. Exception: The cross-sectional area of the equipotential bonding conductor for a swimming or spa pool may be determined as for an earthing conductor, in accordance with Clause 5.3.3.4 (c), where the equipotential bonding conductor is incorporated in a multi-core flexible cord supplying electrical equipment that is required to be removed for maintenance. (c)Telephone and telecommunication earthing systems The equipotential bonding conductors required to connect a telephone and telecommunication earthing system in accordance with Clause 5.6.2.7 shall have a cross-sectional area not less than 6 mm2.


In addition since 1/12/2010, fencing needs to be bonded.


In addition, the power line terminates on my property with a transformer. The distance from the pole to the pool is 70ft, which is sufficient distance away to comply with the regulations regarding general construction but as this pole/transformer carries 19,000 volts and has several earthing wires buried in the ground around it apparently and that these appear to carry current according to the sign, I am wondering if there are increased risks of stray voltage which need to be addressed?

 

[JohnT]

Your code seems very similar to US and Canadian code. It includes the grounding requirement of the Canadian code.

From seeing your power line and the signs, I'd be talking to a power company engineer to get their advice. It could be helpful. The fact that the ground carries current raises a big red flag with me.

The US code doesn't carry any provisions for bonding pavers either, but some people experience problems with stray voltage in the paver deck when it's damp. Of course the pavers are damp whenever the pool is in use. Doing it myself, I'd consider a copper grid connected to the bonding wire placed in the fill below the pavers. I have no first hand experience, but I have looked for a solution in the past and not found any suggestions.

 

[Bama Rambler]

In Australia they use the earth as a conductor (Hence the one wire on the pole to the transformer) That's the reason for the warning about not disconnecting the earthing system while the transformer is energized. It shouldn't cause a problem for you, but John's advice of contacting a power company engineer and explaining everything is a good idea.

 

[JasonLion]

In the US, the primary bonding wire is always #8 solid copper without insulation.

In the US some areas require a conductive grid under pavers, while most settle for a single copper loop all the way around the pool. If there is a grid, it should extend from the pool shell out one meter from the water (or more). Stainless steel is acceptable for the grid if you also have a copper loop. Copper is better for the grid, but tends to get expensive.

The US requires four points of contact, equally spaced around the pool, between the bonding system and a conductive pool shell.

There are quite a number of rules in the US about under-water lighting. Your list appears minimal.

Also, essentially nothing electrical permanently installed, aside from the bonding system, main equipment pad, and appropriate underwater lights, within about 4.6 meters of the water horizontally. There are some exceptions to this, but they are extremely restrictive.

 

[bk406]

I'm still bugged by the grounding rod requirement; both in australia and canada. I understand why the US doesnt do it based on the whole one path to ground idea and the fact the pool bonding system does not function as a ground system does per se.
Any of you guys have any insight to why this is a requirement in some countries but not the US?

 

[Ohm_Boy]

I suppose that if your 'earth' is at some variant of 19K volt potential, you'd want to make sure that the 'bonded grid' from which you may step onto the ground is at the same potential. Earthing the grid makes sense to me for that.

 

[JasonLion]

There are several different possible ways things can go wrong. In some cases grounding is better, in others not grounding is better. Grounding is a problem where you have constant ground currents. Those ground currents will flow through the bonding system earth ground, on through your bonding wire, and on to the household earth ground. Running current constantly through the bonding system and household ground wires creates opportunities for shocks and will cause the bonding wire and ground wires to fail over time.

On the other hand, if an overhead utility wire falls into the pool, not grounding the bonding system substantially increases the distance the current needs to travel before it goes to earth, introducing different risks. In particular, the bonding system will probably be bridged to household ground, and thus run power from the downed utility wire, through the pool, and on into every grounded appliance in your house, creating dozens of shock risk points.

Incidental grounding of the bonding system to earth is fairly common. In most plaster/concrete pools the bonding system is grounded to earth by the concrete, regardless the presence or lack of a separate ground rod. Likewise, an uninsulated buried copper loop running around the pool, which is usually required, can also be a fairly good earth ground, depending on soil type and moisture levels. Using a sacrificial zinc block to reduce corrosion also creates an earth ground. So, as a practical matter, the bonding system is often grounded to earth regardless.

 

[bk406]

I hear what your saying. All in all i guess i'd rather not put in a rod directly connected to the #8. Ground currents, IMO, is what would most likely be encountered with a pool. In that case, not sinking a rod would be the best.

 

[pool250]

In the US some areas require a conductive grid under pavers, while most settle for a single copper loop all the way around the pool. If there is a grid, it should extend from the pool shell out one meter from the water (or more). Stainless steel is acceptable for the grid if you also have a copper loop. Copper is better for the grid, but tends to get expensive.

There are quite a number of rules in the US about under-water lighting. Your list appears minimal.

The top flange of my pool extends out 200mm with a continuous loop of 12mm rebar on top (buried in mortar). This will have the coping pavers on top.
Would this be sufficient instead of the single copper loop?
Alternatively I have read that ordinary reinforcing mesh of 6"X6" sqaures extending out at least 3ft around the pool is sometimes used in the US where local
inspectors allow it. Providing the pavers are properly grouted rather than just sand filled, corrosion from pool water should be minimal.
A 3ft copper grid would be mighty expensive that's even if I could find such a thing in these parts!

Only 12v underwater lights are allowed in Australia so that might explain the lack of regs on this.
I asked the manufacturer of the light (Spa Electrics who make their lights here), if it needed to be bonded and he said it couldn't be because its all plastic.
(apart from 2 fixing screws and the wiring, I would add).

(Apologies for mixing my imperial with my metric - we do that when the imperial measurement is more descriptive!)

 

[JasonLion]

With 12 volt lights the key step is to use a special transformer that isolates the primary and secondary windings so line voltage can never short to the low voltage lines, even if the transformer is damaged. All pool light transformers are made this way here, while normal low voltage outdoor lighting transformers are not. I suspect that any transformer specifically for pools will also be fine there, though I don't really know.

In the US the reinforcing mesh would pass in a fair number of places, but the rebar on the flange would never be enough.

 

[pool250]

Spoke with a knowledgeable guy at the power company and he said he couldnt see that there would be a problem with stray voltage from the
pole earthing system.
The only concerns he had was if the line crossed over the pool and the line broke and fell into the pool, which we agreed would not be a good thing.
Fortunately the line goes in oopposite direction to the pool.
The other issue is if the line touches a tree and the tree becomes live. The line through my property passes amongst thick woodland. The power company
do come every 3 years to cut back any trees which have grown too close and by the looks of things they are due for another prune.
The vegetation manager is going to send out an inspector to inspect the trees.

Thanks everyone, once again for another comprehensive, no stone left unturned, response!

 

[JohnT]

Spoke with a knowledgeable guy at the power company and he said he couldnt see that there would be a problem with stray voltage from the
pole earthing system.
The only concerns he had was if the line crossed over the pool and the line broke and fell into the pool, which we agreed would not be a good thing.
Fortunately the line goes in oopposite direction to the pool.
The other issue is if the line touches a tree and the tree becomes live.

Those are the very reasons for the bonding system. One of the accidents that drove the increased bonding requirements involved a trackhoe touching a power line near a public pool.

Theoretically, even a power line falling into a pool would not harm the occupants IF the pool was properly bonded.

 

[Ohm_Boy]

Theoretically, even a power line falling into a pool would not harm the occupants IF the pool was properly bonded.

Until they got out and walked back to the house, I suppose.

Same holds true if a high-tension line falls on a car, like when a vehicle eats a power pole and drops the lines. The occupants should all be OK until someone opens a door and tries to get out.
Oh, and I recall hearing that this was also a problem with massive static charges building up on helicopters, and that is why military personnel jump out instead of stepping out. Dunno if that one is factual or not.

 

[pool250]

So everything was sorted with the electrician, or so I thought. He would read up on the regs and he agreed to come over yesterday to do the bonding.
Instead 2 guys, one of whom wasn't a qualified electrician, both of whom knew less than me about this (which isn"t much), turned up. I tried to explain as best I could.
The unqualified guy fitted these 4 plastic clamps with about 3ft of cable on each one, which meant they could only go on the walls not the floor.
They told me that they would attach the rest of the cable later on, by soldering and then dab on some grey grease stuff.

After they went I researched a bit more and it soon became apparent that what they had done was probably as badly done as it could possibly get.
Then the guy who should have turned up rang and told me that he was going to charge me for 2 guys even though only one did the work (and that took less than an hour) and even then, one of the clamps hadn't even been tightened onto the bar. Total bill $290

Enough is enough, so today I returned the clamps and took matters into my own hands
and have ordered 16 bronze Erico clamps, a 300ft roll of cable and an 10ft Erico earth stake.

I am hoping that things will improve because at the moment I am having to make decisions which I am not qualified to make but there really dosen't seem to be anyone around where I live, who is qualified, who can do that for me properly and this bonding cant wait any longer as the inside mesh, the mesh on the buttresses and the central box has to go on soon as we are mortaring in a few weeks.

 

[Bama Rambler]

I think you've made the correct descision by taking it over yourself given your circumstances. At least you know how it'll be done and it'll be to the best of your abilities and understanding.

In the U.S. the bonding wire has to be an unbroken loop (or spliced using an approved connector) to every piece of metal in contact with or within 5' of the pool water . If it were me, I'd adhere to that in your situation.

 

[pool250]

I think you've made the correct descision by taking it over yourself given your circumstances. At least you know how it'll be done and it'll be to the best of your abilities and understanding.

In the U.S. the bonding wire has to be an unbroken loop (or spliced using an approved connector) to every piece of metal in contact with or within 5' of the pool water . If it were me, I'd adhere to that in your situation.

Thanks for the support Bama.
I have done it with a continuous cable (in Aus the cable can't be bare).
There are 4 clamps on the floor, 4 on the walls and 4 on the top flange and there will be 4 on the deck.

 

[Bama Rambler]

There's one thing about it, if anybody ever asks, you can tell them, Oh yeah, I know it's bonded correctly!