Grounding or bonding - Not sure what they did

[JoyfulNoise]

Will you explain why because I'm trying to understand. If the bond wire and clamps are buried in the gunite, how is the deck tied in? Our electrician came out prior to gunite and did rough electric (along with the plumber who stubbed plumbing), so it was not a case of saving a trip. We had to have a rough electric inspection and a final electric, so the city inspector (in a city where they can be picky) was fine with the way it was done.

I'm just curious as to what the issue would be.

If the wire is attached INSIDE the gunite shell, it is more secure and can not be tampered with in the future. If it's bonded OUTSIDE the shell in the area where coping/decking would be laid, then there's always the off chance that a future renovation project could sever the bonding loop or the rebar stubs could corrode away. It seems "nit-picky" and over-engineered but that's how a lot of municipal inspection regulations are, they want to avoid any chance of liability even if it is remote.

But it sounds like your PB is doing what is considered OK for your area.

 

[gwegan]

So you have a pre gunite sign off?

 

[philboyj]

If the wire is attached INSIDE the gunite shell, it is more secure and can not be tampered with in the future. If it's bonded OUTSIDE the shell in the area where coping/decking would be laid, then there's always the off chance that a future renovation project could sever the bonding loop or the rebar stubs could corrode away. It seems "nit-picky" and over-engineered but that's how a lot of municipal inspection regulations are, they want to avoid any chance of liability even if it is remote.

But it sounds like your PB is doing what is considered OK for your area.

The bonding wire - at some point has to run outside the gunite shell and back to the equipment pad. So, future construction is always a liability - irrespective of where the connection is made.

The PB is doing this right. Ask for two clamps..lol

Also, bonding in 4 places = 400% factor of safety. You only need one to be connected at any point of time.

 

[Pool Tool]

Be careful not to mix logic with regulation. By design, regulation or codes are written for the one off scenarios or at least to minimize the most potential risk. Yes, as you said the wire has to eventually make its way to all the equipment and could be cut anywhere. But say in 10 years the owner of this pool wants to replace the concrete surround and install pavers. The pieces of rebar that have bond wire attached will be in the deck surround not in the shell. Depending on demo, they could all be cut off at a point where no one could see the clamp or wire. If the paver installers are not familiar with bonding, heck lots of pool builders aren't, what's the chances it gets added. It's strange, but the little bit of work I've done around my pool the bond wire is generally just under the concrete is oddly visible when digging, etc. Again, these are unique scenarios that generally don't happen but they are often what drive the code and the curmudgeonly inspector that forces extra work.

As for the 400% safety factor, I am by no means an expert but there are instantaneous voltage gradients where these bonds may help independently. So is it right or overkill or a few nervous people worried, maybe heck hopefully. But the intent is minimize, rather eliminate, the risk of electrocution. Which is something we can all agree on.

Great discussion and great community!

 

[vermaraj]

This is a case where the code is poorly written so as to confuse what really needs to happen. First what your builder is doing is fine so long as he bonds the rebar in 4 places spread our around the perimeter of the shell. There are many reasons to do so after gunite placement, they all revolve around code enforcement.

Bonding versus grounding: Grounding establishes a minimum level (potential) to measure voltage (potential relative to a given level). Bonding ensures that all components are electrically tied together at this level. When a light operates at 120 Volts we must define 120 Volts relative to what. In residential construction that is relative to zero potential or ground. In an industrial it could be something entirely different.

During World War II the military devised a method of grounding to protect weapons depots from static electricity. Static electricity often makes bombs go boom. They found that burying steel rebar in concrete that is itself buried in moist earth is the single best method of grounding. This method is defined as "Concrete Encased Grounding Electrode" or CEG as it is defined in the code or a UFER, after the man who developed the concept.

It is easy to see that a pool is by far the best grounding electrode on your property. However the equipment that connects to the pool may or may not have the same ground. Thus the purpose of bonding is to ensure that every component that comes into contact with the water in the pool is at exactly the same ground potential level as the shell of the pool.

 

[philboyj]

Wow Vermaraj. That is a great post. Explains everything so clearly.

 

[gwegan]

With all due respect Vermarej is incorrect.

Let us be clear Grounding and Bonding are not the same thing. While they are interrelated they are different and serve different purposes.

Bonding is tying together elements of a pool so they have the same electrical potential. Therefore if one element becomes energized all elements are energized and current will not flow between them. It is designed to capture stray current often generated by the electrical distribution system. It is not intended to act as a ground in any way. One of the consequences of bonding is that it will incidentally capture and hold shorted current or current from bad neutrals. In other words become energized. But because it spreads the current over all conductive surfaces (including the water) the electrical potential of all surfaces and the water is the same. No current can flow and no one gets electrocuted.

Grounding on the other hand is providing an low resistance alternative path for the return flow of electrons to their source. In most systems this is accomplished by a grounding wire attached to most equipment which returns to the main nuetral buss bar. In all pool applications the grounding must be insulated because, in part, we don't want current running through the grounding wire to inadvertently energize the bonding system.

In short bonding is not grounding and grounding is not bonding.

Additionally, while the code may not be explicit on the point, I think it is clearly best practices to have the bond wire clamped to the rebar inside the shell. To clamp in the deck is in my opinion not in compliance with what the code is attempting to accomplish which is to bond each element to the system. The deck should be bonded seperatly.

Finally why are we tying the deck together with the pool? I can't imagine except in some special situations where a structural engineer would approve of that. The engineering plans I have seen generally require different conections. They are structures that behave very differently and a rebar tie would put unnecessary stress on both in my view.

 

[JoyfulNoise]

This is simply an issue of local code regulations and the variability in those regs across municipalities. In the OP's municipal area (Houston), post-gunite bonding of rebar stubs is an acceptable practice. In other areas of the country (like mine in Tucson) post-gunite bonding of rebar stubs is not considered an acceptable method of bonding. We can discuss this all day in the abstract about which is better or worse but the OPs pool bonding setup is fine as it conforms to the local pool building codes in his area.

 

[tim5055]

This is a case where the code is poorly written so as to confuse what really needs to happen.

I will also dispute the fact that the code is poorly written. It is actually very well written when you take into account the corrections being made by gwegan below.

With all due respect Vermarej is incorrect.

Let us be clear Grounding and Bonding are not the same thing. While they are interrelated they are different and serve different purposes.

Bonding is tying together elements of a pool so they have the same electrical potential. Therefore if one element becomes energized all elements are energized and current will not flow between them. It is designed to capture stray current often generated by the electrical distribution system. It is not intended to act as a ground in any way. One of the consequences of bonding is that it will incidentally capture and hold shorted current or current from bad neutrals. In other words become energized. But because it spreads the current over all conductive surfaces (including the water) the electrical potential of all surfaces and the water is the same. No current can flow and no one gets electrocuted.

Grounding on the other hand is providing an low resistance alternative path for the return flow of electrons to their source. In most systems this is accomplished by a grounding wire attached to most equipment which returns to the main nuetral buss bar. In all pool applications the grounding must be insulated because, in part, we don't want current running through the grounding wire to inadvertently energize the bonding system.

In short bonding is not grounding and grounding is not bonding.

Great post!!

 

[vermaraj]

With all due respect Vermarej is incorrect.

One of the consequences of bonding is that it will incidentally capture and hold shorted current or current from bad neutrals.

Please explain how a low impedence shunt, a copper wire, "captures and holds shorted current."

 

[philboyj]

I now know enough about bonding and grounding to last me a few lifetimes. That's where I stop - once I know enough to be dangerous

 

[tim5055]

If anyone has 26 minutes you can watch the video

2014 NEC - Grounding Versus Bonding (26min:26sec) - YouTube

 

[gwegan]

Varmaraj

I'm sorry, I am trying to write something that can be understood by non electricians and electrical engineers.

While my language may not be perfect I've found it is what best describes the functions of these two systems to laypeople.

The effect of a 8 gauge bonding wire tying together the water, pool shell, pump, deck and associated metal parts is that any stray current is spread to all of those parts thus equalizing their electrical potential as to each other. Because they share the same electrical potential current cannot travel between them via a swimmers body thereby reducing the risk of electrical shock and death.

In addition to the link above I suggest you (and anyone else interested) study http://www.mikeholt.com/download.php?file=PDF/Swimming_Pools_and_Spas_2014NEC.pdf

The discussion of bonding starts on page 18. Mike describes it as reducing voltage gradients but it has other implications.

 

[firehunter]

I would like to thank everyone for all the information and discussion on bonding and grounding. I have learned a lot including that you can bond in more than one way. In Houston (not sure which other areas) they bond after gunite. These rebar loops are in the gunite and the copper wire is attached to some of them. In our pool they attached them to six. They will then bend them down and I think they go in the deck, but I will try to take photos of the process and post them in my build thread when they get to that part.

[URL=http://s1159.photobucket.com/user/rschack/media/20160501_085252_zpsx0l5fs7w.jpg.html][/URL]

 

[JayBauman]

Is this always an either/or? In my pool build (Houston-area), my decking was bonded just like it's shown in firehunter's pic above, and the steel cage of pool shell and water features was directly bonded.

 

[IrwinK]

My pool is under construction and they are up to the bonding now, before installing the paver deck.

The bonding loop is around the pool perimeter and fastened in 6 places to green insulated wires that were attached to the rebar in the shell before the gunite.

My question is about a stainless steel handrail that will be installed:
There is one of the green insulated bonding wires attached to the rebar in the shell located right where the rail will go but they didn't attach it to the bonding loop.

The 54" handrail will not be in the pool but will be anchored in cement and extend over to the pool step area. I think they intend to just connect the wire to the rail when I'm thinking it should also be connected at that point to the bonding loop too.

I'm worried of a possible shock from the rail. The PB will be out here tomorrow and they are scheduling an inspection so any info or advise would be greatly appreciated.

 

[gwegan]

If its metal and within five feet of the pool it must be attached to the bonding loop. I prefer uninsulated bonding wire. As long as it is all connected together with clamps it should be ok.

 

[borjis]

speaking of the clamps, what are they made of?

copper? Brass?

that last photo looks maybe like Brass clamp with a steel bolt.

I know they need to be specific as to minimize degradation over time and how certain metals
corrode much faster when in contact with different types.

 

[JoyfulNoise]

I know they need to be specific as to minimize degradation over time and how certain metals
corrode much faster when in contact with different types.

Driving a large zinc sacrificial anode into moist soil will help reduce the instance of galvanic corrosion. It is rarely done on gunite pools and can be done after the build by attaching the anode to the bond wire at the equipment pad.

 

[IrwinK]

My pool passed the bonding loop inspection today.

There will be another inspection of the electrical including the bonding at the equipment before filling the pool.
Wish I was at that point.