"magically grounded" the most important wire in the panel

[wyreman]

They are moving a handicap chair lift and the new unit needs bonded. well sure!
NEC Section 680.26, paragraph 3
"All metal fittings within or attached to the pool structure shall be bonded. Isolated parts that are not over 100 mm (4 in.) in any dimension and do not penetrate into the pool structure more than 25 mm (1 in.) shall not require bonding."

now the old lift was not bonded, never bothered anyone for at least 12 yrs
there was no rebar near the location of the new lift, this will take a lot of chipping to find some building steel

first, pls help me understand:
I am trying to understand where the "sit-potential" lies:
:angel:if there is less earth resistance to flow [anchor bolted chair] than neutral or bonding grid resistance and
lets say a niche light has some leakage
then, in that chlorine water, the chair lift becomes the low impedance path for the stray current.

so we will do whatever it takes to get to an approved gec and bond
i would think a split bolt would grab the rebar to the #8 here just as well as a uffer.

Now, for the delicate part of the question:
Someone who should know better, suggested we just drive a ground rod at the lift without connecting it to the pool grid.
He thinks a ground rod is equal to a center tap on the source xfmr, because, I guess, it has something to do with that it is "metal" and somehow "magically grounded"

He's a fine pipe bender and an all around nice guy. And I certainly have my limitations!

So what is my question?
1. how to sell the chair job to superiors: we have to find rebar or go all the way to the panel =0 for the new chair lift when the old lift had no bond and was just fine.

 

[growler]

They are moving a handicap chair lift and the new unit needs bonded.

So what is my question?
1. how to sell the chair job to superiors: we have to find rebar or go all the way to the panel =0 for the new chair lift when the old lift had no bond and was just fine.

New lift. Permit required? I would assume yes. Contact the local AHJ (authority having jurisdiction). They are the one's to OK the job.

Get whatever you are going to do approved before you do it, saves time and effort.

 

[Gregg Harris]

So what is my question?
1. how to sell the chair job to superiors: we have to find rebar or go all the way to the panel =0 for the new chair lift when the old lift had no bond and was just fine.

How did the old chair pass an annual pool inspection if not bonded?

 

[ritelec]

Contact the local AHJ (authority having jurisdiction). They are the one's to OK the job.

Get whatever you are going to do approved before you do it, saves time and effort.

That's if they return your call... some are nice, return calls and work with you, others I think, think you should know what your doing and don't return.

How did the old chair pass an annual pool inspection if not bonded?

I was doing work at an old day camp, it has a very old pool... I see/saw no signs of bond... It passes every year.

or go all the way to the panel

Correct me if I'm wrong, but shouldn't bonding be able to go to anything thats bonded... and for the most part pool bonding doesn't have to go back to the panel.. ever..??


(I'm looking for the great Mike Holt cartoon.... it show's (I believe) the ground just hitting the equipment and grid)

 

[wyreman]

There has been no inspection for years. Just budget issues.
I work for the stAte.

On sep note,Walked today with simplex FA and they pointed out so many inspections have not been done for years

Annual Hydrant flow
Rusty insp test
gong etc
My boss's boss was the defacto ahj and he just retired
My boss is retiring
I'm just a wyreman but I am supposed to provide direction to new boss - on some things I don't know :/

I do know i need equipotential plane whether they like it or not


In belief, man can do anything

 

[Smart $]

... the old lift had no bond and was just fine.

Under certain circumstances and conditions, bonded parts create a greater potential hazard than not bonded. However, change the circumstances and/or conditions and bonded parts mitigate a potential hazard. The general consensus of NEC proponents believe bonded parts is overall the least hazardous when considering all possible circumstances and conditions.

The old lift not being bonded does not mean a potential hazard never existed. Perhaps the circumstances and conditions over the past 12 years never contributed to an actual notable event.

PS: have no idea what you mean by "sit-potential"...???

 

[wyreman]

Sit potential
Was supposed to make you smile
A play on "step potential "
Difference bet 2 steps w downed high volt power line


Here referring to diference in pot between the unbonded chair (earth) and the pool water / grid (ultimately neutral)


In belief, man can do anything

 

[ritelec]

something...and a link if you want to view wyreman.....

http://forums.mikeholt.com/showthread.php?t=157264

 

[wyreman]

Thx ritelec
I'm really looking for something on
The difference between the neutral (center tap xfmr) and the earth '(rod) for the biggest draw of the current.
In other words, the uselessness of using a rod here


In belief, man can do anything

 

[wyreman]

Correct me if I'm wrong, but shouldn't bonding be able to go to anything thats bonded... and for the most part pool bonding doesn't have to go back to the panel.. ever..??
(I'm looking for the great Mike Holt cartoon.... it show's (I believe) the ground just hitting the equipment and grid)

on that cartoon
the pump, niche light etc are all grounded to the panel
to the gec
and then they are bonded to the pool grid
which is indeed stand alone.

but because of the parallel paths to the gec from all the connected eq
the grid is, ultimately , conected to the center tap on the xfmr

the rod is just a rod

 

[hurk27]

I know this is a long winded but it is a must to understand the reasons why we are required to install equal potential bonding around a pool, this as well as stray voltages are so mis-understood as well as what a ground rod can or can-not really do to prevent a shock hazard, I have seen even well seasoned electrical engineers who don't have a clue about these two subjects, along with inspectors alike, to not understand these two subjects Can set yourselves up to some large liabilities as well a even criminal charges if someone were to get hurt or killed from not following the correct way to make a pool safe, yes there has been quite a few electricians charged with a crime, in some cases even involuntary man slaughter in cases where they did not not follow safety protocall and or the NEC, I think every electrician should know these subjects forward and backwards before they ever work on or around a pool or other similar electrical installations.

It is simply like this: Did you know that you could have a properly grounded (EGC) and protected (breaker/GFCI) load by a pool and a person immersed in water of the pool could still receive a shock large (2 volts or higher) enough to kill them and never trip the GFCI or breaker, and or even if it was tripped, they would still be shocked? if not then you must read on.

The above is why we also must include an equal potential bonding (EPB) system around all bodies of water where a person might likely be immersed in water and can contact earth or something at the potential of earth such as the concrete shell of the pool or the pad/deck around the pool that also has metal items electrical or not that might be at the potential of the service grounding.


First the idea is not to provide a path back to the grounding system for the service, this is not the function of EPB, the idea is to form a connected plane where everything is at the same potential so even if there is such an event such as a lost service neutral or even a bad service neutral that can cause everything that is connected to this service neutral via the main bonding jumper to rise to a voltage potential above the earth reference of 0 volts to be kept at this same voltage rise so there is not a difference of potential.

The reason a bird can sit on a wire that may be several thousand volts above earth potential is that every thing this bird can touch is at the same potential, well maybe a large bird such as an eagle might be able to touch another phase but the idea is the same.

Let's say the voltage drop of the service neutral is about 3 volts from the utility transformer and the service, since all the buildings grounding will also have this same voltage rise from remote earth and any grounding connected to this neutral, this includes this chair lift if it has an electric motor that has an EGC running back to the service, same goes for anything electrical around this pool, if the concrete pad around the pool or even the earth if there is no pad, will have this voltage difference between it and this pad unless the two are bonded together, this also goes for the concrete shell of the pool, or anything else that may be at the potential of the earth as they are in contact with the earth, a ground rod or even a CEE will not have a low enough impedance to earth to remove this voltage or even lower it enough to make it safe, 3 volts might not seem like a lot, but 3 volts across a persons body that is immersed in water can disable that persons mussels enough to make it impossible for them to pull themselves out of the water, or even keep their head above water, it does not take much voltage on a person immersed in water to cause a drowning.

By bonding all these areas together brings them all to the same voltage potential (3v) so even though they have a voltage above earth there is no voltage difference between them so no current can flow across a persons body, but this can only work if you can access the re-bar in the concrete for both the pool and pad/deck to connect to, and or any other metal or concrete that may be in around this pool, this #8 AWG wire has a low enough impedance to remove a difference of potential, a ground rod or other types of electrodes do not have this ability simple ohms law will show this.

but unlike poplar belief, stray voltages do not travel through earth and raise the potential of earth, its always the other way around, it is the conductors we supply or other conductive pathways that are connected to the service grounding that is also connected to the service neutral that brings in the stray voltage, as said it can be a voltage drop on the service neutral, or it can be a voltage drop on the primary neutral because it is also bonded over to the secondary neutral, that may be a mile down the road that has a bad connection and has a voltage rise above earth.

Another way to explain this about ground rods or other types of electrodes can be done like this, ask the person who thinks a ground rod can remove this voltage this question, if you used a ground rod as the neutral return path for a load, via connecting the supply hot to one side of the load then just connect the neutral side of the load to a rod, and this load exceeds 4.8 amps, the rod is at 25 ohms, what would be the voltage on this rod to remote earth, lets just say 3' away from the rod, the math is simple, lets say you have a load of 10 amps, 10 amps x 25 ohms is 250 volts that would drop across this rod, this means that the full 120 volts would drop across the rod, at the 3' shell around the rod you would drop 75% of this voltage which is 90 volts, so a person knelling at 3' feet away from this rod would receive a 90 volt shock if they were to touch this rod, now lets even lower the load to just 2 amps, 2 x 10 is 20 volts, 90% of 20 volts is 18 volts, so even at 2 amps this rod can not lower the voltage enough to protect a person immersed in water, now think about how much current on the service neutral that it would have to be that could cause a 3 volt drop across the neutral, 40, 50 amps?? do you think that this little ground rod can have an effect on that 3 volts? I hope you would think not.

Remember this at 25' away from this rod you will drop the total voltage that is on this rod, that means if this rod is placed 25' away from where a person could contact this chair and earth or the concrete pad or pool shell that is at the potential of earth, and there was 120 volts on the chair you would have a voltage of 120 volts to any earth reference point, so this is why we are to try to bond everything together so even if this happens that everything you can touch is at this same 120 volts potential and there would be 0 volts between these parts and no current can flow through a persons body, and there would be no shock potential, again just like a bird sitting up there on that primary wire at 7200 volts, and he never feels anything.

So this is the reason there is no need to try to run the EPB conductor back to the panel, it would serve no purpose and not make anything any more safe, the EGC that is run with the branch circuit from the service to any load by the pool is all that is needed to cause the breaker and or the GFCI to trip if a fault was to occur in the load, the only way to over come what some call stray voltage such as the bad or under sized neutral problem is to install a EPB conductor to all accessible electrically conductive parts around the pool that a person could come into contact with while immersed in water, and being that this chair lowers a person into the water, it would be extremely important that the chair concrete pad/deck and pool shell are all bonded together so that there is no possible way a person to touch between two points that would have a voltage difference.

I know some will say that this is an existing install and it can remain as is, even if your inspector also agrees with this, to me the liability side of it, will make me do it the safe way just because I would not want to ever live with the thought I had a chance to make something safe but didn't and a child was killed or anyone for that matter, this is what rules the way I approach jobs like this, yes it has been there for years, but it only takes loosing the service neutral one time while a swimmer is in the water to cause the hazard the EPB system is needed, so this is not an IF, it is a when will it happen?

 

[hurk27]

on that cartoon
the pump, niche light etc are all grounded to the panel
to the gec
and then they are bonded to the pool grid
which is indeed stand alone.

but because of the parallel paths to the gec from all the connected eq
the grid is, ultimately , conected to the center tap on the xfmr

the rod is just a rod

Hopefully if you read and studied my previous post, you should now understand that the EGC's run with the supply circuit to loads by a pool only serve to trip the circuit breaker,
A GFCI doesn't even need the EGC to function as just a little current taking another path will cause it to trip, the EGC's have no function in the EPB (Equal Potential Bonding) system of a pool.

The EGC's and the EPB conductors are for two very different purposes that only have one thing in common, that is to eliminate any shock hazard around a pool, actually those EGC's actually cause the reason why we need the EPB because they bring out the reference to the service grounding to the pool area that causes the stray voltage to be on the equipment around the pool, so it is this reason there is no requirement for the EPB conductor to return all the way to the service, again it does not serve a function to do so in the protection scheme of a pool.

And no, even with all the equipment that is bonded to the EPB conductors the EGC's the EPB conductor is not always referenced to the transformer's X0, this is because any voltage drop or bad connection in the service neutral will put this voltage on all that is connected to the service grounding including the EPB system of the pool via the EGC's run to each electrical load at the pool, remember we must also include the primary side of the transformer neutral as also a source of voltage being brought to the pool through the EGC's.

This is the reason why I said the EGC's bring the problem to the pool that we need the EPB system for.

 

[hurk27]

A small tibit, is I totally disagree with the requirement in 680.26(B)(6) exception (a) and (b) where a double insulated pool pump that requires no EGC connected to it, yes we should still run an EGC and yes we still need to run an EPB conductor to it for the possible of a replacement pump requiring it, but if it is the only connection to any EGC back to the service, this requirement to just connect the EGC to the EPB conductor should not have been required, as like I said this is the sole source of the stray current to a pool and it would be safer to not have this connection. in (b) for the heater it allows this if the manufacture require that the EGC and EPB conductor to be kept separate?

 

[wyreman]

Thanks for your long and excellent reply.

Introduction of open neutral voltage was something I hadn't really thought of. Thank you

Also the idea of voltage drop on the EGC back to the panel


I Have at least two practical questions that remain: one is that the concrete guy can't find any rebar nearby at all

So where do I run my bonding wire to grab the grid if not at the panel. Do I time to just keep ripping up the deck until he find some metal

two is that I still don't quite understand where the voltage differential comes from at the chair since this is not an electric motor on there
That's the part I'm having a hard time explaining to the concrete guy is where does the shock come from


The source would be the niche light in the pool not tripping the breaker or the GFI and when they chair lowers the guy down he forms a better return Path then all the other really strong paths.
And also the other problem is that the old chair didn't have any Bonnie Wire on it but that's another question


In belief, man can do anything

 

[ritelec]

Thank you Hurk27

And also the other problem is that the old chair didn't have any Bonnie Wire on it but that's another question

what is Bonnie Wire.................... I only get this on a search ???

 

[wyreman]

:happyno:
watch out you don't get banned for that!

It was a Siri spelling thing on my iphone
"bonding wire" was spelled "Bonnie wire"

 

[kwired]

Thanks for your long and excellent reply.

Introduction of open neutral voltage was something I hadn't really thought of. Thank you

Also the idea of voltage drop on the EGC back to the panel


I Have at least two practical questions that remain: one is that the concrete guy can't find any rebar nearby at all

So where do I run my bonding wire to grab the grid if not at the panel. Do I time to just keep ripping up the deck until he find some metal

two is that I still don't quite understand where the voltage differential comes from at the chair since this is not an electric motor on there
That's the part I'm having a hard time explaining to the concrete guy is where does the shock come from


The source would be the niche light in the pool not tripping the breaker or the GFI and when they chair lowers the guy down he forms a better return Path then all the other really strong paths.
And also the other problem is that the old chair didn't have any Bonnie Wire on it but that's another question


In belief, man can do anything

If you have removed a fair amount of concrete and haven't found any reinforcement to bond to, there likely was never any effective equipotential bonding installed in the first place. I would definitely be contacting the AHJ to determine how to proceed, if anything just to help cover yourself should there ever be an issue involving this installation. Owner is likely not going to like this but you have to protect yourself as well. If you just put it in like it was before, I promise you if someone is electrocuted and they find out you were even partially responsible for that installation you will be a part of any following lawsuit, and will need to provide a good defense for your installation method, the fact the owner didn't want to spend the $$ to do it right probably is not going to work either.

Driving a ground rod is not prohibited, but it still must be bonded to the equipotential bonding system in the vicinity, which makes it somewhat pointless to drive a ground rod in almost all cases.

As far as where does the voltage come from? you are not looking at this from the right perspective.

We bond all metallic items together whether they are electric items or not. This puts everything at the same potential. The pool and it's grounding network could be floating at thousands of volts above ground and users feel nothing because everything is at the same potential, just like a bird sitting on a high voltage line is isolated from other touch potential and feels nothing. Now if you put in one item, even a non powered item like a ladder or diving platform, that is not bonded to the rest of the system, you have a hole in that system and can have touch potential in the vicinity of that item. It is not that that item is "hot" but rather that item is at or closer to "true ground" then the rest of the bonding grid that is operating at a voltage above ground.

 

[wyreman]

:happyno:
watch out you don't get banned for that!

It was a Siri spelling thing on my iphone
"bonding wire" was spelled "Bonnie wire"

And that brings up another point which is that the bonding wire is not accessible or inspectable on any of this equipment.
All the bonding terminals end up being in the pour.
There is no strap on the dive board that you can see, neither the ladder or any other chair.

There have been quarterly inspections here, I found out, but the inspector has no way to determine if there is a bond strapped under the pour.
On the new work, the IOR would have signed off on the ground for the built in dive board etc


The issue I still have difficulty explaining is where the water actuated chair lift can bridge two potentials.
There's no power wire anywhere near the chair lift.
The only gradient I can see so far is the "rod" of the bolts in the concrete deck holding the chair lift in place
offers a lower impedance path back to the source than the path back thru the bonding grid.

This path being for a current leakage in the pool - which is available from the niche light, pump etc

 

[wyreman]

I would definitely be contacting the AHJ to determine how to proceed, if anything just to help cover yourself should there ever be an issue involving this installation. Owner is likely not going to like this but you have to protect yourself as well.

That was the other point.
This is a State job and my boss was the "AHJ"
The only inspectors we ever see are Project Managers on any new work.
Authority is the Division of the State Architect
The old work has always depended on us electricians to review the work and make recommendations to our Supervisors.

This swim pool is a thirty year old install.
Bonding is in the pour.

Issue comes up now because the pool is finally coming into compliance with newer ADA regs.

 

[kwired]

That was the other point.
This is a State job and my boss was the "AHJ"
The only inspectors we ever see are Project Managers on any new work.
Authority is the Division of the State Architect
The old work has always depended on us electricians to review the work and make recommendations to our Supervisors.

This swim pool is a thirty year old install.
Bonding is in the pour.

Issue comes up now because the pool is finally coming into compliance with newer ADA regs.

If you are an employee you may be somewhat less liable than if you were a contractor. If I were in your shoes I would still give the boss, and or the State ARchitect my feelings, concerns, and remind them of what the codes do say. As a contractor I would demand documentation for my records stating they approved it. May not keep me out of any potential lawsuits, but is still something to help defend my actions.

Did you catch the last part I edited into the last post about why voltage may be there and why it needs bonded?

In swimming pools we are not trying to make fault clearing paths with all the bonding - though that is a positive side effect, we are trying to ensure all items within a user's reach are not going to have any potential between them, and it doesn't matter if these items are electric power supplied items or not. By not having those items all bonded simple voltage drop on POCO distribution neutral conductors can be the cause of voltages in a pool, - you would have touch potentials equal to that voltage drop between the bonded items - as they are bonded to the equipment grounding conductor(s) which are bonded to the service grounded conductor, which is bonded to the primary grounded neutral back at the transformer - and other earthed items that do not have a low impedance bond to the EGC or other parts of that network.