Another Pool Question

[Davis Electrical]

Since I haven't done this in awhile, correct me if I'm wrong (and thus reeducate me): A pool subpanel requires a four wire install and a ground rod. Or two. ?

 

[GerryB]

Since I haven't done this in awhile, correct me if I'm wrong (and thus reeducate me): A pool subpanel requires a four wire install and a ground rod. Or two. ?

The pool I did last year I needed two rods.

 

[augie47]

No concrete answer,
680.25 provides the details on a feeder to a pool panel. If you are supplying 240/120 it would be 4 wire as an equipment grounding conductor is required for the feeder.
As far as the ground rod, a pool panel installed in/on the same structure as the service would not require a ground rod (or any grounding other than required by 680.25) If the pool panel is on or in itself a separate structure the 250.30 would require a grounding electrode system at the separate structure.
There is no ground rod requirement associated with a pool install as far as the pool is concerned..

 

[Davis Electrical]

No concrete answer,
680.25 provides the details on a feeder to a pool panel. If you are supplying 240/120 it would be 4 wire as an equipment grounding conductor is required for the feeder.
As far as the ground rod, a pool panel installed in/on the same structure as the service would not require a ground rod (or any grounding other than required by 680.25) If the pool panel is on or in itself a separate structure the 250.30 would require a grounding electrode system at the separate structure.
There is no ground rod requirement associated with a pool install as far as the pool is concerned..

Thanks very much. But, you know, an inground pool is, in fact, a separate structure. "Contrariwise..., if it isn't, it ain't; that's logic." And I understand that but, in this case it IS.

Crazy question but are you sure this whole equipotential thing makes any sense at all? They're essentially saying DON'T drive a ground rod here. But make sure you drive one over there because that other separate structure (like a garage for instance) is made out of concrete and wood and, etc. (?) I don't really need an explanation of gradients; I just need to know if this makes any realistic practical sense.

 

[kwired]

Thanks very much. But, you know, an inground pool is, in fact, a separate structure. "Contrariwise..., if it isn't, it ain't; that's logic." And I understand that but, in this case it IS.

Crazy question but are you sure this whole equipotential thing makes any sense at all? They're essentially saying DON'T drive a ground rod here. But make sure you drive one over there because that other separate structure (like a garage for instance) is made out of concrete and wood and, etc. (?) I don't really need an explanation of gradients; I just need to know if this makes any realistic practical sense.

Whether or not a ground rod is necessary has nothing to do with the presence of a pool. A rod may not even be needed even in a separate building or structure either. What is required at separate structures is a grounding electrode system. If no natural electrodes are present you can use a made electrode and a ground rod is usually the electrode of choice as it is usually the simplest and least expensive made electrode to install.


A ground rod(or any other grounding electrode) and an equipotential bonding system are not installed for same purposes. If you don't know what those different purposes are then your not wanting an explanation of gradients... well lets just say with ground rods you will have gradients that subject the user to potential shock hazard - unless you install many many ground rods and essentially use then as rebar in the pool construction.

A pool needs the equipotential bonding system because even with a very good grounding electrode system there is still a risk of shock potential between items in and around the pool, the equipotential bonding brings all those items to same voltage level. We sort of don't even care if this system is truly grounded, all we care about is there being no voltage between two objects that a user can reach at same time, or a voltage gradient building up in the water around some conductive object that is not bonded to the system.

 

[augie47]

Thanks very much. But, you know, an inground pool is, in fact, a separate structure. "Contrariwise..., if it isn't, it ain't; that's logic." And I understand that but, in this case it IS.

Crazy question but are you sure this whole equipotential thing makes any sense at all? They're essentially saying DON'T drive a ground rod here. But make sure you drive one over there because that other separate structure (like a garage for instance) is made out of concrete and wood and, etc. (?) I don't really need an explanation of gradients; I just need to know if this makes any realistic practical sense.

You are dealing with the NEC and you want "realistic practical sense" ?
kwired summed it up nicely, with the pool equipotettial bond you are working toward an entirely different goal than with a ground rod.
There is a bit of irony in that a pool would definitely be a separate structure but on the other hand you may well be installing only one circuit to the pool itself (light) and the Code does not require a GE at a structure supplied by a single circuit.
I once had a pool with multiple ground rods and the next week I happened to be at a IAEI seminar where a member of CMP 17 was present and his reply as to why they should not be there was "[FONT=&quot]That makes the Equipotential Bonding Grid a Grounding Electrode and therefore much more subject to High voltage incidents"[/FONT] Beyond my pay grade to understand

 

[Dennis Alwon]

Since I haven't done this in awhile, correct me if I'm wrong (and thus reeducate me): A pool subpanel requires a four wire install and a ground rod. Or two. ?

Is the pool panel attached to the house or is the panel on a separate structure? Big difference.

 

[iwire]

you know, an inground pool is, in fact, a separate structure. "Contrariwise..., if it isn't, it ain't; that's logic." And I understand that but, in this case it IS.

The pool is without a doubt at all, a structure. But you do not mount the panel to it, and you do not supply this structure with power other than perhaps one circuit for lighting. One circuit to a structure does not require a grounding electrode system.

Crazy question but are you sure this whole equipotential thing makes any sense at all? They're essentially saying DON'T drive a ground rod here. But make sure you drive one over there because that other separate structure (like a garage for instance) is made out of concrete and wood and, etc. (?) I don't really need an explanation of gradients; I just need to know if this makes any realistic practical sense.

Does it matter if it makes sense to you or is it more important to comply?

In one breath you say you don't want to hear about gradients and in the next breath you want an explanation for all this bonding and grounding. Without talking about gradients it cannot be explained.

 

[Davis Electrical]

Is it fair to say that NEC use of the term structure is in effort to correspond to, and align with, building codes? And we all know why they use the term structure, right?


Be that as it may, I fail to see any significant difference between the subpanel that supplies a swimming pool and the subpanel that supplies, say, a residential garage. They are both structures distantly located that require power. So why a ground rod at one location and not the other? Wouldn't it be fair to say, here, that "truth" (or theory) requires consistency?


You're asking me if it is more important that I be right or more important that I conform and to me the answer is very obvious. We've been screwing up pool installations now for at least 40 years. I know; I was there. The primary issue is safety; do you mean to tell me that with all of our advanced technology there isn't a better way to ensure bathers are not lit up? The equipotential grid really doesn't make any sense if we fail to go that one, last extra mile. And simply providing a metallic gradient-free zone for what reason, stray voltages? does not make sense.

 

[Dennis Alwon]

The use of the ground rod is not necessary to a sub panel connected on the building. The idea is that the initial install of the grounding electrode conductor should protect from surges etc. When a panel is remotely located the surge at that location will not be protected by the service grounding electrode conductor. That is my guess as to why we need a grounding electrode at the remote panel.

The grounding electrode is not there to protect people in the pool.

 

[Davis Electrical]

The use of the ground rod is not necessary to a sub panel connected on the building. The idea is that the initial install of the grounding electrode conductor should protect from surges etc. When a panel is remotely located the surge at that location will not be protected by the service grounding electrode conductor. That is my guess as to why we need a grounding electrode at the remote panel.

The grounding electrode is not there to protect people in the pool.

Well again we are not being consistent here. If it is required at a remote structure to place all bonded at earth potential, then it is required at a pool subpanel which is also a remote structure. I don't believe the code makes this exception. Again, though, it becomes a question of when do things make sense. Does it make sense to make an exception for parking lot lighting? No. But at least this one is specified with the words single branch ckt. Again I would have to question if any of this seperate "equipotential" stuff makes sense.

 

[iwire]

Is it fair to say that NEC use of the term structure is in effort to correspond to, and align with, building codes? And we all know why they use the term structure, right?

For sure, we are in complete agreement with that and I agree with you that a pool is a structure. But again the panel is not mounted to, or in that structure. It does not even supply power to that structure unless there are pool lights. The pumps and such are not part of the pool structure.

Be that as it may, I fail to see any significant difference between the subpanel that supplies a swimming pool and the subpanel that supplies, say, a residential garage. They are both structures distantly located that require power. So why a ground rod at one location and not the other? Wouldn't it be fair to say, here, that "truth" (or theory) requires consistency?

The panel in or on a detached garage supplies power to that structure and requires a grounding electrode system.

The panel supplying power to pool equipment is not supplying power too, or mounted to the pool structure. However if that pool panel is mounted to say a detached pool cabana that panel will require a grounding electrode system.

In my opinion it is consistent.

You're asking me if it is more important that I be right or more important that I conform and to me the answer is very obvious. We've been screwing up pool installations now for at least 40 years. I know; I was there. The primary issue is safety; do you mean to tell me that with all of our advanced technology there isn't a better way to ensure bathers are not lit up? The equipotential grid really doesn't make any sense if we fail to go that one, last extra mile. And simply providing a metallic gradient-free zone for what reason, stray voltages? does not make sense.

The real answer to stray voltages would be the elimination of the current North American distribution system that uses a circuit conductor for grounding. But that is not going to happen any time soon if at all.

The equipotential grid and bonding makes great sense and is pretty much how substations are set up.

 

[iwire]

If it is required at a remote structure to place all bonded at earth potential, then it is required at a pool subpanel which is also a remote structure.

The electrode is required at the building or struture it is mounted to.

So if the pool subpanel is mounted to a remote structure that remote structure.

On the other hand if a new pool subpanel is mounted to the building it supplied from no additional electrodes are required.

It is consistent.

I don't believe the code makes this exception. Again, though, it becomes a question of when do things make sense. Does it make sense to make an exception for parking lot lighting? No. But at least this one is specified with the words single branch ckt.

A better question is what does any grounding electrode in any location really do for us installing systems under 600 volts to ground. The more you look into it the less it seems to do.

Again I would have to question if any of this separate "equipotential" stuff makes sense.

Electrodes have nothing to so with equal potential bonding around a pool. Equal potential bonding is really another topic entirely but at least it relies wire conductors instead of dirt.

 

[kwired]

Is it fair to say that NEC use of the term structure is in effort to correspond to, and align with, building codes? And we all know why they use the term structure, right?

NEC use of the term structure is not necessarily all that clear, it is something that seems to be questioned a lot. "Structure" may be relatively clear, but "separate structure" is not always all that clear. You may have two items that individually qualify as a structure, but if they are somehow connected to one another they may or may not be considered "separate structures"

What is your opinion of a swimming pool on the roof of a high rise hotel? Separate structure or part of the high rise building? Now put same pool on grade level either in the high rise foot print or as an addition just outside of the high rise foot print - but in close proximity, maybe even with a roof over it that is connected to the high rise structure so you never go outside to gain access between the pool and high rise - same question - separate structure or part of the high rise building?

How about a small public community pool. You typically have a building with restrooms/showers/ etc., an area for management operations, maybe or maybe doesn't include sales of snacks, beverages, etc. and often also this building housed filter pumps, heaters, and other equipment directly associated with the pool. About all that is at the pool for electrical equipment is in pool under water lighting, and more remote but still close to pool may be area lighting for night use and or security. That is for a small fairly basic pool. Go to a "water park" and you may find panels scattered all over the place as some amusement type items associated with the pool maybe need additional pumps or other equipment. Those will usually be treated as separate structures and have a grounding electrode - but if associated with a common pool with other areas will still be bonded to the equipotential bonding system of the common pool. Now it is possible(actually very likely) there is concrete encased electrode naturally occurring as part of the equipotential bonding system and a made electrode such as a ground rod is not necessary just because the CEE is present Go back to art 250 and the grounding electrode system requirements.

Be that as it may, I fail to see any significant difference between the subpanel that supplies a swimming pool and the subpanel that supplies, say, a residential garage. They are both structures distantly located that require power. So why a ground rod at one location and not the other? Wouldn't it be fair to say, here, that "truth" (or theory) requires consistency?

Like I mentioned just above - a "ground rod" may not be needed at the separate structure whether it is a garage or a pool. A concrete encased electrode would be required to be used as a grounding electrode at the separate structure if it exists. If a CEE is used a ground rod would not be required - typically the CEE will have much lower resistance than a rod will ever have is main reason why.

You're asking me if it is more important that I be right or more important that I conform and to me the answer is very obvious. We've been screwing up pool installations now for at least 40 years. I know; I was there. The primary issue is safety; do you mean to tell me that with all of our advanced technology there isn't a better way to ensure bathers are not lit up? The equipotential grid really doesn't make any sense if we fail to go that one, last extra mile. And simply providing a metallic gradient-free zone for what reason, stray voltages? does not make sense.

This is where you need to understand the different purpose served by the grounding electrode and the equipotential bonding system. They are not installed for the same reasons and have different properties they bring to the installation. The two are bonded to one another or possibly one is a part of the other, but you have two different concerns with each application.

The grounding elecrode system is there to have a place to bleed transients to - particularly lightning related transients. A couple rods may do a sufficient enough job of this, but all the concrete and steel around a typical pool is likely an even better electrode and probably a good design to include as one even if the pool is semi - remote structure of the equipment room/area.

The equipotential bonding is much more important to direct safety of pool users, even in a pool with no electrical equipment associated with it. Any conductive connection between that pool and any nearby grounded conductor of any electrical system brings potential voltages to the pool. That conductor can bring voltage that occurs across a bad neutral connection miles away in a power company distribution system to your pool. The voltage is between that conductor and true earth(ground) By bonding all conductive objects together even if they are not electrical powered items - ladders, diving platforms, lifeguard station platforms, supports for slides or other objects, you make them all the same potential. They could all be operating at thousands of volts above true ground but are all zero potential to one another and the users that come between them, just like birds on a high voltage line are not able to touch anything of differing potential and are safe sitting there.

 

[Davis Electrical]

The use of the ground rod is not necessary to a sub panel connected on the building. The idea is that the initial install of the grounding electrode conductor should protect from surges etc. When a panel is remotely located the surge at that location will not be protected by the service grounding electrode conductor. That is my guess as to why we need a grounding electrode at the remote panel.

The grounding electrode is not there to protect people in the pool.

I think you're missing the point: both the pool and the separate building are structures. If it is necessary at one, then it is necessary at the other.

 

[augie47]

I think you're missing the point: both the pool and the separate building are structures. If it is necessary at one, then it is necessary at the other.

Thought it was clarified earlier. 250.32 requires a grounding electrode for the panel at a separate structure (it does not require one for a single or multiwire branch circuit).
If you pool structure includes a panel then a GE is necessary. If you circuits come from an existing structure or your panel is mounted to an existing structure you do or need a GE.
Same principal if you build a detached garage and feed it with one branch circuit... no grounding electrode.. if you build a pool it may have a light that needs a circuit.... no grounding electrode...
Equipotential bond = a whole different issue not related to grounding electrodes.

 

[Dennis Alwon]

So you have a pool that is a structure and perhaps there is a light in it-- so what. The code allows me to install a single circuit to a pool without a grounding electrode conductor. If the pool panel is on a separate building then yes it would need a grounding electrode conductor to rods etc but if it is basically a sub panel on the structure it is fed from then it does not need a grounding electrode conductor. Do you install a grounding electrode conductor to every sub panel in a dwelling? No....

I don't think you are listening to what everyone is telling you. You wanted advice or info and we are doing our best to tell you that you are incorrect in your assessment but you don't seem to believe it. That is fine -- I want to know how you are going to get a grounding electrode conductor at the pool. Not the panel but the pool since that is a structure and you seem to think all structure need a grounding electrode conductor. So how would you do that?

 

[david]

I never gave much thought to a pool needing a grounding electrode.

Are you guys saying a pool with a circuit to a chair lift as required by the ADA and a couple of lighting circuits would need a grounding electrode?

And in that case it would not be a good design to run a circuits directly out to the chair lift. I would need a pool deck box to bring my circuits (lighting & lift) to or some other means of providing a connection of the grounding electrode conductor to my equipment grounds?

 

[david]

I don?t think you guys should bash him and keep saying it is one circuit.
I have inspected lots of pools with more than one lighting circuit. Not because of the load but because of the design. I also see a lot of chair lifts being installed at pools.
Moving away from it being one circuit or one multi wire circuit, If there are more than one circuit supplying the pool does it need a grounding electrode?

 

[david]

Like many here I struggle with applying the definition of structure to everything. I am not debating taking that approach base on the definition given for structure.

When a swimming pool is separated from the structure the pool panel is mounted to, is he incorrect for rising the issue? I am going to leave this to you guys, I really struggle with this and I do not have it settled in my mind.
maybe something needs to be added like with mobile homes or in site of or X amount of feet from