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  #1   IP: 65.31.88.231
Old June 6th, 2003, 08:55 AM
syburr syburr is offline
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Posts: 16
Default HELP... Pool Bonding Grid System for Above Ground Pool.

Hi,

I just got off the phone with the local building inspector. I asked him to explain to me what he thought the NEC wanted in a pool bonding grid system for an above ground pool.

He explained to me that the NEC wants a #8 awg solid copper conductor connected to the pool wall, then to the grounding (bonding) lug on the pool pump, then to connect this conductor to the service panel ground or neutral. Is this what the NEC intended?

Can you clear this up for me?

Thanks.
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  #2   IP: 130.76.96.19
Old June 6th, 2003, 11:15 AM
Anonymous Anonymous is offline
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Well there's intent and there's what it says....

First question -- is your pump double insulated? If no, then bond the pool structure (and any other significant metal near the pool) together and attach to pump bonding lug. You do not have to connect the bonding wire to your panel ground bus (per NEC FPN in 680.26.A), and WG would say the intent is do NOT connect it to your panel. Your pump grounding conductor, however, must go back to your panel grounding bus.

If the pump is double insulated, then you must leave a stub of bonding wire near the pump (in case it gets replaced by a non double insulated variant). The NEC also says in this case that the bonding wire must be connected to your pump equipment grounding wire (unless connected elsewhere to the grounding system).

NEC 680.26.4: "Where a double-insulated water-pump motor is installed under the provisions of this rule, a solid 8 AWG copper conductor that is of sufficient length to make a bonding connection to a replacement motor shall be extended from the bonding grid to an accessible point in the motor vicinity. Where there is no connection between the swimming pool bonding grid and the equipment grounding system for the premises, this bonding conductor shall be connected to the equipment grounding conductor of the motor circuit."
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  #3   IP: 65.31.88.231
Old June 6th, 2003, 12:32 PM
syburr syburr is offline
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Join Date: Jan 2003
Posts: 16
Default Confused...

My pump has a grounding lug so my bonding grid wire ends there?

You said "If the pump is double insulated, then you must leave a stub of bonding wire near the pump (in case it gets replaced by a non double insulated variant). The NEC also says in this case that the bonding wire must be connected to your pump equipment grounding wire (unless connected elsewhere to the grounding system). "

So if I have a double insulated pump my bonding grid connects to the green wire serving as the ground for my pump circuit?

How do I get the green wire out of the junction box and still have a weather proof junction box?

Thanks
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  #4   IP: 65.31.88.231
Old June 6th, 2003, 03:42 PM
syburr syburr is offline
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Join Date: Jan 2003
Posts: 16
Default The more I research the more confused I get.

I found this on another site. I don't know if the pool bonding grid system should or should not be connected to the service panel ground.


Posted by fmignella (Member # 3302) on April 24, 2003 07:17 AM :

Article 680-22 of the NEC states " It shall not be the intent of this section to require that the number 8 solid copper bonding conductor be extended or attached to any remote panel board, service equipment or grounding electrode, but only that it shall be employed to eliminated voltage gradients in the pool area".

I was under the impression that the bond wire should start at the panel board and end near the filter? Is this not true? If so, I assume that the bonding wire just has to encircle the pool area and connect to metal ladder pockets, diving board jigs and the frame work of the pool then end at the pump.

[ April 24, 2003, 07:19 AM: Message edited by: fmignella ]

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Posted by russ (Member # 253) on April 24, 2003 07:34 AM :

Write! the bond is to tie everything associated with the pool together including the motor frame.

It is not the same as an equipment ground, which is associated with the electrical supply circuit, but in most cases will end up bonded to the equipment ground through common contact with the motor frame and other items.

That way everything is at the same potential.
If there were to be a voltage induced, there is less a chance that a person would be come a conductor if everthing is at the same potential.

Russ

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Posted by fmignella (Member # 3302) on April 24, 2003 07:54 AM :

Thanks for the information Russ. I was just looking through the NEC handbook at article 680-22 and saw the same thing. The diagram in the hand book looks like you can use the walls of a vinyl lined pool (in ground) as a conductor by just bonding at one point to the metal frame, then from the frame work bonding to the ladders etc.

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Posted by spyder (Member # 1989) on April 26, 2003 03:34 PM :

The pool bond should not tie into the panelboard. During a fault condition (say another circuit not associated with the pool) it could actually cause the pool bonding grid to become energized!!

Only the pool and associated equipment, such as pumps, blowers, heaters, lights, ladders, diving boards should be bonded.

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Posted by iwire (Member # 47) on April 26, 2003 05:09 PM :


quote:
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Originally posted by spyder:
The pool bond should not tie into the panelboard. During a fault condition (say another circuit not associated with the pool) it could actually cause the pool bonding grid to become energized!!
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How would this be different from the equipment grounding conductor that comes out with the feeds, tying the panel ground into the bonding wire?

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Posted by bennie (Member # 800) on April 26, 2003 05:17 PM :

Bob: You got it. The pool conductive objects are directly connected to the neutral at the panel which is connected to the MGN of the distribution system.

Consider this... The active high voltage conductor, at the transformer, breaks loose from the bushing and falls on the neutral. The neutral burns clear back to its source. The pool metal is now at primary voltage.

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Posted by iwire (Member # 47) on April 26, 2003 06:22 PM :

Thanks, Bennie

I got it I just do not know what to do with it.

Could we prevent what you described by feeding the pool circuits with an isolation transformer, have no ground conductors between panel and pool and use GFCIs to clear faults?

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Posted by bennie (Member # 800) on April 26, 2003 07:16 PM :

Bob: The connection of the bonding conductor to the equipment ground of the pump motor, is a loop circuit.

The rebar becomes a big "stray voltage sucker"

Double insulated pump motors, with no bond to the pool equipment and no equipment ground conductor, will break the closed loop.

[ April 26, 2003, 07:17 PM: Message edited by: bennie ]

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Posted by don_resqcapt19 (Member # 4) on April 26, 2003 08:47 PM :


quote:
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680.26(B)(4) Where a double-insulated water-pump motor is installed under the provisions of this rule, a solid 8 AWG copper conductor that is of sufficient length to make a bonding connection to a replacement motor shall be extended from the bonding grid to an accessible point in the motor vicinity. Where there is no connection between the swimming pool bonding grid and the equipment grounding system for the premises, this bonding conductor shall be connected to the equipment grounding conductor of the motor circuit.
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Even with a double insulated motor, the code requires a connection to the service grounding system. I'm not sure why this is needed, but it was added in the 2002 code.
Don

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Posted by bennie (Member # 800) on April 26, 2003 09:00 PM :

That section is a contradiction of the FPN in 680.26(A). The #8 may not run to the service but it is electrically connected. This is a very dangerous situation.

Read: Stray Voltage.org for reasons.

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Posted by bennie (Member # 800) on April 26, 2003 09:08 PM :

Regrounding the equipment ground conductor is the same as regrounding the neutral. There will be some load current flow on the equipment ground conductor to the rebar and on to the transformer.

Transient current from other sources will flow on the rebar to the MGN of the utility.

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Posted by don_resqcapt19 (Member # 4) on April 27, 2003 11:53 AM :

Bennie,
The FPN to 680.26(A) does not say that the bonding shall not be connected to the EGC or other system grounding conductor, it just says that this section (680.26) does not require a connection to these items. Just because there is a current flow on the bonded items does not make an unsafe condition. As long as everything is bonded and the current flow does not create a large voltage drop across the bonded items there is no safety hazard. Even without a connection to the service grounding system, a fault on the primary system can produce current flow across the bonded items. The "stray voltage" problem exists between things that are bonded to the electrical system and the earth or things that are not bonded. The most common cure for the "stray voltage" problem on farms is making sure there is only one neutral to ground bond and that all conductive objects are bonded together and to the EGC. Yes, the additional connections to earth may actually increase the amount of current flowing on the grounding system, but the bonding produces an equal potential plane and eliminates the shock hazard.
Don

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Posted by don_resqcapt19 (Member # 4) on April 27, 2003 12:09 PM :

The substantiation for the change in 680.26(B)(4) was to prevent problems that may be caused by "stray voltage". If the pool bonding system is not connected to the electrical grounding system and someone, using a powered appliance with a 3 wire cord and metallic surfaces, comes in to the pool area, there would be a potential difference in voltage between the outer grounded surface of the appliance and the bonded surfaces of the pool equipment and deck.
Don

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Posted by bennie (Member # 800) on April 27, 2003 12:57 PM :

The NEC is hell bent on grounding everything, NEMA is hell bent on insulating everything.

I can't think of any electric appliance with a three wire cord. I have an electric lawn mower, it has a two wire cord. Double insulated motor.

You can get shocked touching a grounded surface, you won't be shocked if you don't touch it.

Common mode voltage is the problem on dairy farms.
This voltage is between the neutral and the earth.
Creating a path for current flow on the pool bonding system will produce common voltage between the pool and the non-current carrying equipment ground of an appliance. The tie of the pool grid to the neutral does not provide a equal potential, it only assures there is a difference in potential.

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Posted by don_resqcapt19 (Member # 4) on April 27, 2003 05:49 PM :

Bennie,

quote:
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Creating a path for current flow on the pool bonding system will produce common voltage between the pool and the non-current carrying equipment ground of an appliance.
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This is the very reason that bonding is required between the EGC and the pool bonding system.

quote:
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The tie of the pool grid to the neutral does not provide a equal potential, it only assures there is a difference in potential.
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The only possible difference in potential between bonded objects is that caused by the voltage drop between the two bonded objects. It would take a combination of high current on the bonding path and high resistance on this same path to create a hazardous voltage potential.
Don

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Posted by bennie (Member # 800) on April 27, 2003 06:47 PM :

Stray voltage from other sources will only appear on the pool equipment, not on the appliance enclosure. There will be a voltage difference.

This is what many call tingle voltage at a pool.

This voltage has been known to kill cows, according to some of the articles.

Leakage current in the human body must be less than 10 uA in medical diagnostic equipment.

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Posted by don_resqcapt19 (Member # 4) on April 27, 2003 10:44 PM :

Bennie,

quote:
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Stray voltage from other sources will only appear on the pool equipment, not on the appliance enclosure. There will be a voltage difference.
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This is not possible if the pool bonding system is bonded to the electrical grounding system. It is only possible when the connection between the two systems does not exist. The only voltage that can exist between two objects that are bonded is the voltage caused by the voltage drop in the bonding system between the two points of contact or measurement. The current involved in "stray voltage" is too small to create a hazardous voltage drop.

quote:
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This voltage has been known to kill cows, according to some of the articles.
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The most common correction for stray voltage on dairy farms is bonding all noncurrent carrying conductive items to the electrical grounding system. This is exactly what you would be doing when you tie the pool bonding grid to the electrical system grounding conductor.

quote:
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Leakage current in the human body must be less than 10 uA in medical diagnostic equipment.
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The key word is "in". This involves voltages applied to the body without the protection (resistance) of the skin. Very small voltages can be fatal when applied internally.
Don

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Posted by bennie (Member # 800) on April 27, 2003 11:28 PM :

Don: The frame of the appliance is not bonded to the pool metal. It is connected to the same ground point. A bond is a short circuit, a long conductor is an inductor with a voltage difference at each end.

The only way there would not be a potential difference is if the frame of the appliance is connected (shorted) to the pool grid near point of contact.

A bonding jumper will equalize potential between two points, an inductor will not.

This is why the words bonding and grounding should remain the same. They are two different procedures.

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Posted by bennie (Member # 800) on April 27, 2003 11:55 PM :

Measure the voltage difference between the neutral and ground at the appliance. This is common mode voltage.

Bond (short) the neutral to the equipment ground at the appliance, the common mode voltage will go away. Common mode current will then appear as a ground loop.

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Posted by don_resqcapt19 (Member # 4) on April 28, 2003 10:37 AM :

Bennie,

quote:
--------------------------------------------------------------------------------
Measure the voltage difference between the neutral and ground at the appliance. This is common mode voltage.
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The only voltage that you should read between the EGC and the grounded conductor is that caused by the voltage drop in the grounded conductor. The two condctors are connected together at a common point. One has currrent flow, the other doesn't. The voltage that appears can only be based on ohms law and the current and impedance of the grounded conductor.

quote:
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A bond is a short circuit, a long conductor is an inductor with a voltage difference at each end.
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Can you show me the math for this? Thanks.
Don

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Posted by bennie (Member # 800) on April 28, 2003 12:02 PM :

Don: I can't think of an appliance that will be used near the pool metal parts. So lets say the lady has her washing machine under the diving board

The washer draws 10 amps. The No.#12 run is 200 feet in length. Voltage drop is 12.6 volts.

This appears as 12.6 volts common mode voltage at the appliance.

Now consider the pool metal. This metal is connected to the earth and the MGN of the distribution system. Current will be flowing in this conductor. This current can be 180šout of sync with the appliance. The voltage difference can be elevated according to the amount of transient current in the pool system.

Now feature a flashover at the high voltage bushing on the distribution transformer. This arc will raise the voltage at the pool equipment more than at the neutral bus of the service.

I maintain the pool metal should not connect to the electrical system.

I am open to other opinions. This is only my perception.

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Posted by bennie (Member # 800) on April 28, 2003 12:12 PM :

Another point to consider when dealing with open circuit common mode voltage.

Medical diagnostic equipment sensors, placed on the patients skin, are coated with a solution that penetrates the skin to the low impedance parts inside the body.

Clorine and other chemicals in pool water tend to lower the skin resistance considerably. This makes a person more susceptable to detecting low voltage, when closing the common mode open circuit.

Dampness at dairy farms, is a contributing factor in the problem with cows getting zapped.

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Posted by don_resqcapt19 (Member # 4) on April 28, 2003 01:05 PM :

Bennie,
I would agree if you make contact between the grounded conductor near its load end and the pool bonding system that there will be voltage. I do not agree that there would normally be voltage between the pool bonding system and the EGC where the two systems are bonded.

quote:
--------------------------------------------------------------------------------
Now feature a flashover at the high voltage bushing on the distribution transformer. This arc will raise the voltage at the pool equipment more than at the neutral bus of the service.
--------------------------------------------------------------------------------

Why? If the pool bonding system is connected to the electrial grounding system, how can the voltage be greater on the pool equipment than on the grounded conductor?
Don

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Posted by bennie (Member # 800) on April 28, 2003 01:18 PM :

It all comes down to...There is no voltage difference across a bond conductor. There is a voltage difference across an (inductor) equipment ground conductor.

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Posted by don_resqcapt19 (Member # 4) on April 28, 2003 03:22 PM :

Bennie,

quote:
--------------------------------------------------------------------------------
There is a voltage difference across an (inductor) equipment ground conductor.
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I don't understand. Show me the math. At what length does a wire change from a short to an inductor? Doesn't the frequency play a big part in this? Is this really a problem at 60 hz?
Don

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Posted by bennie (Member # 800) on April 28, 2003 05:34 PM :

There was a fatal accident involving a child in a swimming pool. The victim was standing on the concrete bottom of the pool, and touched the metal ladder.

The cause of the lethal voltage was the next door underground service feeder faulting to the earth.

This voltage appeared on the bottom surface of the pool, the ladder was connected to the MGN of the utility.

Had the ladder only been bonded to the rebar, there would be a lot more impedance back to the transformer. The lethal voltage may not have appeared.

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Posted by don_resqcapt19 (Member # 4) on April 28, 2003 07:06 PM :

Bennie,
That tragic case sounds like a lack of bonding between the re-bar in the concrete and the ladder.
Don

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Posted by bennie (Member # 800) on April 28, 2003 07:15 PM :

Don: Rebar oxidizes (rust) this is an insulator. The rebar is insulated from the concrete. The voltage from the faulted line energized the concrete. Perfect conditions to kill someone.

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Posted by bennie (Member # 800) on April 28, 2003 07:31 PM :

Most in ground pools, with rebar, are finished with sprayed on gunite. This material has a fairly high resistance. There will always be a high impedance connection to the rebar.

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Posted by t-bird (Member # 1600) on April 30, 2003 12:59 PM :

I am working on a 30 year old pool which appears to not have been properly bonded when built, or repairs over the years have disrupted the bonding grid. There is not a # 8 solid copper wire connecting the pool moters to anything and the circulation pipes coming from the pool are plastic. I have explained to the customer that these moters (both 240v, not double insulated) have to be connected to the pool bonding grid (i.e. connecting a #8 solid copper wire to the rebar of the pool and then to the moters). In her search for a quicker cheaper solution others ( some electricians and pool people ) have told her that if an 8' ground rod is driven into the ground and attached to the moters then everything will be fine. I told her I wont do this as a solution. Does this suggestion do anything to make her situation safer at all? Thanks

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Posted by charlie (Member # 59) on April 30, 2003 02:29 PM :


quote:
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There was a fatal accident involving a child in a swimming pool. The victim was standing on the concrete bottom of the pool, and touched the metal ladder.
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Bennie, this was reported in the Nov/Dec 2002 edition of the IAEI News (unless I have the wrong incident). A lifeguard stand at a large community pool in the Kansas City area caused a near electrocution when a 12.47 kV line was contacted with a track hoe. 7.6 kV was conducted to earth which caused a voltage gradient and involved the pool. The gradient froze the lifeguard to the lifeguard stand since only one side was bonded to the pool's ground grid. The unbonded side picked up the gradient and passed the current through the lifeguard's body to the pool's ground grid. This incident also involved a worker that was in the hole the track hoe was excavating.

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Posted by bennie (Member # 800) on April 30, 2003 06:14 PM :

I can understand...the 7.6 KV was heading to the nearest MGN to get home. Anyone completing the circuit will have a bad day.

The pool rebar is a good Ufer ground electrode. It is connected to the neutral bus, of the service. It is not bonded (shorted) to the service ground electrode system. Physically it constitutes multi-grounding of the premises system.

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Posted by paul renshaw (Member # 399) on May 01, 2003 07:08 AM :

Hi Bennie, How is it not bonded to the service GES, if it is connected to the neutral bus of the service? Aren't they bonded together at the servce somewhere? If not shouldn't they be?

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Posted by bennie (Member # 800) on May 01, 2003 11:30 AM :

Hello pgr. This topic points out the difference in bonding and grounding. The neutral bus is a supply point not a bonding (shorting) point.

Feature two ground electrodes 100 feet apart. One is the water line, the other is a driven rod.
The water line will have low impedance compared to the rod. More current will flow in the conductor to the water line.

This difference in current, will produce a different potential from each one of the electrode conductors, to the earth. This difference is a common mode voltage producing a common mode current ground loop.

Now feature one run of #4, from the neutral bus, to the water line, then on to the rod. This is bonding. No common mode voltage, except for micro-volts between electrodes out side of building.

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Posted by Ed MacLaren (Member # 19) on May 01, 2003 12:58 PM :


quote:
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Feature two ground electrodes 100 feet apart. One is the water line, the other is a driven rod.
The water line will have low impedance compared to the rod. More current will flow in the conductor to the water line.

This difference in current, will produce a different potential from each one of the electrode conductors, to the earth. This difference is a common mode voltage producing a common mode current ground loop.
--------------------------------------------------------------------------------

I don't see what problem is caused by this? Could you explain it?

In this sketch, both conductors going to the grounding electrode system are connected at the same point on the grounded (neutral) conductor.



Ed

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Posted by bennie (Member # 800) on May 01, 2003 09:59 PM :

The neutral/ground bus is the connection point for the equipment ground wires, the neutral/ground conductor, and the ground electrode conductor.

The neutral bus is not a common bus for the other ground electrodes required to be bonded together to become one electrode.

The first 5 feet of water pipe is the bonding bus. This prevents common mode current flow within the premises.

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Posted by bennie (Member # 800) on May 01, 2003 10:06 PM :

For substantiating my statements refer to...250.24 (C), Grounding Electrode Conductor.

"A grounding electrode conductor" This is a singular statement, not plural, or more than one.

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Posted by don_resqcapt19 (Member # 4) on May 01, 2003 10:42 PM :

Bennie,
What about 250.64(F)?

quote:
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(F) To Electrode(s). A grounding electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system or to one or more grounding electrode(s) individually. The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.
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Posted by bennie (Member # 800) on May 01, 2003 10:48 PM :

Don: That section only validates my statements further. Carefully read each word.

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Posted by don_resqcapt19 (Member # 4) on May 01, 2003 11:01 PM :

Bennie,
250.64(F) makes it very clear that I am permited to run individual grounding electrode conductors from the main bonding jumper to each and every one of my grounding electrodes.
Don

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Posted by bennie (Member # 800) on May 02, 2003 12:27 AM :

Don: A grounded electrode conductor(singular) shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system...( key word electrode system)
or to one or more grounding electrodes individually.( this applys when the electrodes are not bonded and not an electrode system) The grounding electrode conductor(singular) shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it. (key word is "connected to it")when all electrodes are connected to it, it is an electrode system(one electrode).

I can not read this to mean more than one ground electrode conductor can be in a service panel.

The bonding for all electrodes is to be outside of the service enclosure.

The supplemental electrode is required to connect within the 5 foot area of the piping. Not connect back to the neutral bus.

[ May 02, 2003, 12:35 AM: Message edited by: bennie ]

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Posted by bennie (Member # 800) on May 02, 2003 12:40 AM :

To paraphrase the section..."Connected to ground electrodes individually"...means individual electrodes, not separate conductors to the electrodes.

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Posted by hurk27 (Member # 73) on May 02, 2003 03:12 AM :


quote:
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The supplemental electrode is required to connect within the 5 foot area of the piping. Not connect back to the neutral bus.

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In 250.53 (D) (2) It give us the places that we can connect the Supplemental Electrode to.


Supplemental Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(7). Where the supplemental electrode is a rod, pipe, or plate type, it shall comply with 250.56. The supplemental electrode shall be permitted to be bonded to the grounding electrode conductor, the grounded service-entrance conductor, the nonflexible grounded service raceway, or any grounded service enclosure .

Now with that out of the way.
I cant understand why there would be common mode voltage on the pool if the EGC from the pump circuit is connected to the pool bonding wire.
First there has to be a load (current) across a resistance (wire) To have a voltage on the pool bond the only wire that would affect this pool bond would be the neutral from the service to the transformer the voltage drop in this wire would appear on the grounding grid of the whole house as there is no current (at least shouldn't be) on the pool bonding or grounds after the main panel.
yes there will be what we call stray voltage on the grounds that come from the water line because of the parallel connection to another service down the road. but in a normal installation this would be kept to a minimum, yes there could be faults with the power lines I.E. loss of the primary neutral loss of the secondary neutral at ether this service or one down the road but these are not normal and the NEC don't address this. If there is one connection that I could change it would be the bond from the primary neutral to the secondary neutral this connection causes most of the stray voltage problem that we see if it were not there, there would be no common connection to cause the primary to try to draw current from the GE's on the secondary side of the circuits.
The other is the connection of the house water pipe to the main water line at the street. there would be a isolator coupling to prevent the parallel connection of two or more services on the same transformer.

but for the most part the voltages induced into the grounding system of a service is not high enough to cause a problem and in the cases of where an underground service lateral conductors Failed that caused shocks in a pool it was the fact that there probably was no kind of bonding at the bottom of the pool that would of prevented the voltage gradient from the ladder to the pool bottom. the other is these service lateral conductors ran under this pool if I remember right which should not ever been done.


quote:
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Feature two ground electrodes 100 feet apart. One is the water line, the other is a driven rod.
The water line will have low impedance compared to the rod. More current will flow in the conductor to the water line.

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This is true but why would there be any current on these EGC's?
Again this would not be somthing that would be there in a normal installation.
and the lower impedance rod would hold the voltage at a lower level to the earth potential.

The shocks that happen in and around pools are caused by bad instalations and loads on the grounding and grounding connected to the neutral buss after the main service and faulty appliances.
not code compliant installations.
the other side of the equasion is the POCO's could give us some better safegards to prevent the stray current from getting from the primary side of the transformer to the secondary side and the water co's could prevent the parralleling of the neutrals between two services by installing a isolating connection at the streat main.

Stray voltage can only be eliminated when there is a lower impedance path for the current back to the source of the stray voltage thus shorting it out. or a path around the area neening the protection.

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Posted by paul renshaw (Member # 399) on May 02, 2003 07:00 AM :

Bennie,you have a good memory(pgr)
Correct me if I am wrong, but if you establish an equipotential plane at the pool with everything bonded together, how would you be able to receive a shock? Isn't this just like the bird on the wire theory?

[ May 02, 2003, 12:44 PM: Message edited by: paul renshaw ]

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Posted by don_resqcapt19 (Member # 4) on May 02, 2003 08:13 AM :

Bennie,
We don't read words the same way, again! lol
I read 250.64(F) as saying that I can run a grounding electrode conductor (singular) to grounding electrodes (plural) or I can run a grounding electrode conductor (singular) to each of multiple grounding electrodes. Each grounding electrode would have its own grounding electrode conductor.
Don

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Posted by Ed MacLaren (Member # 19) on May 02, 2003 12:55 PM :

Bennie,
I am interested in learning more about your ideas of a "common mode current ground loop."

First, about this statement -

quote:
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The water line will have low impedance compared to the rod. More current will flow in the conductor to the water line.
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- Are you referring to normal (unbalanced load) current, (sketch below) or ground fault current that flows only during fault conditions.



Ed

[ May 02, 2003, 01:03 PM: Message edited by: Ed MacLaren ]

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Posted by bennie (Member # 800) on May 02, 2003 01:58 PM :

The wording was changed in 1999 for editorial clarification purposes, to make it clear that more than one ground electrode conductor could be run to the individual electrodes.

250.81 1996 Edition forbids more than one ground electrode conductor. The so called editorial change is wrong. It was submitted by one individual who apparently did not know the reason for only one conductor.

The editorial change also changed the technology.

The 5 foot rule was adopted in 1993. The ROP's do not mention the interior pipe issue. Later changes to include grounding a separately derived system at the 5 foot portion was rejected, due to the supplemental electrode was for the purpose to replace the water pipe ground. Changing the interior piping to plastic, was the substantiation for connecting the conductor at the 5 foot area.

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Posted by bennie (Member # 800) on May 02, 2003 02:02 PM :

Sorry Ed: Got carried away. I will start a new thread concerning ground loops and other garbage. There is some on this forum who are more informed than I.

Bennie
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  #5   IP: 130.76.32.20
Old June 6th, 2003, 03:57 PM
Anonymous Anonymous is offline
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Join Date: Sep 2002
Posts: 1,999
Default

Syburr asked: My pump has a grounding lug so my bonding grid wire ends there?

I reply: yes, and the pool frame is the other end.

Syburr asked: So if I have a double insulated pump my bonding grid connects to the green wire serving as the ground for my pump circuit?

I reply: Yes.

Syburr asked: How do I get the green wire out of the junction box and still have a weather proof junction box?

I reply: Are you asking about the pump receptacle juntion box or the box on the pump motor itself? The pump box may have a provision (the screw on the box cover). If not, is the pump receptacle conduit metal or the box housing metal? Can you put a clamp there or a screw lug into the box? Finally, do you have another knockout in the pump receptacle box? If so, use a water tight cable connector and run the #8 through that.
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  #6   IP: 148.78.243.121
Old June 6th, 2003, 07:27 PM
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Wgoodrich Wgoodrich is offline
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I can see this forum is not the only place LARGE discussions arise about bonding grid systems of pools. At least everyone seems to be searching for the right answer.

A couple of points I thought I would touch on and again these are my theories on the one question asked.

It was asked if a double insulated pump is origianally installed the NEC still requires that 8 awg copper to be ran to that vicinity to be able to connect to a non double insulated pump motor replacement if that happens. Then it was asked why the NEC changed requiring this 8 awg copper to connect to the equipment grounding conductor of the pool pump branch circuit during the installation of that double insulated pool pump.

It is my opinion that the committee had concern of double insulated pool pumps being replaced by non double insulated pool pumps and the 8 awg copper not being there to ensure equal potential as desired by the NEC. They then decided to have the 8 awg copper bonding grid wire installed on original installation so it would be available if that nondouble insulated pump motor replacement happened later in years. Then this created a concern of an 8 awg bonding grid wire if gradients of current exists would create a shock hazard if this 8 awg bonding grid wire for that nondouble insulated future replacement motor was just floating around near that pump not connected to anything.
Then I believe it was discussed the knowledge that with a nondouble insulated pool pump motor with the casing bonding grid lug also is creating an incidental connection through that motor to the branch circuiut equipment grounding conductor by incidential connection. If this is an accepted practice in the original rule then why not land that 8 awg loose end to that same branch circuit equipoment grounding conductor of the double insulated pool pump. This should be close to the same as the incidental grounding through the motor casing to the motor equipment grouding conductor of the pool pump branch circuit as the original rule was intended accepting this incidental connection between the grounidng system of the branch circuit and the bonding grid.

I suspect this was how it was put together solving their concern of the 8 awg copper wire floating loose in the vicinity of that double insulated pool pump motor. Please be aware I am second guessing the discussions that occurred in the result of the current NEC rule concerning the double insulated to non double insulated replacement motor concern. Hope this sheds some depth to the thoughts of that incidental connection and the new rule for replacement motors concerning that bonding grid wire in the vicinity of the double insulated pool pump motor. I know pools are confusing mostly because each Code version seems to be full of changes and the technical nature of the rules of Article 680.

The FPN note does depict the intent of no intentional connections between the bonding grid system and the structures electrical grounding system. It is known that there is incidental connections such as within the pool pump motor. While not desired it seems to be the only answer to allow this connection within this motor to ensure both the bonding grid system and the equipment grounding system can do it job of protecting life and limb. Some places have to give and in this case there is no good way to avoid this incidental connection within that pool pump motor and full fill the desires of both the equipment grounding systme and the bonding grid system. I suspect the came up with best scenerio they could come up with for both concerns involving that inside incidental connection within that pool pump motor.

Hope this helps

Wg
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Old June 6th, 2003, 07:45 PM
syburr syburr is offline
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Hi,

My pump is NOT double insulated and it has a bonding post. From what I gather from the Authority Having Jurisdiction he expects to see a bare #8 copper awg attached to the pool wall continuing to the bonding lug on the pump motor and continuing on to the service panel ground or neutral.

I have read many differing opinions on this regarding connecting the pool bonding grid system to the equipment grounding system.

Some say don't connect, some say connect. The AHJ says connect so I guess he has the final word.

So my plan is to run the #8 from the pool wall to the pump then to the trench and tape it to the pvc conduit then enter the dwelling near the pvc lb. Inside the dwelling I plan to tape this bare #8 conductor to the EMT and continue on to the service panel and connect this #8 conductor to the ground buss. Does this sound acceptable?

The thing I don't understand is why I couldn't just connect the #8 conductor for the pool bonding grid system to the pump equipment grounding conductor at the pool location. I don't see the benefit of running another conductor back to the service panel.

Thanks
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Old June 7th, 2003, 04:34 PM
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Wgoodrich Wgoodrich is offline
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Try printing out the following copied section of 680.26 of the 2002 NEC. Then show that printed copy to your AHJ suggesting that you have a concern about meeting the intent of the NEC rules after reading that copied section of the NEC. May be you have a local ordinance reversing or creating a revision of that NEC rule in your area only. May be you inspector is not aware of the wording of the NEC, Handbook commentary, or the Fire Protection Agency's note on the subject. If you show him or her this copied section and he or she still rules as the AHJ that you must connect to the electrical grounding system then you have right of appeal or judicial judgement on the AHJ ruling to overrule his or her AHJ ruling. The decision how strong you push what the NEC rule says is up to you, it is your home. Only you must decide. May be the AHJ is just not aware of that rule and intent. May resolve the issue when you show it to him or her. Sometimes that works sometimes it doesn't work. Approach in a questioning factual manner seeking knowledge do not approach in a knowit all manner or you will regret that type approach. Let us know how you come out and Good Luck.

COPED SECTION OF NEC 2002;
680.26 Bonding.
(A) Performance. The bonding required by this section shall be installed to eliminate voltage gradients in the pool area as prescribed.
COPIED SECTION OF NEC "FPN NOTE"
FPN:This section does not require that the 8 AWG or larger solid copper bonding conductor be extended or attached to any remote panelboard, service equipment, or any electrode.
COPIED SECTION OF NEC HAND BOOK COMMENTARY 2002;
The primary purpose of bonding is to ensure that voltage gradients in the pool area are eliminated. The fine print note explains that the 8 AWG conductor's only function is to eliminate the voltage gradient in the pool area. It is not required to provide a path for fault current that may occur as a result of electrical equipment failure. See Exhibit 680.10.

Good luck and wish you success.

Wg
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Old June 9th, 2003, 07:59 AM
syburr syburr is offline
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Hi,

Would it be a bad ideal to connect the #8 awg copper swimming pool bonding grid conductor to the electrical service panel ground buss?

The inspector said I could either connect the bonding grid conductor to the bonding lug on the pump OR connect the bonding grid conductor to the electric service panel ground buss.

If it were his pool he would connect the bonding grid conductor to the electric service panel ground buss.


What are the pros and cons of both connections?

What is the best way to go for safety?

Thanks.
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Old June 9th, 2003, 11:38 AM
Anonymous Anonymous is offline
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This is a tough one, depending on which failure scenarios you are most concerned about and your philosophy regarding bonding and grounding.

If you're afraid of some fault on another circuit, or a lightning strike, dumping a bunch of energy to the service panel ground, having a smaller conductor to the bonding grid is marginally better (higher impedance). This is what you'd get by stopping the bond at the pump motor.

If you're afraid of a fault in the motor AND the motor equipment grounding conductor failing, this could fry people in the pool. Tying the pump bonding conductor back to another ground (such as at the service panel) would protect against this. But so would a GFCI.
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