Inground Pool with grounding problem...

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  #1  
Old 08-11-10, 10:09 AM
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Inground Pool with grounding problem...

I have an inground pool with a pool light that connects to a GFI breaker. The pool light which is 120volt has 3 wires, a hot(black) a neutral(white) and a green(ground).
The pool has metal clips on the edge that hold the pool liner in place and these metal clips are bonded. (see pic)
What is happening is that when people get in the pool and touch the edge of the pool, they are getting a small shock when they touch it.

I have discovered that the source of the problem is the green ground wire that goes to the pool light. When I disconnect the green wire, the problem goes away. When I reconnect it, the problem is back.

Anyone care to take a stab at what is happening here and how to resolve it? Thanks in advance.....

 
  #2  
Old 08-11-10, 10:30 AM
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First thing, do not use this pool at all until the problem is resolved. A small tingle today can be deadly shock tomorrow, especially if it a component that is deteriorating -- voltage leaking to the pool will increase. Leave the green wire attached to the light; it is not producing problem, but it is providing a return path for something else.

Next, try to measure the voltage using a voltage meter. Stick one probe in the water and touch the other to whatever the bathers have been getting shocked from so you can get an objective baseline reading.

Next, turn off all breakers associated with the pool (pump, heater, light, etc) and repeat your test to see if the voltage has gone away. If it has, turn them on one-by-one to see what causes the voltage to return. An inground pool of that age probably does not have GFCI on the filter pump, so that is my prime suspect. You also probably do not have a water bond, except for the niche light ground.
 
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Old 08-11-10, 05:39 PM
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Do you have a small subpanel at the pool where the GFI breaker is located? If so, check to be sure the neutral is isolated from ground.
 
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Old 09-28-10, 01:11 PM
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Test results so far....

In answer to your question, yes there is a sub panel that the pool pump and pool light are located. The sub panel is properly wired and the 'neutral bar' is isolated from ground.
With the power disconnected from the sub panel, and the pool light wires (black and white) disconnected alltogether, there is still a current running thru the (green) ground wire down to the pool light that causes a small shock to anyone in the pool when they touch the metal edge of the pool! I know for a fact that the edge of the pool is connecting with wire that makes up part of the Bonding Grid.

At best guess, am I to assume that the source of this current originates back at the main panel where the ground from the sub panel connects to the 'neutral bar'?

My only option at present is to leave the pool light totally disconnected for now.
In this way, there is no current or shock at all, but does not allow for the pool light to ever be used.
 
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Old 09-28-10, 11:27 PM
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Let me try something but I can not garranite it will work with your sistuation however let me try this methold.,

turn off the house main breaker.,, I know I heard ya but what I am try to is elemated the stray soruce so if the house main breaker is off if the current drop or voltage drop to zero then turn all the branch breakers off and turn the main back on and check it again if still zero current turn it on one at time until you get the voltage reading and make note of what circuit it serve.

Did you check the pool pump motour bonding if good or what ?

I know the bonding conductor it should be 10mm˛ { #8 AWG } or larger but check around the pool area to make sure and check all the luminaire junction box to make sure the connections are good and tight.

do you have subpanel in the garage ?? if so check the netural and ground connection to make sure they are good few case I have ran into with bad one it may cause stray voltage show up.

Merci.
Marc
 
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Old 09-29-10, 06:38 AM
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You could be feeling voltage drop on the utility neutral. With the way the NEC requires grounding and bonding to be done, you are literally connecting the pool ground to the utility neutral. I would turn off the main, and check for voltage at the pool where people are getting shocked. If it goes away, then there is probably some kind of secondary ground fault on your property. Turn on breakers one by one until the voltage shows up again.

If the voltage is still present with your main turned off, then the source of the voltage is not from your property and the power company should be called. Like I said eariler, you could be feeling voltage drop from the utility primary neutral if you are on a long single phase run or there is a bad connection on the utility primary neutral somewhere, or there could be a fault on a neighbor's property, or there could be a fault on a utility primary underground cable.

Let us know how this turns out.
 
 

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