Proper grounding and requirements for inground pool with paver patio

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steveg_nh said:
Thanks Jason. I think I get it now. The bond "ring" acts like a "shield" on both sides of it. As long as it is all encasing it will grab whatever stray current it can whether from the side, above, below, directly in front to behind. Etc.
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Bonding grids, rings, systems, etc don't act as a shield or "grab" any stray current.

A while back a wrote this explanation to help clear up some of the confusion on the whole bonding thing. Here it is:...

Bonding and grounding are two often misunderstood concepts. To start, we will look at grounding first. In the 120 volt electrical supply system for your pool pump there are 3 wires. Hot, Neutral, and ground. The hot and Neutral serve to move power from the source and back to the source so the pump can run. The ground wire in this system serves only as a non resistive conductive path back to source should something happen internally in the pump. For example, if, for some reason, the hot wire came in contact with the motor housing, the housing could become energized. Without the ground present, the housing could sit there waiting to shock any unsuspecting person or animal who happened to touch it. You would be the conductor to ground. Ground being the ground you are standing on. Now, because the resistive properties of the ground you are standing on are too high for the current to short circuit back to the source, it would most likely not trip the overcurrent protection (fuse, breaker). A couple of times here I have referred to "source". This is the power company transformer on the pole out at the street. The hot and neutral connections are both on this transformer and the returning current wants to get back to what is called the center tap on the transformer either via the grounding system or the neutral system. If there is a ground wire present in the circuit, the hot wire coming in contact with the motor housing would immediately trip the overcurrent protection as there would be a dead short in the system.

Bonding. The really miss-understood concept.
Have you ever experienced a static shock?...You know, you shuffle your feet across a carpet in the dry season and touch a metal doorknob. If you were bonded to that doorknob when you shuffled across the floor you would not have felt it when you touched it. Everything in the universe has what is referred to as electrical potential. Humans have a certain potential, a piece of steel has its own potential, water its own, etc, etc, etc. Most times this potential is not different enough to feel it. When you shuffle your feet on the carpet though, your potential changes from that of the doorknob. When you get close enough to the doorknob though both you and the doorknob want to get to the same potential. when that happens, a spark jumps the gap and evens out the potential. Fortunately there is little amperage behind it so there is no chance of getting electrocuted. Now, lets look at your pool. your pool pump is grounded back to the source thru the ground wire. But, it still is at some level of potential. Your pool water is at some other level of potential, your heater at its own level, heck, the ground you are standing on is at some level of potential. This means that all of the items in the vicinity have some varying degree of electrical potential. Under most circumstances these potentials are so close to each other that you never feel any kind of shock. however, every once in a while something happens to change the potential of one of the items. It could be a stray voltage induced from an underground electrical service, It could be a slight resistive leakage of current in your pumping system. What ever it is there is a potential difference. Now imagine you are getting out of the pool and as you touch the metal side of the pool you get the shock of your life. Hopefully not enough to kill you but a good shot none-the-less. Guess what? You just became the bonding conductor in the system. Had all of the components in the system been bonded together by the #8 bonding wire you never would have felt it. The wire is a non-resistive path between all of the components and since electricity is lazy, it will take the least resistive path. This bonding system will also protect you if you were standing on the ground and decided to touch the water to see how warm it is. If the bond is in place there would be no potential difference between the water and the ground even if there were a stray current floating around.

Hopefully this helps clear some of this up

I also noticed that in one of the posts there was mention of the bond grid tied to the ground bar in the panel. This is not recommended. In fact I don't recall seeing it mentioned in the NEC code
 
Very helpful, excellent write up. Thanks!

- - - Updated - - -

danpik said:
I also noticed that in one of the posts there was mention of the bond grid tied to the ground bar in the panel. This is not recommended. In fact I don't recall seeing it mentioned in the NEC code
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Not on my setup at least. The bonding rod is driven into the ground separate from the panel grounds.
 
In the US tying the bonding system to the electrical panel ground is allowed, but discouraged. In Canada connecting the bonding system to the panel ground is required. There are pros and cons to such a connection, which people debate endlessly. Briefly, additional grounds make it more likely that the breaker will trip, which is good, but in the presence of ground currents will cause the bonding wires to constantly carry current which will cause corrosion, and eventual failure, of the bonding wire, which is bad.

Having a ground rod on the bonding system is discouraged in both the US and Canada.

Older versions of NEC code did not allow direct connection of the bonding system to panel ground. However, such connections are going to happen anyway, for example the pump chassis and junction boxes for underwater lights are normally both grounded and bonded. So the can't connect rule was taken out of the code.
 
It doesn't terminate in the usual sense, it should form a continuous loop around the pool. Wires can come off of that loop to connect to things that need to be connected to it, but they would not be considered terminations.
 
Interesting. So it doesn't actually "connect" to a ground rod or the panel?

I know a ground rod was driven into the ground near the sub panel for the pool outside. I assumed that was for the bonding, as I assumed the sub panel ground went back to the main panel. I admit I didn't pay much attention to what the electrician did. He does pools a lot, and all inspections passed. But I admit I'm curious!
 
Depending on distance from the house, sub-panels sometimes have their own ground rod(s).

The purpose of bonding is to keep everything at the same potential. It doesn't really matter what that potential is relative to the power lines or ground, just that it be the same potential everywhere, so there is no reason for it to be connected to either the panel or a ground rod. As mentioned above, it is sometimes connected to the panel ground indirectly, due to some things that are bonding also being grounded.
 
So this is interesting. I read the code over, and it seems like it doesn't prohibit the ground rod on the bond wire, but just doesn't require it. But in looking at my pool panel, I'm really can't tell what I have. :)

I know there is a ground rod installed next to the panel. Just not sure what it connects to. I have the #8 bare wire going right into the ground, near where the ground rod was hammered in, but it could also be the bond wire just coming up from the pool trench. I only have the one #8 bare wire coming out of the ground.

That wire, which is obviously the bond wire, then goes to the bond lug on the sub panel, to the booster pump, then the filter motor, then the heater, etc, etc.

I'm wondering if that ground rod was in fact for the panel, but I'm trying to figure out how to confirm it. I hate to ask the electrician another question. He's been very good, I but I'm driving him nuts as I try to get this project done. And I'm confident he knows what he's doing, as he's corrected the inspector a few times on the requirements, and been right every time. I'd say 75% of his work in the fall and spring is pools.
 
So I took a look inside my main panel, and the pool sub panel. I have the two hots, the neutral, and a ground. So it appears the sub panel grounds back to the main panel, not a ground rod. So I'm back to thinking the ground rod is connected to the bonding wire. Is there a way to test somehow to confirm? I can call the electrician, but like to confirm things myself too. I can look at some pictures I have too, from when the trench was open.
 

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There is no easy way to be sure without digging up enough to trace the connection. The ground rod is presumably connected to either bond or ground, and they are likely connected together somewhere, so resistance is going to low regardless of which is directly connected to which.
 
There are sometimes different requirements for the size of the wire connecting a ground rod to a panel. You could open up the sub-panel and see what size wire was used to provide the panel's ground. In my case it was a #2 stranded which is easily identifiable as being different from the #8 bare used for most of the bonding circuit.
 
The panel does have two large ground wires in it. Hard to determine where the second one is going. I know one of them goes back to the main panel in the basement, with the 2 hots and neutral. I'm not sure a pic would help much. The bare #8 wire is NOT inside the sub panel anywhere (I wouldn't have expected it to be either).

I read a lot about bonding and ground rods though, and nowhere does it say why you shouldn't do it, only that it's not required. If it's not a big deal and doesn't do any harm, then I guess I don't care much.

As for the panel, if since it does have its ground connected back to the main panel, I can't see why that it would ALSO be connected to a ground rod.
 
You could perhaps use an ohm meter and measure for continuity.

Turn off the power at the main breaker.
temporarily disconnect the bonding wire from teh sub panel.

Put one lead of the ohm meter on teh ground rod, the other on the gound bus inside the sub panel. If there is no reading on the meter, the electrical ground and the rod are not connected.

If the meter pegs out, then they are connected.

You could perform the same test between the gound rod and the bonding wire. etc etc ...
this might give you a clue what is going on with it.

Dont forget to reconnect the bonding wire to the sub panel.
If it still doesnt make sense to you then, you might give the electrician a call.
 
I thought of that actually, but I'd have to dig up the ground rod. It's all covered up already. I'll just give him a call.

Regarding the question though about connecting the equipotential bonding to a ground rod, what harm could/does it do?
 
steveg_nh said:
As for the panel, if since it does have its ground connected back to the main panel, I can't see why that it would ALSO be connected to a ground rod.
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There are requirements for some sub-panels to have their own ground system connection (could be ground rod, water or gas pipe connection) within a minimum distance of the sub-panel. This has something to do with the separation of neutral and ground paths in sub-panels and some potential problems with open neutral faults in those situations. Sorry, I don't recall the specifics but don't assume a sub panel never has to have an additional ground.
 
Hmmm. Very interesting. I'm wondering then, if that is the other heavy ground wire I'm seeing in there. Can't see why it would be going underground, as it's way to large in gauge to be for the light int the pool or the outlet on the post behind the pool. Just goes to show you, there's a lot to know about electrical stuff when you get in to the more complicated stuff like this. I always thought two ground paths were a no no. I'll call the electrician and see what he did.
 
Divin Dave, an ohm meter won't tell you anything. The two systems (grounding and bonding) will be connected at the pump, so the ground rod and bonding wire are connected one way or another. An ohm meter is not be able to tell if the ground rod is directly connected to the bonding wire, or indirectly through the panel ground (unless you temporarily disconnect the two systems).

steveg_nh, Two paths to ground can cause problems, on the other hand they sometimes prevent worse problems. Electrical code is full of tradeoffs. You should see some of the arguments on the code panel discussion forum. They are often trying to trade off risks from many different failure modes to find the best solution. You have already had two professionals say the system is safe (electrician and inspector). At this point any change is very likely to be for the worse.
 

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