The pump's case is grounded therefore grounding the bond wire right?

hwy17

Well-known member
Mar 17, 2021
157
Northern California
This isn't a question of bonding vs. grounding, I understand the concept of equipotential bonding is distinct from grounding. I just want to confirm my understanding that the pump's casing is connected to the electrical system earth via the ground wire on the plug, and therefore the bond wire is connected to the electrical earth by that connection too.

On an AGP the bond wire is buried a significant length. Doesn't this create the potential for a ground loop if there is a difference in potential between that ground contact and the house ground, or the utility ground for that matter?
 

ajw22

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Jul 21, 2013
24,886
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
It does but that is the way it is done.

The pump is both bonded and grounded in separate locations.
 
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JamesW

TFP Expert
Mar 2, 2011
24,090
This isn't a question of bonding vs. grounding, I understand the concept of equipotential bonding is distinct from grounding. I just want to confirm my understanding that the pump's casing is connected to the electrical system earth via the ground wire on the plug, and therefore the bond wire is connected to the electrical earth by that connection too.

On an AGP the bond wire is buried a significant length. Doesn't this create the potential for a ground loop if there is a difference in potential between that ground contact and the house ground, or the utility ground for that matter?
There are usually several pieces of equipment that are both bonded and grounded where the bond and ground both connect to the same metal frame.

So, yes, they are connected, but it's not done intentionally.

The bonding system does effectively constitute a grounding electrode.

For subpanels in a detached building, a separate grounding electrode is sometimes used.

Both grounding electrodes should be bonded together by the equipment grounding conductor.

So, there should not be much difference in potential.

Also, the neutral at the pool equipment is not grounded. So, any current going through the bonding grid would have to go from the main panel neutral to the main panel ground and back to the pool equipment ground and then to the bonding grid and then through the earth to the transformer neutral.

The neutral in the main panel is grounded and the neutral at the transformer is also grounded.

Since both neutrals are grounded, there will be some current that travels through the ground from the house grounding electrode the the transformer grounding electrode.

The amount of current going through the ground depends on the impedance of the ground, the impedance of the neutral wire between the house and the transformer and the amount of current that the neutral needs to carry.
 
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JamesW

TFP Expert
Mar 2, 2011
24,090
Since the neutrals are grounded at the house and the transformer, the ground becomes a parallel path for current.

The current is divided such that the voltage drop for each path is equal.

If the primary neutral is 1 million times more conductive than the ground, then only 1 millionth of the current will go through the ground.

If the primary neutral is disconnected, then the ground is forced to carry the neutral current.

If a single 10 amp 115 volt appliance is turned on, the ground has to carry the current.

If a second 10 amp appliance on the opposite hot leg is turned on, then both 115 volt appliances are in series across the 230 volt hot wires. They are in series because they are both connected to the neutral bar.

As long as the amps are equal, both appliances will get the same voltage at 115 volts.

However, if the amps are not equal, the loads are still in series but the voltage will be unequally distributed. One might get 80 volts and the other would get 150 volts.

The ground will carry some neutral current, but the voltage will still be unequally distributed.
 
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hwy17

Well-known member
Mar 17, 2021
157
Northern California
@JamesW Thank you, I consider myself to have a reasonably firm grasp on split phase wiring, that all fills in some blanks for me, confirms some of my assumptions, and of course some of it is over my head.

Let me ask you this, our main panel was last updated in the 1950's, I don't believe I've ever laid eyes on our neutral grounding rod. Say that we don't have one, either because it was improperly installed without one, or they weren't required, or it has become too corroded. In that case, does adding this new grounding electrode to the system pose any hazards? From what you explained I take it that as long as our neutral connection to the transformer is good, this new ground will carry some current between it and the transformer ground proportionate to it's impedance, but that will be insignificant.
 

JamesW

TFP Expert
Mar 2, 2011
24,090
You're not really adding a grounding electrode intentionally, but it is effectively a grounding electrode.

For your house wiring, I would have to recommend that you have a qualified professional check anything you felt needed to be checked.

I would not be comfortable commenting on what you have or might have or what might need to be done.

For your new installation, have an electrician who is familiar with pool electrical code do the work or at least advise you on what's needed.

Also have them inspect any work completed to make sure that it is safe and compliant to local code.
 

hwy17

Well-known member
Mar 17, 2021
157
Northern California
The supporter badges make it quite clear this forum operates on donations and I applaud that, but I think my post history will show that in the short time I've been here I've been doing as much of the helping as asking.
 
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