How To Test Pool/Marina Grounding and Bonding Grid

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TVH

Senior Member
After discussing pool electrical hazards with my neighbors I often hear questions relating to the proper testing of the pool grounding and bonding grids. What test(s) can be conducted to confirm proper grounding/bonding of the pool and is the electrical technician required to provide a document confirming safe conditions other than the testing of the GFCI?
This subject would also make a good illustration for the "graphic of the day" section of your web site.
Info very much appreciated.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
After discussing pool electrical hazards with my neighbors I often hear questions relating to the proper testing of the pool grounding and bonding grids. What test(s) can be conducted to confirm proper grounding/bonding of the pool and is the electrical technician required to provide a document confirming safe conditions other than the testing of the GFCI?
This subject would also make a good illustration for the "graphic of the day" section of your web site.
Info very much appreciated.

I don't see how you can "test" it or provide a document confirming it is 'safe".

I think you can inspect it and make a determination if it meets current NEC requirements and state that the GFCI was tested and found to be functioning.
 

kwired

Electron manager
Location
NE Nebraska
With swimming pools the equipotential bonding is fairly simple concept - you bond everything that is conductive so it is all at the same potential. How do you test it to see if bonding jumpers are still intact - I don't know, but generally they will be unless someone did some work that disturbed something.

Marinas and other similar applications is pretty much impossible to install equipotential bonding. Even if you tried to, where do you stop? There is always a possibility of a voltage gradient at the boundary of where you installed it.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
One of the methods that Mike used was to measure the voltage between the service grounding electrode and "remote earth" (that is earth outside the influence of any grounding electrode or grounded object, often defined as being at least 50' from any such object). Then, leaving the remote earth connection in place, he would look for the same voltage on all of the bonded pool items. If that voltage is all the same, then the bonding is complete as everything has been energized to the voltage of the electrical grounding system. One issue with this is that part of the voltage you measure between the grounding electrode and the remote earth connection is the voltage drop on the service neutral between the utility transformer and the main bonding jumper. Also, where the primary of the utility transformer is connected line to neutral, you will have voltage from the voltage drop on the primary neutral. Load changes while you are testing will change the neutral to earth voltage. One way to compensate for that would be to use two meters and two people, always looking for the meters to read the same voltage.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Mike Holt had a video but it sounds like the link didn't work or the video was taken down.

Don described part of how Mike checked the bonding. The other part was just a simple continuity check of all the bonded items including the concrete around the pool. He also checked continuity at/in the water to assure it was bonded.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Little Bill contacted Mike and here is his response about the video that was taken down

It was removed because it was not totally complete… I need to add additional video on checking ‘resistance.’ I should have this done by next week.
 

Sahib

Senior Member
Location
India
If the voltage remains zero between any two of all of the bonded pool items, the equipotential bonding is okay. Isn't it?
I think it may be tested that way periodically with considerable current flowing in GEC so that there exists voltage in at least one of pool equipotential bonding conductors with reference to remote ground.
 
Last edited:

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Mike Holt sent me this and asked me to pass it on. It's a check list on testing/checking the bonding in & around the pool and pool equipment. I believe he is still working on updating his video but this is a good list to go along with the video.

Checking the Swimming Pool Electrical System to Ensure that It’s Safe from Electrical Shock
CAUTION: Before you go any further, you must understand electrical fundamentals, the concept of neutral-to-earth, and the bonding requirements contained in the NEC. Visit http://www.mikeholt.com/swimmingpoolbonding.php, watch the three videos listed, download and print my PDF document on Article 680 of the National Electrical Code.
1. Bonding System Inspection. Do a visual review of the pool bonding system and note all equipment that needs to be tested to ensure that it’s properly bonded such as:

  • Pool pump motors
  • Heat pump
  • Salt chlorinator
  • Hand rails that make contact with water.
  • Hand rails that do not make contact with water.
  • Pool lights if they are metal
2. Verify that all metal parts are bonded to the service neutral. Measure the resistance between the meter socket enclosure, service equipment, or grounding electrode conductor to all metal parts of the electrical system and pool that are required to be bonded. The resistance that is measured should be no more than one ohm (after the meter has been recalibrated to account for the resistance of wire used for the measurements). If the resistance from the service neutral to any metal part is not less than one ohm, then you must investigate why and this must be corrected.
Note: I suggest you use an analog multimeter such as a Tekpower TP7244L, with the resistance setting of X1.
3. Verify that a concrete pool shell is bonded to the service neutral.* First determine the Neutral-to-Earth voltage by placing one lead of the volt meter to the meter socket enclosure, service equipment, or grounding electrode conductor, and the other lead to a point in the earth that is at least 15 ft from any metal parts in the earth. This voltage reading should be less than 3 volts. Now measure the voltage between the meter socket enclosure, service equipment, or grounding electrode conductor to the water in the pool at four different locations. If the voltage is zero at all locations, then this means that the pool shell steel is bonded to the electrical system. If your volt reading is not zero, then you need to contact Mike Holt at Mike@MikeHolt.com on how to proceed further.
Note: I suggest you use an analog multimeter such as a Tekpower TP7244L, with the voltage setting of 10V.
4. Verify that the perimeter decking around the pool is bonded to the service neutral.* First determine the Neutral-to-Earth voltage by placing one lead of the volt meter to the meter socket enclosure, service equipment, or grounding electrode conductor, and the other lead to a point in the earth that is at least 15 ft from any metal parts in the earth. This voltage reading should be less than 3 volts. Measure the voltage between the meter socket enclosure, service equipment, or grounding electrode conductor to the perimeter decking to at least six points (6, 12, 18, 24, 30, and 36 inches from the pool water) at two locations around the pool. If the voltage reading should be near zero volts, and not the measured neutral-to-earth voltage.
Note: I suggest you use an analog multimeter such as a Tekpower TP7244L, with the voltage setting of 10V.
Ensure NEC Compliance
Remove the covers from all equipment (service disconnect, panels, time clocks, pool light transformers, pool light junction boxes, switch boxes, pool motors, heat pump motors, etc.) that is related to the pool system in any way. TURN OFF POWER BEFORE YOU REMOVE COVERS.
Inspect the wiring within all equipment to ensure that all wiring is Code compliance;

  • Are the conductors sized properly for the loads?
  • Does each circuit have proper overcurrent protection?
  • Does each conductor terminate on to a single terminal?
  • Torque all conductor terminals to manufactures instructions.
  • Has an equipment grounding conductor been run to all equipment?
  • Is the equipment grounding conductor, when of the wire type sized properly?
  • Ensure that the neutral conductor is not in contact with the equipment grounding conductor except at service equipment.
  • Covers are installed and have proper fit for all enclosures.
  • What is the voltage rating of the light(s) in the pool.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Definitely a work in progress. Some typos I noticed at first have been corrected already.

Sent from my XT1585 using Tapatalk

I went back and edited a few of them. I didn't take time to look at them all.
I should have looked it over good and edited my copy before posting but I didn't read that close.
 

Sahib

Senior Member
Location
India
. Verify that all metal parts are bonded to the service neutral. .
. Verify that a concrete pool shell is bonded to the service neutral.

. Verify that the perimeter decking around the pool is bonded to the service neutral.


Won't bonding to EGC satisfy above requirements?
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Won't bonding to EGC satisfy above requirements?

This is not about how to accomplish the bonding, it's about how to verify that it is bonded.

But yes, the EGC would provide a bonding point IF there was no break in it back to the neutral in the service equipment.
The point is to verify that EVERYTHING, associated with the pool and anything conductive/metal in close proximity to the pool is bonded together.
 

Sahib

Senior Member
Location
India
Little Bill: Your wording in post 14 sounded (or it so seemed to me) as if to bond to neutral directly. Also if pump motor doubly insulated, it should not be bonded. Should it?
 

Fulthrotl

~Autocorrect is My Worst Enema.~
After discussing pool electrical hazards with my neighbors I often hear questions relating to the proper testing of the pool grounding and bonding grids. What test(s) can be conducted to confirm proper grounding/bonding of the pool and is the electrical technician required to provide a document confirming safe conditions other than the testing of the GFCI?
This subject would also make a good illustration for the "graphic of the day" section of your web site.
Info very much appreciated.

here is what i have done in the past to verify bonding on swimming pools. specifically wet niches.

1. shut off all power to pool.
2. take a fluke megger, i used the 1587, as it gives applied working voltage to the circuit under test.
3. tape one lead to a piece of pvc conduit.
4. attach the other lead to the pool ground.
5. stick lead on pvc pipe into pool, touching lead to pool light bezel.
megger @ 1000 volts between bezel on pool light, and earth ground.
6. you should read 0.0 megohms, as it should be a dead short.
7. however, your megger should also tell you how many volts it is maintaining
across the test circuit, and it'll be somewhere between 1 and 1,050 or so,
depending on the specific fluke you are testing with.
8. you should only see 1 or 2 volts displayed.

summary:
with 1000 volts applied to the pool, there is a difference of potential of only
one or two volts between the pool water, and the earth. this means the pool
light is correctly bonded.

it also means that a person perfectly grounded, sticking their hand in the pool
water when it became energized with 1,000 volts, might be subject to a 1 or 2
volt shock.

over the years, i've had three AHJ's agree with this assessment of correct bonding
of a wet niche fixture.
 
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