Continuity test for pools and metal lights

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November 10, 2022

How to Verify that a Pool is Safe from Electric Shock in accordance with the National Electrical Code

By Mike Holt,

Before you start this process, you must understand electrical fundamentals, the concept of neutral-to earth voltage, and the bonding requirements contained in the National Electrical Code. This can be accomplished by visiting http://www.mikeholt.com/ swimmingpoolbonding.php, watch the three videos listed, and download and print the document covering Article 680 of the NEC.

Caution: This document is written to be used by a qualified licensed electrician, who understands safe work practices. The instructions contained in this document don’t require any circuit to be energized, so it’s advised that all power to all enclosures be turned off prior to removing the covers.

1. Bonding System Inspection.

Do a visual review of the pool bonding system and note all metallic parts of pool equipment that need to be tested to ensure they’re properly bonded in accordance with the Code:

• Pool pump motors.

• Heat pumps.

• Salt chlorinator.

• Hand rails that make contact with water.

• Hand rails that don’t make contact with water.

• Pool lights if they have metallic parts.

• Diving boards and similar features that have metallic parts.

2. Verify that all metal parts are bonded to the service neutral.

Step 1. Turn off power to the pool equipment.

Step 2. Remove all 8 AWG bonding conductors from all pool equipment, such as pool motor(s), heat pump(s), and the salt chlorinator. Do not remove the bonding conductor to the pool light or screen enclosure.

Step 3. At the service equipment, terminate one lead from the ohmmeter to the intersystem bonding terminal, a split-bolt connector on the grounding electrode conductor, or the ground bar within the service disconnect.

Step 4. Measure the resistance between the service equipment enclosure or grounding electrode conductor (not the grounding electrode) to the 8 AWG bonding conductors, pool junction box, pool light(s), metal handrails, screen enclosure, and any other metal part that is required by 680.26(B) to be bonded.

If the resistance doesn’t exceed one ohm, after the meter has been recalibrated to account for the resistance of wire used for the measurements, then that metal part is properly bonded.

If the resistance exceeds one ohm, that metal part isn’t properly bonded and you must determine the reason for the problem and correct it. Because this is an unsafe condition, nobody should be permitted to enter the pool until repairs have been completed.

Note: I suggest using an analog multimeter such as a Tekpower TP7244L, with the resistance set to X1. A digital meter will give you the same value as an analog meter, but I like to “see” the needle move to the expected value. When I use digital meters, I see the digital numbers jump around and the “range” will often auto adjust to a different one.

Because we’re trying to measure everything from the utility secondary neutral (not the earth), we don’t want to begin measuring from a grounding electrode. The reason we want to measure from the utility neutral is because, in the event of a fault, this is the conductor on which the fault current will travel to the secondary winding (effective ground-fault current path) to clear the fault.

This voltage reading should be less than 3V. If that value is exceeded, then there is a problem with the utility primary or secondary neutral conductor (most likely the secondary neutral conductor).

Step 2. Measure the voltage between the service equipment or the grounding electrode conductor to the perimeter decking at least six points (6, 12, 18, 24, 30, and 36 inches from the pool water) and at least two locations around the pool.

If the deck has 6” x 6” structural steel wire mesh as part of the bonding grid, then the voltage reading at all six points should be near zero volts for all points. If the deck isn’t bonded at all, then the voltage at all six points will be the NEV voltage.

Step 3. Measure the neutral-toearth voltage between the service equipment or the grounding electrode conductor to the concrete pool perimeter decking in at least six points (6, 12, 18, 24, 30, and 36 inches from the pool water) and at least two locations around the pool.

If the measured neutral-to-earth voltage is zero at all locations, then the concrete pool perimeter decking contains structural reinforcing steel that’s properly bonded.

If an 8 AWG bonding copper conductor is in the concrete deck between 18 and 24 inches from the pool water, then the voltage immediately over the bonding conductor will be zero; the further you measure from the bonding conductor, the higher the displayed voltage will be, up to the NEV voltage.

Ensure NEC Compliance

Turn off power to all equipment, then 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, and so one) that is related to the pool system in any way.

Inspect the wiring within all equipment to ensure it is in compliance with the National Electrical Code:

• 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 comply with manufacturer’s instructions.

• Has an equipment grounding conductor been run to all equipment?

3. Verify that the concrete pool shell is bonded to the service neutral.

Step 1. Determine the neutralto- earth voltage (NEV) by placing one lead of the voltmeter to the service equipment enclosure or grounding electrode conductor (not the grounding electrode), and the other lead to a point in the earth that’s at least 15 feet from any metal parts in the earth.

This voltage reading should be less than 3V. If that value is exceeded, then there is a problem with the utility primary or secondary neutral conductor (most likely the secondary neutral conductor).

Step 2. Measure the neutral-toearth voltage between the service equipment or grounding electrode conductor to the water in the pool in at least four different locations. If the neutral-to-earth voltage is zero at all measured locations, then the concrete pool shell’s reinforcing steel is properly bonded.

If the volt reading isn’t zero, then the pool shell isn’t bonded. Because this is an unsafe condition, nobody should be permitted to enter the pool until the problem has been corrected. Contact Mike Holt at Mike@MikeHolt.com on how to proceed.

Note: I suggest you use an analog multimeter such as a Tekpower TP7244L, with the voltage set to the 10V range. A digital meter will give you the same value as an analog meter, but I like to “see” the needle move to the expected value. When I use digital meters, I see the digital numbers jump around and the “range” will auto adjust to a different one.

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

• Ensure that the neutral conductor isn’t in contact with the equipment grounding conductor except at the service equipment.

• For all enclosures, verify that the covers are installed and fit properly.

• Verify that the voltage to the pool light(s) doesn’t exceed 15V.

Notice: This is a first draft version of this document dated 7/12/17, if you have any comments, please send them to Mike@MikeHolt.com, AFTER you have watched all videos on my website located at http://www.mikeholt.com/ swimmingpoolbonding.php.

As a leading expert on grounding and the NEC, Mike Holt has made it his purpose to keep people safe, and to teach electricians what to do to make sure that your pools, spas and hot tubs are safe to swim in. The risk associated with swimming pools is that of electric shock, due to a reduction of body resistance because a person is wet, and also the possibility that a person is in contact with earth potential.

Image from Mike Holt Enterprises