By The Electrical Power Research Institute (EPRI)
The Electrical Power Research Institute (EPRI) has published this guide to demonstrate the Equipotential Bonding Validation Procedure.
The following measurements provide a useful way to determine the adequacy of the equipotential bonding at an inground swimming pool.
The measurements also provide a way to understand what specific bonding connections are suspect or questionable, based on the measurement result versus the expected results described in the comments section of the table, which can be viewed at the following link: http://www.cmiwebsite.com/ validation-procedure.
The measurements are going to be slightly different at every pool depending on the design and the construction materials, but the procedure is universally useful for equipotential bonding assessments. For additional insight visit https:// strayvoltage.epri.com/Resources. aspx 1. Required hardware:
• One True RMS AC multimeter.
• One two-foot (or longer) conductive metal grounding electrode – (preferably copper or steel).
• One wire lead (at least 50 feet long) and at least 14-gauge insulated wire.
• One bucket with salted water to wet various test points.
• Two stainless-steel or copper plates or bars with contact surface area of at least 50 square inches. Example: 24” long by 2.5” wide or any other dimensional combo of at least 50 square inches.
• One 20K ohm load resistor applied across the test leads where specified.
Note: The 20K load resistor — built into a double banana jack test lead accessory — is not easy to find but can be easily fabricated by the user. A 3Kohm Fluke SV225 is a suitable replacement to eliminate static voltage and can be found online.
2. Identify a suitable “earth reference point” at least twenty feet away from the pool deck area and at least twenty feet away from the circulating equipment, and drive the conductive metal electrode to a depth of one foot or deeper into the earth. This reference point will be used for many of the voltage benchmarking measurements. If the soil is dry, it is useful to pour a few gallons of pool water onto the soil where the metal electrode is placed.
3. Conduct each measurement twice: Once with the load resistor and again without the load resistor These are recorded as the (load resistor or VR measurement) and the (open-circuit or VOC measurement).
Measuring both ways should reduce the chance of any measurement errors caused by static charge or phantom voltage readings.
Notes: It is normal and expected that the readings with the load resistor across the meter leads will be at least several tenths of a volt lower than the same readings without the load resistor. As an example, a 4.2 volt reading without the load resistor may become a 3.8 volt reading with the load resistor.
The readings with the load resistor are used for eliminating static voltages but should not be used for calculating expected exposure and perceptible shock currents.
For more information on calculating shock and exposure currents refer to https://strayvoltage.epri.com/ for the appropriate procedure.
A 20K load resistor measurement will be important in determining whether voltage differences are present between pool water and pool walking surfaces.
4. Procedure: Set the meter for AC Volts and record in the data sheet the following measurements: a) The free air measurement with the test leads not connected to any surfaces. b) The measurement with the test leads solidly connected to one another. c) The measurement with one lead connected to a suspected energized surface and the other lead in open air.
For the remaining items, record the measurement both with and without the load resistor a) Between the remote earth reference point and the bonding lug on the circulating pump. b) Between the remote earth reference point and the water bond mechanism. c) Between the remote earth reference point and the pool water at four equally spaced locations around the perimeter of the pool. d) Between the remote earth reference point and the walking surface at four equally spaced locations around the perimeter of the pool. e) Between the pool water and the pool deck at points within the human reach and contact areas of the deck and the coping around the water’s edge. f) Repeat the previous measurement near any bonded light niches, ladders, or handrails.
A useful way to document the readings is by using a hand-drawn sketch of the pool area and logging the readings on the sketch.
Alternatively, a table such as the one found at http://www.cmiwebsite. com/validation- procedure can also be used.
Processes are routinely updated and improved upon, so checkback periodically for the latest measuring procedures.