Understanding equipotential planes can prevent problems, said Graham Cassellius, an Alliant Energy ag representative since 2008. Cassellius has conducted more than 250 stray voltage investigations and has worked with Alliant Energy’s cost-sharing grants on more than 280 farms.
An equipotential plane (EPP) is an area where wire mesh or other conductive elements are embedded in or placed under concrete, bonded to all metal structures and fixed nonelectrical equipment that may become energized, and connected to the electrical grounding system to minimize voltage potentials within the plane and between the planes, the grounded equipment and earth.
“By bonding all of this metallic equipment together, it greatly reduces the voltage potential between any two points that an animal could simultaneously contact,” Cassellius said.
Providing an EPP minimizes a voltage potential from developing that can cause abnormal animal behavior or reduced productivity.
Equipotential planes prevent a difference in voltage on surfaces an animal can touch, he said. Starting in 1996, EPPs are required for new construction in all areas where electrically grounded equipment is near livestock, especially in milking parlors.
EPPs must be installed in confinement areas with concrete floors where metallic equipment is located that may become energized and is accessible to livestock, including milking parlors, tiestall barn milking facilities, wood-framed freestall barns with metal support posts, metal-framed freestall barns and robotic milking stations, Cassellius said.
The means of bonding to conductive elements is obtained by pressure connectors or clamps of brass, copper, copper alloy or an equally substantial approved means, according to the American Society of Agricultural and Biological Engineers (ASABE). Concrete floors, walls and footings of confinement areas must contain conductive elements effectively bonded together and be either reinforcing steel or mesh, or solid bare copper conductors.
All conductive equipment, structures or surfaces accessible to each other and from a concrete floor of a confinement area must be bonded together to create an equipotential plane, according to the ASABE. The term “confinement area” includes areas located outdoors without structure, such as feeding floors and holding areas. Confinement areas that do not contain electrically supplied equipment or systems connected to an electrical equipment grounding conductor system are not required to comply with the requirements.
If a dairy producer is building new construction or a retrofit, it is important to make sure the electrician has proper training in EPPs, Cassellius said. Alliant and other energy companies offer specialized training for electricians working with the unique conditions found on livestock operations. Ask your contractor about the training their employees have.
State laws vary, but in many locations an inspection of bonding methods that become encased in concrete or covered by concrete is required before the concrete is poured. It is usually considered to be the responsibility of the installer of the wiring to notify the inspection authority sufficiently in advance to allow the inspection to be completed before wiring is concealed in any manner.
EPPs are also required in electrically heated waterers where animals can come in contact with heating components. “Wire mesh cattle panel or rebar grid embedded in concrete and bonded to a transition plane makes a very effective EPP for waterers,” Cassellius said. “Driven ground rods tied together with copper wire create an EPP if mesh wasn’t installed in the concrete.”
If a producer has old heated waterers, he or she can check for ground rods under the unit. Cassellius said, “If there aren’t any, they should remove the waterer and install the rods (or have them professionally installed) at a 45-degree angle underneath where the cattle will stand when drinking. Most waterers should have two to six ground rods depending on the size and location of the waterer.”
He advised if using drop-in- style heaters to keep cattle water tanks from freezing, they should be grounded with copper wire coil in the water reservoir. A coiled 36-inch No. 6 solid copper (No. 8 solid copper minimum) should be placed in the bottom of the reservoir, or the copper wire should be connected to the EPP or ground rods (if present).
Cassellius also recommends using 240-volt heaters, removing heaters when not in use, taking measures to protect the outlet from corrosion and testing continuity before re-installing.
All waterers with electricity to them should use silicone wire nuts (blue). “The space below a cattle waterer is a terrible environment for electrical connections,” he said. “The constant moisture will eventually lead to corrosion. One of the best methods of preventing corrosion on the electrical connections is using the blue silicone-filled wire nuts. They should be used if an electrician installs the waterer and are also available at most hardware stores.”
A way to avoid electrical issues with waterers in new construction of freestall barns may be non-electric ground tube waterers. Heat from a 20- to 24-inch tube buried 7 feet deep will keep a waterer ice-free in barns with high water usage, Cassellius said.
It is also important to be aware of EPPs in robotic milking units. An EPP should be included in the concrete floor at the exit and entry to the robot box, including the holding area. If EPP isn’t already required throughout the freestall, there does need to be a “transition plane” from the EPP to the freestall barn.
He said an EPP transition plane minimizes the voltage potential between the cow’s front feet and back feet as she moves on and off the equipotential plane.
It is also important to watch for issues with electric fence controllers. Cassellius recommends checking that the size is appropriate for fence length, grounding is independent from any building’s grounding system (there should be at least 50 feet between the fence grounding and any building grounds or metallic water lines), and higher-output controllers are used – as they often need more than three ground rods (20-mile fencers and up).
Many energy companies offer free inspections for electrical issues, correction of unsafe wiring and can help implement strategies to reduce stray voltage. Many offer a stray voltage investigation following the completion of wiring projects on dairy operations.
“The last few years have been rough on our farming communities, and the funding opportunities available through energy companies can help livestock operations make long-overdue improvements to their electrical system that will improve safety as well as energy efficiency,” he said.
Cassellius spoke at the 2020 Grassworks Grazing Conference, held annually in Wisconsin.
For information about what laws apply for your location, search your state’s electrical regulations online. Your local energy provider is also a great resource for questions on local inspection laws.
Kelli Boylen is a freelancer based in northeast Iowa.