TINY OFF-GRID HOUSE PROTECTION FROM LIGHTNING STRIKES AND ELECTRICAL SURGES
Photo courtesy of Grainger
The Tiny Off-Grid House photovoltaic (PV) array requires an unobstructed view of the southern sky. An open field maybe the ideal location. However, this may expose the structure to lightening strikes.
According to the National Weather Service “each year in the United States there are about 25 million cloud-to-ground lighting flashes and about 300 people struck by lightning. Of those struck, about 30 people are killed and others suffer lifelong disabilities. Most of these tragedies can be prevented.”
Even in the absence of lightning, an atmospheric static charge can also cause a buildup of high voltage (or current) on electrical lines. So grounding is needed in any kind of environment. (2023 NEC Article 250.64(C) Grounding Electrodes).
Photo courtesy of Tom McDonald Contracting
A “detachable" 12” tall copper lightning rod (Strike termination device) attached to the center of the roof ridge should offer protection from lighting strikes. Although a lighting rod does not invite lightening strikes, if one does occur, the lightning will be directed to the path of least resistance from the rooftop copper clad lightening rod to the ground (Internationally known as Earthing). A lightening rod directs the lightning flow through a continuous, low-impedance, ground electrical conductor (GEC) #6 - #4 rated American Wire Gauge (AWG), stranded copper conductor protected in green nonconductive sheathing, bonded to a ground rod embedded in the earth. It is preferable to have a continuous GEC; however, if a splice is necessary, only irreversible compression type connectors listed as ground and bonding equipment should be used. The lighting rod(s) is tethered (bonded), by the grounding conductor, to a copper clad 8’ ground rod(s) which safely dissipates the electrical energy in to the ground. Since electricity always tries to return to its source, the ground rod is not intended for ground faults (Between two hot wires or a hot and a neutral) but to dissipate static electricity buildup or external electrical surges from lightning strikes to its source, the ground.
Photo courtesy of Commons.Wikimedia.org
A 8’ (2.5M) L, > 0.625” Dia, or longer and not less than 1/2” (12.70mm) dia, copper (Atleast 10 mils protective coating) coated steel core ground rod with a >90,000 psi tensile strength (Prevents bending of the rod when being driven into ground) neutralizes and protect electrical appliances and batteries from electrical surge problems and electrical shocks NEC 250.52 The ground rod is inserted 8’ into the preferably soft ground or below the frost line. Some local authorities may require two ground rods. If so, they should be installed not less than 6’ (1.8 m) apart. However, only one rod will be needed if it can be proven resistance to earth ground is < 25 Volts.
The buried grounding rod(s) should be installed atleast 2 feet away from the metal exterior of the trailer frame to avoid interference and from the footings or a foundation; if any. The conductive copper wire travels directly down to the grounding rod in the shortest distance possible, down the port side wall; concealed behind the metal siding for aesthetics, then emerging out the bottom where it is bonded to the grounding rod.
The grounding wire should be secured to the ground rod on the backside of the connector (AKA: Acorn) not the screw side to prevent the connector screw from damaging the conductor.
Besides a lightning strike protective system installed on the Tiny Off-Grid House, whole house surge protection should also include types 2 or 3, load side Surge Protection Devices (SPD). The latter will be discussed in further detail in our blog “Tiny Off-Grid House Surge Protection Device.”
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