Grounding the Outdoor Camera Poles
An installer is commissioning 12 outdoor camera poles in a parking lot. Each camera draws about 4 VA at 24 volts AC from a single 100 VA transformer in the building. Video is over coax. At each pole, the installer drove an 8-foot ground rod and bonded the camera housing, the pole, and the coax shield to that rod. The coax shield is also bonded to the building ground at the head-end. During wet weather, staff report video hum bars, occasional camera reboots, and a technician felt a tingle when touching a pole and standing on wet pavement. The building has a grounding electrode system at the service. The transformer secondary is not grounded. The installer says each pole needs its own ground rod for lightning protection and that low-voltage systems do not require grounding.
1. Evaluate the grounding and bonding arrangement. What is causing the symptoms?
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The arrangement creates multiple ground references. Each isolated ground rod can sit at a different earth potential, especially during wet weather or nearby lightning activity. Bonding the coax shield at both the pole rod and the building head-end creates a ground loop through the coax shield. That loop can cause hum bars and reboots, and it can put voltage differences between the pole and nearby earth.
The technician’s tingle is a safety warning. It may indicate a potential difference between the pole and wet pavement, a faulty transformer or camera power supply, or a neutral-to-ground problem on the building side. Low-voltage systems still require equipment grounding and bonding, and the installer’s statement that low voltage needs no grounding is incorrect. The system should be de-energized and tested before anyone touches the poles again.
2. What NEC grounding and bonding requirements apply, and what should be changed?
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The building’s grounding electrode system must be the common reference. If ground rods are installed at the poles, they must be bonded to the building grounding electrode system so they are not isolated electrodes. The coax shield should be bonded to the building grounding electrode system at the point of entry, and any remote bonding should be done in a way that does not create a parallel ground loop. Isolators or baluns may be needed on the video circuit.
Equipment grounding and bonding must be maintained for the camera housings and power equipment. Surge protective devices should be listed for the application and bonded to the same grounding system. The installer should not rely on a separate rod at each pole as the only ground. The design should be corrected by a qualified person, and the transformer secondary and camera power supplies should be checked for faults.
3. What immediate safety actions and testing steps should the technician take?
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The technician should stop work, treat the poles as energized, and keep others away. Using a non-contact voltage tester and a properly rated digital multimeter, the technician should check for AC voltage from pole to earth, pole to building ground, and coax shield to building ground. The transformer and camera power supplies should be de-energized and inspected for damaged insulation, loose connections, and neutral-ground faults.
After repairs, the technician should re-test before energizing and document the readings. If voltage is present with the source off, an induced or foreign voltage source must be investigated. The technician should not stand on wet pavement while touching a suspect pole. If the tingle condition returns, the system should remain off until a qualified electrical contractor evaluates the grounding and power supply.