Testing, Inspection, Turn-On and Work Zone Safety
Inspection and testing
Acceptance work includes hold-point inspections, continuity, insulation resistance, ground resistance, loop testing, conflict-monitor checks, detection verification, pedestrian signal checks, preemption, and a burn-in. Ground resistance is commonly specified at 25 ohms or less; if it fails, add a supplemental electrode and retest. Insulation resistance should be high, not a dead short. Document every test.
Turn-on and work zone
Before turn-on, notify the agency, verify all displays and phases, check coordination and time-of-day plans, confirm detection and preemption, and inspect pedestrian accessibility. Work zone safety follows MUTCD Part 6: temporary traffic control plan, taper, buffer space, flagger, high-visibility apparel, and spotter for equipment near traffic.
Worked example: A new installation shows a ground resistance of 40 ohms. The specification requires 25 ohms or less. Adding a second ground rod at least 6 ft away and bonding it to the electrode system may lower resistance; retest with a fall-of-potential meter. Do not simply sign off because the cabinet is bonded; the electrode-to-earth resistance is the measured value. The reasoning is that bonding connects metal parts, while grounding resistance describes the electrode’s contact with earth.
Traps: energizing before inspection; testing only one phase; no conflict-monitor test; missing as-built; work zone signs placed without a taper; no spotter; failing to document retests.