1926.600 — the overhead line rule kills people on data center sites.
A large campus has utility feeds crossing the property, temporary power to the trailers, and an enormous amount of lifting. Contact between a boom and an energized overhead line is one of the few genuinely predictable fatalities in construction.
Equipment shall be operated so that a clearance of at least 10 feet is maintained from any energized overhead line rated 50 kV or below. Above 50 kV the clearance increases — 10 feet plus 0.4 inch for each kV over 50 kV, or twice the length of the line insulator but never less than 10 feet. In transit with the boom lowered and no load, the required clearance reduces but does not disappear.
The controls that actually work are, in order: have the line de-energized and visibly grounded; or install insulating barriers; or set a physical barricade that makes the encroachment impossible. A dedicated spotter is a supplement to those, not a substitute. “The operator will be careful” is what the investigation report always quotes.
§ Where the lines are on a data center site
- The incoming utility feed — often overhead to the property line even where the campus distribution is underground.
- Temporary construction power — poles and drops that move as the site develops and are rarely on any drawing.
- Existing campus feeds on a live expansion — the most dangerous case, because the line is energized and serving production load.
- Adjacent property lines within reach of a boom swinging over a lay-down yard.
§ The other requirements that get cited
Seat belts provided and worn on all equipment, except equipment designed only for standing operation and equipment without rollover protection.
Reverse signal alarm audible above the surrounding noise on bidirectional machines — or an observer signalling it is safe to back up. On a data center site the surrounding noise may be a running generator test, which raises the bar.
Raised equipment blocked — dump bodies, buckets and scissor lifts must be blocked or otherwise secured before anyone works underneath.
Parked equipment secured — brakes set, blades and buckets lowered to the ground, wheels chocked on an incline.
Inspection before use each shift, with defective equipment removed from service.
§ Struck-by is the exposure that persists into operations
Struck-by remains one of construction’s leading causes of death, and on a data center site the exposure does not stop at substantial completion. Deliveries, generator fuel trucks, crane picks for equipment replacement and vacuum trucks all continue into the operating life of the building.
The mixed condition is the dangerous one: an operating campus with a construction zone, where operations staff on foot use routes that construction traffic now crosses. Their orientation covered arc flash. It did not cover the haul road that appeared last month.
This is the same governance problem as the energization boundary and the multi-employer doctrine — two employers, one site, and a boundary that has to be somebody’s explicit job.
A crane picking a rooftop condenser on an operating campus, with a documented lift plan, a certified operator and a signal person — and the swing radius crossing an energized 12.47 kV overhead feed to the existing building. The lift plan addressed the load. Nobody drew the line on the plan.
Construction next to live power
Expansion projects put contractors next to energized equipment they do not own and cannot see. Our onsite classes work from your site plan and one-line.
Onsite training The energization boundary