Art 210 requires stationary equipment that takes up 50% of a circuit's capacity to be a dedicated circuit. Other than engineering or usage convenience considerations, is there a safety issue? I recently had to repair a damaged installation that apparently was modified by a maintenance person AFTER initial construction, so that it violated the 50% rule. They tapped into a large role up door opener (in a commercial building) to provide power for a couple of convenience outlets. I don't like driving customers away by re-engineering existing installations because of code issues which aren't obvious safety issues. Anyone have some perspective about what is so dangerous about violating the 50% rule?
As I see it, the problem with violating such a rule would be that if/when other high-power appliances are connected to the circuit, there could be a high incidence of nuisance tripping.
That in itself wouldn't be a problem so long as the OCPD and cables are properly sized. The only real safety issue I can see is that regular nuisance trips might lead to some uninformed person deciding to uprate the breaker in order to "solve" the problem. Then it could most definitely be a safety problem.