When do current NEC requirements not apply to existing facilities? Are existing installations grandfathered so that code violations are not applicable since they have been operating under those conditions for years or are they subject to upgrading for safety reasons? I recently visited a site that was awash with safety violations such as improper overcurrent protection, excessive mounting heights for service disconnect switches, below minimum working clearances, etc. Must these be corrected now or only if other work is being done on the system itself?