Special Systems
Information Technology Equipment Rooms (645), Emergency Systems (700), Legally Required Standby (701) and Optional Standby (702)
NFPA 70 National Electrical Code, 2023 edition · Reviewed 2026-09-21
The three Article 7 "alternate source" systems are tested mostly by contrast: how fast each must come on line, whether its wiring may share raceways with normal wiring, what kind of transfer switch it needs, and whether selective coordination is required. Article 645 is tested for its disconnect and under-floor cable rules. Written from the 2023 text (the Florida edition; 2023 section numbers throughout).
1. The three standby systems side by side
| 700 Emergency | 701 Legally required standby | 702 Optional standby | |
|---|---|---|---|
| Who requires it | Life safety — codes/AHJ (egress lighting, fire pumps, alarms) | Codes/governmental agency for non-life-safety loads (heating, ventilation, sewage, industrial processes) | The owner's choice (comfort, data, processes) |
| Time to power | ≤ 10 seconds (700.12) | ≤ 60 seconds (701.12) | none |
| Supply duration | ≥ 2 hours; batteries/UPS for emergency illumination ≥ 1½ hours at ≥ 87½ % voltage (700.12(C)) | ≥ 2 hours (701.12(C)) | sized for the load the user selects; automatic-connection systems supply the full load or use an EMS per 750.30 (702.4) |
| Wiring separation | Kept entirely independent of all other wiring except the listed cases (700.10(B)) | May share raceways, cables, boxes and cabinets with general wiring (701.10(A)) | May share (702.10) |
| Transfer equipment | Automatic, listed and marked for emergency use; electrically operated, mechanically held; supplies only emergency loads; no meter-mounted switches; no reconditioned switches (700.2, 700.5) | Automatic, listed for emergency or legally required use; electrically operated, mechanically held; no meter-mounted; no reconditioned (701.2, 701.5) | Interconnection/interlocking/transfer equipment preventing inadvertent interconnection; meter-mounted transfer switches permitted where listed and approved (702.5) |
| Selective coordination | Required, with all supply-side and load-side OCPDs, by a licensed PE or qualified persons, documented (700.32) | Required (701.32) | Not required |
| SPD | Listed SPD in or on all emergency switchgear, switchboards and panelboards (700.8) | no |
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