Short answer: Article 700 covers emergency systems that a law or code requires for life safety, such as egress lighting. Article 701 covers legally required standby systems, required by a governmental agency for loads such as some ventilation, smoke removal or sewage systems, whose loss could create hazards or hamper rescue or firefighting. They are classed separately from Article 700 emergency loads. Article 702 covers optional standby systems that the owner chooses, such as a home generator. All three need transfer equipment that keeps the backup source from feeding back into the utility. Emergency systems carry the strictest rules for separation, testing, wiring and coordination.
PSI lists emergency systems in the Special Occupancies, Equipment and Conditions subject area of the Texas Journeyman exam, which has 6 scored NEC Knowledge questions. Generators fall under Motors and Generators: 5 scored NEC Knowledge questions and 2 scored Calculations questions. PSI does not say how many cover standby systems alone. The Texas Journeyman Practice Pack has 1,000 original questions and 10 timed mock exams in the real two-part format, with step-by-step solutions for every calculation. Try free practice questions without signing up. Get the full pack for US$39 with one payment.
Tsai Electro is an independent learning site. Not affiliated with TDLR, PSI or NFPA. We explain the ideas in our own words and do not reproduce NEC text. Check every rule and table value in your own 2026 NEC, and follow your supervisor and the local inspector.
Which article applies
| Article 700 Emergency | Article 701 Legally required standby | Article 702 Optional standby | |
|---|---|---|---|
| Who requires it | A law, code or authority, for life safety (NEC 700.1) | A governmental agency, for designated loads classed separately from emergency loads (NEC 701.1) | Nobody; the owner chooses it (NEC 702.1) |
| Typical loads | Egress lighting, exit signs and other life safety loads | Some ventilation, sewage, communications and process loads | Homes, farms, businesses where an outage is a nuisance or costs money |
| Strictness | Highest | Middle | Lowest |
The article does not depend on the size of the generator. It depends on why the system is required. The same building can have all three, each with its own transfer equipment and wiring.
Transfer equipment
- Optional standby. Transfer equipment, interlocking or another approved interconnection means is required and must be listed. It must prevent the backup source and the utility from being connected at the same time (NEC 702.5(A)). On a home generator this is a transfer switch or a listed interlock kit for that panel.
- Emergency. Emergency transfer equipment may supply only emergency loads (NEC 700.6(D)). Optional loads go on their own transfer switch.
- Load control relays. A listed automatic load control relay can switch emergency lighting, but it cannot be used as transfer equipment (NEC 700.26).
Emergency wiring and controls
- Marking. Boxes and enclosures for emergency circuits are permanently marked as part of an emergency system, and exposed cable or raceway is marked at intervals of not over 25 feet (NEC 700.10(A)).
- No multiwire branch circuits. Emergency branch circuits cannot be part of a multiwire branch circuit (NEC 700.19).
- Switches. Emergency lighting switches are arranged so only authorized persons control them. Switches in series and 3-way or 4-way switches are not used (NEC 700.20).
- No total darkness. The failure of one lighting element must not leave an area that needs emergency lighting in total darkness (NEC 700.16(B)).
- Selective coordination. Emergency overcurrent devices must be selectively coordinated with all supply-side and load-side devices, so a fault opens only the device nearest to it on the supply side (NEC 700.32(A)).
Testing, records and signs
- Testing. Emergency systems are tested on a schedule approved by the authority having jurisdiction (NEC 700.4(B)), and a written or digital record of tests and maintenance is kept (NEC 700.4(D)).
- Sign at the service. A sign at the service entrance equipment shows the type and location of each on-site emergency power source (NEC 700.8(A)).
Worked example: battery capacity for emergency lighting
Where storage batteries or a UPS supply emergency illumination, they must carry the load for at least 1 1/2 hours without the voltage falling below the limit the rule sets (NEC 700.12(B)(4)).
A 24 V battery system supplies 240 W of emergency lighting.
- Current: 240 ÷ 24 = 10 A.
- Ideal capacity: 10 A × 1.5 h = 15 ampere-hours, assuming a steady 24 V.
- This is a starting point, not the battery you buy. The real battery is chosen from the manufacturer’s discharge data, battery aging and the voltage the rule requires.
Check yourself
- A homeowner adds a portable generator inlet and an interlock kit. Which article applies? Article 702, optional standby.
- Can a transfer switch for egress lighting also carry the office receptacles? No. Emergency transfer equipment supplies only emergency loads.
- How long must batteries supply emergency illumination? At least 1 1/2 hours.
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Find Articles 700, 701 and 702 faster on exam day
NFPA 70, National Electrical Code, 2026 Edition (softcover). Highlight the scope of each article, the transfer equipment rules and the 700 wiring and coordination rules, starting with the scope of each article. The Texas exam is open book. PSI allows a soft-bound NEC with highlighting, underlining and notes made in advance. Loose-leaf, spiral-bound and ring-bound copies are not allowed, and only permanent index tabs made or supplied by the NEC publisher are permitted; homemade and third-party tabs are not.
FAQ
What is the difference between emergency and standby systems?
Emergency systems are legally required for life safety. Legally required standby systems are required by a governmental agency for designated loads whose loss could create hazards or hamper rescue or firefighting, and are classed separately from emergency systems. Optional standby systems are the owner’s choice.
Does a home generator need a transfer switch?
Not always a separate switch. A permanently connected optional standby system needs listed transfer equipment or a listed interlock, such as an interlock kit for that panel, that prevents the generator and the utility from being connected at the same time.
Can emergency and normal loads share a transfer switch?
No. Emergency transfer equipment supplies only emergency loads.
Are standby systems on the Texas Journeyman exam?
PSI lists emergency systems in Special Occupancies, Equipment and Conditions (6 scored NEC Knowledge questions) and generators in Motors and Generators (5 scored NEC Knowledge and 2 scored Calculations questions).
Sources checked October 2026
- PSI Candidate Information Bulletin, Texas electrician examinations (updated September 15, 2026): https://test-takers.psiexams.com/api/content/bulletin/1682
- NFPA 70, National Electrical Code, 2026 Edition, Articles 700, 701 and 702
