E2 Emergency and Standby Systems 3 — Questions and Answers
Question 1: Which of the following loads is most likely served by a Legally Required Standby System (Article 701) rather than an Emergency System (Article 700)?
- Exit lighting in a hospital
- Fire alarm system
- HVAC for heating a refrigerated warehouse (Correct answer)
- Egress illumination in a high-rise
Correct answer: HVAC for heating a refrigerated warehouse
Legally Required Standby Systems (Article 701) serve loads required by code for industrial and commercial processes but not directly life-safety, such as HVAC for cold storage.
Question 2: Under NEC 701.12, a legally required standby generator must restore power within:
- 10 seconds
- 30 seconds
- 60 seconds (Correct answer)
- 120 seconds
Correct answer: 60 seconds
Article 701.12 allows up to 60 seconds for legally required standby systems to restore power, unlike the 10-second requirement for emergency systems.
Question 3: A commercial inspector finds emergency generator feeder conductors in the same conduit as normal-power feeders. This is:
- Acceptable if the conduit is metallic
- Acceptable if THHN conductors are used
- A violation of NEC 700.10 (Correct answer)
- Acceptable if the emergency feeder is larger
Correct answer: A violation of NEC 700.10
NEC 700.10(B) requires emergency system wiring to be kept entirely independent of other wiring in separate conduits, cables, or raceways.
Question 4: Storage batteries used as an emergency source under NEC 700 must be:
- Lead-acid type only
- Automatically charged and maintained by a dependable charging means (Correct answer)
- Manually tested weekly by facility staff
- Rated for 24-hour operation minimum
Correct answer: Automatically charged and maintained by a dependable charging means
NEC 700.12(A) requires storage batteries used for emergency systems to be automatically charged and maintained in a fully charged condition.
Question 5: For a required periodic test of an emergency generator, NEC 700.3(B) requires testing under load for at least:
- 15 minutes monthly
- 30 minutes at least every 36 months under load conditions simulating the actual load
- 2 hours annually
- 30 minutes monthly (Correct answer)
Correct answer: 30 minutes monthly
NEC 700.3(B) requires emergency generators to be tested monthly at not less than 30% of the EPS nameplate rating for 30 minutes.
Question 6: An emergency system transfer switch must be listed and approved for emergency use and must transfer all _______ conductors simultaneously.
- Grounded (neutral)
- Ungrounded (hot) (Correct answer)
- Equipment grounding
- All circuit conductors including neutral
Correct answer: Ungrounded (hot)
NEC 700.5 requires the transfer switch to simultaneously transfer all ungrounded conductors, ensuring full circuit switching without backfeed hazards.
Question 7: Under NEC 700, which of the following is NOT an acceptable alternate power source for an emergency system?
- Stored electrical energy (batteries)
- Generator set
- Separate service from a different utility substation on the same grid section (Correct answer)
- Unit equipment with integral battery
Correct answer: Separate service from a different utility substation on the same grid section
A separate service from the same utility grid section does not qualify because a single utility failure could knock out both sources; true independence is required.
E2 Emergency and Standby Systems 3
Which of the following loads is most likely served by a Legally Required Standby System (Article 701) rather than an Emergency System (Article 700)?