E2 Plan Review and Inspections 3 — Questions and Answers
Question 1: During a plan review, an inspector sees that the one-line diagram shows a 2000A service with a single 2000A disconnect. The building also has an emergency generator. Which NEC section governs the number and grouping of service disconnects?
- NEC 230.71, which limits service disconnecting means to a maximum of six disconnects (Correct answer)
- NEC 230.82, which permits up to ten disconnects for large commercial buildings
- NEC 700.12, which governs emergency system power supply
- NEC 225.33, which addresses outdoor feeder disconnects
Correct answer: NEC 230.71, which limits service disconnecting means to a maximum of six disconnects
NEC 230.71 permits a maximum of six disconnects for a service, and all disconnects must be grouped together.
Question 2: An inspector is reviewing plans for a restaurant kitchen and notices that the equipment grounding conductors for all circuits are shown as the same size. What potential issue should be investigated?
- Equipment grounding conductors must all be the same size per NEC 250.122
- NEC 250.122 requires EGCs to be sized based on the rating of the overcurrent device protecting each circuit (Correct answer)
- The issue is only relevant if circuits exceed 100A
- Equipment grounding conductor size is determined solely by the phase conductor size
Correct answer: NEC 250.122 requires EGCs to be sized based on the rating of the overcurrent device protecting each circuit
NEC 250.122 requires equipment grounding conductors to be sized based on the ampere rating of the overcurrent protective device in the circuit, so larger circuits need larger EGCs.
Question 3: A commercial plan review shows a 208Y/120V panelboard feeding a dedicated computer room. The plans indicate that isolated ground receptacles will be installed. What must the inspector verify on the plans?
- That the isolated ground receptacles are connected to a separate grounding electrode system
- That the isolated ground circuit includes an insulated equipment grounding conductor run back to the panel, and the panel enclosure is still grounded (Correct answer)
- That all circuits in the computer room use isolated ground receptacles only
- That the isolated ground system is connected directly to building steel
Correct answer: That the isolated ground circuit includes an insulated equipment grounding conductor run back to the panel, and the panel enclosure is still grounded
NEC 250.146(D) requires isolated ground receptacles to include an insulated EGC back to the source, while the panel enclosure must remain grounded.
Question 4: While reviewing commercial plans, an inspector finds that a rooftop HVAC unit disconnect is shown mounted on the rooftop adjacent to the unit. The unit is fed by a 460V feeder. Which requirement is most critical to verify?
- That the disconnect enclosure is rated for outdoor, wet locations (NEMA 3R or better)
- That the disconnect is located within sight of the unit and is readily accessible per NEC 430.102 (Correct answer)
- That the feeder conduit is rigid metal conduit only on rooftops
- That a ground fault circuit interrupter is installed for the disconnect
Correct answer: That the disconnect is located within sight of the unit and is readily accessible per NEC 430.102
NEC 430.102(B) requires a disconnect within sight of motor-driven equipment, and NEC 430.107 requires it to be readily accessible.
Question 5: During a rough-in inspection of a commercial building, the inspector observes that flexible conduit (FMC) is used for the final connection to a rooftop air handler. The run is 10 feet long. What NEC requirement applies?
- FMC is limited to 6 feet for equipment connections per NEC 350.30(A)
- FMC over 6 feet requires a bonding jumper per NEC 250.118 since it may not provide an adequate ground path (Correct answer)
- FMC cannot be used for equipment above 277V
- No limitation applies as long as the conduit is secured every 4.5 feet
Correct answer: FMC over 6 feet requires a bonding jumper per NEC 250.118 since it may not provide an adequate ground path
FMC longer than 6 feet may not provide an adequate ground path, so NEC 250.118 requires a bonding jumper in parallel with FMC exceeding this limit.
Question 6: A commercial plan review reveals that all branch circuit conductors are shown as 12 AWG copper. Some circuits have 30A breakers for dedicated equipment. What code issue does this present?
- 12 AWG is acceptable for up to 30A if rated at 90°C
- 12 AWG copper is only rated for 20A overcurrent protection per NEC 240.4(D), so 30A breakers are not permitted (Correct answer)
- 30A breakers are allowed on 12 AWG if the equipment nameplate requires it
- The 30A breakers are acceptable if AFCI protection is provided
Correct answer: 12 AWG copper is only rated for 20A overcurrent protection per NEC 240.4(D), so 30A breakers are not permitted
NEC 240.4(D) limits 12 AWG copper to a maximum 20A overcurrent device; 30A breakers on 12 AWG violate this requirement.
Question 7: An inspector reviewing plans for a commercial office building sees that receptacle circuits in an open office area are not shown with AFCI protection. The building is a new 2023 NEC project. What should the inspector require?
- AFCI is only required in dwelling units and does not apply to commercial offices
- The inspector should verify the applicable edition of the NEC adopted locally, as AFCI requirements for commercial have expanded in recent editions (Correct answer)
- Require AFCI on all receptacle circuits since the 2023 NEC mandates it for all occupancies
- No action is needed since commercial spaces are exempt from AFCI requirements
Correct answer: The inspector should verify the applicable edition of the NEC adopted locally, as AFCI requirements for commercial have expanded in recent editions
AFCI requirements have expanded with each NEC edition, and applicability in commercial spaces depends on the locally adopted code edition; the inspector must verify the adopted edition.
E2 Plan Review and Inspections 3
During a plan review, an inspector sees that the one-line diagram shows a 2000A service with a single 2000A disconnect.
The building also has an emergency generator.
Which NEC section governs the number and grouping of service disconnects?