NEC 210.19(A) Informational Note / high-rise office Single Line Diagram
What it means on the job
This branch circuit EXCEEDS the enforced 3% maximum, so it is not compliant. Calculation (single-phase): Vd = 2 x I x R x L / 1000 = 2 x 20A x 1.93 x 85 / 1000 = 6.56V. The circuit is 120V nominal, so VD% = 6.56V / 120V x 100 = 5.47% — NOT 2.7% (2.7% only results from erroneously dividing by 240V, the wrong nominal for a 120V circuit). At 5.47% the drop exceeds both the project-enforced 3% branch maximum and the NEC 210.19(A) Informational Note 3% recommendation. To meet 3% (3.6V max) at 20A over 85 ft would require roughly 8 AWG copper, or the load/length must be reduced.
Tested in 2 CraftIQ puzzles
- whats-wronghigh-rise office Office TI: Voltage Drop on Branch Circuit
- code-checkhigh-rise office Office TI: Branch Circuit Voltage Drop
Related NEC sections
NEC 110.27 / NFPA 70E
Battery cabinets must remain closed to prevent accidental contact with live DC bus bars and to contain any thermal event. Open cabinets also violate NEC 110.27 regarding guarding of live parts and create arc flash hazards.
NEC 210.11(C)(3)
NEC 210.11(C)(3) requires at least one 20A branch circuit to supply bathroom receptacle outlets. This circuit is permitted to supply receptacles in multiple bathrooms. The key restriction is that no other outlets (lights, exhaust fans, etc.) from other rooms can be on this circuit — it must serve only bathroom receptacles. GFCI protection is separately required by NEC 210.8(A)(1).
NEC 210.12(A)
This installation is fully code-compliant. NEC 210.12(A) requires AFCI protection for all 120V, 15A and 20A branch circuits supplying outlets and devices in dwelling unit bedrooms. A 15A combination-type AFCI breaker with 14 AWG wiring is correctly matched (NEC Table 310.16 rates 14 AWG at 15A). Tamper-resistant receptacles are required per NEC 406.12 in all dwelling unit locations. This is a textbook installation that IBEW halls use as a baseline example of proper bedroom circuit design.
NEC 210.20(A)
NEC 210.20(A) requires that continuous loads (3+ hours, which applies to IT equipment) not exceed 80% of the branch circuit breaker rating. Loading to 95% will cause nuisance tripping and violates the continuous load derating requirement.
NEC 210.4(B)
When a shared neutral (multi-wire branch circuit) is used, the neutral must be identified as to which circuits it serves. Additionally, simultaneous disconnect of all ungrounded conductors sharing the neutral is required.
NEC 210.52(B)(1)
The NEC requires a minimum of two 20A small appliance branch circuits to serve the kitchen countertop receptacles. A refrigerator is permitted (but not required) to be on one of these circuits. However, best practice is to provide a dedicated circuit for the refrigerator so that a tripped breaker on the small appliance circuit does not de-energize the refrigerator and spoil food.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.