City of Lilburn Pavilion Design
This two-story city-owned 9,500 SF building project involved the demolition of the existing structure in preparation for the pavilion. The pavilion’s main level consisted of an open area with restrooms while the basement level contained a green room, restrooms, general storage, a service area, and a vestibule area.
The Electrical scope involved first getting power to the building from the power source (utility pole mounted transformer) being approx. 200 feet away from the Main Distribution Panel (MDP) located in the vestibule area of the basement. As such voltage drop calculation (NEC Table 9) was necessary to ensure appropriate efficiency of operation to avoid potential malfunction or poor performance. The National Electrical Code (NEC), 210-19(a) (FPN 4) and 215-2 (b) (FPN 3), recommends 5% voltage drop for feeder circuits and 3% for branch circuits. This analysis was used to support the Riser one-line design.
Secondly, power (branch circuits) to the Master Equipment List (MEL) from the MDP was analyzed following guidance in the National Electrical Code (NFPA 70). To generate the Electrical Panel Schedule, calculation was performed in an excel spread sheet in accordance with the NEC requirements (220.40 and 220.42). When sizing the branch-circuit conductors, the minimum branch-circuit conductor size has an allowable ampacity not less than 125 percent of the continuous load (NEC 210.19(A)(1)). When sizing overcurrent protection (NEC 240.4), the overcurrent device rating was not less than 125 percent of the continuous load [210.20(A)]. The conductor amperage rating was chosen in accordance with the 75°C column of Table 310.15(B)(16). The overprotection for each branch circuit were sized per NEC 310.15 which protects conductors based on their ampacities. The supply to these conductors were protected per the standard circuit breakers represented in NEC 240.6.