Electrical Systems Existing Conditions & Building Load Summary Technical Assingment#2 Due October 26, 2004 Table of Content: Page 1 ~ Single Line Diagram 1 2 ~ Electrical System Narrative 2-3 3 ~ Lamp and Ballast Table 4 4 ~ Major Mechanical Equipment Electrical 5 5 ~ NEC Load Calculation 6-10 Lighting ~ Electrical Faculty Consultant: Professor Martin Moeck
Single Line Diagram
Electrical System Narrative The electrical power distribution configuration for the is a radial system. The exterior pad mounted transformer, owned by PSE & G Utility, steps down the electricity from delta utility voltage to 480Y/277 building utilization voltage. The electricity enters the building through one main feeder and into one main distribution panel with a 2000A three pole circuit breaker with ground fault protection. The 480Y/277V, three phase, four wire, 50K A.I.C. Main Distribution Panel services other distribution panels and equipment throughout the building. All fluorescent lighting is run at 277V; Main mechanical equipment is run at 480V. All computer labs are serviced through dedicated panel boards with two full sized neutral conductors and a dry type step down transformer with K-factor protection. All remaining loads running at 120V are serviced by 208/120V dry type transformers to panels located in one of the electrical room or closets in the building. For lighting and receptacle panels: All panels for use at 240 V AC maximum incorporate circuit breakers with a minimum rating of 10K A.I.C.; All panels for use at 480/277V incorporate circuit breakers with a minimum rating of 25K A.I.C. (Building specifications, section 16470-3) Emergency Power Systems: Emergency power is activated by an Area Monitor Panel that monitors when an area protected bye a normally off emergency lighting is turned off inadvertently or by a general power failure. In the event of a power outage, the Area Monitor Panel activates an outdoor 200KW diesel powered, single ball bearing, four pole generator with a stationary glycol cooled, compression ignition, four cycle engine. The generator is equipped with a 24V electric starting system and a lead acid battery. Overcurrent protection is provided by a 500A, 3pole circuit breaker. The generator is connection to three automatic transfer switches and one normally off 208/120V panel located in the main electrical room. The first 100A, 3 phase automatic transfer switch services a normal/emergency distribution panel that provides 277V emergency lighting. The second 150A, 3 phase automatic transfer switch services a Normal/Standby Distribution Panel that provides power to hot water circulation pumps, the buildings one elevator, and two 208/120V emergency power panels. The third automatic transfer switch services the buildings fire protection. Fire protection is provided by a 20 HP fire pump. The feeder for the fire pump feeds off of the building s main line before the Main Distribution Panel. Overcurrent Protective Devices: The main feeder to the Main Distribution Panel receives overcurrent protection in the form of 2000A, 3 pole, main circuit breaker with ground fault protection. The majority of panels are main lug with a circuit breaker at the Main Distribution Panel. Panels off of distribution panels requiring step down transformers contain enclosed circuit breakers after the transformer. Overcurrent protection for the elevator is provided by a 60A, three pole fused disconnect switch. Fused switch combination starters are used for the jockey pump and the hot water circulation pumps.
Electrical System Narrative (Continued) Location of Equipment: The main distribution panel and emergency controls are located in the main electrical room on the first floor. All motor controls for the Mechanical and HVAC systems are located in the mechanical room also located on the first floor. Three more secondary electrical rooms, contain secondary distribution, receptacle, lighting, and computer panels. Typical Lighting Systems: The typical lighting systems for the interior of the are fluorescent troffers, compact fluorescent downlights, and direct/indirect linear fluorescent pendants operating at 277V. Incandescent, low voltage, aisle lighting is found in the auditorium with its dimming being controlled from a dimming panel located in a nearby dimming booth. The exterior lighting contains High Pressure Sodium sources mounted on the walls, with Metal Halide sources illuminating the parking area. Power Factor Correction: This electrical system contains no power factor correction systems nor have I heard any indication of any being installed after construction and operation. However, specifications call for individual pieces of equipment to utilized high power factors. Important Design Requirements: Reliability during school time hours is an important design factor. Being in a down town district, security is a main concern. In the event of a power outage, power must be maintained for security and lighting systems immediately to provide security for the students and faculty of the school.
Lamp & Ballast Table
Major Mechanical Equipment Table - electrical loads
Major Mechanical Equipment Table electrical loads
NEC Building Design Load Calculation Major Mechanical Motors:
NEC Building Design Load Calculation (Continued) Receptacle Load: Takeoffs per section per floor Lighting Load:
NEC Building Design Load Calculation (Continued) Miscellaneous Equipment:
NEC Building Design Load Calculation (Continued) Feeder ampacity from total load: Comparison of NEC Load to Existing Feeder & Main Distribution Panel: Existing feeder is sized as 5 sets of 4#600kcmill From NEC Table 310.16, 600kcmill copper conductors, under 75 degrees C are rated for 420 Amps. 5 x 420 A = 2100 A My value of 1738.14 is lower than 2100A therefore, the feeder is properly sized. The difference can be attributed oversizing of feeders that I did not account for. The overcurrent protection is rated for 2000A. Since the NEC load is below 2000A the panel is appropriately protected. The main feeder and main distribution panel are properly sized.