Case Study
Ensuring the City of Raleigh’s Emergency Preparedness is Backed Up
When emergencies or disasters strike, people turn to governments for protection and recovery efforts. So it’s vital for governments themselves to be prepared at all times to act quickly and appropriately in emergencies. The headquarters of Raleigh, N.C.’s city government – called the Avery C. Upchurch Government Complex – is also the command post for many agencies in times of crises. The complex had two existing generator sets to provide power for emergency lighting, the computer center and the emergency 911 communications center. However, it had no backup for the building’s heating or cooling systems, or for the other departments that needed to be staffed during emergencies.
An engineer, who was hired by the city, designed a solution to provide backup power to the entire building. The peak load was calculated between 800 kilowatts to 1000 kilowatts (kW) during the hot summer months so a minimum of a 1 megawatt genset would be required. As a margin of safety, the engineer determined that an 1100kW genset would be the best solution along with a redundant system. The city sent out a request for bids.
National Power Corporation proposed a 1500kW Generac Modular Power System (MPS) consisting of two Generac Gemini 750kW modules. Each module would have two 375kW gensets in each enclosure and a small PowerManager System Controller that would be installed up to 1,200 feet away. The MD750 units can be installed as a single 750kW generator set. But they have paralleling switches and totally independent support systems that allow each generator set to operate separately.
As the successful bidder, we provided the city government with an 1125kW redundant system and a 3000A service entrance rated closed transition transfer switch. As a result, the city of Raleigh saved a considerable sum of money. The four generator sets that were installed actually cost less than if redundant 1100kW sets were installed. The city saved money because only 2250 amps of wire were pulled instead of the 3300 amps of wire that would have been required for a redundant system using two 1100kW generator sets. No freestanding paralleling switchgear was needed.
The engineer designed the system so that the existing gensets continue to supply their emergency loads with a 10-second start requirement, according to the National Fire Protection Association Section 110 (NFPA 110) regulations. When the Generac 750kW modules come on line within 10 to 25 seconds, the 3000A service entrance rated transfers the MPS system to the load and transfer switches downstream from the MPS system assume the normal service is available and retransfer to the MPS bus. When utility power returns, after a return to normal power time delay, there is a closed transition back to the normal source. The Generac MPS modules cool down, shut off and are ready for the next power interruption.
The installation went smoother and quicker than expected. The entire system was “commissioned and load tested within one day,” our staff noted. “This was unheard of prior to the advent of Generac’s MPS solution. A similar system utilizing four generator sets, discreet components and standard paralleling switchgear would have taken a week to commission.”
