Figure 1. Known as the Department of Public Safety Communications, the county's 911 Call Center is responsible for receiving emergency calls within Frederick County and dispatching fire and rescue and law enforcement units as needed


Located one hour west of Washington, DC, and Dulles International Airport, Frederick County is the northernmost point in the Commonwealth of Virginia, with Winchester as its county seat. Formed in 1743, the county currently has a total area of 415 miles and a population of about 75,000. In 2007, a two-story, 70,000-square-foot (sq-ft) building was designed and built near the Winchester Regional Airport to combine the offices of the Frederick County 911 Call Center, the Frederick County Sheriff’s Department, and the Fire and Rescue headquarters.

Known as the Department of Public Safety Communications, the county’s 911 Call Center is responsible for receiving emergency calls within Frederick County and dispatching fire and rescue and law enforcement units as needed. Public safety is the single most important mission for the entire building. In addition, an 8,000-sq-ft, single-story ancillary building was constructed to house an evidence lab and processing rooms, vehicle forensic and maintenance bays, and law enforcement storage.

Having a reliable backup power system to protect these vital public safety networks was an integral part of the design/build blueprint from day one, according to Gary Ball, project coordinator for general contractor Howard Shockey & Sons, Inc., (Shockey), Winchester, VA. The lives and safety of county citizens in the event of severe weather or a utility power outage was the number one concern.

Working closely with the building designer, AECOM, which has an office in Virginia Beach, VA, Shockey turned to Trumbo Electric, Broadway, VA, for engineering and technical support. John Knepper, Jr., P.E., Trumbo vice president, toured the new buildings with Lee Anna Pyles, director of public safety communications for Frederick County, along with Sheriff Robert Williamson and former director of fire/rescue Gary DuBrueler to determine the emergency load needs for the facility, which were varied and highly sophisticated.


Pyles explained that the heart and soul of the new complex was founded on the provision of emergency services. There was no room for a failed response for any one of these first responders. The county has 14 full-time communications officers with at least two on duty 24/7/365. All EMD-certified, these officers answer 911 and non-emergency phone calls and dispatch the calls for service. “We manage law enforcement and fire/EMS for the county and for the towns of Middletown and Stephens City,” said Pyles. “There are 11 fire stations in Frederick County and over 100 sworn law enforcement officers. Last year, we responded to 272,000 phone calls; 53,448 of those were 911 calls- that’s 147 emergency calls per day.”

Defining Emergency Power

All public safety offices and facilities must be maintained for communications and dispatch of county emergency services. The county wanted the new facility to have full emergency backup power to be able to completely function in any emergency. The original design called for a 1,250-kW emergency generator system with one generator to back up the entire facility. However, the county’s budget for the facility was not adequate to meet this demand. Cost-savings alternatives were investigated in an attempt to bring the project into budget without compromising the needs for the facility.

One cost-savings alternative that was considered was to provide emergency power only for the most critical needs, such as the 911 center, data processing facilities, and lighting. This would have required most of the HVAC to be lost during a power outage. “Without HVAC, many functions would be limited to several hours of service in the event of an extended power failure during severe weather conditions,” Pyles said. “We finally determined that full backup power was essential to our core mission.”

“When failure is not an option, the components most needed are superior reliability, redundancy, and serviceability,” Knepper said. He went on to explain the complex problems posed by selecting the traditional choice of a single, large-displacement engine generator: not only would it take well over a year to be delivered, but if this single-engine generator failed, there would be no backup (redundant) power source.

Knepper determined that the greatest need for the facility was an integrated approach to generator paralleling that would provide the reliability and redundancy demanded by a building filled with first responders.

“In exploring choices, we looked at several alternatives, including options that involved paralleling smaller generators,” Knepper said. Ultimately, he recommended a Modular Power System (MPS) from Generac Power Systems (Generac), Waukesha, WI. “This is an integrated approach to generator paralleling that is cost competitive with large single gen sets and traditional paralleling systems.”

In a Generac MPS, each genset backs up the others in the system. This means that critical loads for the Call Center, Sheriff’s Department, or Fire and Rescue Service would each get redundant protection. And there was another important feature-serviceability. The Generac MPS has built-in redundancy, which would allow the Center’s individual units to be taken off-line for routine maintenance while retaining total coverage for critical circuits. Generac MPS generators use high-volume, highly reliable, over-the-road truck or industrial engines that can easily be serviced by qualified diesel technicians.

Furthermore, the space allotted for electrical equipment within the new facility did not allow for conventional generator paralleling switch gear. With the Generac MPS, switching is incorporated into each generator and is networked to the digital PowerManager parallel controller. This eliminates the need for large paralleling switch gear in the building.

Figure 2. All emergency calls in Frederick County are routed through its Department of Public Safety Communications


Finally, when the Public Safety Building needs to expand, the county can add units quickly and easily as they are needed. Frederick County could purchase the generating power needed today without fear of over spending on a larger system that might never be utilized.

”What I find significant about this solution,” Knepper said, “is that all connections between the utility and generator sources are made at the automatic transfer switch for the building. I like the simple RS485 communications interface between the generators and paralleling controller. Automatic control through the building energy management system will limit the load that is applied to the generators in the event that one generator fails. This will allow the most critical systems-like building life safety loads, general lighting throughout and the Emergency Operations Center itself-to continue to operate should either generator fail,” he said.

Pyles, Williamson, and DuBrueler agreed with the standby power plan for the Center, and the project was approved in fall 2006.

Details of a Highly Reliable Generator System

Knepper ordered the MPS System from Generac. Trumbo Electric prepared the drawings and specifications for the emergency power system. A representative of the distributor, Kelly Generator and Equipment, Inc., Owings, MD, was there every day during the installation and helped through every phase of the job. “For each step of this installation, from technical advice on modular type paralleling systems and what equipment to order, to availability and fast delivery, we had praiseworthy support from both Kelly and Generac,” Knepper said.

Based on this good counsel, the significant components of the building’s electrical service, distribution and generation system that Knepper purchased for the public safety building include:

  • 1,600-amp (A), 480-volt (V), three-phase utility power service
  • Two by 500-kW MPS diesel engine generators
  • 6,000-gallon Convault brand concrete diesel fuel tank equipped with internal secondary containment.
  • Zenith ZBTS bypass isolation automatic transfer switch (ATS) designed to allow uninterrupted operation should the transfer switch require service or repair. It is rated 1,600 A at 480 V, three phase and is designed to transfer the entire facility to generator power
  • Liebert brand 65-kilovolt-ampere (kVA)/ 52-kW online double-conversion uninterruptible power supply (UPS) to provide uninterrupted power to the emergency communications and operations center in the event of loss of utility power. It is equipped with battery capacity for 20 minutes of operation at full load. Typically, the generator will be on-line and providing emergency power within 10 seconds of loss of utility power. An external maintenance bypass is provided to allow uninterrupted operation in the event that the UPS requires maintenance or repair.
  • Surge protective devices (SPD) are installed at the service entrance and at distribution panel boards serving ECC and EOC electronic equipment

Knepper explained that the entire facility is classed as emergency load and therefore requires a stand-by power generator capable of carrying 100 percent of the total load. The generators must be capable of coming online within 10 seconds of power failure. This meant that the fuel tank had to be sized for 72 hours of operation at 100 percent load, including power generators and boilers.

Knepper explained that the automatic transfer switch was purchased through Kelly Generator, supplier of the Generac modular power system. The UPS and fuel tank were sourced separately by Trumbo Electric to complete the package. The UPS was purchased from Liebert Corporation through the Richmond, VA, sales office and the fuel tank was purchased from Core Engineered Solutions, Herndon, VA.


Figure 3. Generac's solution provided redundancy not available from other solutions

Nothing but Good Service

Steve Richman, the Public Safety Building facility maintenance supervisor, said, “I was not here when the system was installed. But we have had nothing but good service from the Generac system as well as from Kelly Generator. We’ve had a few minor power outages since I’ve been here. When these occurred, the generators immediately went to work and performed perfectly. We exercise the engines for 20 minutes every Monday morning at 7:00 a.m. and they never miss a beat. This is a first-class system and very good quality equipment which allows me to sleep well each night.”

Finally, Knepper said, “I know this is a highly reliable generator system because I have had zero calls for service. In my line of work, it doesn’t get any better than that.”

Sidebar: Significant Facts

  • The building houses the County Sheriff’s Office, Fire and Rescue Services, Emergency Communications Center (ECC), and Emergency Operations Center (EOC).
  • Emergency egress and exit lighting systems are equipped with unit-mounted batteries to provide instant illumination in the event of power failure.
  • The fire alarm is equipped with battery backup. The strobes and horns are wired to separate circuits to allow silencing of the horns without deactivating the strobe lights, therefore not disrupting the ECC operations during alarm conditions.
  • There are two incoming telephone service lines to the building.
  • A number of spare telecommunication and power conduits easily accommodate future expansions.
  • The Center has redundant HVAC for the ECC and EOC as required by NFPA 1221.
  • The building is protected by a wet pipe sprinkler system. ECC and EOC areas are equipped with a pre-action sprinkler system to protect the areas from accidental water discharge. The Communications Equipment Room is protected by a FM-200 fire suppression system.