Emergency Power For Fire, Life Safety Systems
- Details
- Published on Wednesday, 28 September 2011 08:12
Today emergency and standby systems are used to provide backup power for building systems to provide assurance that life safety systems and critical equipment can maintain their operation during a power outage. The use of these systems almost comes as second nature when designing large, complex facilities. Yet, how well do you know the specific requirements for these systems?
Questions we must consider include:
- When is emergency and standby power required?
- What are the requirements for the design of an emergency and standby power system?
- What building fire safety systems need to be provided with emergency and standby power?
What is it?
In general terms, as defined in NFPA 70: National Electrical Code (NEC), there are three types of emergency and standby power: emergency power, legally required standby power, and optional standby power. Emergency power is required by codes for systems whose operations are essential for safety to human life.
When is it required?
The basic requirements for where the provision of an emergency and standby power is necessary come from the building and fire codes. Whether the local jurisdiction follows NFPA 5000: Building Construction and Safety Code, NFPA 1: Fire Code, NFPA 101: Life Safety Code, the International Building Code (IBC), or the International Fire Code (IFC), the requirements are reasonably consistent. Each of these codes broadly defines the fire, life safety, and critical operations power systems (COPS) that require emergency and standby power systems. While the building codes primarily deal with requirements for new or remodeled buildings, the requirements of the fire codes and NFPA 101 may also apply to existing buildings, as such there may be retroactive emergency and standby power issues to be addressed under these documents.
Specific requirements for emergency and standby power will vary based on building occupancy type, facility use, and critical function. With these parameters, the need for emergency or standby power is determined and described in either a building or fire code. For example, the 2009 IBC requires emergency power for:
- Emergency voice/alarm communications systems in Group A assembly occupancies
- Exit signs
- Means of egress illumination
- Fire alarms and exhaust ventilation in HPM facilities
- Power operated doors in detention facilities.
- Some of the places where the IBC requires standby power include
- Smoke control systems
- Emergency voice/alarm systems in large covered mall buildings
- Accessible means of egress elevators and platform lifts
- Horizontal sliding doors used for egress
- Membrane structure auxiliary inflation systems
- Mechanical vestibule and stair shaft ventilation systems and fire detection systems for smokeproof enclosures.
While the 2009 edition of the IBC and NFPA 5000 have similar requirements for emergency and standby power (such as high-rise buildings and healthcare facilities) there are some requirements that differ slightly. Some of these differences include:
- NFPA 5000 identifies elevators in towers that are used as a second means of egress, in such buildings, the elevator equipment, communications, machine room cooling, and controller cooling all must be provided with normal and standby power.
- Also in NFPA 5000, in buildings more than 120 ft in height, a first responders use elevator must be provided that is served by standby power.
NFPA 101 and NFPA 99
The 2009 edition of NFPA 99 identifies three classifications of essential electrical equipment categories based on the level of criticality of the systems served:
- Life safety branch
- Critical branch
- Equipment system.
The life safety branch is defined as:
A subsystem of the emergency system consisting of feeders and branch circuits, meeting the requirements of Article 700, of NFPA 70 and intended to provide adequate power needs to ensure safety to patients and personnel, and that is automatically connected to alternate power sources during interruption of the normal power source.
The life safety branch of the emergency system provides the emergency power for:
- Illumination of the means of egress
- Lighting of the exit and directional signage
- Fire detection and alarm system
- Non-flammable medical gas system and vacuum systems alarms
- Hospital emergency communication systems
- Task lighting, battery charger, and selected receptacles in generator set location
- Elevator control, communication, and lighting
- Automatic operating egress doors
- Auxiliary fire alarm system functions.
The critical branch is defined as:
A subsystem of the emergency system consisting of feeders and branch circuits supplying energy to task illumination, special power circuits, and selected receptacles serving areas and functions related to patient care and that are connected to alternate power sources by one or more transfer switches during interruption of normal power source.
The critical branch may be divided into multiple branches. The critical branch is dedicated for use in powering specific circuits related to patient care and includes the following:
- Task illumination, selected receptacles, and fixed equipment in critical care areas using anesthetizing gas
- Isolated power systems in special environments
- Task illumination and selected receptacles in patient care, medication preparation, pharmacy dispensing, and nurses stations
- Task illumination and receptacles in specialized patient care areas
- Nurse call systems
- Bone, blood, and tissue banks
- Other selected illumination and receptacles.
In order to be able to meet the time requirements of these two essential equipment categories, it is typically necessary to have some combination of stored power and generator power solution.
The equipment system is defined as:
A system of circuits and equipment arranged for delayed, automatic, or manual connection to the alternate power source and that serves primarily 3-phase power equipment.
The equipment system is allowed to serve the following delayed-automatic or manual connection to the alternate power source:
- Heating equipment serving various treatment spaces
- Patient rooms under specific conditions
- Certain elevators
- HVAC systems for select areas
- Hyperbaric and hypobaric facilities
- Autoclaving equipment
- Controls for the above listed equipment
- Other selected equipment.
Fire codes
While the fire codes are companion documents to the building codes, remember that the fire codes are an occupancy and use enforcement document, not a construction enforcement document per se. As such, it is unusual to find requirements in a fire code that would require a new system to be installed in an existing building under a fire code. The typical requirements of a fire code will be to maintain the systems in the building that were required under the version of the code followed when the building was first built.
Exceptions to this distinction would include:
- Substantial changes made in building construction, occupancy, or use after the adoption of the code
- Existing buildings, structures or operations that were not legally in existence prior to adoption of the code
- Specific hazardous conditions when specifically addressed by the code
- Existing facilities that have been identified as constituting a distinct hazard to life or property.
With this basic differentiation, the following are some of the primary fire code implications for emergency and standby power.
Design requirements
Once the building code establishes the need for an emergency and standby power system, their design requirements are found in installation standards, such as the 2008 NEC. Article 700 of NFPA 70 establishes the ground rules for emergency system’s components, equipment and their installation. The article addresses basic requirements for these systems, defines circuit wiring, sources of power, and emergency system circuits. In accordance with Section 700.12, the emergency lighting and emergency power must be available within 10 seconds of a failure of the normal building power supply. This can be accomplished by:
- A storage battery that can maintain the load for a minimum of 1.5 hours without a voltage drop below 87.5% of normal
- Generator set that automatically starts on failure of normal service that has an automatic transfer switch for all required circuits (if the generator requires greater than 10 seconds to develop power, an auxiliary power supply must be provided until the generator can pick up the load)
- A UPS that meets the requirements of one of the two means described above
- Separate service (where approved by the authority having jurisdiction)
- Fuel cell with a rating and capacity to supply and maintain the total load for not less than two hours of full demand operation.
Similarly, Article 701 of the 2008 NEC covers installation requirements for legally required standby systems. Article 702 of the NEC covers these requirements for optional standby systems.
COPS
In the 2008 edition of NFPA 70 a new Article 708: Critical Operations Power Systems was added to the mix of emergency and standby power. COPS raises the bar for the reliability of power systems well above previous versions of NFPA 70.
The article provides for the protection of vital infrastructure facilities that, if destroyed, would disrupt public health, safety, or national security. The intended application would be for facilities such as communications centers, air traffic control centers, hazardous materials handling, financial data processing, transportation centers, and other at-risk structures. Potential exposures to these facilities would include natural disasters, such as hurricanes and tornados, and manmade disasters such as terrorist acts.
Reason for COPS
For many years the NEC has addressed the need for emergency power in buildings to assist in getting people safely out of buildings. The focus on emergency power in assembly and healthcare facilities in particular has enhanced the safety for high occupancy facilities and in the facilities where the occupants may have limited ability to be moved.
Over the past 20 years we have witnessed many disasters including devastating wind storms, hurricanes, and floods, many of which have caused loss of power to many of the key emergency management operations. Such emergency management facilities need to be operational in order to appropriately respond to these incidents. Other recent events that have raised concern over reliability, operation, and approach to building emergency and standby systems include the Sept. 11, 2001 attacks, threats of biological terrorist attacks, and threats of attacks on our infrastructure.
COPS have been developed to provide guidance on the design of power systems for facilities or parts of facilities that require continuous operation for the reasons of public safety, emergency management, national security, or business continuity. These facilities may include:
- Air traffic control centers
- Chemical, petrochemical, and hazardous material (including biohazard) handling facilities
- Communications centers, telephone exchanges, cellular tower sites
- 911 call centers
- Central station service facilities (fire and security system monitoring)
- Financial, banking, business data processing facilities
- Hospitals and associated support facilities
- Police, fire, civil defense facilities including power for radio repeater operations
- Emergency evacuation centers
- Transportation infrastructure –airports, rail stations, seaports
- Municipal infrastructure –water and sewer treatment facilities
- Fuel supply pumping stations (i.e. natural gas distribution and delivery infrastructure
- Offices and facilities deemed critical to continuity of government
- Radio and television stations.
Similar to the approach taken to Articles 700 and 701, the determination on where COPS is required is from the authority having jurisdiction (AHJ) in the form of emergency management directors, fire officials, police officials, building officials, Federal Emergency Management Agency, and others.
In accordance with Section 708.4, a risk assessment must be conducted for COPS to:
- Identify hazards (naturally occurring and human caused)
- Determine the likelihood of their occurrence
- Assess the vulnerability of the power system to those hazards
- Evaluate the need for physical security
- Develop a mitigation strategy.
The system is required to be commissioned and periodically tested.
A facility with a COPS is required to have a documented plan that considers emergency operations, and response, recovery, and continuity of operations.
As our world continues to change, the applications for emergency and standby power should be expected to continue to play a key role in providing reliable power for our most critical needs. The more we come to rely on consistent delivery of power to run our world, the more we will need to rely on emergency and standby power.
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