Integrating fire systems with HVAC controls
With building sophistication comes the need for a BAS to allow for nearly seamless operation of various interrelated equipment.
By Craig Studer, PE, Arup, Chicago
The bigger the building, the more sophisticated the building systems become. With the advent of smart building technology, heating, cooling, electrical, lighting, security, and other systems need monitoring and intercommunication for optimized efficiency and operation. With sophistication comes the need for a BAS to allow for nearly seamless operation of various interrelated equipment. Each manufacturer’s BAS has its own protocol for monitoring conditions and communicating operational directives to maintain the proper building environment and efficiency.
Like a BAS, fire protection and life safety systems have evolved into sophisticated computer-based systems, requiring the use of a fire detection and alarm system control panel to allow monitoring, communication, and proper operation when an emergency arises. Often fire protection and life safety systems must interact with other building systems to provide a proper level of protection.
While the fire alarm system is fully capable of performing the necessary actions to accomplish the building systems’ responses, there can be some efficiencies accomplished by using the BAS, including minimizing additional equipment, expediting system acceptance testing, reducing installation costs, sharing, and consolidating information at a central location where the mechanical equipment can be precisely monitored during emergency incidents.
Smoke control systems are a good example of the marriage of building mechanical systems with fire protection/life safety systems. Fans are starting or stopping; dampers are opening or closing; doors are closing, opening, or unlocking; elevators are being recalled. Both the BAS and fire alarm systems have jobs to do, but, like dancing, someone has to lead. It seems that the BAS is the natural choice under these circumstances, but there are issues that must be recognized and reconciled.
There are several things to consider when determining whether a BAS should be used to control the smoke control system. One would be the ability of the various systems that normally have independent network communications to have a common communications. It is advantageous to have the fire alarm system, BAS, and other related systems share a common infrastructure network to facilitate communication and redundancy. This also can have the benefit of cost savings.
Another consideration is the acceptability of the BAS to control the smoke control system operation. The International Building Code (IBC) has been adopted by a large portion of the United States. IBC Section 909 covers smoke control systems, including where they are required, the procedures for determining system parameters, the acceptable methods that may be used to accomplish smoke control, and the requirements to document the system’s actual performance. It recognizes that the smoke control system is a life safety system and must maintain the same high level of reliability required for any type of fire protection or life safety system.
IBC Section 909 requires smoke control systems to be initiated by sprinkler system or smoke detection system operation. It also requires systems providing control input or output to the mechanical smoke control systems to comply with Section 907, Fire Alarm and Detection Systems, and NFPA 72, National Fire Alarm and Signaling Code. Most importantly, it states that such systems must be equipped with a control unit that complies with UL 864 and has to be listed as smoke control equipment.
UL 864 requirements address control units and accessories used for many NFPA standards, including NFPA 72 and NFPA 92, Standard for Smoke-Control Systems. (Note: 92A and 92B have been combined in the 2012 edition to a single standard: NFPA 92, Standard for Smoke Control Systems.) Each system is tested by UL, which then lists the complying equipment under the “UUKL” designation in its product directory. The BAS must meet these requirements and be listed in order to control a smoke control system.
In addition to listed components, the BAS must comply with NFPA 72 requirements such as circuit type, reliability, wiring arrangements, and limitations and they must be used by the BAS for all portions related to the smoke control system.
The smoke control system may consist of equipment that will be used as part of the normal HVAC system. The equipment includes supply fans, exhaust fans, their associated dampers and variable air volume (VAV) boxes, as well as ductwork. Where buildings include parking levels, garage exhaust fans used for removing carbon monoxide from vehicle exhaust may be used under fire conditions. This system must be controlled to place all equipment into the proper configuration for smoke control sequences, such as the operation of a sprinkler system.
In the case of garage exhaust fans, they normally are controlled to operate when a certain level of carbon monoxide is exceeded. These fans could be shut off if ambient conditions are satisfied. Under fire conditions, the BAS will need to override the fans’ normal conditions to accommodate emergency conditions.
Similarly, building HVAC supply fans and exhaust fans will play different roles under smoke control conditions. For example, one method of smoke control is to create a “pressure sandwich” so that the fire floor is maintained in a negative condition compared to the adjacent floors. To accomplish this, the building’s HVAC system must revert from providing supply and exhaust air to all floors and reconfigure to smoke control conditions. To do this, the BAS must configure dampers and possibly modify fan operation to keep the fire floor in a negative condition by providing positive pressurization above and below the fire floor or by exhausting the fire floor.
The next consideration is the ability of the BAS and the fire alarm system to coordinate with each other. A smoke control system is required to have a firefighters’ smoke control panel. The purpose of this panel is to provide a visual display of the current status of the smoke control system. This enables the responding firefighters to make effective decisions, including the option to manually override automatic system operation at the panel through the use of the panel’s three-position (“on-auto-off” or “open-auto-closed”) switches to change the smoke control sequence to accommodate actual conditions.Whatever the operational conditions, it is necessary to prepare a sequence of operation matrix for each floor condition to ensure that the BAS will respond properly to any fire alarm system input.
Most firefighters’ smoke control panel configurations are simplified to minimize operator error during manual operation such as duct cavitation or overpressurization. Each fan is provided with its own three-position switch, but in lieu of providing individual control for each damper in the system, a single three-position switch is provided for each smoke control zone to allow all dampers for that smoke zone to move to their proper position. In addition, this single switch must also initiate any other smoke zone related action. Similarly, fan control can be combined when multiple fans provide a common smoke control function. However, some jurisdictions may require each piece of equipment to have its own control. Consequently, it is necessary to coordinate the system sequence matrix and proposed level of system control with the authority having jurisdiction (AHJ) to determine the acceptable system configuration and operation.
It is critical that the controls contractor and the fire alarm contractor closely coordinate each system action so that all functions that take place under automatic mode are exactly duplicated under manual operation of a panel switch on the firefighters’ smoke control panel. Such functions include fan shutdown, fan operation, damper operation, door closings, doors/windows opening (for make-up air on smoke exhaust systems), and door unlocking as examples. In many cases, other contractors (such as the security system contractor in the case of unlocking secure doors) must provide input for proper smoke zone arrangement. The detailed sequence of operation matrix previously discussed must be implemented by all parties to ensure that a manual initiation of a sequence at the firefighters’ smoke control panel will duplicate the same sequence as an automatic initiation of a smoke control sequence.
Start the process early
Whether the project is design-build, design-bid-build, or another delivery method, it is important to determine early in the design process what will be integrated with the BAS and how. Proper detailed planning by all parties is necessary to provide a successful design and avoid confusion, hasty field modifications, lost time, and additional costs during construction.
The very first task is to confirm that integration for the project is viable. The proposed schedule needs to be evaluated to verify that complicated integrated systems can be properly installed and tested in time to obtain a Certificate of Occupancy. Integrated systems require multiple vendors; close inter-trade coordination and troubleshooting can be difficult to manage under compressed construction schedules. If part of the integrated system package is deficient at the end, the AHJ may determine that the life safety component of the integrated system is compromised and deny occupancy. Often, projects will attempt to obtain a Temporary Certificate of Occupancy to allow certain contractual, nonconstruction functions at the site to proceed while completing minor construction work. But, again, the AHJ will still require properly operating life safety systems first.
A successful design process is difficult to achieve, partly due to the way most design is accomplished. Drawings and specifications are isolated into specific disciplines. As with the systems themselves, it is natural to be zeroed in on what is critical to get your work properly defined. Coordination is required by not only each engineering discipline, but also each related installing trade and even equipment vendors to establish a design path and the integration architecture to make it work.
As part of the design process, it is critical to designate one individual to take the role of systems integrator. In the case of smoke control systems, this person needs to have a well-rounded background in low-voltage signaling and control systems, as well as electrical and mechanical systems. The job will entail supervising the design process and documentation to confirm that the integration process is properly covered by each discipline and that the appropriate equipment is specified and installed.
The integrator will need to review the drawings to verify that references to other disciplines’ drawings or additional detail is included to provide sufficient information regarding interoperability requirements. Similarly, the integrator can review the specification sections to determine that the integration process is properly covered. Depending on the situation, it may be useful to prepare a separate specification section that covers the integration requirements and refer to the other related sections to tie things together. Similarly, each individual system specification section can refer to the integrated system specification, closing the design loop.
The design process also should establish the initial sequence of operation for all integrated systems. As discussed earlier, the final matrix can be prepared by the contractors based on actual installed conditions. But an initial matrix will help clarify engineering goals and provide a path for the construction team.
Inspection and testing
Integrated systems require enough time to test to verify that the systems interoperability is functioning properly. In the case of a smoke control system, the HVAC systems have additional issues. The mechanical equipment involved with smoke control must be modified to comply with smoke control code requirements in addition to the BAS control requirements. It is important that the engineer, as well as the installing contractor and the equipment vendor, understand the impact of these requirements on providing an approved complete installation.
Normal HVAC fans used for smoke control functions must be equipped with 1.5 times the number of belts to provide redundancy. Their motor’s service factor is increased. HVAC ducts that are used for smoke control and traverse smoke zones must be tested at 1.5 times their design pressure with leakage of no more than 5% of the design flow. Standard HVAC ducts are tested to less stringent requirements.
System smoke dampers that affect the performance of the smoke control system also are monitored to confirm that they modulate to their proper position under smoke control system initiation. They are inspected and tested to confirm that they have been provided with end switches and that the BAS is providing correct status of their positioning.
Other issues concerning control of smoke control systems include the operation of the fans. It is necessary to verify that supervision of power downstream of the disconnects is being accomplished. The system must provide status indication of this condition at the firefighters’ smoke control panel and at the control unit. Also, testing must confirm that the initiation of a smoke control sequence will allow the fans to start and operate in its smoke control mode despite the status of the normal fan controls or safeties. The smoke control circuiting must bypass any such obstructions that could prevent proper performance.
As touched on previously, security systems often need to be integrated for proper operation of smoke control systems. Sometimes a smoke control system, such as an atrium exhaust system, requires secured doors and/or windows to open on alarm initiation to provide make-up air to allow the system to perform as intended. All such fenestrations must be tested for each scenario.
In the case of all these conditions, testing must confirm that these functions work correctly both under automatic and manual modes, as well as with normal or emergency power.
The inspection and testing of integrated systems is usually exasperating and time-consuming, and often requires multiple rounds of retesting before all the deficiencies are corrected. This is often due to all of these different systems being completed late in the schedule and not enough time to “get the kinks out” prior to testing. Anything that can expedite the commissioning process is appreciated by everyone.
One of the advantages of using the BAS to control the smoke control system is the system’s ability to modify operating conditions to accommodate actual ambient conditions through the use of variable frequency drive fans. The design of smoke control systems is based on many variable conditions, including temperature, wind conditions and the quality or “tightness” of the construction. These conditions tend to make adjusting and testing of the smoke control system difficult at best.
The typical building construction project is always under time constraints. Even under the best conditions, final testing of the smoke control system is done under tremendous pressure to get it done quickly so the building can obtain its certificate of occupancy. More often than not, only preliminary adjustments have been accomplished and additional adjustments must be done during testing.
When it comes to testing the smoke control system, there are at least two components that are interrelated and each has its own issues. The individual zone smoke control system performance may vary from one zone to another. The stair pressurization systems may be (and often are) overpressurized, causing deficient door opening forces. Many test sessions extend deep into the night in an exasperated attempt to adjust the systems to meet smoke control system criteria.
A BAS can help minimize test stress by adjusting the fan speed of individual fans that have variable frequency drives. In the situation of excessive stair pressurization, the individual fan can be “dialed back” to limit its airflow to the stair, resulting in a lower level of pressure affecting door opening forces. Similarly, for individual zone smoke control system performance, the fan speed can be adjusted on a zone-by-zone basis, based on the fire alarm signal received by the BAS.
The downside to this operation is that the BAS controls are typically located remotely to the fire alarm control panel and the firefighters’ smoke control panel, both of which normally reside in a fire command room. BAS controls and system components are usually located for the convenience of the building’s staff and HVAC equipment. Under test conditions, additional personnel may be required to man the BAS controls to effect any required modifications during testing.
While modifying fan output for each smoke zone condition is a more expedient end to obtain approval, it also provides future opportunities to inappropriately change the settings, possibly making the system ineffective. Care must be taken to limit access to this programming and provide logging procedures to document when and why changes are made.
After all the work done by the engineers, contractors, inspectors, and the AHJ, the integrated system operation is approved and the owner receives its final certificate of occupancy. However, the project is not over. It is critical that the owner receives and carefully stores all record documents related to the integrated system. As a building ages, things change. Systems are modified. When these things happen, the contractors making the changes can use the documentation to maintain the interoperability of the integrated system as well as revise the drawings to reflect changes made. In addition, the modified systems should be retested to confirm their revised performance. Documentation of the testing is required to be incorporated with the existing record documents.
Even if buildings do not change, a BAS that is integrated with fire protection and life safety systems needs to be tested at least semiannually for dedicated systems or annually for nondedicated systems, as required by NFPA 92, to confirm the correct operation is still being maintained. That retesting should include physical verification of system functions. Experience has shown that elements of a smoke control system begin to show minor issues during the first year. Some systems that are three years old could have more serious issues if they have not been regularly tested.
Many owners are unaware of the retesting requirements or defer testing due to cost or other issues. The longer these systems exist without regularly scheduled retesting, the greater the probability that they will not function properly when an emergency arises and may result in loss of life. If it was important enough to integrate these systems in the first place, it should be important enough to confirm their continued proper operation.
Integrating fire protection and life safety systems with BAS can be cost-effective and provide a more efficient operation, but it is imperative that the equipment is listed for the purpose, the design and installation is well planned and coordinated, and the system is properly maintained over its lifetime.
Studer is an associate at Arup and heads the Fire Engineering Group in Arup’s Chicago office. For the past 15 years, he has been involved in special inspection services for smoke control systems for projects throughout the U.S. and has previously served on several NFPA technical committees, including for NFPA 3, now titled Recommended Practice on Commissioning and Integrated Testing of Fire Protection and Life Safety Systems.
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