How to properly integrate fire alarm systems and HVAC systems

Organizing the coordination with the engineering team is key to a successful system integration project.

12/13/2017


This article has been peer-reviewed.Learning Objectives

  • Explain the purpose of fire alarm-HVAC system integration.
  • Recognize how the electrical and mechanical engineers and contractors work together for successful system integration.
  • Understand NFPA 72: National Fire Alarm and Signaling Code to ensure code compliance with system integration.

For engineers, coordination is a term that is critical when integrating a fire alarm system with an HVAC system or building automation system (BAS). Although for contractors installing the systems, this can be difficult. However, coordination at the design stage of the project can help ease the process for everyone involved.

The reason for any fire alarm to connect with an HVAC system or a BAS is strictly to control the spread of smoke from the fire source on a floor (or given area) to all of the other floors (or areas) in a building. For example, a small fire occurred in a newly opened 5-floor apartment building in the state of New York. While a building tenant was washing clothes in the laundry room located on the 1st floor, the clothes dryer was not drying clothes to the tenant’s satisfaction. The tenant decided to place a towel above the dryer to cover an air intake into the dryer plenum. As the tenant waited in their apartment, the towel heated, crystalized, and produced a sizable amount of smoke, although without much actual flame. Figure 1: This graphic is a typical fire alarm sequence-of-operation matrix. A good, detailed fire alarm sequence-of-operation matrix will detail how all inputs and outputs relate to each other. Courtesy: JENSEN HUGHES

The smoke entered the HVAC ductwork, activating the smoke detectors on the 4th- and 5th-floor corridors, which then caused total evacuation of the building. By the time the fire department arrived, the smoke in the corridors on the upper levels had dispersed and neither the fire department nor the tenants could locate the source of the smoke. At about the same time, the tenant on the 1st floor found the burned towel and other minor damage from the now self-extinguished fire and told the fire department what happened. (The fire was not large enough for sprinkler activation, and there was only heat detection in the laundry room.) The building owner replaced the faulty dryer and repaired the minor damage. However, in this example, the transmission of smoke to the upper levels could have been avoided with properly installed and maintained duct-type smoke detection. In this case, the building was small. High-rise and other complex buildings offer different challenges.

As another and more tragic example, on Nov. 21, 1980, a fire on the 1st floor of the MGM Grand Hotel and Casino in Las Vegas sent smoke through the stair and elevator shafts, resulting in significant smoke and loss of life on multiple floors of the building stairwells. Whether on a small or grand scale, smoke movement through HVAC system ductwork presents a significant risk to building occupants.

 Figure 2: This is an HVAC control switchgear with fire alarm control relays located directly adjacent. Proper installation of control relays in accordance with NFPA 72 is critical to proper HVAC interface. Courtesy: JENSEN HUGHESCoordination at the design stage

While model building codes and installation standards have attempted to adequately address this issue, much of the real “coordination” is still left to installing contractors who are often forced to address integration issues that they either know little about, have little direct control over, or even worse, have not budgeted for appropriately. It is important to remember that the engineers involved in the design of these two systems have the responsibility to do the same. Coordination at the design stage will help the installation stage go smoother.

Traditionally, integration between fire alarm systems and HVAC systems has been limited to dry-contact-type relays. This approach allows the fire alarm system to do what it does best (detect, notify, and activate emergency controls) while allowing an HVAC system or BAS to do what it does best (manage the air quality of the building). It also allows individual skilled contractors to focus on their own specialty with fairly limited coordination and interface.

In many ways, NFPA 72: National Fire Alarm and Signaling Code reflects this traditional interface view. The code requirements for emergency control of HVAC systems is found in Section 21.7 of the 2016 edition of NFPA 72, where it states that the “provisions of Section 21.7 shall apply to the basic method by which a fire alarm system interfaces with the heating, ventilating, and air conditioning (HVAC) system.”

Figure 3: This is a poor example of fire alarm control unit wiring, including a wired relay providing HVAC shutdown and off-site supervising station connection.  Poor workmanship results in poor emergency control interfaces. Courtesy: JENSEN HUGHESAs such, many long-standing code requirements remain. For instance, any listed appliance or relay connected to the fire alarm system used to initiate control of protected-premises emergency control functions must be located within 3 ft of the controlled circuit or appliance (NFPA 72-2016, Section 21.7.2). Installing the wiring between the fire alarm control unit and the relay or other appliance must be monitored for integrity.

This requirement can be avoided if the fire safety function is wired in a fail-safe fashion. For example, if the fan that needs be shut down when the fire alarm system smoke detector actuates shuts down automatically if the circuit wiring controlling the fan is cut, then the system is wired in a fail-safe mode and the circuit wiring controlling the fan does not have to be monitored for integrity. This is another instance where coordination between the design engineers is important.

Also, a contractor is allowed to program smoke detectors mounted in the air ducts of HVAC systems to initiate either an alarm signal at the protected premises or a supervisory signal at a constantly attended location or supervising station (NFPA 72-2016, Section 21.7.4). Design engineers performing this work should be aware of this allowance and not specify that an alarm should occur from a duct-type smoke detector. However, beyond these and a few other requirements, NFPA 72 code is rather silent on fire alarm and HVAC interfaces. This is particularly true when an integrated BAS will be used.

Building automation and integration

Figure 4: A typical fire alarm system duct smoke detector on a return air HVAC duct.  Such duct detection is the most basic form of HVAC interface, providing shutdown of the air handling unit upon detection of smoke. Courtesy: JENSEN HUGHESBuilding automation is not a new concept, but it is experiencing difficulties in becoming the norm rather than the exception. BAS appeals to building owners because they can visualize the potential for the BAS to save money and create efficiencies. BAS can provide savings in the initial installation and in future updates. The future updates may become necessary to take advantage of future savings. However, it is often the future updates that can cause difficulties where the BAS has been integrated with the fire alarm system.

As previously noted, the construction process traditionally requires that each of the specialized construction trades complete their tasks essentially independently of each other. However, close coordination between the responsible contractors is required to ensure that the BAS will do what it is supposed to do. The wiring is the backbone of successful coordination. This is why a contractor must truly understand the operational requirements of the BAS before the first cable is installed. Here is where the engineer must ensure that the BAS operational characteristics are explicitly spelled out to ensure everyone involved in the project (including the owner) understands the BAS operation.

As with any complicated wiring system, it’s important to understand the details. Unlike most signed contracts, a contractor should not take an agreement to wire a BAS lightly. It is important that both the engineer and the contractor follow a few key rules, which are outlined below:

  • The contractor should ensure he or she understands how the engineers want the system to work and determine whether or not they have developed an operational matrix to aid in that understanding.
  • The engineer and the contractor need to research the specified products that will be supplied to ensure the products will actually perform as the manufacturer’s marketing and sales people say they will.
  • Inevitably, contractors are going to submit a different vendor if the specifications allow for an “or equal” product. The engineering team must decide whether or not it is in the owner’s best interest to allow for substitutions, and they must verify that the chosen vendors, and even the specific technicians for the job, can make the specified or substituted product meet the operational requirements. Additionally, the engineering team and the contractors must be in attendance for the required acceptance testing, balancing, and commissioning to ensure the integration has been completed according to expectations.

While current practice involves the installation of separate building systems for fire alarm, HVAC control, security, lighting control, and building process automation, the long-term goal of BAS is to seamlessly integrate all of these systems into one BAS. The major drawback to this concept comes from the fact that the suppliers of these systems must maintain their own systems. In the fully integrated BAS scenario, someone must have sole responsibility to ensure interoperability of all of the systems. Some suppliers have recognized the need for interoperability of their systems with other manufacturers and have developed software solutions. Electrical contractors with a strong background in communications may hold an edge when installing BAS, and the engineer may want to include those qualifications as a requirement in the specifications. But inevitably, providing specific training for the contractors for more efficient installations will become imperative.


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