SSA Integrate - Fire
alarms and BAS
The
integration of Building Automation System and fire alarm systems can result in
overall reduction in equipment, installation, and maintenance costs while still
maintaining the level of safety required for these systems to operate.
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 building automation system (BAS) to allow for nearly seamless operation of
these various interrelated equipment.
When
the fire alarm system takes control of equipment that is not a listed component
of the fire alarm control unit, the fire alarm system must either override the
natural operating mode of the building equipment or pass off that command via a
simple switch or data communications to the building mechanical systems.
Likewise, each manufacturer’s BAS has its own protocol for monitoring
conditions and communicating operational commands to maintain the proper
building environment and efficiency. There are also standard open communication
protocols such as LonTalk and BACnet that can be used to
communicate with a multitude of equipment from various manufacturers in order
to achieve an integrated building system.
The
communication protocol for a fire alarm control unit to communicate to and from
its indicating (input), initiating (output), and sometimes notification
appliances is typically an analog or digital communications signal carried over
what is referred to as a signaling line circuit (SLC). Because communications
signals are typically proprietary protocol, each SLC is dedicated to a specific
manufacturer’s equipment and cannot include connection of incompatible devices
that use a different signal protocol.
Therefore,
in order to integrate system alarm and control functions with the BAS in a
manner other than relay logic, fire alarm system manufacturers had to also
design and support the open communication protocols used for building
automation, in a manner that would not compromise the integrity or the
operation of the fire alarm system. This process of sharing information between
both fire alarm and BAS came to be known as bridging, or open gateway
processing. Because of the strict code and listing requirements of fire alarm
systems, much of this communication has been primarily limited to one-way
communication. However, some manufacturers of both fire alarm and BAS do produce
equipment such as gateways that are listed for bi-directional communication
with their equipment.
Make a case of a building with separate building automation and
fire alarm systems: When the building engineer receives a call from an occupant
complaining about increased temperature or whistling air within the ductwork
and finds that the fan is shut down or a damper is closed, the building
engineer is more apt to call a controls contractor to investigate the problem
before he calls their fire alarm service provider. Should the problem be
related to an override of controls by the fire alarm systems, not only does the
building engineer have to wait for the controls contractor to diagnose the
problem, he also has to call the fire alarm contractor to come out and fix the
problem. This process can take time to correct; meanwhile, building occupants
are uncomfortable and inconvenienced.
Sometimes this can even lead to finger-pointing between the two
service providers as to whose problem it really is. In this scenario, the fire
alarm control of a fan or a damper is required to be ahead of the hand-off-auto
switch for the power to the equipment so the inadvertent shutdown of the
equipment does not inhibit the operation of the fire alarm feature. A failure
of the fire alarm system control relay could shut down the fan or close the
damper without an alarm being present on the fire alarm system or fault
condition occurring on the fire alarm control unit.
Because many components that affect air and smoke movement within
a building are shared between HVAC and fire alarm systems, let’s take a step
backward in the evolution of the building process. When building systems are
being commissioned for proper operation by either an authority having
jurisdiction (AHJ) or an independent third-party group, coordination must occur
between multiple trades. At this point in the construction process, each trade
is independently looking to complete its own scope of work and more often than
not is under pressure to finish the specific scope in a designated timeframe.
Sometimes this leaves a disconnect between the fire alarm and mechanical trades
that results in disruption during start-up and commissioning.
The integrated system approach allows for those individuals
responsible for controlling air movement to be focused on proofing and
balancing the mechanical system, while the fire alarm contractors focus on the
detection and annunciation of the alarm events. Much in the same manner as
referenced in the previous example, the problems can get resolved more
expeditiously and the systems can be brought on-line.
If we focus on the installation of a building management system
(BMS) and a fire alarm system, we see many similarities. Each of these control
systems is classified as low-voltage systems that communicate to their
respected devices through an analog or digital signal. Their wiring methods and
materials are similar, and often their respective equipment is located in the
same general area and is performing the same basic functions with one
significant difference: the fire alarm system uses individual point addressable
monitor and control modules while the BAS uses digital input/output driver
assemblies that communicate with different protocols.
Why is this important? Because the BAS still requires individual
pairs of conductors to each point being controlled or monitored by the digital
input/output module, resulting in more wire being needed and longer
installation time.
When
considering SSA system integration, the ability of the BAS to control a
smoke control system operation falls under the auspice of the jurisdiction’s
building code, often based on the model building codes. The IBC has been
adopted by a large portion of the United States and is used in this article as
an example. IBC Section 909 covers smoke control systems, 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 fire alarm system.
Section
909 requires smoke control systems to be initiated by sprinkler system or smoke
detection system operation, depending on the type of system being designed. 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, and 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.
Using
a fire/smoke damper that is part of an engineered smoke control system
complying with International Building Code Section 909 as an example,
at each damper location we have a smoke detector for detection of smoke, an
actuator that controls the opening and closing of the damper, and an end switch
to provide positive confirmation of the damper open and closed position.
Because the fire alarm system already needs to have circuitry to this location
for individual smoke or duct smoke detectors, that same pair of wires can be
used to monitor the open and closed position of the damper, essentially
eliminating two pairs of wires back to the BAS controller. The position status
signals of the damper can then be transmitted from the fire alarm system,
through the gateway, and into the BAS along with the active alarm point
information. This leaves the wiring to the actuator as the only BAS wiring
needed at the damper location.
As
another example, let’s use a stairway pressurization fan that is being
controlled by a variable frequency drive (VFD). Typically, a VFD would be
connected to the BAS via a digital signal while the fire alarm system would
provide override of the VFD using dry contacts to stop it or put it into a
smoke mode condition. Allowing the BAS to perform all of the control functions
permits the adjustment of the fan speed through the BAS to regulate for
atmospheric conditions by employing other equipment connected to the BAS, such
a digital differential pressure sensors. Using the BAS solely for control
eliminates any connection to the fire alarm system, with the activation
commands being sent through the gateway.
Taking
advantage of the aforementioned efficiencies gained by integrating the BAS with
the fire alarm system requires planning in the design process. This planning
process is the same whether it is a design build or a design assist type of
project delivery. The building owner and operator must be involved in the
process of establishing the design criteria or at the least have influence over
it. In a typical design build or design assist process, the integration of
these two systems is an afterthought and often never considered. The end user
must be made to understand that the efficiencies gained by integration will pay
dividends long into the lifecycle of the building.
Integrated
systems require enough time to test and to verify that the system
interoperability is functioning properly. It is important that the engineer as
well as the installing contractor and the equipment vendors understand the
impact of these requirements on providing an approved and code compliant
installation.
Due
to the complexity of these systems and the required integration, testing must
confirm that the functions and sequences work correctly under both automatic
and manual modes.
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 caused due to all of these different
systems being completed late in the schedule and not enough time to “get the
kinks out” prior to final testing. Anything that can expedite the commissioning
process is beneficial to the overall project.
One
of the advantages of using the BAS as an integrated part of the smoke control
system is the system’s ability to modify operating conditions to accommodate
actual ambient conditions through the use of VFDs. 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 testing and adjusting of the smoke control system
difficult at best.
Integrating
BAS can help minimize test stress by adjusting the fan speed of individual fans
through programming. In a situation of excessive stair pressurization, the
individual fan can be adjusted 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 monitor the BAS controls to make any required modifications.
While
modifying fan output for each smoke zone condition is a more expedient method
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.
Take a note: Fire
condition is determined by the Fire Alarm Control Panel. AHU will automatically
shutdowns the whole system with associated interlocks.
Question: How can the reliability of the fire alarm system be
maintained while mixing
data with other non-emergency inputs?
Answer: In reality the fire alarm
system reliability is unaffected by other integrated systems when using the
BACnet protocol due to the required use of the gateway interface. The gateway
keeps the other signals on the network form affecting the fire alarm system.
Question: Building automation systems are
more and more residing on an owner's IT network. If a BACnet gateway is used to
interface to the fire alarm system, instead of hardwired connections, this
device would reside on the owner's network which is likely not UL listed. Have
you come across this concern?
Answer: The BACnet gateway itself is
required to be listed, but not the system. So the fire alarm system devices or
zones would be connected to the listed gateway and then the other side of the
gateway would be connected to the network allowing the objects to be
transmitted to the BAS, for example. Once again we are still required to use
the listed gateway as the interface but the balance of the non-fire alarm
system equipment does not need to be listed for fire alarm use. Having said
that there are changes proposed to NFPA 72-2019 that would allow direct
connection to the Ethernet or a network under certain conditions. These
proposed changes have not yet been officially adopted.
Question: Do you recommend integrating the
building fire alarm system and the BAS in an office building that undergo
tenant fit-outs on a continuous basis?
Answer: With any system design in any
building or occupancy planning is imperative. Knowing beforehand that the
occupancy is to be offices and knowing that tenant fit-out occur on a regular
basis, it is incumbent on the original system designer to include system
changes and expansion in his or her design. Just because frequent changes to a
system are expected does not preclude integrating all of the systems. It does
require more coordination and provided that happens the systems should remain
reliable.
Question: Does OEO override designated and
alternate recall operation?
Answer: No, just the opposite. All
recall features (elevator lobby smoke detectors for example) would input to the
OEO controller and it would relinquish OEO or those floors in recall.
Question: How would elevator shunt trip for
a sprinkled hoistway or elevator equipment room operation work into the OEO
sequence of operation?
Answer: As stated previously, when
these types of operations occur during or prior to OEO, these operations would
take priority over the OEO and all OEO for the affected elevators would cease
and all signs and voice messages would revert to “Do Not Use The Elevators, Use
The Stairs” operation.
Question: How would the use of BACnet
interface to emergency control systems, requiring supervision of control
wiring, address this code requirement?
Answer: NFPA 72-2019 (and previous
editions) require supervision to within 3 ft of the controlling device or no
supervision if the device operation is fail-safe, meaning if the connection to
the device is severed, the emergency device operates as required. The gateway
could be determined as the connection to the controlling device and as long as
that was within 3 ft of the controller it would be considered code-compliant.
This is unlikely to happen and other design considerations will need to be
considered to ensure that the performance of the emergency control system is
code compliant. Given the many types of configurations, there can be no one
definitive answer to the problem until the actual field condition is evaluated.
