Fire Alarm Control Panels
By Frank Saisa
Fire alarm control panels..... We know all about them right? Well, for those who only have a mild understanding or need a refresher course, this article is for you.
Some may think that a fire alarm system is simple in nature; a fire alarm device initiates some type of evacuation signal, as a result everyone leaves the facility. The nature of a fire alarm system for a layperson could be that simple, providing the evacuation signal is respected.
This true concept is the end result of the Fire Protection Engineer and Installation Technicians who custom build these systems for a specific facility. These systems are specified and installed in accordance with Local and National codes. When these codes are properly applied the end result is a system that operates safely for the occupants and first responders. This article will help us with the significant differences of the many Fire alarm panel options that are available.
A Fire alarm Control panel or unit in some cases is the controlling component for the Fire Alarm System. The panel receives information from environmental sensors designed to detect changes associated with the environment and monitors operational integrity. This panel may also supply electrical energy to operate any associated sensor, control, transmitter or relay. There are four basic types of panels: Coded panels, conventional panels, addressable panels, and multiplex systems.
Our focus today in this article is to explain the differences between Addressable and Conventional panels. We are also going to include an important function of Fire Suppression which is releasing. We will look into the benefits of using releasing in an addressable or Conventional system.
Conventional panels have been around ever since electronics became small enough to make them viable. Conventional panels are normally used at smaller sites or with special applications. A conventional system employs one or more initiating device circuits (IDC’s) connected to sensors wired in parallel. The sensors are devised to decrease the circuit’s resistance when the environmental influence on any sensor exceeds a predetermined threshold.
In a conventional system the information density is limited to the number of circuits used. A small map of the building is often placed near the main entrance with the defined zones (IDC circuits) drawn up with an annunciator panel to accompany it, or an LCD interface to display the information. The information may be a little different when the system is used in smaller area such as a computer room; it is likely that there will be an LED panel which will act as a zone map.
The main drawback with conventional panels is that one cannot tell which device has been activated within an IDC circuit, unless an optional annunciator is installed at the control. Although the zone of activation is apparent at the control, emergency responders cannot tell which device in that zone is in alarm at the control panel. Based upon the type of detector installed, you may be able to walk through the detectors within the zone to determine the units(s) which were activated by observing the detectors LED. Some Conventional panels have activation relays which follow the state of the panel. There can also be external relays in some conventional systems; these relays are usually activated with voltage output via wire (for those who don’t know this). The functions on a conventional panel are not programmed. Changing the panels operation would be done with switches, toggles, and buttons.
We are going to shift our focus to Addressable systems. Addressable panels are usually much more advanced than their conventional counterparts and have a higher degree of programming flexibility, which includes single point programming. Addressable fire panels were introduced by manufacturers during the microcontroller boom in the mid 1980’s.
We learned about the zonal concept and some of the pros and cons. We would like to delve into the concept of Signaling Line Circuit loops. They are commonly referred to as SLC’s and can be networked (through Nodes or Data Gathering Panels) for larger types of applications. Depending on the protocol used, a loop can monitor and control several hundred devices. Some protocols permit any mix of detectors and input/output modules, the rest are usually restricted to 50% of each.
Each device on an SLC has its own address, so the panel knows the state of each individual device connected to it. SLC’s can accommodate most devices on the same loop, which includes but is not limited to Smoke detectors, heat detectors, Duct detectors, and input/output modules.
We understand that conventional panel’s activations are usually pre-determined by design and output voltage, when wired as such. We may ask ourselves, how an Analog addressable panel tells our outputs to operate. The explanation is quite simple, it employs a concept called mapping. This process is also called “cause and effect” or programming (rules, etc.). Mapping is the process of activating outputs based on the activation of inputs. Traditionally, when an input device is activated (or groups of inputs), an output device or group of output devices (or relay) is activated.
Programming options allow customization to each level of a system. Zones, detectors, and devices are all areas that can be individualized based upon the application. Zones usually divide a building or area into different sections. Addressable devices can individualize a detector or device. Addressable smoke detectors can be set for different modes; this includes day/ night sensitivity settings and can also be programmed in groups for specific functions. Heat detectors can be programmed for rate of rise, fixed, temperature settings, and thermal lag.
There are many operations that an analog addressable panel can perform. The portion of the fire panel that allows these fairly complex programming capabilities is based upon Boolean logic. For instance instead of a traditional zone system wiring scheme, you can program a cross zone scenario; this replaces wiring zone relays, for those who remember this.
The next topic is releasing panels. Releasing panels are to be respected and designed by qualified individuals for whatever field of suppression it employs.
Releasing panels are capable of using solenoids or generators to disperse fire-fighting chemical agents such as FM-200 or water located throughout a building. A releasing panel usually will have a manual abort switch to suspend an accidental release which could damage property or equipment. Releasing capability can be part of both addressable and conventional panels. Releasing is an additional function of these controls above and beyond the notification signals found in non-releasing panels. Releasing panels based upon programming and device of activation may have a programmable delay period between the device activation and the commencement of the releasing event.
We, cannot reiterate the importance of having experienced factory trained or NICET certified Technicians (in the related suppression field) to work with this type of equipment. There are many functions of a Releasing panel that must be respected.
Discharging chemicals can be an expensive, labor intensive mistake. The Chemicals can run in the thousands, depending on your site and don’t forget any evacuation of a computer room or affected area will cost the customer money and efficiency. The next important thing to know and respect with regard to these systems are shutdowns. Some systems have computer and power related shutdowns. Although there are precautions in place that would eliminate these shutdowns from inadvertently activating, mistakes can happen.
The design, installation, and inspection are pertinent to alleviating a false activation. There are times that the Chemical can be mistakenly discharged or the computer room can be shutdown. What if you activate both functions at the same time? Complete chaos is a good word for it. Design and installation mistakes can be critical and at times, if certain criteria are not met, you can have a full blown false activation, and witness this chaos.
Zoned systems employ relays that are external or built into the panel board. Cross zoned systems need a combination of 2 zones to activate a given output or function, I.E. shutdowns or Agent releasing. Normally, zoned conventional systems are wired for the purpose of shutdown or releasing on the activation of the second zone. There are some newer releasing panels that have the capability to set dip switches for cross zone or other auxiliary functions.
Analog Addressable systems for releasing can be programmed in a variety of ways. A matrix can be created to release on any amount of detectors in alarm and other options. Addressable SLC’s can be programmed by row, type of detector, or any combination specified by the Engineer or architect. The control panel’s functions (addressable) can be programmed for individual detectors, which is more involved than a zoned conventional panel. All detectors, input/output functions, and auxiliary functions are programmed on an Addressable panel.
These are some of the functional differences of conventional and addressable panels. There are many options and applications relating to both addressable and conventional panels. The type of panel you install depends on an adequate facility/site assessment and adherence to local and national codes.