In the video below, watch as ORR VP of Engineering Lee Kaiser finishes his explanation of "How to Operate Your Fire Panel." Topics in this video include the fire alarm sequence, the difference between conventional and addressable fire panels, and the circuits used in each panel.
Lee: "There are two types of panels that we typically use in fire alarm systems: conventional panels and addressable panels.
Conventional panels are sort of the older panels out there. The way they work is they respond to a change in an electrical current. There's a normal current passing through a circuit and then when a smoke detector sees smoke, contacts close in that device. It changes the current going back to the panel. The panel senses that and goes into alarm. That's basically how conventional systems work.
Conventional systems work off zones and we'll show you that in the next slide. They get a nickname called a zone panel. Who's heard of a zoned panel? When we say zoned panel, we're really talking about a conventional panel. They're simple. They don't have any record of the history of what's happened on the system and there's no software or programming. These zones here, most panels will have multiple zones and you're wholly dependent on the installing contractor to layout the zones in such a way that you get some geographical information about what's happening in the building when a system goes in alarm.
We may layout zones by floor. There's a zone for the first floor, zone for the second floor, zone for the third floor or maybe we'll layout zones by function. Maybe we'll have one zone for the pull stations. One zone for the water flow switches. On the sprinkler system. That's sort of how that can be done.
Now addressable systems are what we're expecting more today and are much more common. In an addressable fire alarm panel, we add a microprocessor to give us basically a little computer, an intelligent system. Instead of responding to changes in electrical current flow, now we're sending data back and forth between the panel and the devices in the field. This building is equipped with an addressable fire alarm system. That's an intelligent detector there and it's sending data back to the fire alarm panel to tell the panel what's going on with that detector.
Each device in the system has an address, that's why we call it addressable. It knows specifically that that's the device that something's going on with. Now you're dependent on the technician that's installing the system to program it correctly, so that the addresses are done in a way that I know that it's Detector A in Training Room B that's going off. I can locate the room now with the device that's having the problem.
There are a couple circuits that we want to review. Initiating device circuits are common to conventional panels. Again, they work off of changes in electrical current flow. They initiate a system action. But it doesn't identify the specific device. If we want that we use an addressable system and the signaling line circuit. That's the data communication circuit for inputs into the panel. Again, it transmits signals and data, as data.
Common to both panels are this other circuit here at the bottom of the NAC circuit, notification appliance circuit. That's an output circuit from the panel, to output to the notification devices, the horn strobes, the noisemakers, light flashers, so that we can affect an evacuation of the building when there's a fire alarm. Those are what get connected to the NAC circuits.
The Fire Alarm Sequence
To step through a little normal fire alarm sequence, we've got a panel. We've got two smoke detectors. This is the signaling line circuit, the input circuit and the NAC circuit, the output circuit with the horn strobe connected. When we get smoke at one detector, then it sets off the NAC circuit and we affect evacuation of the building.
Let's complicate this a little bit by talking about a suppression system. We like to talk about suppression systems 'cause at our heart we're sort of a suppression focused company. What do we add when we make this a fire suppression system? Well, first off we have to have something to release to suppress the fire. So we'll add a cylinder. It's gonna have a control head or some sort of releasing device, piping, and a nozzle. Also have to add some way to control that control device and that's a releasing circuit.
Releasing Circuit and Manual Releases
On the releasing circuit we have something called an agent disconnect switch so we can do a physical disconnect of that circuit while we're doing maintenance on the circuit and not have an accidental discharge. We also add a manual release station. Looks like a pull station, but it's to manually dump the system instead of waiting for it to automatically sense a fire. If I'm working in the room where the suppression system is and I see a fire, well I can just go to the manual release and pull it and get the system dump.
We have a couple more things. When we put smoke in one detector, then we get the first alarm level. We're gonna have multiple alarm levels in a suppression system. When we get the smoke at one detector, we're gonna do a general alarm in the building. But we're not gonna release the gas yet. We'll wait to confirm that we really have a fire in the room and get smoke at another detector. That technique "one detector, two detectors" is called cross-zoning.
When we get smoke at the second detector, we're gonna activate a pre‑discharge alarm. Which is a local alarm just in the room that's being protected. A couple other things happen. We'll start to prepare the room for discharge so we'll use relay outputs from the panel to send signals to shut down HVAC, maybe shut down the power, maybe close down some dampers for air that's serving the room, as well as start the time clock ticking. There's usually a 30-second countdown once we get to sensing the smoke in a protected room before the system discharges.
Abort Switch and Discharge Alarm
Now we have an option in that 30 seconds to stop it if an abort switch is installed. We can go to the abort switch and hold it down and stop the release. There are a couple different ways that those work. But in general if you hold it down, it'll stop. Let's say I press it at 22 seconds and I hold it. Well it'll stop at 22 seconds. If I release it then it'll count down the rest of the way and discharge. Or I could hold it there and have someone else investigate if there's really a fire. If they find that there's no fire, then they could reset the panel.
The last thing if we don't press the abort switch and we allow the time clock to run out, then we're gonna have a discharge of the system at the end of 30 seconds. We'll also have a local discharge alarm outside the room, usually a strobe letting people know that the system is discharged inside the room. If you're standing inside the room and it discharges, you're gonna know it happened. It's gonna be pretty obvious to you. But outside the room people will need to know that the system discharged."
Thank you for watching this week's video on Conventional and Addressable Panels. This video concludes Problem 1 from our 2016 Seminar titled "Causes and Cures: Top 7 Fire Protection Challenges." Check back next week for the first video installment from Problem 2: Frequent Panel Troubles.
"Causes and Cures: Top 7 Fire Protection Challenges" Seminar Videos Index
Problem 1: How to Operate Your Fire Panel