a) Do most buldings’ fire alarm systems (of today) NOT call the fire dept? b) Also, if the sprinker system is triggered, does it trip the fire alarm? c) Last, someone told me that the fire alarm can also trigger the sprinkler system. While you’ll see this on TV for comedic effect, is there any truth to this? - Jinx
In most modern sprinkler systems, there is always pressure in the pipes leading to the heads. There is not a seperate valve that is triggered by a central alarm that opens valves to certain circuits, if you will. Rather, each sprinkler is independant of the others, and are activated by heat. Otherwise, alot of equipment would get water damage that wasn’t in danger. As the fire spreads, more heads will kick on as needed. The fire detection system is seperate, and it is possible to have a sprinkler system without a fire alarm system.
There are other systems that run “dry”, but most systems that you or I encounter are not.
When you say “most buildings’ fire alarm systems” do you mean most buildings?
Most houses?
Most commercial buildings?
Most government buildings?
The answers certainly depend…
A lot will depend on the specific set-up of the building you’re talking about.
Of the two buildings I’ve had occasion to stand a security watch at, the alarm system would automatically call the appropriate authorities following a trigger of the active sensors or a change in fire main pressure.
I’d expect any reasonably large HVAC equipped building to have an equivalently automated alarm system.
And for the last question…
One of the building had a fire main booster pump to blow out the sprinkler head seals in certain portions of the system by upping the pressure. Basically made sure that certain objects stored in those parts of the building didn’t get so much as a chance to get above room temperature.
I doubt that’s very common outside of industrial settings.
I am the senior technician for a small fire alarm company.
a: Many fire alarms do communicate with a central monitoring company that is responsible for notifying the fire department. There are also many systems that only sound an alarm locally in the building they are protecting. The requirements as to which fire alarm systems must be monitored change from juristiction to juristiction.
b: NFPA #72 requires that a sprinkler in the building protected by a fire alarm system must trip the fire alarm when water flows through the system. Also, the valves controlling the sprinkler system must be supervised. If a control valve is turned more than 1 1/2 turns, it must cause a supervisory condition on the fire alarm control panel.
c: There are sprinkler systems that will flow water out of all the sprinkler heads when a fire alarm is tripped. These are called deluge systems and are mainly used in industrial applications. I have never seen one in an office building or a school as you may have seen in movies. The systems my company tests that are set up like this are in the conveyors feeding coal into the furnaces of a power plant.
d: There are many systems that sre full of air rather than water. The air holds a valve keeping the water contained. When the link on a sprinkler head melts, it allows the air pressure to drop opening the valve to allow the water to flow to the head that has opened. These systems are often used in unheated buildings where water in the pipe could freeze…
There is also a double interlock system that requires a head to open, allowing the air to bleed off and also an electric interlock controlled by smoke detectors to open before the water can flow.
I hope I have been helpful without boring you
I spent about 13 years managing security/operations in high rise commercial buildings in Chicago.
Pygmy Rugger’s post and link explains how a sprinkler functions very well. Typically, any time a sprinkler head goes off, that triggers an alarm that in many cases (it may be mandated by some local codes) is automatically transmitted to the fire department. A 911 call is also made by security or the engineers to verify that there is a waterflow alarm on whatever floor, whatever zone.
Actual fires aren’t the only type of alarm that the system makes - there are various ‘trouble’ alarms - when some component in the system isn’t working just exactly right. If there is going to be maintenance performed that requires any zone, or part of th system to be off-line, the fire department needs to be notified.
I recall having the security firm we used have to supply 2-3 extra guards to do nothing but walk floor to floor on fire watch whenever we’d have the system shut down.
The Viking Firecycle™ is similar to what you’ve described, but uses rate of rise detectors in conjunction with a fused sprinkler head to permit water flow. Additionally, when a RoR head sees thermal drop below threshold, water flow will cease until/if temperature rise closes the RoR head again.
Just to add to longhair75’s excellent post (I always appreciate a reference to an NFPA standard);
The double interlock system that’s mentioned (also called a preaction system) is becoming more and more common in today’s office buildings. If you have a computer server room, you don’t want to risk the down time caused by a leaking sprinkler head or pipe. The system is maintained full of air, not water. The sprinkler control valve is held closed either electrically or hydraulically. If there’s a fire, the smoke will set off a smoke detector in that space. When a smoke detector or pull station in the space is activated, the control valve for the sprinkler system will open, filling the sprinkler piping with water. Then the heat opens the sprinkler head, allowing the water to discharge onto the fire.
The big problem with these preaction systems is that they’re only ~72% effective. A “normal” wet pipe sprinkler system is 96-97% effective, the things almost never break. Preaction systems require so many things to go right to operate that they’re not as effective.
As for regular dry systems (pipes filled with compressed air), they are more common than you first might think. Anywhere with an outdoor sprinkled area, such as department store with an outdoor garden shop, or a sprinkled parking garage, or even a single story building with an unheated attic will more than likely have a dry system. Dry systems don’t freeze, so you can leave them outside without worrying about the system failing. In my part of the country dry systems are very common because of unheated attics.
Dry systems are required to flow more water than a wet system, since the delay (up to 60 seconds) in getting water on the fire allows a larger fire, so more water is needed to knock it down.
Still, to reiterate what others have said about the OP, activating a fire alarm in most places will not set off the sprinkler system. I say most places, because there are systems (deluge systems, Halon/Halon replacement systems, foam systems, CO2, systems, etc) that a pull station will set off. You can tell, though, which pull station does what, since they’re usually arranged like this.
Did NYC alarm work back in the 80s. Not much to add except:
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Private homes like our suburban townhouses have “wet” systems. They are much cheaper and have less things to go wrong. In our case, the upstairs toilet is at the very end of the circuit. This is so that fresh water is constantly circulating through the pipes going to the sprinklers. If the sprinkler head ever opens, the water won’t be all gross from being trapped in the pipes for God knows how long. These pipes are connected to the house water main before the second shutoff valve, so that if the water is shut off (some people do this when they go on vacation) the sprinklers and the upstairs toilet will still work. Handy when you’re doing plumbing work, lemme tell you.
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The compressed air that everyone has mentioned in dry systems is connected to a small pump that periodically turns on to compensate for tiny leaks. Otherwise, the pressure would bleed down eventually and trigger the valve.
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The valve that has been mentioned is buried inside a large fixture. It’s not a valve like you’d think; a better analogy is a tripwire. Resetting it requires that bolts and a faceplate be removed, etc. Shutting the valve is not a casual “turn this handle” affair.
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Dunno about other cities, but I’ve never seen a wet system in a commercial building in NYC; I’m pretty sure it’s against code (aside from legacy systems).
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Weirdest system worked on: a foam dispersal system in a cardboard factory.
Of course, this was 20 years ago. YMMV.