jculber

So in this campus we are remodeling, we are doing the new fire alarm system. On previous jobs, it has always been designated to one person to pull the wire, make up the devices, and do all the piping. The same person on every job. Well on this job (the campus) we are all kind of doing it and I am finding I really don't understand it. The one guy gave me a quick run through and all I got out of it was " blah blah blah series, blah blah blah parallel, blah notifier, etc." Also something about piping it in a loop because there are some devices that can't be spliced. Is there anything out there I could get that would help me in understanding fire alarm more?

Thanks

480sparky

I am going to assume you are installing a non-addressible system.

In a nutshell, a non-addressible system simply looks at a circuit and checks for three things: 1. A short, 2. An open, or 3. A known reisistance.

Imagine a parallel set of wires going from the FA panel to each detection device (pull station, smoke or heat detector, etc.). At the end of the circuit, there is a resistor installed, appropriately called the End-Of-Line Resistor (or ELR/EoLR).

In normal circumstances, that resistance is 'seen' by the panel, and all is good. If a device is removed, or there is an open connection somewhere along the line, the panel sees this and lets the building's occupants know by sounding a buzzer. This is known as a 'local' alarm.

If, however, a pull station is pulled, or a smoke or heat detects smoke or heat, the circuit is basically shorted out by that device. When the panel detects the short, it goes into full alarm mode. Power is sent out over the notification (strobes, horns, etc) circuit and you have the flashing lights and the ear-piercing warbles.

If the system is monitored, a central station is notified and the fire department is dispatched.

Because this type of system is only looking for the ELR for normal operation, you can't branch out like you would a typical power circuit. The circuit must be in one single line until the ELR.

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All responses based on the 2008 National Rat Code.

jculber

alright, all of that makes sense. So now what is the difference between an addressable and non-addressable system?

Peter D

Generally speaking, all modern fire alarm loops run in what's called a "Class A loop" meaning that the loop starts at the panel, goes to each device, and then the same loop returns to the panel. This is done for redundancy in case there is a break or fault in the loop.

The initiating loop (pull stations, smoke detectors, etc) and the notification loop (horn strobe, bells, etc) are usually both wired class A, at least in my area they are. It really all depends on your local codes as every state and area has greatly varying rules for fire alarm systems.

480sparky

An addressible system is a bit more digital. Each device is programmed with a binary code, and those codes are programmed into the panel.

The panel then systematically 'searches' for each and every code, over and over, constantly 'looking' for the digitial code in each device. If a device is removed, it fails to 'respond' to the panels' search, and the local alarm is sounded.

One advantage is you can branch out anywhere along the circuit. There's no ELR that the panel is looking for as it's looking for the digital codes of the devices.

Another advantage is you can program each device with a specific location. Non-addressible systems generally return a broad area to signifiy an area. "Zone 1" may be 1st floor, "Zone 2" would be 2nd floor, "Zone 3 is the tamper switch on the backflow..... With an addressible system, the panel may be able to tell you exactly which device is sounding the alarm: "North Hallway, East Door" or "Elevator Pit".

If you're installing an addressible system, then each device should have it's binary code laid out on the prints.

__________________
All responses based on the 2008 National Rat Code.

480sparky

Class A loops are common, but I've done my share of Class B loops as well.

The difference is with a Class A, the circuit is routed out through the devices, and back to the panel. The ELR is then placed there. In a Class B, the ELR is somewhere out in the building. Could be anywhere, and unless you wired it, or the person who did was smart, you may find yourself on a long hunting expedition.

With Class A's, you know the ELR is in the panel. The advantage of this is let's say a problem develops in the circuit. The local alarm detects an open and sounds the local alarm.

Peter D shows up, and locates the problem..... it's somewhere between the pull station in the South Hall and the smoke detector in the laundry. It's Friday, 3:00, and Pete's already got 46 hours in this week.

In order to get things back up and running, he can simply split the ciruit into two, put an ELR at the pull station and another at the smoke. Doing a bit of rewiring at the panel, he reroutes the second circuit from where the panel ELR was to the detection side of the panel, resets the system, and he's got the sysytem back to 100% operation pretty quickly.

Now Pete can spend a more casual day next week tracking down the exact location of the problem. This is a handy method if it's a late-at-night or weekend call. Pete can come back at a more convenient time and locate the exact problem. Solve the problem, and rewire back to the original state.

__________________
All responses based on the 2008 National Rat Code.

Shado

Cool...having never been involved in a FA install....this info starts a good understanding.

Can anyone recommend a book or similar for more education?

__________________
- Dave ........

"Beware of the Rat....he has no Master...he works how & where he wants...."

te12co2w

480. Very good, no nonsense, simple explanation. I'm going to copy it if you don't mind. Thank you I wonder if there is a way to get printer friendly versions of these threads. or would that violate some ethical standard?

te12co2w

[quote=480sparky;61631]Class A loops are common, but I've done my share of Class B loops as well.

The difference is with a Class A, the circuit is routed out through the devices, and back to the panel. The ELR is then placed there. In a Class B, the ELR is somewhere out in the building. Could be anywhere, and unless you wired it, or the person who did was smart, you may find yourself on a long hunting expedition.


I've been on a couple of those hunting expeditions. Packing around a 10' ladder, opening boxes, watch out for all the kids in the hall.

480sparky

That's why I always leave a list of the ELR locations in the panel.

At if at all possible, I put them in pull stations.

__________________
All responses based on the 2008 National Rat Code.

leland

Good basic coverage of FA ckts here.
The big thing with them is supervision of the ckts.
Any ckt associated with either initiation (smokes,heats pulls etc),or notification (bells horns,strobes etc).Must be supervised,That is done with the EOL as stated.
Now a twist:
These ckts are combined with both types of ckts. Parallel and series.

essentially a parallel/series ckt.
Meaning: the ckt is parallel but each leg (pos/neg) is actually wired in series with itself. This ensures the supervision.

At the end of each splice there should be no more than 2 conductors under any connection.
(perhaps someone more technologically advanced can post a typical FA ckt)

Class 'A' ckts (feed/return) cannot share the same conduit/cable assembly,for reasons stated above. So that is part of the reason you are pipeing in a 'loop'.

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manchestersparky

Keep in mind if you are dealing with a class A fire alarm system, the supply and return must be in different conduits AND there are limits on how close they can be run together. Class A has a whole ot more rules when your doing the conduit runs.
I always marked on the device with a sharpie marker EOL - where the end of line resistor was. I too always tried to get them in a pull station.

MDShunk

A show of hands... how many people have found the EOL resistor in the panel on class B circuits?

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BryanMD

This thread should be a sticky.

Very well done Ken. Thanks

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Peter D

All the time....it's required that the EOL be in the FACP cabinet.

leland

Please State the code,article,And or reference for this.

__________________
"When one American is not worth the effort to be found, we as Americans have lost" (Rolling Thunder MA 1)

Peter D

My bad. I should have said "around here." It's a local code requirement.

leland

This would be (back in the day) A class 'B' preferred ckt.
Most commonly used before the panels would accept a class "A" ckt.
Not a bad system,Again for reasons described above.

Now they have changed then they changed back:

class-A-B to X-Y for initiation
And for audibles, some other crap.....
But like the elevator codes, they went back to the 'Tried and true'.

__________________
"When one American is not worth the effort to be found, we as Americans have lost" (Rolling Thunder MA 1)

leland

I hate to repeat myself but........ Your in Massachusetts as I am.
So..... between Boston and Springfield I have never been exposed to that condition. (And Boston is tough).
General area: so I can be on my toes.

__________________
"When one American is not worth the effort to be found, we as Americans have lost" (Rolling Thunder MA 1)