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Fire Alarm -- Maintenance

Stop look see everything that the panel says before proceeding
Before trying to troubleshoot, read everything the panel is saying. Often, the panel is going to indicate just where to go or what to look at.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer






Can Stopping to Look at the Panel and Think Save Time?

By Douglas Krantz

Sometimes, even after a lightning storm, what seems like a whole gaggle of troubles is really only a few small troubles in disguise. Taking some time to look over the situation before diving in to fix the troubles will save time later.

Lightning Strike

A short while ago, after a lightning strike, I was presented with 90 troubles on a fire alarm panel.

It was a large hotel, with 8 dataloops (Signaling Line Circuits or SLCs) between the fire alarm control panel and all the devices. The 90 troubles sounded overwhelming, but that's what I was given to work with.

First, Look at the Display

When confronted with lots of problems, don't start by trying to fix any of them. Look at the display, it is there to tell you lots of things.

In this case, the display showed that all the devices were on only one dataloop (SLC). Knowing this, I could concentrate on one area of the building rather than going all over the place.

Next, Check the Loop Controller to See Which Devices are Talking

Keep in mind, the devices that are working normally won't show up as troubles. To find out which ones work, disconnect the dataloop at the panel and then the working devices will be listed at the end of the queue.

Here, the number of faults jumped from 90 to 117.

That told me a couple of things. I learned that 27 devices on the loop still worked. I also now knew that the datacard on the fire alarm panel also probably still worked because it could detect the devices that worked.

Looking Through the Display

I could either go through the 90 original devices on the display to find which ones were bad, or go through the 27 new devices that were talking to find the last device that was working.

To me, 27 seemed easier than 90.

All 27 added troubles were on the top floor. Assuming that the dataloop would follow some logic and go from one end the hall to the other, I checked the 27 working device descriptions to see where the dataloop stopped.

I could see that the last hallway smoke detector that worked was Hall By Room 634, and the last room detector that worked was in Room 633.

I had taken the time to do all of this without leaving the fire alarm control panel.

Going and Looking

I reconnected the dataloop so the working devices, when looked at, would flash.

Then, carrying a ladder, and with a building engineer following, I went and looked to see which smoke detectors were actually flashing, indicating they were working.

Sure enough, the smoke detector in the Hall By Room 634 was flashing, but the ones further down the hall weren't flashing.

Stick Your Head Above the Ceiling

At the detector Hall By Room 634, I followed the wires above the ceiling. I found the wire going to room 633, which had shown on the panel as working.

Tugging on wires, I found the other wire went to Room 634, which did not show up on the list of devices that worked.

I had found the wire I had to concentrate on, the one that worked at one end (Smoke by Room 634) and didn't work at the other end (Smoke in Room 634).

Listen to Others

As I tugged on the wire going to room 634, the building engineer said "the other detectors are flashing." The tugging had only wiggled the connection on the hallway smoke detector, so pulling down that smoke detector, I tightened the connections at that detector.

The connections were only slightly loose, but the lightning dancing around the building had found the loose connections, jumped the gap, and slightly corroded the connection. This effectively stopped the connection from conducting normal data.

Tightening the connection allowed the data to go through a good connection again and that much was fixed.

In essence, all the troubleshooting so far involved lifting just one ceiling tile. Taking a little time early had saved a lot of time later.

Recheck the Panel

The panel now showed only two troubles, an RTU (Roof Top HVAC Air Handling Unit). This would have been where the lightning entered the fire alarm system.

Grabbing a fire alarm module to my truck so I wouldn't have to return for the module later, we went to the RTU. I replaced the module because it wasn't flashing, and returned to the fire alarm panel to find the display normal.
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This lightning damage was repaired in 2 hours (including drive time).

Our company looked like a hero because, before trying to find the problems in field wiring, I took time to read the panel and analyze the situation.

When troubleshooting, especially at the start, take your time: it will save a lot of troubleshooting time.






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Douglas Krantz

Describing How It Works
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Electrical Flow


On this website, most references to electrical flow are to the movement of electrons.

Here, electron movement is generally used because it is the electrons that are actually moving. To explain the effects of magnetic forces, the movement of electrons is best.

Conventional current flow, positive charges that appear to be moving in the circuit, will be specified when it is used. The positive electrical forces are not actually moving -- as the electrons are coming and going on an atom, the electrical forces are just loosing or gaining strength. The forces appear to be moving from one atom to the next, but the percieved movement is actually just a result of electron movement. This perceived movement is traveling at a consistent speed, usually around two-thirds the speed of light. To explain the effects of electrostatic forces, the movement of positive charges (conventional current) is best.

See the explanation on which way electricity flows at www.douglaskrantz.com/
ElecElectricalFlow.html
.