Douglas Krantz - Technical Writer - Describing How It Works
Get the Book Make It Work - Convetional Fire Alarms
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Why Won't the Panel Show the Detectors?

Many causes for the devices not communicating... FACP isn't programmed, device not addressed, an open wire, shorted wires, reverse polarity device

Hi Douglas,

I have a problem with an addressable fire alarm panel. The panel indicates that it's OK, but the detectors are not seen on the panel. Only the sounders are displayed.

What could be wrong? The panel does not display any fault.

Thank you, J R
There may be one problem many problems. Without knowing some things about the system, however, I couldn't guess.
  • What make and model of panel are you working with? Who makes it and what model it is makes quite a difference.

  • Is it a new system, just turned on for the first time, or maybe in stages of installation? Or is it an existing system that's been in place for years?

  • Did the system show the detectors originally, and now suddenly the panel doesn't show them? Or has it always done that?

  • What are you doing to show the sounders, but not the detectors? Is everything disconnected? Are some wires disconnected?

  • If some wires are being disconnected, which ones? The wires going to the sounders? What about the wires going to the detectors?

Before making a guess, I need to know the answers to these questions.

Douglas Krantz

Further Question

Mr. Krantz

These are answers to the questions asked;
  • The make is Zeta. The model is the Simplicity Plus Analogue Addressable Fire Alarm Panel.

  • It is a new panel in stages of installation.

  • It only shows the sounders and connecting the wire and configured panel.

  • After addressing the sounders, the sounders were displayed but detectors were not shown.

  • The panel shows the number of devices.

Thank you, J R

Remember, you are not just troubleshooting the panel; you are troubleshooting a whole building wide fire alarm system. Also, keep in mind, unless the installers of the fire alarm system are all very experienced, very few fire alarm systems are ever wired totally correctly the first time. Don't worry about the mistakes, everyone makes mistakes, your job is to fix all the mistakes and any other problem.

You have to ask yourself some questions.

The sounders show up on the panel. The sounders can be wired directly to the panel on Notification Appliance Circuit (NAC) loops, or the sounders can be connected to the Signaling Line Circuit (SLC) loop. Are the sounders that are showing up on the panel the ones that are connected to the panel itself on a NAC loop, or are they the ones connected to the SLC loop? If they are connected directly to the panel, they can be ignored completely for now and your attention should only be on the detectors.

Programming the Detectors

There are two places that need programming. The panel and the devices. Is the panel completely programmed? If not, the panel might not be set up to even look for the detectors. Before checking to see if the detectors are even connected, make sure the panel is programmed because without programming the panel, the detectors won't be seen by the panel.

Also check the detectors. Are they programmed with their addresses? Your description doesn't show for sure one way or another. If the detectors aren't programmed, they won't be seen by the panel.

Use a Voltmeter at the Panel

The next step is to use the voltmeter.

Disconnect the loop wires completely from the panel. Wait a full minute and then check the voltage of the SLC (Signaling Line Circuit) on the panel. Measure the voltage on the loop terminals of the panel itself. Watch out, sometimes, even without wires in the screw terminals of the panel, you have to tighten down the screws on the terminals before you can get an accurate reading. Make sure the screws are tight.

The voltage you see on the panel probably will not be steady. Don't worry about that. Just look at the voltage for a little while and get familiar with the voltage and how it acts.

Next, reconnect the loop and look at the voltage again. The voltage may become more unsteady, but if the voltage is there on the terminals, you need to start checking to make sure the voltage gets to the detectors.

Then again, if the voltage at the panel detector drops to zero, you have a short on the wires or a device is wired incorrectly. With a short, disconnect the wires from the panel and find and fix the short. With an incorrectly wired device, find the device that's wired wrong and fix the wiring.

Use a Voltmeter at the Devices

Go to the farthest detector and see if the voltage you read at the panel is there. If the voltage isn't there, divide and conquer to figure out where the voltage stops and fix the wiring.

Technical Support

If the detectors still aren't showing up on the panel after checking out the possibilities, then call Technical Support for the manufacturer.

Talking to them before checking these things out means that they will tell you to check these things out anyway before they will discuss the rest of the system. In other words, if you check these things first, you'll save a lot time with technical support.

Douglas Krantz
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