Douglas Krantz - Technical Writer - Describing How It Works

Can I Move the Horn/Strobe Without Setting Off the Alarms?

By Douglas Krantz | Maintenance

Can I Move the Horn/Strobe Without Setting Off the Alarms?

Can I Move the Horn/Strobe Without Setting Off the Alarms?

Greetings Douglas, Greetings Douglas,

I'm tasked with relocating a red fire horn/strobe. I'm wanting to raise it up about 2 feet on the wall. It's 1900 box with the conduit coming down to the box.

Will the fire alarm system go off if I remove the horn/strobe (disconnect it) and raise it up about 2 feet above its current position?

It's currently blocking the yellow loading dock fan from positionally functioning correctly.

Please Help.

Thank You, JC

Disconnecting the horn/strobe, or even unplugging it from the wall will cause the fire alarm panel to go into trouble, and call the monitoring company to report the trouble condition. This is to ensure that the disconnected horn/strobe will be replaced, properly.

Normally, the panel is supervising the wires in the circuit, and the circuit itself is called a Notification Appliance Circuit, or NAC, for short. To supervise the circuit, the panel runs a continual continuity check of the horn/strobe wiring. If a wire breaks, or comes loose from a connected horn/strobe, the continuity of the wiring is broken. The panel detects the broken continuity, and the whole fire alarm system goes into trouble.


No, the fire alarm system probably won't sound the alarms when the horn/strobe us disconnected.

Never, ever, count on that.

If something else goes wrong while working on the fire alarm system, the system could go into alarm. Going into alarm when disconnecting, moving, or replacing a horn/strobe is an extremely rare event, but there is always a slim chance of that happening.

Make sure that management knows what you're doing. When things go wrong, if they know about possible problems, they'll feel more comfortable. Also, they might have conditions for performing the work, like, so production won't be shut down, perform the moving of the horn/strobe after hours.

Central Station Monitoring

Before doing anything with a fire alarm system, always put the whole system on test with the monitoring company. That way they will take no action to dispatch the fire department or call on site to report the trouble.

While the fire alarm system is "On Test" with the monitoring company, if there is a real fire, you are the person responsible to call the fire department. Also, make sure the system is not on test when you leave the site, because when you are not on site, someone has to be able to call the fire department.

When you're through, check the fire alarm panel to make sure it is normal and only shows a green power-on light. Any yellow lights have to be investigated and fixed.

Once you're sure the fire alarm system is normal, call the monitoring company to check that all troubles, supervisories, or alarms they have received are cleared at their end. If something is not cleared at their end, check to see what you have to do at your end to clear it.

When everything is normal, then have the monitoring company take it off test so, if there's a fire, they will again take the action of calling the fire department.


Fire alarm horn/strobe wiring is not normal wiring. When just sitting there, standing by, the panel is supervising the wires (performing a continuity check of the wires). The voltage polarity of the wires is backward so the continuity checking of the wires cannot turn on the horns and strobes.

When sounding the alarm, the panel will reverse voltage polarity so the power coming in on the wires will provide power to the horns and strobes.

In other words, don't use your voltmeter to confirm that the horn/strobe is wired correctly. Instead, before disconnecting any wires from screw terminals, use the phone's camera to show the exact wiring. That way, the exact wires that came off the screw terminals will be the same wires that go back onto the same terminals.


The horn/strobe is part of a life-safety system. If some part of the system doesn't work, an occupant in the building might be injured, or worse. Using the "drill" button on the panel, test the horn/strobe after moving it.

Before testing, work with management to make sure they are comfortable with the entire facility hearing the full fire alarm. Also, make sure the management knows about possible shutting down of processes, like belts, doors, or other actions that the fire alarm system takes when there is an alarm.

Management may have the test performed after hours.

CYA Paperwork

If it aint on paper, it didn't happen, so says the Minnesota State Fire Marshal.

Moving the horn/strobe, and the testing of the moved horn/strobe has to be described in the CYA Paperwork. If management for the site doesn't want the test, then the name of the person telling you to hold-off, and the reason they give for not testing should by on the CYA Paperwork.

You are correct, normally, no one reads the paperwork. But, then again, if something goes horribly wrong, everyone will read the CYA Paperwork. Make sure it's there.

Douglas Krantz

Greetings Douglas

I have to say that your response to my question could not have been more thorough. I greatly appreciate it and I will let you know how things go. Your email has made me feel very comfortable. Thank you for what you do.

Please add me to the Short Circuit News Letter.

Thank You, JC
Life Safety
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