Douglas Krantz - Technical Writer - Describing How It Works

Will a Reverse-Wired Device Stop Other Devices?

By Douglas Krantz | Maintenance

Will a Reverse-Wired Device Stop Other Devices?

Will a Reverse-Wired Device Stop Other Devices?

Greetings Douglas,

If the first smoke detector is reversed polarity, can this cause the smokes not to talk to the others?

Thank You, TS

All manufacturers have designed their building-wide fire alarm systems to be wired a specific way. The manufacturers show how to wire the devices in the installation sheets that come in the boxes included with the devices.

If the installation sheet is lost, the installation sheet is available on the web.

The first thing to assume, though, when a smoke detector isn't installed exactly the way the manufacturer shows in the installation sheet, is that something is going to go wrong.

If It's an Addressable Smoke Detector

On every addressable circuit (Signaling Line Circuit or SLC), the Fire Alarm Control Panel provides the power used to operate the addressable devices. The panel's power supply for the SLC is very weak - it can be shorted out extremely easily. For the devices on the circuit to be able to communicate with the panel (talk to the panel), the weak power supply is supposed to be that way.

In most cases, if any device like an addressable smoke detector is reverse wired, it will short out the panel's Signaling Line Circuit, or SLC. When that happens, no device on the SLC will work - at all.

If that smoke detector is the only reverse-wired addressable device on the SLC, once the detector is wired correctly, the SLC should start working after a minute or so. Then the other smoke detectors will communicate with the panel (talk to the panel).

If It's a Conventional Smoke Detector

When a conventional smoke detector is reversed wired, it will either not work at all, not work correctly, or in some cases, the manufacturer shows in their installation sheet that it will still work.

Even when the installation sheet indicates that a reverse-wired smoke detector will still work, I, personally, will never reverse-wire a smoke detector. A fire alarm system is a depended-on, life-safety system. I don't want to make mistakes.

Technical Support

Before contacting the manufacturer's technical support team, make sure that all devices, including all smoke detectors, are wired according to the manufacturer's installation sheets.

After making sure all devices are connected according to the sheets, test the whole system to make sure it works. You need to perform this test for you to have confidence the whole system works.

On your CYA Paperwork, write down the reason for the test, and the fact you actually performed this test. (No one reads the CYA Paperwork, unless something has gone horribly wrong. Then the CYA Paperwork had better be there.)

After testing the system, if something in the system doesn't work, then contact the manufacturer's technical support team. They know the system, and can help you troubleshoot from there.

When contacting them, make sure you have information ready for them:
  • The manufacturer's name
  • The model number of the fire alarm control panel
  • The model number of any device that isn't working

Also, let them know about the detector that had been mis-wired. When they are trying to help you, that information can help them.

Douglas Krantz
Life Safety
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