120 Volt smoke alarms with alarm contacts

We get questions whether FireCAD can be used to connect 120 volt smoke detectors either singly or in tandem. Yes, it can and here's how it's done.

In the project below we have placed the following devices:

  • A Firelite FACP in the electrical room.
  • A Firelite monitor module in the foyer of the apartment.
  • Four 120volt Gentex smoke detectors with alarm contacts.
  • A Generic circuit breaker panel.


The circuit breaker panel is an assembly which is configured with one 20 amp breaker. More can be added using the assembly editor.


Choose the "VAC" circuit from the breaker panel. Connect one smoke detector. This can be any single smoke detector because when we connect the tandem circuit later it will supply both power and interconnection functionality to the other detectors.


Now choose the zone originating at the monitor module and connect one smoke detector to it.


The result is:

  • One detector connected to the 120 volt power circuit and labeled "VAC" accordingly.
  • Another detector is connected to the zone originating at the monitor module and labeled "Z1" accordingly.



Now make the tandem connection by selecting the T1 (tandem output) circuit from the project circuits list.


Connect all the smoke alarms to this circuit.


Now all the smoke alarms except the T1 (tandem output) (labeled VAC) show the circuit number T1.


Now use the Draw Circuit Wirepath command.


The riser and cable/wire legend is shown below.


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