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Brett Stewart

VRF Tech Support & Equipment Verification Southwest District

48GC Package Unit & System Sensor Smoke Detector D4120 Setup

Smoke detectors can be used in many different residential and commercial applications. They can be utilized using the smoke shutdown or thermostat terminals on most of your package units and split systems. When smoke is detected the indoor fan will shut off by breaking your low voltage circuit through your smoke detector.

When wiring up a smoke detector on a package unit such as a 48GC, you will utilize your smoke shutdown terminals on the control board in the unit. Your field supplied 18/8 stranded two wire will run from your smoke shutdown terminals in your unit to the AUX A contacts on your smoke detector which is six and sixteen. Six is common and sixteen is normally closed.

If your unit doesn’t have a set of smoke shutdown terminals on the control board to use you would then break “R” or “G” on the terminal strip or wire nut junction in the unit. Breaking “R” will kill power to your thermostat and stop all unit and fan operations. Breaking “G” will kill power to the indoor fan and stop indoor fan operation.

  • Remove the factory Jumper that is installed on your smoke shutdown terminals to hook up your two wire that goes to your smoke detector.
  • When breaking “R” one wire goes from “R” on the terminal strip to “C” on the smoke detector, your second wire goes from “NC” on the smoke detector back to your red wire in your unit that goes down to “R” on the thermostat.
  • When breaking “G” one wire will wire nut with “G” your green wire in the unit going to the thermostat and then to “C” on the smoke detector, your second wire will land on “NC” on the smoke detector and land back on “G” on the terminal strip in the unit.

Disclaimer: The technical statements, information and recommendations contained herein are believed to be accurate as of the date hereof, but Mingledorff’s does not make representations or warranties, express or implied, as to its accuracy, its completeness, or the results to be obtained. The information is being provided for informational purposes only and is intended for use by persons having adequate skill and expertise regarding the proper selection, use and application of the products and recommendations and at their own risk and discretion. 

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