Orion System Lead Controller - Manual (Page 45)

Lead/Lag Controller Technical Guide
Appendix A - Sample Confi gurations
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2 Lead/1 Lag Example - Controlling 3 Roof Top Units
2 Lead / 1 Lag Example - Controlling
Roof Top Units
The user would like to use the Lead/Lag Controller to control 3
Roof Top Units that are feeding a large surgery suite. They need 2
of the units to run all of the time. RTU-1 and RTU-2 will run fi rst,
and at the end of the Changeover Interval, RTU-2 will shut off,
and RTU-3 will be energized. After the next Changeover Interval,
RTU-1 will shut off and RTU-2 will be brought back on. We select
2 Lead/1 Lag as the control method. Each RTU has its own supply
air temperature sensor and is trying to maintain 55°. If the supply air
gets above 60° on one of the RTUs, it will be shut down, the third
unit will be brought on, and an alarm will be sent. See Figure 84.
Figure 84: Lead/Lag Status after Confi guration