Operations Common To All Rooftop Units - Lennox Prodigy 2.0 Application Manual

1
SEE AFTERMARKET CONTROLLER INSTALLATION
INSTRUCTIONS FOR WIRING INFORMATION.
1
BYPASS
DAMPER
1
SUPPLY STATIC
PRESSURE
SENSOR
Figure 29. Constant Air Volume Unit in Bypass Zoning Application
When in thermostat mode and configured for discharge air temperature control, the M3 Unit Controller can provide up to four
stages of mechanical heating and cooling operation. Variable air volume units using a variable frequency drive on the supply
fan and operating in a zoning application must use this control mode. Although not as common, constant volume units in
either single-zone or bypass zoning applications may also use this control mode. To operate correctly, a Lennox or
third-party thermostat or unit control must provide the following wiring connections to the M3 Unit Controller:
1. Ventilation demand
2. Occupied demand
3. Heating demand
4. Cooling demand
In this control mode the M3 Unit Controller will control all cooling and heating staging to maintain the discharge air
temperature set points set in the M3 Unit Controller (typically 55°F for cooling and 110°F for heating). A third-party unit
control, or a thermostat can provide these inputs to the M3 Unit Controller. For example, if the unit control passes along a
demand for cooling then the M3 Unit Controller will activate the refrigeration system and increase or decrease cooling
stages to maintain the discharge supply air temperature set point. Along with providing control of the rooftop unit, the M3
Unit Controller will also provide error codes and diagnostic information.
AFTERMARKET
RTU
CONTROLLER OR
THERMOSTAT

19.1.3. Operations Common to All Rooftop Units

The following sequence of operation information applies to all rooftop units regardless of M3 Unit Controller control mode,
unit type or zoning application.
19.1.3.1. Occupied Demand
Upon receiving occupied and ventilation demands from the a zoning control the M3 Unit Controller adjusts the fresh air
damper to either a fixed minimum position or allows it to modulate based on a carbon dioxide sensor (demand control
ventilation). The carbon dioxide sensor can be wired directly to the M3 Unit Controller, to another controller that can monitor
the sensor and pass a signal to the M3 Unit Controller for damper control, or to both the M3 Unit Controller and another
device for monitoring through the desired man-machine interface while the M3 Unit Controller maintains damper control.
24VAC
COMMON
VENTILATION DEMAND
1 HEATING DEMAND ONE
AFTERMARKET
RTU CONTROL­
HEATING DEMAND TWO
LER
COOLING DEMAND ONE
COOLING DEMAND TWO
OCCUPIED DEMAND
24VAC THERMOSTAT
W1 W2 Y1
R C G
24VAC
COMMON
VENTILATION DEMAND
HEATING DEMAND
COOLING DEMAND
OCCUPIED DEMAND
Figure 30. Variable Air Volume Unit in Zoning Application
24VAC THERMOSTAT G
L
R C G W1 W2 Y1 Y2 OCP O
SENSOR
G 24VAC
SENSOR OUTPUTS
IAQ
L
Y2 OCP O
R C
AI1
HUM TMP D01
Page 77
SENSOR
24VAC
SENSOR OUTPUTS SMOKE
IAQ
24VAC
R C
DI1
AI1
HUM TMP
D01 D02
R C
HUMIDISTAT
SMOKE INPUTS
24VAC
DI1
D02
DI2 DI3 DI4 C
R C R R
INPUTS HUMIDISTAT
DI2 DI3 DI4 C
R R