83
22. Sequence of Operation
22.1. Unit Controller Control Modes
Unit controller can operate in several different control modes. The selection of these control modes will depend upon
several factors:
Unit type - constant air volume with MSAV.
Room application (single-zone, bypass zoning or zoning)
Which device will control rooftop unit staging and unit operation (thermostat / third-party controller or the M3 unit
controller)
The desired level of unit heating and cooling staging (2 heat / 2 cool or 4 heat / 4 cool)
22.1.1. Unit Controller In Room Sensor Mode
When in the room sensor mode, the M3 unit controller can provide up to four stages of mechanical heating and cooling
operation. Constant volume units in single-zone applications can use this room sensor mode. The room sensor will
provide space temperature information to the M3 unit controller. The M3 unit controller houses all space temperature set
points and controls all rooftop unit staging and general operation. The M3 unit controller also determines unit error codes,
provides diagnostic information and maintains safe operation limits. It is important to note that scheduling and/or set point
control requires the use of a L Connection Network Control Panel.
HUM
AI1
TMP
D01 D02
DI1
DI3DI2
DI4
24VAC
R
C
24VAC
C
24VAC
THERMOSTAT
G
OCP
C
G
W1 Y1
W2
Y2
O
L
R
SENSOR
OUTPUTSSENSOR
IAQ
SMOKE
R
HUMIDISTAT
INPUTS
R R
C
RELATIVE HUMIDITY FOR
HUMIDITROL OR SUPERMARKET
REHEAT OPTION
RH SENSOR ROOM SENSOR
Figure 27. Constant Air Volume Unit in Single-Zone Application
22.1.2. Unit Controller In Thermostat Mode
When in the thermostat mode, the M3 unit controller can provide up to two stages of mechanical heating and cooling
operation. Three stage cool operation is possible with special setting described in section 2.1.1.
Constant volume units in either single-zone or bypass zoning applications can 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 one
4. Heating demand two
5. Cooling demand one
6. Cooling demand two
In this configuration, either the thermostat or unit control will control the rooftop unit staging and general operation. The
M3 unit controller functions primarily to determine unit error codes, provide diagnostic information and maintain safe
operation limits.
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