Specifications

CONTROL OF HEATING AND COOLING
EQUIPMENT
The system heating and cooling equipment is operated by
the monitor thermostat in response to the zone conditions (if
configured as a VVTt monitor thermostat) of each zone con-
troller associated with the system. The monitor thermostat
uses the Zone Caller, Reference Zone, and System Mode to
determine the requirements of the system.
The monitor thermostat can control the heating or cooling
stages of the equipment and an economizer (if applicable).
During equipment operation, zone temperature conditions
can be improving, staying the same, or becoming worse. The
monitor thermostat will analyze the conditions and trends
and determine how to stage the equipment.
To protect the equipment, the monitor thermostat utilizes
a time guard function to prevent excessive equipment cy-
cling. To prevent excessive temperatures, high and low tem-
perature limits can be set by the monitor thermostat to de-
energize stages of equipment operation based on a comparison
of supply air temperatures to system operating limits. The
monitor thermostat can also lockout heating or cooling based
on outside air temperature.
Heating/Cooling Equipment Interface — The
heating/cooling equipment is interfaced to the monitor ther-
mostat through a single zone relay pack when the monitor
thermostat is configured as a Monitor Only thermostat. The
heating/cooling equipment is interfaced to the monitor ther-
mostat through a cooling/heating relay pack when the moni-
tor thermostat is configured as a VVT Monitor thermostat.
Through the relay pack, the monitor thermostat is able to
control:
• two stages of cooling
• two stages of heating
• fan operation
• reversing valve operation or economizer operation (aux-
iliary relay)
System Switches — The system switches are located
on the bottom right corner of the monitor thermostat. The
system switches control the system mode function. See
Fig. 29. The system switches can be set to a fixed position
(locked) through configuration and can also be controlled
over the network (through software).
NOTE: The heating and cooling relays cannot be forced. If
the fan relay is forced, the heating and cooling relays will be
dropped. The minimum run time settings in category 4,
options 17 and 18 will be ignored.
SYSTEM HEAT SWITCH — The monitor thermostat heat
switch has two settings. When the heat switch is set to OFF,
the monitor thermostat cannot select system heat mode. When
the heat switch is set to AUTO, the monitor thermostat is
able to select system heat mode.
To control the heat switch setting, configure category 4,
option 22. The range is from 0 to 2. When the option is set
to 0, the thermostat will follow the setting of the mechanical
heat switch. When the option is set to 1, the thermostat will
perform as if the heat switch is set to AUTO (regardless of
the mechanical switch setting). When the option is set to 2,
the thermostat will perform as if the heat switch is set to
OFF (regardless of the mechanical switch setting). The set-
ting of 0 is the default setting.
SYSTEM COOL SWITCH — The monitor thermostat cool
switch has two settings. When the cool switch is set to OFF,
the monitor thermostat cannot select system cool mode. When
the cool switch is set to AUTO, the monitor thermostat is
able to select system cool mode.
To control the cool switch setting, configure category 4,
option 21. The range is from 0 to 2. When the option is set
to 0, the thermostat will follow the setting of the mechanical
cool switch. When the option is set to 1, the thermostat will
perform as if the cool switch is set to AUTO (regardless of
the mechanical switch setting). When the option is set to 2,
the thermostat will perform is if the cool switch is set to OFF
(regardless of the mechanical switch setting). The setting of
0 is the default setting.
Fig. 29 — System Switch Locations
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