Johnson Controls WT-4002-MCR Installation Instructions Manual page 14

In a DA room thermostat configuration, the branch line
pressure increases in response to an increase in room
temperature. When the room temperature is within the
±1F° (±0.6C°) dead zone around the setpoint, the
branch line pressure is regulated at the setpoint
pressure, and the pneumatic actuator is at the
minimum heat (cool or neutral) position.
When the room temperature rises above the setpoint
plus the dead zone, the branch line pressure increases
proportionally to the increase in temperature. The
proportional factor is defined by the gain/sensitivity
value.
When the room temperature decreases below the
setpoint minus the dead zone, the branch line pressure
decreases proportionally to the decrease in
temperature. The proportional band defines the
temperature range, where the branch line pressure
changes proportionally to the change in temperature.
Note: The setpoint pressure, dead zone,
gain/sensitivity, and proportional band are adjusted
using the menu buttons on the WT-4000 Series Room
Thermostat.
Wireless Operation
The WT-4000 Series Pneumatic-to-DDC Room
Thermostats are designed to monitor and control
pneumatic HVAC systems. The room thermostats are
equipped with a 2.4 GHz IEEE 802.15.4 radio that
communicates via a wireless mesh network. The
wireless mesh network forms itself, and data
communications enable remote monitoring,
adjustment, and trending to provide longer and more
dependable and maintenance-free operation.
Note: For each room thermostat in the wireless mesh
network, only one object can be written at a time, and
the next object cannot be written for at least 5 minutes.
WT-4000 Series Pneumatic-to-Direct Digital Control (DDC) Room Thermostats Installation Instructions
In a wireless mesh network, the room thermostat
operates as a battery-powered end node. Being an end
node, the room thermostat does not operate as a router
to relay data for other devices in the mesh network.
Instead, the room thermostat communicates with the
wireless mesh network as an individual device that
transmits and receives its own data only, to and from
the WT-BAC-IP Gateway or through other
WT-ROUTER Routers.
During wireless operation, an antenna icon appears in
the upper-right corner of the LCD when the room
thermostat communicates with the wireless mesh
network (Figure 16). The number below the antenna
icon represents the number of devices that the room
thermostat can communicate with. It is desirable that
the room thermostat have two devices it can
communicate with. With two devices, if one
communication link fails, then the other communication
link can be used without delaying any transmissions.
Figure 16: LCD during Wireless Communication
When the room thermostat is installed in buildings with
common sheetrock walls, the nominal radio
communication range of the room thermostat is
approximately 200 ft (61 m). If the room thermostat is
located more than 200 ft (61 m) from the WT-BAC-IP
Gateway, then WT-ROUTER Routers must be installed
to relay data generated by the room thermostat back to
the WT-BAC-IP Gateway.
14