Contemporary Controls BAST-221C User Manual page 17

System modes available to the user are dependent on control type chosen from Engineering
Menu (tyPE) or BACnet object [MSV7] Control Type for BW2 model and [MSV8] Control Type
for B2 model.
Dual Stage Heat and Cool with Auto Changeover - The default control type in the thermostat is
set to Heat and Cool with Auto Changeover. Mostly used for standalone operation. Based on an
algorithm using setpoint, current temperature, and deadband, the thermostat will switch
between Cool and Heat modes automatically. In this control type, the user will be presented with
a choice of Heat or Ventilation@Heat when the thermostat is in Heat mode (automatic), and
Cool or Ventilation@Cool when the thermostat is in Cool mode (automatic).
Dual Stage Heat and Cool with Manual Changeover – This control type is similar to Heat and
Cool with Auto Changeover but in this control type the thermostat will wait for a command from
user or BACnet supervisor to switch between Cool and Heat modes. In this control type, the
user will be presented with a choice of Heat or Ventilation@Heat when the thermostat is in Heat
mode (manual command), and Cool or Ventilation@Cool when the thermostat is in Cool mode
(manual command). The user can also choose to switch between Cool and Heat modes using
the MODE button.
BACnet controlled – The built-in thermostat algorithm can be bypassed completely, and the
thermostat can be controlled over the BACnet network with commands from supervisor device.
The logic executing in the supervisor (such as Niagara or Sedona logic) can control the
thermostat over the BACnet network. To put the thermostat in BACnet network control mode,
use the Lock [AV18] object bit 9: Control DOs by thermostat algorithm "0" (default) or BACnet
supervisor "1" (add decimal=512).
Cool Only (nullified/disabled in firmware), and Heat Only (nullified/disabled in firmware) control
types are listed in the BACnet object and Engineering Menu object but are not available for use.
They are nullified/disabled in the firmware.
Fan Output in Heat Mode
By default, the BASstat thermostat will not provide Fan output signal when in Heat Mode since
most HVAC comfort systems such as RTU systems provide their own fan control signal based
on a delay after a call for heating. This can be configured from Engineering Menu item (F-Ht) or
BACnet object [BV15] Fan Output For Heating. The default value is "0". To enable fan control
signal output for heating coming from the BASstat, set this value to "1".
Algorithm
• A PID adaptive control algorithm is applied to minimize overshoot, in addition to
proportional band (Stage Width) and derivative (Differential) calculation.
When the thermostat is active (either the heating or cooling stage is on), a "Working
•
( )" icon will be shown on the LCD.
Stage 1 operation will show the icon (
•
UM-15090000-AA4
). Stage 2 operation will display ( ).
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