Contemporary Controls BASstat BAST-421C-B2 User Manual page 15

supervisor "1" (add decimal=512).
Cool Only and Heat Only modes (nullified/disabled in firmware) are control types listed in the
BACnet object and Engineering Menu object but are not available for use.
Control type is only configurable by the installer using Engineering Mode Menu or BACnet
supervisor. The installer must decide the control type suitable for the application, set it to a
static value, or program the BACnet supervisor to change the control type automatically. The
default control type is set to 4-Pipe Cooling or heating with Auto Changeover. Manual
Changeover can be used to prevent excessive automatic changeover between cooling and
heating system modes.
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.
System Mode
• The default control type, modulating cooling and heating with automatic
changeover, allows the thermostat to operate as fully stand-alone. Manual
Changeover allows restriction of mode selection to Cool only or Heat only where
necessary. Control Type can be selected in (tyPe) or [MSV8].
• For manual changeover control, cooling or heating system modes can be
selected by pressing the MODE button or using a BACnet command to
object [MSV1]. In application where user control needs to be limited, the
lock button function can be used to disable MODE button.
• Occupied Cooling [AV0] and Heating [AV3] set points and Unoccupied
Cooling [AV8] and Heating [AV9] setpoints can be set individually. Minimum
deadband [AV7] can be programmed as well.
Modulating Valve Offset
• The minimum control analog output voltage (low limit) for the modulating valves
(AO1 and AO2) is set to 0 volts. These values can be changed at [AV11] for AO1
and [AV27] for AO2. The setting is measured as an LSB range of 0~125.
Assigned Current Temperature
A current temperature value can be assigned thru BACnet AV-1 to take place of
•
the onboard temperature sensor value. The assigned value is valid if BACnet
communication is driving a flip-flop signal to (BV-16: heartbeat signal) within the
(AV-29: Heartbeat Rate time) period (in seconds). Otherwise, the assigned
temperature will revert back to the onboard sensor reading.
UM-15093000-AA1
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