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Thermostat (single mode heat/cool/ventilation, BACnet MS/TP) · BACnet points list
Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat BACnet points list
Updated 11 November 2026
The BAST-121C-B2 is a wall thermostat for single-mode heat/cool/ventilation control (on/off or modulating) that talks BACnet MS/TP. It exposes temperatures, setpoints, mode and fan commands, relay status and control, occupancy and the thermostat setup values as BACnet objects.
This page lists 62 BACnet objects for the Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat — 48 of them writable — with each object’s type, instance number, name, engineering units and access. It is re-typed from Contemporary Controls’s own free documentation, linked below.
- Manufacturer
- Contemporary Controls
- Model
- BASstat BAST-121C-B2 Single Mode Thermostat
- Equipment
- Thermostat (single mode heat/cool/ventilation, BACnet MS/TP)
- Equipment type
- Thermostats, sensors & meters
- BACnet objects
- 62 (48 writable)
- Transport
- BACnet MS/TP
- Firmware
- Not stated
- Default device instance
- 700001
- Also known as
- BAST-121C-B2, BAST-121-B2, BASstat 121C
Reference only, provided as-is: verify against Contemporary Controls’s current documentation and the live device before use. Not official Contemporary Controls information. Terms of use.
BMS integration notes: Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat
Turn the thermostat outputs on with On-Off Control (BV 5), set occupancy with Occupancy Command (BV 14), and write the system mode, cooling and heating setpoints and fan mode. Read the space temperature, occupancy status, output status and fan speed.
Minimum points to map
The short list most integrators start with — enough to run the unit from a BMS. Map more as the job needs.
| Object | Name | Why | Access |
|---|---|---|---|
| BV 5 | On-Off Control | Thermostat outputs on/off (1 = on) | Write |
| BV 14 | Occupancy Command | 0 = occupied, 1 = unoccupied | Write |
| MV 1 | System Mode | Cool, heat or ventilation mode | Write |
| AV 0 | Cooling Temperature Setpoint | Occupied cooling setpoint | Write |
| AV 3 | Heating Temperature Setpoint | Occupied heating setpoint | Write |
| MV 0 | Fan Mode | 1 = auto, then fan speeds | Write |
| AI 0 | Current Temperature | Space temperature in use | Read |
| BI 0 | Occupancy Status | 0 = occupied, 1 = unoccupied | Read |
| BI 2 | Cooling-heating Status | Heating/cooling output active | Read |
| MV 5 | Fan Speed Status | Current fan speed | Read |
Enable & remote start
On-Off Control (BV 5) switches the thermostat outputs. Occupancy Command (BV 14) only takes effect when the ESI contact is disabled in Lock (AV 18 bit value 64); by default occupancy comes from the ESI dry contact.
Heartbeat & communication loss
A space temperature written to Space Temperature via BACnet (AV 1) is only used while the BMS keeps toggling Heartbeat Signal (BV 16) within the Heartbeat Rate (AV 29) period, in seconds; otherwise the thermostat reverts to its own sensor.
Sensors & values from the BMS
Set Temperature Source (MV 3) to 3 (Assigned through BACnet) and write the space temperature to AV 1, toggling BV 16 as a heartbeat.
Network setup
- BACnet MS/TP: MAC address set in the Engineering menu (Addr, 1-127) or AV 20; baud 9600-76800 set with bAud or Baud Rate (MV 6).
- Device instance = devH x 1000 + devL in the Engineering menu, or write Device Instance (AV 21) once online.
- The manual gives 700001 as the default device instance, MAC address 1 and 38400 baud.
Watch out for
- Lock (AV 18) is bit-coded: add the bit values to lock buttons, ignore the ESI or door contact, block changes to the comms settings or hand the relays to BACnet (512).
- The manual text calls the Lock object AV17 in places and the heartbeat rate AV-29; the object table numbers are used here.
- System Mode (MV 1) can only be changed within 1 minute after Options (AV 37) is set to 1.
- Relay control BVs only drive the relays when Lock bit 9 (512) hands the outputs to the BACnet supervisor.
Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat BACnet objects
Type: AI, AO, AV, BI, BO, BV, MI/MO/MV (multi-state) · Access: Read read-only, Write writable, Command writable with a priority array.
| Description | States | |||||
|---|---|---|---|---|---|---|
| AImin | 0 | Current Temperature | °F/°C | Read | ||
| AI | 1 | Active Temperature Setpoint | °F/°C | Read | ||
| AI | 2 | Built-in Temperature Sensor | Built-in Temperature Sensor Reading | °F/°C | Read | |
| AI | 3 | Remote Temperature Sensor | Remote Temperature Sensor Reading | °F/°C | Read | |
| AI | 8 | Modulating/ Floating Output 1 | % | Read | ||
| AI | 13 | Analog Input 1 Value | Analog Input 1 Percentage Value | % | Read | |
| AVmin | 0 | Cooling Temperature Setpoint | °F/°C | Write | ||
| AV | 1 | Space Temperature via BACnet | Assigned Current Temperature | °F/°C | Write | |
| AVmin | 3 | Heating Temperature Setpoint | °F/°C | Write | ||
| AV | 4 | Hr-Running Time | Running Time of Valve (Hr.) | h | Write | |
| AV | 5 | M-Running Time | Running Time of Valve (M.) | min | Write | |
| AV | 6 | Sec-Running Time | Running Time of Valve (Sec.) | s | Write | |
| AV | 8 | Unoccupied Cool Setpoint | Unoccupied Cooling Setpoint | °F/°C | Write | |
| AV | 9 | Unoccupied Heat Setpoint | Unoccupied Heating Setpoint | °F/°C | Write | |
| AV | 10 | Integral-Cycle Time | Integral Time and Output Cycle Time | s | Write | |
| AV | 11 | Analog Minimum Output | Minimum Output Voltage in Digital Value When Reach Low Limit for AO1 | Write | ||
| AV | 12 | Span Offset | Span Offset for AO1 | Write | ||
| AV | 13 | Low Setpoint Limit | Low Limit for Setpoint Temperature | °F/°C | Write | |
| AV | 14 | High Setpoint Limit | High Limit for Setpoint Temperature | °F/°C | Write | |
| AV | 15 | Temperature Offset | Offset for Current Temperature | °F/°C | Write | |
| AV | 16 | Proportional Band- Stage Width | Proportional Band or Stage Width | °F/°C | Write | |
| AV | 17 | Stage Differential | °F/°C | Write | ||
| AV | 18 | Lock | Bit-coded lock: buttons, ESI/door contacts, comms settings, DO control | Write | ||
| AV | 19 | Control Out Percentage | Percentage of Modulating/ Floating Control Output | % | Write | |
| AV | 20 | MAC Address | Write | |||
| AV | 21 | Device Instance | BACnet Device Instance | Write | ||
| AV | 23 | Cooling Short Cycle | Cooling Short Cycle Delay | min | Write | |
| AV | 24 | Cooling Maximum Cycles per Hour | Write | |||
| AV | 25 | Heating Short Cycle | Heating Short Cycle Delay | min | Write | |
| AV | 26 | Heating Maximum Cycles per Hour | Write | |||
| AV | 29 | Heartbeat Rate | Communication Heartbeat Minimum Rate | s | Write | |
| AV | 37 | Options | Options (mode reset) | Write | ||
| AV | 39 | Minimum cooling temperature setpoint | °F/°C | Write | ||
| AV | 40 | Maximum Heating temperature setpoint | °F/°C | Write | ||
| AV | 46 | Minimum Off Time | s | Write | ||
| AV | 47 | Minimum On Time | s | Write | ||
| BImin | 0 | Occupancy Status | Status of Occupancy | Read | 0=Room Occupied, 1=Room Unoccupied | |
| BImin | 2 | Cooling-heating Status | Status of Cooling/Heating Control Output | Read | 0=Close & Off, 1=Open & On | |
| BI | 3 | Relay 1 Status | Status of Relay 1 (Output Stage 1) | Read | 0=Off, 1=On | |
| BI | 4 | Relay 2 Status | Status of Relay 2 (Output Stage 2) | Read | 0=Off, 1=On | |
| BI | 9 | Relay 7 Status | Status of Relay 7 (Fan) | Read | 0=Off, 1=On | |
| BI | 10 | Dl 1 Status | Status of Digital Input 1 | Read | 0=Off, 1=On | |
| BI | 17 | Fan Status | Read | 0=Off, 1=On | ||
| BV | 0 | Occupancy Contact Definition | Occupancy(DI1) Contact Definition | Write | 0=N.O., 1=N.C. | |
| BV | 1 | Cooling Direct- Reverse Acting | Modulating Cooling Direct/ Reverse Signal Output | Write | 0=Direct (0 To 10V), 1=Reverse (10 To 0V) | |
| BV | 2 | Heating Direct- Reverse Acting | Modulating Heating Direct/ Reverse Signal Output | Write | 0=Direct (0 To 10V), 1=Reverse (10 To 0V) | |
| BVmin | 5 | On-Off Control | On/Off Control of Thermostat Outputs | Write | 0=Off, 1=On | |
| BV | 6 | Temperature Scale | °C/ °F | Write | 0=°C, 1=°F | |
| BV | 7 | Relay 1 Control | On/Off Control of Relay 1 (Stage 1) | Write | 0=Off, 1=On | |
| BV | 8 | Relay 2 Control | On/Off Control of Relay 2 (Stage 2) | Write | 0=Off, 1=On | |
| BV | 13 | Relay 7 Control | On/Off Control of Relay 7 Fan | Write | 0=Off, 1=On | |
| BVmin | 14 | Occupancy Command | Room Occupancy Setting | Write | 0=Occupied, 1=Unoccupied | |
| BV | 15 | Fan Output for Heating | Disable/ Enable Fan Output for Heating | Write | 0=Disable, 1=Enable | |
| BV | 16 | Heartbeat Signal | Heartbeat Pulse Input | Write | 0=Off, 1=On | |
| MVmin | 0 | Fan Mode | Write | 1=Auto, 2=Low, 3=Med., 4=Hi | ||
| MVmin | 1 | System Mode | Working Mode: Heat, Cool or Ventilation | Write | 1=Cool Mode, 2=Heat Mode, 3=Ventilation @ Cool Mode, 4=Ventilation @ Heat Mode | |
| MV | 3 | Temperature Source | Current Temperature Source | Write | 1=Built-In Temp. Sensor, 2=Remote Temp. Sensor, 3=Assigned through BACnet | |
| MV | 4 | Lowest Fan Speed | Lowest Fan speed in Auto Fan mode | Write | 1=Stop, 2=Low, 3=Med., 4=Hi. | |
| MVmin | 5 | Fan Speed Status | Read | 1=Stop, 2=Low, 3=Med, 4=Hi | ||
| MV | 6 | Baud Rate | Baud rate (BACnet MS/TP) | Write | 1=9600 bps, 2=19200 bps, 3=38400 bps, 4=57600 bps, 5=76800 bps | |
| MV | 7 | Display Options | LCD Display Options | Write | 1=T & Time (if available), 2=SP & Time (if available), 3=T & CO2 (if available), 4=CO2 & Time (if available), 5=SP & CO2 (if available), 6=T & RH (if available), 7=T & Valve (if available) | |
| MV | 8 | Control Type | Control Type Selection | Write | 1=Cool Only, 2=4-Pipe Cooling or Heating Manual Changeover, 3=4-Pipe Cooling and Heating Auto Changeover, 4=Heating Only |
No points match these filters.
Object ID lookup: Contemporary Controls BAST-121C-B2 point IDs by name
AI0Current TemperatureAI1Active Temperature SetpointAI2Built-in Temperature SensorAI3Remote Temperature SensorAI8Modulating/ Floating Output 1AI13Analog Input 1 ValueAV0Cooling Temperature SetpointAV1Space Temperature via BACnetAV3Heating Temperature SetpointAV4Hr-Running TimeAV5M-Running TimeAV6Sec-Running TimeAV8Unoccupied Cool SetpointAV9Unoccupied Heat SetpointAV10Integral-Cycle TimeAV11Analog Minimum OutputAV12Span OffsetAV13Low Setpoint LimitAV14High Setpoint LimitAV15Temperature OffsetAV16Proportional Band- Stage WidthAV17Stage DifferentialAV18LockAV19Control Out PercentageAV20MAC AddressAV21Device InstanceAV23Cooling Short CycleAV24Cooling Maximum Cycles per HourAV25Heating Short CycleAV26Heating Maximum Cycles per HourAV29Heartbeat RateAV37OptionsAV39Minimum cooling temperature setpointAV40Maximum Heating temperature setpointAV46Minimum Off TimeAV47Minimum On TimeBI0Occupancy StatusBI2Cooling-heating StatusBI3Relay 1 StatusBI4Relay 2 StatusBI9Relay 7 StatusBI10Dl 1 StatusBI17Fan StatusBV0Occupancy Contact DefinitionBV1Cooling Direct- Reverse ActingBV2Heating Direct- Reverse ActingBV5On-Off ControlBV6Temperature ScaleBV7Relay 1 ControlBV8Relay 2 ControlBV13Relay 7 ControlBV14Occupancy CommandBV15Fan Output for HeatingBV16Heartbeat SignalMV0Fan ModeMV1System ModeMV3Temperature SourceMV4Lowest Fan SpeedMV5Fan Speed StatusMV6Baud RateMV7Display OptionsMV8Control Type
Integration notes
- From the BACnet Object Table (manual pages 28-36). The table is shared across the BASstat family; rows printed in grey (objects this model does not use) are left out.
- Access is from the Readable/Writable column; R/W objects are shown as writable.
- Temperature objects follow the Temperature Scale object (BV 6: 0 = °C, 1 = °F).
Check it against the live device. A points list tells you what the controller can expose; the unit in front of you may differ by firmware or installed options. This list is provided as-is for reference only and may contain mistakes — confirming it before you write, map or commission anything is up to you (terms). Easy BACnet scans a network for BACnet IP devices from an Android phone, reads every object on the BASstat BAST-121C-B2 Single Mode Thermostat and exports what it actually has to Excel — free. New to BACnet? Start with what a BACnet points list is and what the object types mean.
Questions about the Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat
How many BACnet points does the Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat have?
This list has 62 BACnet objects: 6 analog inputs, 30 analog values, 7 binary inputs, 11 binary values, 8 multi-state values. The exact set on a given unit depends on its firmware, installed options and configuration.
Which Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat BACnet points are writable?
48 of the 62 objects accept a write. Points marked Command have a priority array: a write holds until it is released, so release it back to automatic when you are done.
Where is the official Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat BACnet documentation?
The source is BAST-121C-B2 Single Mode Thermostat User Manual (UM-15095000-AA1), published free by Contemporary Controls at https://www.ccontrols.com/pdf/um/BAST-121-B2-usermanual.pdf.
What are the minimum BACnet points to integrate the Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat?
Start with BV 5 On-Off Control (Thermostat outputs on/off (1 = on)); BV 14 Occupancy Command (0 = occupied, 1 = unoccupied); MV 1 System Mode (Cool, heat or ventilation mode); AV 0 Cooling Temperature Setpoint (Occupied cooling setpoint); AV 3 Heating Temperature Setpoint (Occupied heating setpoint); MV 0 Fan Mode (1 = auto, then fan speeds); AI 0 Current Temperature (Space temperature in use); BI 0 Occupancy Status (0 = occupied, 1 = unoccupied); BI 2 Cooling-heating Status (Heating/cooling output active); MV 5 Fan Speed Status (Current fan speed).
How do I enable BMS control of the Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat?
On-Off Control (BV 5) switches the thermostat outputs. Occupancy Command (BV 14) only takes effect when the ESI contact is disabled in Lock (AV 18 bit value 64); by default occupancy comes from the ESI dry contact.
Does the Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat need a BACnet heartbeat or have a communication timeout?
A space temperature written to Space Temperature via BACnet (AV 1) is only used while the BMS keeps toggling Heartbeat Signal (BV 16) within the Heartbeat Rate (AV 29) period, in seconds; otherwise the thermostat reverts to its own sensor.
Can the BMS supply sensor values to the Contemporary Controls BASstat BAST-121C-B2 Single Mode Thermostat?
Set Temperature Source (MV 3) to 3 (Assigned through BACnet) and write the space temperature to AV 1, toggling BV 16 as a heartbeat.
How do I check these points on the real BASstat BAST-121C-B2 Single Mode Thermostat?
Scan the network with a BACnet IP browser such as Easy BACnet, open the device and compare its object list with this table. Anything missing is usually an option that isn't installed or a point that is disabled in the controller's configuration.
More Contemporary Controls BACnet points lists
- Thermostat (single mode heat/cool/ventilation, Wi-Fi BACnet IP)
Contemporary Controls BASstat BAST-121C-BW2 Wireless Single Mode Thermostat
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Also known as: BAST-121C-BW2, BAST-121-BW2, BASstat 121C Wi-Fi - Thermostat (multi-stage heat/cool, Wi-Fi BACnet IP)
Contemporary Controls BASstat BAST-221C/CH-BW2 Wireless Multi-Stage Thermostat
Contemporary Controls BAST-221C and BAST-221CH (with humidity) Wi-Fi thermostats for multi-stage heating, cooling and ventilation, such as rooftop units.
Also known as: BAST-221C-BW2, BAST-221CH-BW2, BASstat BW2, BASstat 221C - Thermostat for 2-stage HP systems (BACnet MS/TP)
Contemporary Controls BASstat BAST-321HP-B2 Heat Pump Thermostat
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Also known as: BAST-321HP-B2, BAST-321-B2, BASstat 321HP - Thermostat for 2-stage HP systems (Wi-Fi BACnet IP)
Contemporary Controls BASstat BAST-321HP-BW2 Wireless Heat Pump Thermostat
Contemporary Controls BAST-321HP-BW2 Wi-Fi thermostats for single or dual compressor heat pumps with auxiliary heat.
Also known as: BAST-321HP-BW2, BAST-321-BW2, BASstat 321HP Wi-Fi - Thermostat for modulating 4-pipe FCUs (Wi-Fi BACnet IP)
Contemporary Controls BASstat BAST-421C-BW2 Wireless Modulating Fan Coil Thermostat
Contemporary Controls BAST-421C-BW2 Wi-Fi thermostats for 4-pipe fan coils with modulating or floating valves.
Also known as: BAST-421C-BW2, BAST-421-BW2, BASstat 421C
Source: BAST-121C-B2 Single Mode Thermostat User Manual · UM-15095000-AA1. Object names, instances and units are reproduced as published; descriptions are our own.