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Unit ventilator (terminal unit) controller · BACnet points list

Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) BACnet points list

Updated 28 October 2026

Short answer

Application 6679 controls a unit ventilator to the Nesbitt Cycle W sequence on a Siemens BACnet PTEC controller over BACnet MS/TP. It modulates the heating coil valve, an optional chilled water valve or DX stage, and the outdoor air damper with a discharge air low limit; it also handles morning warm-up and cool-down, night override and free cooling. Heating-only units are run by holding HEAT.COOL at HEAT.

This page lists 88 BACnet objects for the Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) — 75 of them writable — with each object’s type, instance number, name, engineering units and access. It is re-typed from Siemens’s own free documentation, linked below.

Manufacturer
Siemens
Model
BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W)
Equipment
Unit ventilator (terminal unit) controller
Equipment type
VAV boxes & fan coils
BACnet objects
88 (75 writable)
Transport
BACnet MS/TP
Firmware
Newer than revision Bx40
Also known as
PTEC 6679, Application 6679, App 6679, 550-493PA, Siemens unit ventilator, Nesbitt Cycle W
Source document
BACnet PTEC Controller Unit Vent - Heating and Cooling, Nesbitt Cycle W, Application 6679, Application Note · 140-1184 · rev. 2018-01-23
Download CSV 88 rows Download EDE B.I.G.-EU JSON Manufacturer PDF ↗ Download Easy BACnet Mobile App Google Play

BMS integration notes: Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W)

Integration in brief

Address the controller on the BACnet MS/TP trunk (manually or with auto addressing), then release the unit to application control. The BMS commands occupancy with DAY.NGT (BO 29) and the day setpoints, turns free cooling on and off with FREE CLG (BO 23), and reads room temperature, fan status, outdoor air damper position, the low temperature detector and the error status.

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.

ObjectNameWhyAccess
BO 29DAY.NGTDAY = occupied, NIGHT = unoccupiedCommand
BO 23FREE CLGFree cooling / economizer enableCommand
AO 6DAY CLG STPTOccupied cooling setpoint, °FCommand
AO 7DAY HTG STPTOccupied heating setpoint, °FCommand
BO 5HEAT.COOLCurrent mode: HEAT or COOLCommand
BO 50FANFan on/offCommand
AI 4ROOM TEMPSpace temperatureRead
AO 62OA DMPR POSOutdoor air damper position, %Command
BI 26LOW TEMP DETLow temperature detector; ON = trippedRead
AO 99ERROR STATUSController error codeCommand

Enable & remote start

Occupancy is DAY.NGT (BO 29). With a wall switch on DI 2 and WALL SWITCH (BO 18) = YES, the switch sets it; standalone with no switch the controller stays in day mode; on a network the field panel or BMS commands DAY.NGT. NGT OVRD (BO 21) shows a temporary night override from the room unit button.

Sensors & values from the BMS

The field panel (or PPCL) turns the free cooling/economizer function on and off by writing FREE CLG (BO 23).

Network setup

Watch out for

Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) 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.

Note: the source document has no read/write column, so access here is inferred from the object type (inputs read-only, values writable). Confirm on the live controller before writing.

88 of 88 shown
Type
Access
Show
Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) BACnet Points List
DescriptionStates
AO1CTLR ADDRESSController MS/TP addressCommand
AO2APPLICATIONApplication number running in the controllerCommand
AO3TEMP OFFSETRoom temperature calibration offset°FCommand
AImin4ROOM TEMPRoom temperature from the room unit°FRead
BOmin5HEAT.COOLCurrent heating/cooling modeCommand0=COOL, 1=HEAT
AOmin6DAY CLG STPTDay (occupied) cooling setpoint°FCommand
AOmin7DAY HTG STPTDay (occupied) heating setpoint°FCommand
AO8NGT CLG STPTNight (unoccupied) cooling setpoint°FCommand
AO9NGT HTG STPTNight (unoccupied) heating setpoint°FCommand
AO10OADPR MINPOSOutdoor air damper minimum position%Command
AO11RM STPT MINLowest setpoint allowed from the room unit°FCommand
AO12RM STPT MAXHighest setpoint allowed from the room unit°FCommand
AI13RM STPT DIALSetpoint from the room unit dial or keypad°FRead
BO14STPT DIALUse the room unit setpoint dialCommand0=NO, 1=YES
AI15DISCH TEMPDischarge air temperature°FRead
BO18WALL SWITCHWall switch connected to DI 2Command0=NO, 1=YES
BI19DI OVRD SWRoom unit night override buttonRead0=OFF, 1=ON
AO20OVRD TIMENight override durationhCommand
BO21NGT OVRDNight override statusCommand0=DAY, 1=NIGHT
BOmin23FREE CLGFree cooling (economizer) enableCommand0=DISABL, 1=ENABLE
BI24DI 2Digital input 2Read0=OFF, 1=ON
BI25DI 5Digital input 5Read0=OFF, 1=ON
BImin26LOW TEMP DETLow temperature detection thermostat (LTDT)Read0=ON, 1=OFF
BO27DX COOLINGDX cooling coil usedCommand0=NO, 1=YES
BOmin29DAY.NGTDay/night (occupancy) modeCommand0=DAY, 1=NIGHT
BO30WRMUP.COOLDNMorning warm-up / cool-downCommand0=OFF, 1=ON
AO31AOV1 SPANAOV1 output spanVCommand
AO32AOV1 STARTAOV1 output start voltageVCommand
AO33AOV2 SPANAOV2 output spanVCommand
AO34AOV2 STARTAOV2 output start voltageVCommand
AO35AOV3 SPANAOV3 output spanVCommand
AO36AOV3 STARTAOV3 output start voltageVCommand
AO37AO DIR.REVAnalog output direction reverse (additive code)Command
AO38AOV1Analog output 1 (0-10 V)VCommand
AO39AOV2Analog output 2 (0-10 V)VCommand
AO40AOV3Analog output 3 (0-10 V)VCommand
BO41DO 1Digital output 1Command0=OFF, 1=ON
BO42DO 2Digital output 2Command0=OFF, 1=ON
BO43DO 3Digital output 3Command0=OFF, 1=ON
BO44DXDX cooling outputCommand0=OFF, 1=ON
BO45DO 5Digital output 5Command0=OFF, 1=ON
BO46DO 6Digital output 6Command0=OFF, 1=ON
BO47DO 7Digital output 7Command0=OFF, 1=ON
AI48AI 3Spare analog input 3%Read
AI49AUX TEMP AI4Auxiliary temperature input on AI 4°FRead
BOmin50FANFan commandCommand0=OFF, 1=ON
BI51DI 3Digital input 3Read0=OFF, 1=ON
BI52DI 4Digital input 4Read0=OFF, 1=ON
BO53NGT HW HTGHot water coil at night (YES) or steam (NO)Command0=NO, 1=YES
BO54NGT CLG MODECooling allowed in night modeCommand0=NO, 1=YES
AO59DO DIR.REVDigital output direction reverse (additive code)Command
AO60HTG OUTPUTHeating coil output%Command
AO61CLG OUTPUTCooling coil output%Command
AOmin62OA DMPR POSOutdoor air damper position%Command
AO63CLG P GAINCooling loop proportional gainCommand
AO64CLG I GAINCooling loop integral gainCommand
AO65CLG D GAINCooling loop derivative gainCommand
AO66CLG BIASCooling loop bias%Command
AO67HTG P GAINHeating loop proportional gainCommand
AO68HTG I GAINHeating loop integral gainCommand
AO69HTG D GAINHeating loop derivative gainCommand
AO70HTG BIASHeating loop bias%Command
AO75CMP MIN OFFCompressor minimum off timeminCommand
AO76CMP MIN ONCompressor minimum on timeminCommand
AO77OA LOOPOUTOutdoor air (discharge) loop output%Command
AO78CTL TEMPTemperature the controller is controlling to°FCommand
AO79CLG LOOPOUTCooling loop output%Command
AO80HTG LOOPOUTHeating loop output%Command
AO81OA P GAINOutdoor air loop proportional gainCommand
AO82OA I GAINOutdoor air loop integral gainCommand
AO83OA D GAINOutdoor air loop derivative gainCommand
AO84OA BIASOutdoor air loop bias%Command
AO85SWITCH LIMITLoop output below which mode may switch%Command
AO86SWITCH TIMEMinimum time before heat/cool switchoverminCommand
AO88NGT DBANDNight mode fan deadband°FCommand
AO89MORN DBANDMorning warm-up / cool-down deadband°FCommand
AO90SWITCH DBANDTemperature deadband for heat/cool switchover°FCommand
AO92CTL STPTActive control setpoint°FCommand
AO93DISCH STPTDischarge air low limit setpoint°FCommand
AO98LOOP TIMEControl loop intervalsCommand
AOmin99ERROR STATUSController error status codeCommand
AO106STPT SPANRoom unit setpoint adjustment span°FCommand
AO121DEW POINTRoom dew point°FCommand
AO122ENTHALPYRoom enthalpyBtu/lbCommand
AO124SENSOR SELRoom unit / sensor select code (additive)Command
AI125RM CO2Room CO2ppmRead
AI126RM RHRoom relative humidity%Read
BO127PPCL STATEPPCL program loaded or emptyCommand0=EMPTY, 1=LOADED

Integration notes

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. Easy BACnet scans a network for BACnet IP devices from an Android phone, reads every object on the BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) 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 Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W)

How many BACnet points does the Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) have?

This list has 88 BACnet objects: 7 analog inputs, 56 analog outputs, 6 binary inputs, 19 binary outputs. The exact set on a given unit depends on its firmware, installed options and configuration.

Which Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) BACnet points are writable?

75 of the 88 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. The source has no read/write column, so this is inferred from object type.

Where is the official Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W) BACnet documentation?

The source is BACnet PTEC Controller Unit Vent - Heating and Cooling, Nesbitt Cycle W, Application 6679, Application Note (140-1184), revision 2018-01-23, published free by Siemens at https://sid.siemens.com/api/khub/documents/0NkzXUXj3oVvMx1ClkA9JQ/content.

What are the minimum BACnet points to integrate the Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W)?

Start with BO 29 DAY.NGT (DAY = occupied, NIGHT = unoccupied); BO 23 FREE CLG (Free cooling / economizer enable); AO 6 DAY CLG STPT (Occupied cooling setpoint, °F); AO 7 DAY HTG STPT (Occupied heating setpoint, °F); BO 5 HEAT.COOL (Current mode: HEAT or COOL); BO 50 FAN (Fan on/off); AI 4 ROOM TEMP (Space temperature); AO 62 OA DMPR POS (Outdoor air damper position, %); BI 26 LOW TEMP DET (Low temperature detector; ON = tripped); AO 99 ERROR STATUS (Controller error code).

How do I enable BMS control of the Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W)?

Occupancy is DAY.NGT (BO 29). With a wall switch on DI 2 and WALL SWITCH (BO 18) = YES, the switch sets it; standalone with no switch the controller stays in day mode; on a network the field panel or BMS commands DAY.NGT. NGT OVRD (BO 21) shows a temporary night override from the room unit button.

Can the BMS supply sensor values to the Siemens BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W)?

The field panel (or PPCL) turns the free cooling/economizer function on and off by writing FREE CLG (BO 23).

How do I check these points on the real BACnet PTEC Unit Vent Controller - Application 6679 (Heating and Cooling, Nesbitt Cycle W)?

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 Siemens BACnet points lists

Source: BACnet PTEC Controller Unit Vent - Heating and Cooling, Nesbitt Cycle W, Application 6679, Application Note · 140-1184 · rev. 2018-01-23. Object names, instances and units are reproduced as published; descriptions are our own.