Easy BACnet
  1. Home
  2. BACnet points lists
  3. Siemens
  4. BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat)

Fan coil unit controller · BACnet points list

Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) BACnet points list

Updated 28 October 2026

Short answer

Application 6646 runs a fan coil unit with staged cooling and electric heat on a Siemens BACnet PTEC unit conditioner controller over BACnet MS/TP. The cooling loop switches up to two stages (2-position valves or compressors) at set loop percentages with minimum on and off times, and the heating loop time-modulates up to three electric heat stages. The fan runs in day mode or cycles with demand.

This page lists 76 BACnet objects for the Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) — 62 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 Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat)
Equipment
Fan coil unit controller
Equipment type
VAV boxes & fan coils
BACnet objects
76 (62 writable)
Transport
BACnet MS/TP
Firmware
Newer than revision Bx40
Also known as
PTEC 6646, Application 6646, App 6646, 550-496PA, Siemens fan coil electric heat, Unit Conditioner
Source document
BACnet PTEC Controller Unit Conditioner - Fan Coil Unit Two-Stage Cooling and Electric Heat, Application 6646, Application Note · 140-1173 · rev. 2014-07-17
Download CSV 76 rows Download EDE B.I.G.-EU JSON Manufacturer PDF ↗ Download Easy BACnet Mobile App Google Play

BMS integration notes: Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat)

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, and reads room temperature, fan, cooling and heating stage status 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
AO 6DAY CLG STPTOccupied cooling setpoint, °FCommand
AO 7DAY HTG STPTOccupied heating setpoint, °FCommand
BO 5HEAT.COOLCurrent mode: HEAT or COOLCommand
BO 46FANFan on/offCommand
AI 4ROOM TEMPSpace temperatureRead
BO 41CLG STG 1Cooling stage 1 on/offCommand
BO 43HTG STG 1Electric heat stage 1 on/offCommand
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.

Network setup

Watch out for

Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) 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.

76 of 76 shown
Type
Access
Show
Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) BACnet Points List
DescriptionStates
AO1CTLR ADDRESSController MS/TP addressCommand
AO2APPLICATIONApplication number running in the controllerCommand
AO3RMTMP 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
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
AI15AUX TEMPAuxiliary temperature input°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
BI24DI 2Digital input 2Read0=OFF, 1=ON
BI25DI 3Digital input 3Read0=OFF, 1=ON
BI26DI 4Digital input 4Read0=OFF, 1=ON
BI27DI 5Digital input 5Read0=OFF, 1=ON
BI28DI 6Digital input 6Read0=OFF, 1=ON
BOmin29DAY.NGTDay/night (occupancy) modeCommand0=DAY, 1=NIGHT
AI30AI 3Spare analog input 3%Read
AI31AI 4Spare analog input 4°FRead
AO32AOV1Analog output 1 (0-10 V)VCommand
AO33AOV2Analog output 2 (0-10 V)VCommand
AO34AOV3Analog output 3 (0-10 V)VCommand
BOmin41CLG STG 1Cooling stage 1 output (valve or compressor)Command0=OFF, 1=ON
BO42CLG STG 2Cooling stage 2 output (valve or compressor)Command0=OFF, 1=ON
BOmin43HTG STG 1Electric heat stage 1 outputCommand0=OFF, 1=ON
BO44HTG STG 2Electric heat stage 2 outputCommand0=OFF, 1=ON
BO45HTG STG 3Electric heat stage 3 outputCommand0=OFF, 1=ON
BOmin46FANFan commandCommand0=OFF, 1=ON
BO47DO 7Digital output 7Command0=OFF, 1=ON
BO50DO 8Digital output 8Command0=OFF, 1=ON
AO58MTR SETUPMotor enable/reverse setup (additive code)Command
AO59DO DIR. REVDigital output direction reverse (additive code)Command
BO60CYCLE FANCycle the fan with demand in day modeCommand0=NO, 1=YES
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
AO71CLG 1 ONCooling loop % that starts cooling stage 1%Command
AO72CLG 1 OFFCooling loop % that stops cooling stage 1%Command
AO73CLG 2 ONCooling loop % that starts cooling stage 2%Command
AO74CLG 2 OFFCooling loop % that stops cooling stage 2%Command
AO75CLG STG CNTNumber of cooling stagesCommand
AO76CLG MIN ONCooling stage minimum on timesCommand
AO77CLG MIN OFFCooling stage minimum off timesCommand
AO78CTL TEMPTemperature the controller is controlling to°FCommand
AO79CLG LOOPOUTCooling loop output%Command
AO80HTG LOOPOUTHeating loop output%Command
AO81AVG HEAT OUTAverage heating output%Command
AO82HTG STG MAXStaged heat maximum, percent%Command
AO83HTG STG MINStaged heat minimum, percent%Command
AO84STAGE FANFan stage setting, % (not described in the guide)%Command
AO85SWITCH LIMITLoop output below which mode may switch%Command
AO86SWITCH TIMEMinimum time before heat/cool switchoverminCommand
AO88HTG STG CNTNumber of electric heat stagesCommand
AO89HTG STG TIMEElectric heat cycle timeminCommand
AO90SWITCH DBANDTemperature deadband for heat/cool switchover°FCommand
AO92CTL STPTActive control setpoint°FCommand
AO98LOOP TIMEControl loop intervalsCommand
AOmin99ERROR STATUSController error status codeCommand
AO106STPT SPANRoom unit setpoint adjustment span°FCommand
AI121DEW POINTRoom dew point°FRead
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 Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) 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 Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat)

How many BACnet points does the Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) have?

This list has 76 BACnet objects: 8 analog inputs, 47 analog outputs, 6 binary inputs, 15 binary outputs. The exact set on a given unit depends on its firmware, installed options and configuration.

Which Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) BACnet points are writable?

62 of the 76 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 Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat) BACnet documentation?

The source is BACnet PTEC Controller Unit Conditioner - Fan Coil Unit Two-Stage Cooling and Electric Heat, Application 6646, Application Note (140-1173), revision 2014-07-17, published free by Siemens at https://sid.siemens.com/api/khub/documents/L7SSrBCn3y4Q~8CKKeP~EA/content.

What are the minimum BACnet points to integrate the Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat)?

Start with BO 29 DAY.NGT (DAY = occupied, NIGHT = unoccupied); 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 46 FAN (Fan on/off); AI 4 ROOM TEMP (Space temperature); BO 41 CLG STG 1 (Cooling stage 1 on/off); BO 43 HTG STG 1 (Electric heat stage 1 on/off); AO 99 ERROR STATUS (Controller error code).

How do I enable BMS control of the Siemens BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat)?

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.

How do I check these points on the real BACnet PTEC Unit Conditioner - Application 6646 (Fan Coil Unit Two-Stage Cooling and Electric Heat)?

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 Conditioner - Fan Coil Unit Two-Stage Cooling and Electric Heat, Application 6646, Application Note · 140-1173 · rev. 2014-07-17. Object names, instances and units are reproduced as published; descriptions are our own.