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Air handler preheat controller · BACnet points list
AAON PREHEAT-X Controller BACnet points list
Updated 28 October 2026
The PREHEAT-X controls modulating SCR or SSR preheat plus up to six fixed heat stages to hold a leaving air temperature. It can run stand-alone, from an AAON unit controller over E-BUS, or from a BAS over its own BACnet MS/TP port. The object list is small: 9 read-only AIs (setpoint in use, stages on, modulating output, temperatures, alarm bitfield), 16 read-only BIs (inputs, relay states, alarms) and 3 writable AVs for remote enable and the leaving and entering air setpoints.
This page lists 28 BACnet objects for the AAON PREHEAT-X Controller — 3 of them writable — with each object’s type, instance number, name, engineering units and access. It is re-typed from AAON’s own free documentation, linked below.
- Manufacturer
- AAON
- Model
- PREHEAT-X Controller
- Equipment
- Air handler preheat controller
- Equipment type
- Rooftop units, AHUs & DOAS
- BACnet objects
- 28 (3 writable)
- Transport
- BACnet MS/TP
- Firmware
- Not stated
- Also known as
- PREHEAT-X, PREHEATX, Preheat-X, G086640, AAON preheat controller, Orion PREHEAT-X
BMS integration notes: AAON PREHEAT-X Controller
Set COM MODE to BACNET and give the controller a MAC address, device ID and baud rate on the COMM CONFIG screens. The BAS enables preheat with AV 1, sends the leaving air setpoint on AV 2 and the entering air enable setpoint on AV 3, and reads leaving air temperature, stages and alarms. Rewrite the AVs after any controller reset.
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 |
|---|---|---|---|
| AV 1 | Remote Enable | Preheat enable from the BAS (1 = enabled) | Write |
| AV 2 | Remote Leaving Air Setpoint | Leaving air temperature setpoint, °F | Write |
| AV 3 | Remote Entering Air Setpoint | Preheat runs below this entering air temp, °F | Write |
| BI 3 | Preheat Enable Status | Preheat is enabled | Read |
| AI 8 | Leaving Air Average Temp | Average leaving air temperature | Read |
| AI 3 | Modulating Output Position | Modulating heat output | Read |
| AI 2 | Number of Heat Stages On | Fixed heat stages running | Read |
| AI 4 | All Alarms Bitfield | Bit-coded active alarms | Read |
Enable & remote start
With COM MODE = BACNET, AV 1 Remote Enable (or the HEAT EN binary input, whichever comes first) enables preheat. The emergency shutdown input must be wired as a normally closed 24 VAC contact; when it opens all outputs drop and an alarm is raised.
Network setup
- COMM CONFIG screens: COM MODE = BACNET (choices BACNET, EBUS, S-ALONE; default S-ALONE).
- MAC address 0-128, default 0.
- Device ID start 0-30000, default 15000.
- MS/TP baud 9600, 19200, 38400, 57600 or 76800; default 38400.
Watch out for
- AV 1-3 are volatile; the BAS must rewrite them after a power loss or reset.
- Default MAC address is 0; change it if another device already uses 0.
- A high leaving air temperature alarm shuts the heat off and needs a manual reset.
AAON PREHEAT-X Controller 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 | |||||
|---|---|---|---|---|---|---|
| AI | 1 | Active Controlling Setpoint | Leaving air setpoint now in use | Read | ||
| AImin | 2 | Number of Heat Stages On | Fixed heat stages running | Read | ||
| AImin | 3 | Modulating Output Position | Modulating heat output | Read | ||
| AImin | 4 | All Alarms Bitfield | Bit-coded alarm status | Read | Bits: 1 BadLeavingAir1, 2 BadLeavingAir2, 3 LowLeavingAir, 4 HighLeavingAir, 6 BadEnteringAir, 7 CommAlarm, 8 ShutDownAlarm (0 and 5 reserved) | |
| AI | 5 | Entering Air Temperature | Entering air temperature | Read | ||
| AI | 6 | Leaving Air Temp Sensor 1 | Leaving air sensor 1 (LAT1) | Read | ||
| AI | 7 | Leaving Air Temp Sensor 2 | Leaving air sensor 2 (LAT2) | Read | ||
| AImin | 8 | Leaving Air Average Temp | Average of LAT1 and LAT2 | Read | ||
| AI | 9 | Reset Input Percentage | Setpoint reset input, percent | Read | ||
| BI | 1 | Enable Input Value | Heat enable binary input | Read | 0=Off, 1=On | |
| BI | 2 | Shutdown Input Value | Emergency shutdown binary input | Read | 0=Off, 1=On | |
| BImin | 3 | Preheat Enable Status | Controller enable status | Read | 0=Off, 1=On | |
| BI | 4 | Alarm Relay Status | Alarm relay state | Read | 0=Off, 1=On | |
| BI | 5 | Heat 1 Relay Status | Heat stage 1 relay state | Read | 0=Off, 1=On | |
| BI | 6 | Heat 2 Relay Status | Heat stage 2 relay state | Read | 0=Off, 1=On | |
| BI | 7 | Heat 3 Relay Status | Heat stage 3 relay state | Read | 0=Off, 1=On | |
| BI | 8 | Heat 4 Relay Status | Heat stage 4 relay state | Read | 0=Off, 1=On | |
| BI | 9 | Heat 5 Relay Status | Heat stage 5 relay state | Read | 0=Off, 1=On | |
| BI | 10 | Heat 6 Relay Status | Heat stage 6 relay state | Read | 0=Off, 1=On | |
| BI | 11 | Emergency Shutdown Alarm | Emergency shutdown alarm | Read | 0=Off, 1=On | |
| BI | 12 | Leaving Air Sensor 1 Alarm | Leaving air sensor 1 failure | Read | 0=Off, 1=On | |
| BI | 13 | Leaving Air Sensor 2 Alarm | Leaving air sensor 2 failure | Read | 0=Off, 1=On | |
| BI | 14 | Low Leaving Air Temp Alarm | Leaving air below the low limit | Read | 0=Off, 1=On | |
| BI | 15 | High Leaving Air Temp Alarm | Leaving air above the high limit | Read | 0=Off, 1=On | |
| BI | 16 | Entering Air Sensor Alarm | Entering air sensor failure | Read | 0=Off, 1=On | |
| AVmin | 1 | Remote Enable | Preheat enable from the BAS (volatile) | Write | 0=Disabled, 1=Enabled | |
| AVmin | 2 | Remote Leaving Air Setpoint | Leaving air setpoint from the BAS, 35-90 °F (volatile) | °F | Write | |
| AVmin | 3 | Remote Entering Air Setpoint | Entering air enable setpoint from the BAS, -40 to 90 °F (volatile) | °F | Write |
No points match these filters.
Integration notes
- BACnet only works with COM MODE set to BACNET on the COMM CONFIG screens (default is S-ALONE).
- The three AVs are volatile: values written by the BAS are lost when the controller resets, so the BAS must write them again after a power cycle.
- In BACnet mode, preheat is enabled by the BACnet command or the binary input, whichever comes first.
- AI 4 is a bit string; bit 7 is a communication alarm and bit 8 the emergency shutdown alarm.
- Source is the PREHEAT-X Technical Guide, AAON P/N G086640 Rev. F (February 2, 2024), Appendix B.
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 PREHEAT-X Controller 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 AAON PREHEAT-X Controller
How many BACnet points does the AAON PREHEAT-X Controller have?
This list has 28 BACnet objects: 9 analog inputs, 3 analog values, 16 binary inputs. The exact set on a given unit depends on its firmware, installed options and configuration.
Which AAON PREHEAT-X Controller BACnet points are writable?
3 of the 28 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 AAON PREHEAT-X Controller BACnet documentation?
The source is PREHEAT-X Technical Guide (Appendix B: BACnet) (G086640), revision Rev. F, 2024-02-02, published free by AAON at https://www.aaon.com/hubfs/G086640-PREHEATX-TGD-E.pdf.
What are the minimum BACnet points to integrate the AAON PREHEAT-X Controller?
Start with AV 1 Remote Enable (Preheat enable from the BAS (1 = enabled)); AV 2 Remote Leaving Air Setpoint (Leaving air temperature setpoint, °F); AV 3 Remote Entering Air Setpoint (Preheat runs below this entering air temp, °F); BI 3 Preheat Enable Status (Preheat is enabled); AI 8 Leaving Air Average Temp (Average leaving air temperature); AI 3 Modulating Output Position (Modulating heat output); AI 2 Number of Heat Stages On (Fixed heat stages running); AI 4 All Alarms Bitfield (Bit-coded active alarms).
How do I enable BMS control of the AAON PREHEAT-X Controller?
With COM MODE = BACNET, AV 1 Remote Enable (or the HEAT EN binary input, whichever comes first) enables preheat. The emergency shutdown input must be wired as a normally closed 24 VAC contact; when it opens all outputs drop and an alarm is raised.
How do I check these points on the real PREHEAT-X Controller?
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 AAON BACnet points lists
- VAV / zone controller
AAON VAV/Zone BACnet Controller (VAVZB)
Pressure-independent and pressure-dependent VAV boxes and zone dampers controlled by the AAON VAV/Zone BACnet controller.
Also known as: VAVZB, VAV/Zone Controller, ASM02426, ASM02427, ASM02661, ASM02662, SS1116, SS1146, G067750 - Rooftop unit / air handler controller
AAON VCB-X Controller
AAON packaged rooftop units, air handlers, DOAS and water-source units controlled by the Orion VCB-X (OE335-26B-VCBX) unit controller.
Also known as: VCBX, VCB-X, Orion VCB-X, OE335-26B-VCBX, V28940, WattMaster VCB-X, AAON VCB-X BACnet - Rooftop unit / air handler controller
AAON VCCX2 Controller
AAON rooftop units, air handlers and DOAS units controlled by the VCCX2 (ASM01698) unit controller.
Also known as: VCC-X2, VCCX, VCC-X, ASM01698, Orion VCCX2, SS1088
Source: PREHEAT-X Technical Guide (Appendix B: BACnet) · G086640 · rev. Rev. F, 2024-02-02. Object names, instances and units are reproduced as published; descriptions are our own.