Home
BACnet points lists
Hydrotherm
KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge

Commercial boiler controller · BACnet points list

Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge BACnet points list

Updated 4 November 2026

Short answer

On Hydrotherm KN2, KN4 and rAy boilers the HeatNet control is linked to BACnet through a HeatNet bridge that translates its Modbus registers into a fixed object list. The BMS writes heat demand, the system setpoint (with a countdown failsafe timer), outdoor-reset settings, DHW setpoint and the clock. Read-only objects give plant temperatures, boilers on, modulation, raw spare inputs and per-boiler run time, cycles, temperatures, modulation and status flags for up to 16 boilers.

This page lists 75 BACnet objects for the Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge — 18 of them writable — with each object’s type, instance number, name, engineering units and access. It is re-typed from Hydrotherm’s own free documentation, linked below.

Manufacturer: Hydrotherm
Model: KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge
Equipment: Commercial boiler controller
Equipment type: Boilers & water heaters
BACnet objects: 75 (18 writable)
Transport: BACnet IP, BACnet MS/TP
Firmware: Bridge configuration 2.40+ (2.50+ for some points); HeatNet firmware 2.70 / 3.48+ for some points
Also known as: KN2, KN-2, KN4, KN-4, rAy, HeatNet, HeatNet bridge, KNSLM, Mestek
Source document: KN2/KN4/rAy BACnet Bridge Objects · v2.50

Instance calculator. This list prints one unit; the other units follow a formula. HeatNet V3 boiler control (Hydrotherm KN, RBI) instance calculator →

Download CSV 75 rows Download EDE B.I.G.-EU JSON Manufacturer PDF ↗ Compare with your scan Download Easy BACnet Mobile App Google Play

Reference only, provided as-is: verify against Hydrotherm’s current documentation and the live device before use. Not official Hydrotherm information. Terms of use.

BMS integration notes: Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge

Integration in brief

Connect the BMS to the master (boiler 1) HeatNet control. Write BV 1 HeatDemand to call for heat and AV 2 Setpoint for the system setpoint, and keep reloading AV 1 SetpointTimer so the plant does not fall back to its local setpoint. Read header/supply/return temperatures, boilers on, modulation and the per-boiler alarm and failed flags.

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 1	HeatDemand	Heat demand from the BMS (1 = heat)	Write
AV 2	Setpoint	System setpoint, 40-220 °F	Write
AV 1	SetpointTimer	Failsafe countdown; reload before it reaches 0	Write
AI 144	OperatingSetpoint	Active setpoint in use	Read
AI 3	HeaderTemp	Header / system temperature, °F	Read
AI 1	BoilersOn	Number of boilers running	Read
AI 2	Modulation	System target modulation, %	Read
BV 1005	Boiler##_Running	Boiler 1 firing (add 32 per boiler number)	Read
BV 1002	Boiler##_Alarm	Boiler 1 alarm (add 32 per boiler number)	Read
BV 1003	Boiler##_Failed	Boiler 1 failed (add 32 per boiler number)	Read

Enable & remote start

BV 1 HeatDemand puts the boiler (plant) into heating mode when set to 1; 0 removes the demand. The setpoint the BMS writes is AV 2 Setpoint.

Heartbeat & communication loss

AV 1 SetpointTimer (0-65535 s) is a BMS failsafe countdown. The BMS must reload it periodically; if it reaches zero the control assumes the BMS has stopped and reloads its own saved local setpoint. Writing any read/write variable reloads the timer to 60 s if it is below 60 (on control firmware below 2.70 only writing the setpoint does this).

Sensors & values from the BMS

AV 3-7 and BV 2 set up outdoor air reset; there is no writable outdoor temperature or flow value on this bridge.

Network setup

The HeatNet bridge comes as a BACnet IP or a BACnet MS/TP version (an extra-cost option); it translates the HeatNet Modbus registers to these objects.
BACnet IP bridge defaults, from Mestek's separate 'HeatNet Communication Protocols' v1.01 document (not the object list): IP 192.168.1.24, mask 255.255.255.0, BACnet MAC 11, BACnet node 11.
BACnet MS/TP bridge defaults (same HeatNet Communication Protocols document): MAC 11, BACnet node 11, 38400 baud.
To set the clock, write AV 8-14 (month, day, year, hour, minute, second, weekday) and then write 1 to BV 3 SetClock.

Watch out for

If SetpointTimer runs out, the plant quietly returns to its local setpoint.
Per-boiler objects are listed at the boiler 1 instance; offset them by boiler number using the formulas in the notes. Boiler 1 is the master or stand-alone boiler.
Per-boiler modulation (AI 128-143) does not work in AA/High Fire, T1 or T2 modes.
The bridge polls the HeatNet Modbus registers continuously; a few less important registers are not carried over to BACnet.

Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge 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.

75 of 75 shown

Type

Binary

Access

Units

Show

Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge BACnet Points List
			Description			States
AVmin	1	SetpointTimer	BMS failsafe countdown; reload before it reaches zero; 0 – 65535 seconds	s	Write
AVmin	2	Setpoint	System setpoint written by the BMS; 40 - 220 °F (4.5 – 104.4 °C)	°F	Write
AV	3	OARSetpoint	Outdoor temperature at which the boiler shuts down; 40 – 100 °F (4.5 – 37.8 °C)	°F	Write
AV	4	OARHighWaterTemp	Water setpoint at the high outdoor temperature; 60 – 190 °F (15.6 – 87.8 °C)	°F	Write
AV	5	OARHighAirTemp	High outdoor air temperature reset point; 50 – 90 °F (10 – 32.2 °C)	°F	Write
AV	6	OARLowWaterTemp	Header/supply setpoint at the low outdoor temperature; 70 – 220 °F (21.1 – 104.4 °C)	°F	Write
AV	7	OARLowAirTemp	Low outdoor air temperature reset point; -35 – 40 °F (-37.2 – 4.4 °C)	°F	Write
AV	8	SetMonth	Clock set value: month (0 = January); 0 (January) – 11 (December)	months	Write
AV	9	SetDay	Clock set value: day; 1 – 31	days	Write
AV	10	SetYear	Clock set value: year (0-99); 0 – 99	years	Write
AV	11	SetHour	Clock set value: hour; 0 – 23	h	Write
AV	12	SetMinute	Clock set value: minute; 0 – 59	min	Write
AV	13	SetSecond	Clock set value: second; 0 – 59	s	Write
AV	14	SetWeekday	Clock set value: weekday; 1 (Monday) – 7 (Sunday)		Write
AV	15	DHWSetpoint	DHW setpoint; 40 – 200 °F (4.4 – 93.3 °C)	°F	Write
BVmin	1	HeatDemand	BMS heat demand: 1 puts the boiler plant into heating		Write	0=no heat demand, 1=heat demand
BV	2	OAResetEnable	Enable outdoor air reset		Write	0=disabled, 1=enabled
BV	3	SetClock	Write 1 to load the Set... values into the clock		Write	1=set the clock
BV	1000	Boiler##_Disabled	Boiler is disabled		Read	0=enabled, 1=disabled
BV	1001	Boiler##_LocalOverride	Local Override (member boilers only)		Read	0=no override, 1=override
BVmin	1002	Boiler##_Alarm	Boiler Alarm		Read	0=ok, 1=alarm
BVmin	1003	Boiler##_Failed	Boiler Failed		Read	0=ok, 1=failed
BV	1004	Boiler##_MemberError	Member Alarm or Failed		Read	0=ok, 1=error
BVmin	1005	Boiler##_Running	Boiler is running/firing		Read	0=off, 1=running (firing)
BV	1006	Boiler##_PumpOn	Local pump is on/running		Read	0=off, 1=on (running)
BV	1011	Boiler##_Spare4Interlock	Spare 4 (application defined) Interlock		Read	0=open, 1=closed
BV	1013	Boiler##_FlowInterlock	Local Flow Interlock		Read	0=open, 1=closed
BV	1015	Boiler##_MainValve	Main Valve		Read	0=closed, 1=open
BV	1017	Boiler##_BlowerOn	Blower is on/running		Read	0=off, 1=on (running)
BV	1018	Boiler##_IgnitionAlarm	Ignition Circuit Alarm		Read	0=ok, 1=alarm
BV	1020	Boiler##_HighLimit	High Limit		Read	0=ok, 1=tripped
BV	1023	Boiler##_SoftwareOperator	Software Operator Tripped		Read	0=not tripped, 1=tripped
BV	1024	Boiler##_HeaderSensorNA	Header Sensor not available (detected)		Read	0=detected, 1=not available
BV	1025	Boiler##_SupplySensorNA	Supply/Outlet Sensor not available (detected)		Read	0=detected, 1=not available
BV	1026	Boiler##_ReturnSensorNA	Return/Inlet Sensor not available (detected)		Read	0=detected, 1=not available
BV	1027	Boiler##_OutsideSensorNA	Header Sensor not available (detected)		Read	0=detected, 1=not available
BV	1029	Boiler##_DamperProve1	Combustion Air Damper Prove (J10B)		Read	0=not proven, 1=proven
BV	1030	Boiler##_Master	This is the Master Boiler		Read	0=member, 1=master
BV	1031	Boiler##_Detected	Boiler ## is detected (present)		Read	0=not detected, 1=detected
BV	2000	Boiler##_AAHighFire	AA/High Fire Input		Read	0=open, 1=closed
BV	2001	Boiler##_HeatDemand	Heat Demand (Local Override) Input		Read	0=open, 1=closed
BV	2002	Boiler##_4to20Remote	4 to 20ma Remote Input		Read	0=open, 1=closed
BV	3000	Boiler##_DHWSensorEnabled	DHW Sensor has been enabled in the menus		Read	0=disabled, 1=enabled
BV	3001	Boiler##_DamperProve2	Combustion Air Damper Prove		Read	0=not proven, 1=proven
BV	3003	Boiler##_BlowerFault	Blower fault		Read	0=ok, 1=fault
BV	3004	Boiler##_BlockedInlet	Blocked Inlet		Read	0=blocked, 1=ok
BV	3005	Boiler##_BlockedFlue	Blocked Flue		Read	0=blocked, 1=ok
BV	3006	Boiler##_DHWInput	DHW Input		Read
BV	3007	Boiler##_LowFireInput	Low Fire Input		Read
BV	3008	Boiler##_DHWFault	DHW Fault		Read	0=ok, 1=fault
BV	3009	Boiler##_DHWSensorNA	DHW Sensor is not available (detected)		Read	0=detected, 1=not available
BV	3011	Boiler##_OpLimitClamp	Boiler input is limited (clamped) due to high supply (outlet) temperature		Read	0=not clamped, 1=clamped
AImin	1	BoilersOn	Number of boilers running		Read
AImin	2	Modulation	System target modulation	%	Read
AImin	3	HeaderTemp	Header / system temperature	°F	Read
AI	4	SupplyTemp	Supply temperature	°F	Read
AI	5	ReturnTemp	Return temperature	°F	Read
AI	6	OutsideTemp	Outside air temperature	°F	Read
AI	7	Spare1	Raw A/D value of spare input 1		Read
AI	8	Spare2	Raw A/D value of spare input 2		Read
AI	9	Month	Clock: month (0-11)	months	Read
AI	10	Day	Clock: day	days	Read
AI	11	Year	Clock: year (0-99)	years	Read
AI	12	Hour	Clock: hour	h	Read
AI	13	Minute	Clock: minute	min	Read
AI	14	Second	Clock: second	s	Read
AI	15	Weekday	Clock: weekday		Read
AI	16	DHWTemp	DHW temperature	°F	Read
AI	48	Boiler01_Runtime	Boiler 1 run time on the current board (boiler n = 47 + n)	min	Read
AI	64	Boiler01_Cycles	Boiler 1 cycle count (boiler n = 63 + n)		Read
AI	80	Boiler01_SupplyTemp	Boiler 1 supply (outlet) temperature (boiler n = 79 + n)	°F	Read
AI	96	Boiler01_ReturnTemp	Boiler 1 return (inlet) temperature (boiler n = 95 + n)	°F	Read
AI	112	Boiler01_DHWTemp	Boiler 1 DHW sensor temperature (boiler n = 111 + n)	°F	Read
AI	128	Boiler01_Modulation	Boiler 1 modulation (boiler n = 127 + n)	%	Read
AImin	144	OperatingSetpoint	Active setpoint in use (heating, DHW, reset or 4-20 mA)	°F	Read

Object ID lookup: Hydrotherm KN2 / KN4 / rAy boilers point IDs by name

AV1SetpointTimer
AV2Setpoint
AV3OARSetpoint
AV4OARHighWaterTemp
AV5OARHighAirTemp
AV6OARLowWaterTemp
AV7OARLowAirTemp
AV8SetMonth
AV9SetDay
AV10SetYear
AV11SetHour
AV12SetMinute
AV13SetSecond
AV14SetWeekday
AV15DHWSetpoint
BV1HeatDemand
BV2OAResetEnable
BV3SetClock
BV1000Boiler##_Disabled
BV1001Boiler##_LocalOverride
BV1002Boiler##_Alarm
BV1003Boiler##_Failed
BV1004Boiler##_MemberError
BV1005Boiler##_Running
BV1006Boiler##_PumpOn
BV1011Boiler##_Spare4Interlock
BV1013Boiler##_FlowInterlock
BV1015Boiler##_MainValve
BV1017Boiler##_BlowerOn
BV1018Boiler##_IgnitionAlarm
BV1020Boiler##_HighLimit
BV1023Boiler##_SoftwareOperator
BV1024Boiler##_HeaderSensorNA
BV1025Boiler##_SupplySensorNA
BV1026Boiler##_ReturnSensorNA
BV1027Boiler##_OutsideSensorNA
BV1029Boiler##_DamperProve1
BV1030Boiler##_Master
BV1031Boiler##_Detected
BV2000Boiler##_AAHighFire
BV2001Boiler##_HeatDemand
BV2002Boiler##_4to20Remote
BV3000Boiler##_DHWSensorEnabled
BV3001Boiler##_DamperProve2
BV3003Boiler##_BlowerFault
BV3004Boiler##_BlockedInlet
BV3005Boiler##_BlockedFlue
BV3006Boiler##_DHWInput
BV3007Boiler##_LowFireInput
BV3008Boiler##_DHWFault
BV3009Boiler##_DHWSensorNA
BV3011Boiler##_OpLimitClamp
AI1BoilersOn
AI2Modulation
AI3HeaderTemp
AI4SupplyTemp
AI5ReturnTemp
AI6OutsideTemp
AI7Spare1
AI8Spare2
AI9Month
AI10Day
AI11Year
AI12Hour
AI13Minute
AI14Second
AI15Weekday
AI16DHWTemp
AI48Boiler01_Runtime
AI64Boiler01_Cycles
AI80Boiler01_SupplyTemp
AI96Boiler01_ReturnTemp
AI112Boiler01_DHWTemp
AI128Boiler01_Modulation
AI144OperatingSetpoint

Integration notes

Per-boiler binary values are printed once as Boiler##_<name> with an instance formula and are listed here at the boiler 1 instance: 1000-series base + (n - 1) x 32, 2000/3000-series base + (n - 1) x 16. Boiler 1 is the master or stand-alone boiler; members are 2-16.
Per-boiler analog inputs are printed as ranges and listed here for boiler 1 only: Runtime AI 48-63, Cycles AI 64-79, SupplyTemp AI 80-95, ReturnTemp AI 96-111, DHWTemp AI 112-127, Modulation AI 128-143 (boiler n = boiler 1 instance + n - 1).
Bridge configuration 2.50+ is needed for AV 15 (with HeatNet firmware 2.70+) and for AI 112-144 and BV 3000-3011 (with HeatNet firmware 3.48+).
This list has fewer per-boiler flags than the KNSX and KN HeatNet V3 lists (no LWCO, VFD, gas-prove or operator interlocks), and adds BV 3004-3008 (blocked inlet/flue, DHW input, low-fire input, DHW fault).
The document describes Boiler##_OutsideSensorNA with the same text as HeaderSensorNA ('Header Sensor not available'); the name suggests the outside sensor.
Weekday values here run 1 (Monday) to 7 (Sunday).

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 KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge 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 Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge

How many BACnet points does the Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge have?

This list has 75 BACnet objects: 23 analog inputs, 15 analog values, 37 binary values. The exact set on a given unit depends on its firmware, installed options and configuration.

Which Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge BACnet points are writable?

18 of the 75 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 Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge BACnet documentation?

The source is KN2/KN4/rAy BACnet Bridge Objects (v2.50), published free by Hydrotherm at https://www.literature.mestek.com/dms/Hydrotherm%20Boilers/HeatNet/KNSLM%20BACnet%20Objects%20v2-50.pdf.

What are the minimum BACnet points to integrate the Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge?

Start with BV 1 HeatDemand (Heat demand from the BMS (1 = heat)); AV 2 Setpoint (System setpoint, 40-220 °F); AV 1 SetpointTimer (Failsafe countdown; reload before it reaches 0); AI 144 OperatingSetpoint (Active setpoint in use); AI 3 HeaderTemp (Header / system temperature, °F); AI 1 BoilersOn (Number of boilers running); AI 2 Modulation (System target modulation, %); BV 1005 Boiler##_Running (Boiler 1 firing (add 32 per boiler number)); BV 1002 Boiler##_Alarm (Boiler 1 alarm (add 32 per boiler number)); BV 1003 Boiler##_Failed (Boiler 1 failed (add 32 per boiler number)).

How do I enable BMS control of the Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge?

BV 1 HeatDemand puts the boiler (plant) into heating mode when set to 1; 0 removes the demand. The setpoint the BMS writes is AV 2 Setpoint.

Does the Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge need a BACnet heartbeat or have a communication timeout?

Can the BMS supply sensor values to the Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge?

AV 3-7 and BV 2 set up outdoor air reset; there is no writable outdoor temperature or flow value on this bridge.

How do I check these points on the real KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge?

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 Hydrotherm BACnet points lists

Source: KN2/KN4/rAy BACnet Bridge Objects · v2.50. Object names, instances and units are reproduced as published; descriptions are our own.

Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge BACnet points list

BMS integration notes: Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge

Minimum points to map

Enable & remote start

Heartbeat & communication loss

Sensors & values from the BMS

Network setup

Watch out for

Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge BACnet objects

Integration notes

Questions about the Hydrotherm KN2 / KN4 / rAy boilers - HeatNet BACnet Bridge

More Hydrotherm BACnet points lists

Hydrotherm KN / KN+ Series boilers with HeatNet V3 control

Hydrotherm KN Series (KNSX) boilers - HeatNet BACnet Bridge