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BACnet instance calculator · boiler gateways (Laars, Peerless, Raypak, AERCO and more)

ProtoNode BACnet Device Instance Calculator (Boilers)

Free browser tool · nothing is uploaded · 5 November 2026

Boiler makers use FieldServer ProtoNode gateways to put Modbus boilers on BACnet. Every boiler becomes its own BACnet device numbered Node_Offset + Node-ID, and every one carries the same objects.

Short answer

Device instance = Node_Offset + Node-ID. Node_Offset is 50000 unless someone changed it in the ProtoNode Web Configurator, and the Node-ID is the boiler's Modbus address (on AERCO, the A-bank DIP switch value). Node-ID 3 is device 50003.

ProtoNode calculator

0-4194000
1-255
or a range of node-id (modbus address) to

The calculator needs JavaScript. The formula and a worked example are below.

Which unit is this device?

    How the numbers are built

    device instance = Node_Offset + Node-ID

    PartMeaningRange
    Node_OffsetProtoNode setting, default 50000 (BN_Node_Offset on Raypak)0-4194000
    Node-IDBoiler's Modbus address / node ID (AERCO: A-bank DIP switches)1-255

    Each boiler on the ProtoNode's RS-485 bus shows up as its own BACnet device; inside it the object instances are the same on every boiler. Pick the equipment below to see its objects.

    Worked example: Node_Offset 50000, Node-ID 3

    The first objects for Node_Offset 50000, Node-ID 3 on the Laars HTD, worked out with the formula above (Laars HTD):

    Unit typeDevice instanceFor
    Boiler / controller device50003Node_Offset 50000, Node-ID (Modbus address) 3

    Source

    Formula and objects from Vendor Protocol Mapping (LAARS Vendor Mappings for the ProtoNode FPC-N34 / FPC-N35) · 4404 · rev. Document Revision 14.B, October 2020 (manufacturer document ↗), re-typed in our points list. Object names are shown as printed.

    Check it against the live device. The calculator applies the formula from the manufacturer’s documentation; the gateway in front of you may expose fewer objects or use other numbers after a firmware change. Easy BACnet scans a network for BACnet IP devices from an Android phone and reads every object on them — a quick way to confirm one unit before you map a whole building.

    Questions

    How do I work out a ProtoNode instance number?

    Device instance = Node_Offset + Node-ID. Node_Offset is 50000 unless someone changed it in the ProtoNode Web Configurator, and the Node-ID is the boiler's Modbus address (on AERCO, the A-bank DIP switch value). Node-ID 3 is device 50003.

    Why does every boiler have the same object numbers?

    The ProtoNode makes one BACnet device per boiler from the same profile, so the objects repeat and only the device instance changes. Point your BMS at the right device instance and the objects line up.

    Hamilton's BDB-CDB shows up at 50032. Why?

    Its ProtoNode profile uses Node-ID 32, so the default device is 50000 + 32.

    Is this ProtoNode calculator official?

    No. It applies the formula printed in ProtoNode's own documentation to the points list in our library. Confirm the numbers against a scan of the live device before you map or write anything.

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