Engineering notes
BACnet device IDs: a clash and the object disappears
Each DDC and gateway needs its own device instance. Two cabinets left at 260001 — the head-end sees one, loses one. Write the ID before delivery.
Makers ship DDCs with the same default instance. Three AHU cabinets land on BACnet/IP with that ID. The head-end shows one device; two cabinets are “offline”. The switch gets the blame. Two nodes, one instance, one network.
Consultants usually issue an ID range by floor or plant. We put that range on the schedule and on the cabinet label. An MS/TP–IP router is also a device — do not reuse a DDC number. Changing an ID after the graphics are drawn costs more than one line on the order.