BACnet MS/TP daisy chain works fine when tested individually but devices in the middle of the chain drop offline when all units power up simultaneously. Problem appears intermittent or load-dependent.
Mixed cable gauges (e.g., 18 AWG and 20 AWG on same daisy chain) cause impedance mismatches, signal reflections, and collisions on the bus. While each gauge meets the spec individually, mixing them violates MS/TP wiring standards.
Verify the actual wiring installed:
If gauges are mixed:
Isolate problem segments (before replacing cable):
After replacing cable:
Monitor for improvements: