Troubleshooting Scenarios

The graphic shows Auto/Run, yet the fan or valve ignores the BAS. Walk the control chain from the HOA and VFD faceplate through safeties and the BACnet priority array before rewriting logic.

Controllers flake online/offline, commands lag, or the whole trunk feels "slow." Treat MS/TP as both a protocol and a two-wire network: map the trunk, then prove polarity, baud, Max Master, termination, and token health with a capture.

A freeze-stat trip or cracked-coil near-miss after a cold night. Stabilize the unit, preserve evidence, then verify the full protection chain: sensors → sequences → hardware fail-safes → trending — don't just reset and leave.

Hot/cold complaints while duct static sits high or hunting. Use the Field Kit trend group for static pressure — static, setpoint, fan speed, and VAV damper positions together — then prove whether the problem is fan control, damper response, or a false sensor.

Space or duct temperature on the graphic doesn't match a calibrated thermometer. Prove the full input path — physical sensor, wiring, raw value, scaling, and display — before replacing controllers or rewriting sequences.

Equipment "isn't sequencing right," but the real issue may be mode, enabling conditions, or a higher-priority write. Define the question, trend setpoint/actual/command/feedback/mode together, then prove which boundary failed before changing programming.