Application

Sequence of Operation
Performing the Automated Fault Detection and Diagnostics
10
Siemens Industry, Inc. Application Note, App 2520 140-1217
2015-05-06
2. The tubing connections for the air velocity sensor may be reversed. Re-pipe if HI
and LO connections are incorrect.
3. The sensor or the VAV Actuator may be faulty.
Controller could not reach CLG FLOW MIN or below—CHK STATUS =
8
1. The actuator may be loose on the shaft. Check that the set screw is fully tightened
against the damper shaft. Follow these torque guidelines:
– 70 ± 5 inch pounds—solid metal
– 37 ± 2 inch pounds—plastic, graphite, composite, or hollow metal (Hollow
metal shafts require an insert to prevent shaft damage.)
2. The tubing for the air velocity sensor may be pinched, disconnected, or cracked.
Check the tubing and correct as needed.
3. The tubing connections for the air velocity sensor may be reversed. Re-pipe if HI
and LO connections are incorrect.
4. Box sizing information may be incorrect. Check the values of the following points
and correct as needed:
– DUCT AREA
– FLOW COEFF
– CLG FLOW MIN
– CLG FLOW MAX
5. Motor setup information may be incorrect. Check the values of the following points
and correct as needed:
– MTR SETUP
– MTR1 TIMING
– DMPR ROT ANG
6. The box may not have been balanced correctly. Contact your local Siemens
Industry representative.
7. The air velocity sensor may need calibration. Set CAL AIR to YES to run the
calibration sequence. When CAL AIR returns to NO, indicating that the sequence is
finished, run the checkout procedure again to see whether the problem has been
corrected.
Controller could not reach CLG FLOW MAX or above—CHK STATUS =
16
1. Check for the problems described immediately above for CLG FLOW MIN.
2. The box may be starved for air, because either the central air-handling unit is off or
there is low duct static.
Controller did not read low (zero) flow when damper closed—CHK
STATUS = 32
1. Check for the problems described above for CLG FLOW MIN.