CVHE-SB-32A 19
~ Opening the external ice contacts/remote communicated (Tracer)
~ Satisfying an evaporator entering water temperature setpoint
~ Surging for 15 minutes.
Problem 43: IGV will not move in the Service Test Manual mode.
Corrective Action:
1 Verify the CLD LED comes on solid. Verify there are no Stepper module diagnostics.
2 Verify we are in a Stop mode, Diagnostic Stop mode, or Run mode. All other modes the
Manual Vane Control will not work.
3 Is the IGV travel percentage increasing? If so there is a problem with the motor or Stepper
module drive circuit.
4 Are we in a “Stop” mode after being in a Limit mode. The limit bit may be set so do a power
down to clear.
5 Will not work in post lube or initialization in preparing to start.
6 On power up, does the Stepper module do a BPI search? If not, the Stepper module could be
held up in the Initialize mode internally. On a power up, the Stepper module looks for
communication with the Chiller, Starter and Circuit modules. If it doesn’t hear from any one of
them, it stays in the Initialize mode and will not do BPI or Manual Vane Control. If no BPI,
check the IPC wiring. Also, if trying to start the chiller, the mode will stay in initialize.
Problem 44: IPC Buffer Diagnostics
Corrective Action:
1 Clear Language Display is not communicating. Replace the CLD or the Chiller module is not
communicating and needs replacing.
Problem 45: KW reads high by a factor of 3, with optional PT installed.
Corrective Action:
1 Software change made 11/93 to CLD. X-13650448-02 Rev. E or later corrects the problem.
Problem 46: Loading Problems
Corrective Action:
1 Unit is in External Stop and when released, requires 3.5 minutes to get the vanes to desired
point of operation (typically 50 degrees). This is close to the maximum rate that the
compressor can load because the fastest the vanes will move is 1250 steps every 5 seconds.
2 If Soft Load Control is Enabled, the Soft Control parameters can be adjusted to meet the
requirements of the system. If the chiller is allowed to ramp up faster than needed it could
over shoot the leaving chilled water temperature setpoint and potentially be current limited. If
this overshoot is too rapid and causes excessive current draw, the adaptive control will force
an unload to approximately 70%. This could cycle several times before stabilizing.
If Soft Load Control is Disabled or the loading is not from initial startup, The LWT Control
Proportional, Integral and Derivative gains can be adjusted to allow system adjustment to
properly follow the load. Typical changes should be small. 1-2% proportional gain change or
0.01% integral gain changes. Always adjust proportional gain first. This is the coarse
adjustment, while integral is the fine and derivative is the micro adjustment.
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