Filter
Top Products
UNIT TROUBLESHOOTING
PROBLEM POSSIBLE CAUSE CORRECTIVE ACTION
Unit does not run
PIC control is OFF
Check for correct power or blown fuses (F2).
Correct any deficiencies.
Faulty connections
Check LEDs on control module (PSIO). If LED is not solidly
illuminated, check for loose connections. If all wires and
connectors are secure, replace PSIO module as described
on page 112.
PIC control has incorrect time
Verify control shows correct time. If incorrect, enter correct
time.
Supply fan HOA switch in OFF position
Safety controls are tripped
Verify HOA switch is in the AUTO position.
Check low-temperature thermostat and high-pressure switch
(VAV units only). Reset switches if necessary.
PIC control left in Quick Test
(Display shows Mode 38)
Using the local interface device, exit Quick Test.
Press 5 TEST, and then ENTR to exit.
Unit is configured for and is currently
in Demand Limit Mode (CV units only)
Verify that unit should be in the Demand Limit mode. If not,
cycle power to PIC to release unit from Demand Limit
mode.
Unit is in Smoke Evacuation or Fire Shut-
down mode (Display shows 35 or 37)
Verify that unit should be in one of these modes. If not,
check for shorted input on Fire Shutdown or Evacuation.
Minimum inverter set point too low
(VAV units only)
Adjust minimum to 20% at 4 mA signal and 100% at 20 mA
signal.
No heat
No fan status
Check status of SFS (4 STAT). If SFS is OFF, check supply
fan status switch for proper operation. Switch must be ON
for heat coil to function properly.
Heat coil valve (HCV) is forced closed
Check status of HCV (5 STAT). If HCV is forced, remove
force and check operation.
NO hot water or steam available,
no power if electric heat
Check source and correct any problems found.
Electric heater safety tripped Reset heater safety. Check for proper operation.
No power to valve
Check for blown fuse (F6). Replace if necessary. If fuse
is intact, check for proper connections. Check transformer
output.
No power to electric heater control
Check for blown fuse (F5). Replace if necessary. If fuse
is intact, check for proper connections. Check transformer
output.
Incorrect reading from space temperature sensor,
supply-air temperature sensor, or return-air
temperature sensor (VAV units)
Check status of sensor readings for accuracy.
Replace sensor if defective.
Configuration error
Check configuration for proper heating set point and
Submaster Gain (SMG). An improper SMG can cause the
heating valve to be held closed.
Overheating
Heat coil valve (HCV) is forced open
Check status of HCV (5 STAT). If HCV is forced, remove
force and check operation.
Incorrect reading from space temperature sensor,
supply-air temperature sensor, or return-air
temperature sensor (VAV units)
Check status of sensor readings for accuracy. Replace
sensor if defective.
Configuration error
Check configuration for proper heating set point and
Submaster Gain (SMG). An improper SMG can cause the
heating valve to be held open.
No cooling
No fan status
Check status of SFS (4 STAT). If status is OFF, check
switch for proper operation. Supply fan status switch must
be ON for cooling coil to function properly.
Cooling coil valve (CCV) is forced closed
Check status of CCV (5 STAT). If CCV is forced, remove
force and check operation.
No chilled water available Check source of chilled water. Correct any problems found.
No power to cooling coil valve
Check for blown fuse (F3). Replace if necessary. If fuse
is intact, check for proper connections. Check transformer
output.
Incorrect reading from space temperature sensor,
supply-air temperature sensor, or return-air
temperature sensor (VAV units)
Check status of sensor readings for accuracy. Replace
sensor if defective.
Configuration error
Check configuration for proper cooling set point and
Submaster Gain (SMG). An improper SMG can cause the
CCV to be held closed.
Overcooling
Cooling coil valve (CCV) is forced open
Check status of CCV (5 STAT). If CCV is forced, remove
force and check operation.
Incorrect reading from space temperature sensor,
supply-air temperature sensor, or return-air
temperature sensor (VAV units)
Check status of sensor readings for accuracy. Replace
sensor if defective.
Configuration error
Check configuration for proper cooling set point and
Submaster Gain (SMG). An improper SMG can cause the
CCV to be held open.
LEGEND
CV — Constant Volume
VAV — Variable Air Volume
113