Carrier 39L Series Installation, Operation, And Start-Up Instructions page 114

PROBLEM
No fan status
Mixed-air dampers forced closed to outside air
No power to damper actuator
Mixed-air dampers
Incorrect reading from space temperature sensor
will not operate
or supply-air temperature sensor
Configuration error
No fan status
Inlet guide vanes (IGVs) forced closed
No power to IGV actuator(s)
Unit not main-
taining desired
static pressure
Loose IGV linkage
(VAV units only)
Incorrect reading from static pressure transducer
Configuration error
IGVs forced open
High-Pressure Switch (HPS) is incorrectly set
or defective
High-Pressure
Switch keeps
tripping unit
Static pressure sensor reads incorrectly
OFF (VAV only)
Configuration error
No power, blown fuse
Individual
actuators
do not function
Linkage is jammed or binding
No control signal
Incorrect submaster gain
Oscillating
output
(HCV, CCV, IGV,
Input sensor is fluctuating (supply-air
MIXD, etc.)
temperature sensor, static pressure transducer)
Loose connections
Sensor Sensor out of calibration
not reading
correctly
Defective sensor
UNIT TROUBLESHOOTING (cont)
POSSIBLE CAUSE
114
CORRECTIVE ACTION
Check status of SFS (4 STAT). If supply fan status switch is
OFF, check switch for proper operation.
Check status of MIXD (5 STAT). If MIXD is forced, remove
force and check operation.
Check for blown fuse (F7). Replace if necessary. If fuse is
intact, check for proper connections. Check transformer
output.
Check status of sensor readings for accuracy. Replace sen-
sors if defective.
Check configuration for proper SMG and MDP (minimum
damper position). If MDP is set to zero, then dampers will
stay closed when enthalpy is unsuitable. An improper SMG
can cause the MIXD to be held to the MDP setting. Check
for proper damper set point. If damper set point is forced to
incorrect value, remove force.
Check status of SFS (4 STAT). If SFS is OFF, check supply
fan status switch for proper operation.
Check status of IGV (5 STAT). If IGVs are forced, remove
force and check operation.
Check for blown fuse (F4). Replace if necessary. If fuse is
intact, check for proper connections. Check transformer for
proper output.
Check IGV linkage for tightness and proper adjustment.
Check status of sensor reading for accuracy. If reading is
in error, check for plugged sensing line and check sensor
calibration. Replace sensor if defective.
Check configuration for proper static pressure set point.
Also, check SMG. An improper SMG can cause the IGVs to
be held closed.
Check status of IGV (5 STAT). If IGVs are forced, remove
force and check operation.
Using squeeze bulb, check trip point of HPS. Adjust as re-
quired. Check for plugged lines. Replace if defective.
Using local interface device and squeeze bulb with gage,
verify static pressure reading is correct. Adjust or replace
sensor as required.
Check configuration for proper static pressure set point.
Check SMG. An improper SMG can cause the IGVs to be
held open.
Check fuses of specific actuator for function failure.
Fuses are as follows:
F1 — PSIO control module
F2 — Power
F3 — Cooling coil
F4 — IGVs — supply fan
F5 — DSIO or option module
F6 — Heating coil
F7 — Mixed-air dampers
F8 — Smoke control or return-air damper
F9 — Exhaust-air damper
F10 — IGVs — return fan
F11 — 39NX sizes 74, 92; 2nd IGV actuator, supply fan
F12 — 39NX sizes 74, 92; 2nd IGV actuator, return fan
F13 — Preheat coil
Using manufacturer's instructions, correct and adjust
linkage. Check operation.
Using Quick Test and a voltage meter set to measure cur-
rent, verify that the proper control signal (4 to 20 mA) is be-
ing sent to the actuator. Refer to wiring diagram for
appropriate terminals.
Using Control Loop Checkout procedure, page 108, adjust
the SMG until the output steadies.
Verify sensor reading. If reading is fluctuating, determine
cause (i.e., loose connections, partially plugged static pres-
sure sensing lines). Correct or replace sensor if necessary.
Verify all connections are secure.
Voltage type sensors (i.e., static pressure, space tempera-
ture, outdoor-air temperature, return-air temperature, rela-
tive humidity, and velocity pressure) can be calibrated using
manufacturer's instructions.
If a sensor cannot be calibrated and its reading is consid-
ered unacceptable, replace sensor. Once sensor is re-
placed, verify new sensor is reading correctly.