Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual page 261

SYMPTOM
Bearing noise
High velocity air noise
Rattling or whistling
noise in airstream
CFM lower than system
requirements
High current draw
(motor)
Electric heat inoperative
Heater cycles
Improper temperature
regulation
No hot water or steam
heat
Water outside condensate pan
*May be serial number specific.
Table 51 — Unit Troubleshooting (cont)
POSSIBLE CAUSES
Defective bearing
Lack of lubrication
Loose bearing
Bearing misaligned
Foreign material/dirt inside bearing
Corrosion between bearing and shaft
Fan speed too high
Ductwork too restrictive
Low static pressure
Registers and grilles too restrictive
Loose dampers, grilles, or splitters
Obstructed dampers or grilles
Sharp elbows in ductwork
Sudden expansion /contraction of ductwork
Turning vanes loose or not properly installed
Fan rotating backwards
Fan speed too slow
Duct system has more resistance than designed
Diffusers closed
Motor overload
Low line voltage
Electric heater manual reset tripped
Broken heating element
Electric heater fuses blown
Inoperative electric heating circuit contactor
Airflow switch interlock not closed
Airflow marginally insufficient
Intermittent power supply due to improper
installation
Erratic thermostat operation due to improper
location or frequent resetting
Air system characteristics are not in accordance
with the job requirements
Defective hot water or steam valve actuator
motor
Broken control linkage from actuator to valve
assembly
Defective hot water or steam control valve
Plugged or improper condensate drain.
Coil blowoff due to:
— Excessive airflow
— Dirty coil
— Improper coil reversal.
— Ingestion through intake or exhaust.
— Unit has been torn down and reassembled.
— Lack of diffuser on blow-through coil
application.
— Condensate from 39M coil header.*
For 39MW only:
Coil connection housing field joints.
Leakage between access panels and frame.
Repair/replace bearing.
Lubricate bearing.
Adjust bearing support or bearing on shaft.
Align bearing properly.
Inspect and clean bearing.
Clean or replace bearing as required.
Check fan speed.
Increase duct size for proper air velocity.
Decrease fan speed to obtain proper pressure.
Replace with correctly sized registers and grilles.
Adjust as needed.
Remove obstruction(s).
Install larger radius elbows.
Install proper ductwork transitions.
Tighten or adjust as needed.
Reverse any two power leads to the fan motor.
Check fan RPM.
Enlarge ductwork to match system requirements.
Open diffusers.
Reduce system load or use larger motor.
Consult power company about increasing line
voltage.
Determine cause of cutout and reset switch.
Replace element.
Replace fuses.
Repair/replace as needed.
Check airflow sensing tube location and operation in
airstream. Repair/replace as needed.
Airflow switch may chatter and cycle heater circuits off
and on. Or, automatic reset may open and close, causing
a similar situation. Check unit airflow requirements and
clean the system.
Recheck installation procedure. Check contactor
operation and safety cutout switches. Refer to heater
wiring diagram.
Check thermostat installation instructions. Be certain
that the thermostat location is not subjected to adverse
temperature changes, such as those caused by opening
doors or windows. Check for thermostat tampering.
Check the supply-air fan is delivering adequate volume
and velocity. Check air system balance. Be certain that
heating coils are operating.
Repair/replace as needed.
Repair/replace as needed.
Repair/replace as needed.
Ensure drain properly installed and clean.
— Ensure airside system has been properly balanced.
— Check evaporator coil for cleanliness and wettability.
— Ensure coil short fin faces upstream.
— Ensure louvers or hoods are properly installed.
— Look at reassembly points for lack of seals or poor
reassembly.
— Provide diffuser.
— Splash baffles with rubber seal installed (SMB040040).*
Ensure joints between housing and curbs and housing of
unit have been properly flashed and gasketed.
Ensure all retainers and latches closed.
Replace leaking panels or doors.
261
POSSIBLE REMEDIES