261
Table 51 —
Unit Troubleshooting (cont)
*May be serial number specific.
SYMPTOM
POSSIBLE CAUSES
POSSIBLE REMEDIES
Bearing noise
Defective bearing
Repair/replace bearing.
Lack of lubrication
Lubricate bearing.
Loose bearing
Adjust bearing support or bearing on shaft.
Bearing misaligned
Align bearing properly.
Foreign material/dirt inside bearing
Inspect and clean bearing.
Corrosion between bearing and shaft
Clean or replace bearing as required.
High velocity air noise
Fan speed too high
Check fan speed.
Ductwork too restrictive
Increase duct size for proper air velocity.
Low static pressure
Decrease fan speed to obtain proper pressure.
Registers and grilles too restrictive
Replace with correctly sized registers and grilles.
Rattling or whistling
noise in airstream
Loose dampers, grilles, or splitters
Adjust as needed.
Obstructed dampers or grilles
Remove obstruction(s).
Sharp elbows in ductwork
Install larger radius elbows.
Sudden expansion /contraction of ductwork
Install proper ductwork transitions.
Turning vanes loose or not properly installed
Tighten or adjust as needed.
CFM lower than system
requirements
Fan rotating backwards
Reverse any two power leads to the fan motor.
Fan speed too slow
Check fan RPM.
Duct system has more resistance than designed Enlarge ductwork to match system requirements.
Diffusers closed
Open diffusers.
High current draw
(motor)
Motor overload
Reduce system load or use larger motor.
Low line voltage
Consult power company about increasing line
voltage.
Electric heat inoperative
Electric heater manual reset tripped
Determine cause of cutout and reset switch.
Broken heating element
Replace element.
Electric heater fuses blown
Replace fuses.
Inoperative electric heating circuit contactor
Repair/replace as needed.
Airflow switch interlock not closed
Check airflow sensing tube location and operation in
airstream. Repair/replace as needed.
Heater cycles
Airflow marginally insufficient
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.
Improper temperature
regulation
Intermittent power supply due to improper
installation
Recheck installation procedure. Check contactor
operation and safety cutout switches. Refer to heater
wiring diagram.
Erratic thermostat operation due to improper
location or frequent resetting
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.
Air system characteristics are not in accordance
with the job requirements
Check the supply-air fan is delivering adequate volume
and velocity. Check air system balance. Be certain that
heating coils are operating.
No hot water or steam
heat
Defective hot water or steam valve actuator
motor
Repair/replace as needed.
Broken control linkage from actuator to valve
assembly
Repair/replace as needed.
Defective hot water or steam control valve
Repair/replace as needed.
Water outside condensate pan
Plugged or improper condensate drain.
Ensure drain properly installed and clean.
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.*
— 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).*
For 39MW only:
Coil connection housing field joints.
Leakage between access panels and frame.
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.
