Carrier AERO 39MN Installation, Start-Up And Service Instructions Manual page 161

SYMPTOM
Motor Does Not Run at
Full Speed
Motor Overheats
Excessive Motor Noise
Motor Runs and Then Slows
Excessive Motor Bearing Wear
Loose Fan Belt
Drive Noise
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 40 — Unit Troubleshooting (cont)
CAUSE
Low voltage at motor terminals
Supply wiring to motor too small
Overloaded motor
Motor fan is clogged, preventing motor cooling
Mounting bolts loose
Rigid coupling connectors
Worn motor bearings
Fan rubbing on housing
Partial supply voltage loss
High load due to over-tensioned drive
Excessive overhung load caused by a small
diameter motor sheave
Improper motor position
Worn sheaves
Worn or damaged belt
Sheave(s) not tight on fan/motor shaft(s)
Belts contacting guard(s)
Belts too loose or too tight
Belts and sheaves mismatched
Belts not length matched (multiple belt set-up)
Misaligned sheaves
Belts worn
Belts dirty or oily
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
— 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.
Check supply voltage and correct voltage loss.
Rewire with properly sized wire.
Reduce motor load or replace with larger motor.
Clean motor fan.
Tighten bolts.
Replace with flexible connectors.
Replace bearings and seals.
Adjust housing.
Check for loose/dirty connections.
Verify supply voltage.
Check belt tension and load.
Replace with larger sheave.
Adjust tension.
Replace sheaves.
Check sheave alignment and replace belt(s).
Tighten sheaves.
Adjust or tighten belt guard mounts.
Adjust belt tension.
Install proper belts.
Install matched belts.
Align sheaves.
Replace belts.
Replace belts.
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 (SMB04-0040).*
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.
160
REMEDY