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Sophomore Series 4000 & 5000 Cabinet - Classroom Air Handler - Owner's Manual - Installation, Operation, and Service Instructions
2.
Problem - Supply Fan Not Running
a. Check for proper speed control operation.
b. Check for proper control signal at fan motor and relay.
c. Check for “supply VAC” at fan relay and motor.
3.
Problem - Excessive Noise
a. Blower wheel rubbing- Check for proper positioning and clearance of blower wheel. Adjust wheel as necessary.
b. Loosen blower wheel - Ensure wheel is properly tightened on motor shaft.
c. Blower wheel out of balance - Replace blower.
d. Motor mounting - Motor mounts may have come loose.
4.
Problem - Damper Not Opening or Working Improperly
a. Does the air handler require “occupied signal” to enable actuator? Check for any open “safety circuits”
b. Ensure damper circuitry is enabled; check for 24vac at actuator, check for control signal at actuator. If signals are present
and actuator not functioning replace actuator.
c. Determine if damper position is controlled from an Air Quality device. If an Air Quality device is present test device output
for DC voltage and actuator for corresponding DC voltage “during occupied state”.
d. Check for mechanical obstruction.
7.3 Cooling Troubleshooting
1.
Problem - Temperature drop between mixed air and supply is less than 18°F. If it is more than this, the unit is
operating properly.
a. Confirm fan and compressors are running at full speed, and check amperage draw.
b. Check for unit running low suction psi, possible dirty evaporator or filter, clean as needed.
c. Test for over or under charged unit; adjust accordingly.
2.
Problem - Related to iced over evaporator coil
a. Confirm fan and compressors are running at full speed.
b. Check for dirty air filter.
c. Check for dirty evaporator coil.
d. Possible restrictions in the line, TXV capillary tube or evaporator.
e. Check thermostat set point. (If room temperature drops below 70°F (21°C), the evaporator may ice over during extended
operation.
f. Check for low refrigerant charge.
NOTE:
Mechanical cooling should not operate when outside temperature is below 60°F (17°C), as the economizer (“free cooling”)
will be in operation.
