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724-746-5500 | blackbox.com
724-746-5500 | blackbox.com
Page 117
Chapter 5: Maintenance
Symptom: Control is erratic.
Probable Cause: Wiring improperly connected or broken.
Recommendation: Check wiring against electrical drawing.
Symptom: Compressor fails to start
Probable Causes/Recommendations:
a. Temperature setpoint too high. Adjust to desired temperature.
b. Compressor internal overload protector is open. Check compressor for short circuit or ground.
c. Complete loss of refrigerant charge (low pressure safety switch tripped). Locate and repair leak. Recharge system.
d. Condenser pressure too high (high pressure safety switch tripped). Check condenser for obstructions.
e. Minimum off time has not expired. Wait for time to expire.
Symptom: System short of capacity.
Probable Causes/Recommendations:
a. Temperature setting too high. Increase temperature setpoint.
b. Discharge air short cycling back to return. Check air barrier between hot/cold aisles.
c. Low airflow.
1. Check filters. Replace as needed.
2. Check for and clear any obstructions across or in the (supply) discharge air stream. Clear coil fins of debris.
3. Check evaporator coil for bent fins.
4. Check correct rotation of fans.
d. Low refrigerant (indicated by bubbles in sight glass). Check for leaks. Repair and recharge system.
e. Expansion valve stuck or obstructed (short cycling or continuous running). Remove valve and clear obstruction or replace valve.
f. Clogged drier/strainer (feels cold). Replace with new drier/ strainer.
Symptom: System short of capacity (CRDX-W-FS-12KW, CRDX-W-FS-24KW, CRDX-G-FS-12KW, CRDX-G-FS-24KW).
Probable Causes/Recommendations:
a. Low water–water/glycol flow.
1. Check for leaks. Repair and recharge system.
2. Check for obstructions in supply/return lines.
3. Check for clogged strainer (if applicable).
b. Supply water temperature too high. Check chilled water supply.