Filter
Top Products
724-746-5500 | blackbox.com
Page 116
724-746-5500 | blackbox.com
Chapter 5: Maintenance
5.1.6 A/C System
Check the refrigerant sight glass on a monthly basis while the unit is running and ensure it is free of bubbles. Bubbles in the sight
glass indicate a low refrigerant charge or a clogged filter-drier. Check for humidity in the refrigerant by viewing the color of the
indicator in the center of the sight glass and comparing it to the color scale on the outer ring. If humidity is present, the system
must be evacuated and recharged.
Check the superheat and sub-cooling temperatures semi-annually and ensure they are within the range shown in the refrigerant
pressure/temperature table (Tables 2-9–2-11) in Section 2.10.3. If necessary, adjust the refrigerant charge to achieve the correct
values. If the
refrigerant level is low, check the system for leaks.
5.2 Troubleshooting
Turn off all power to the unit before conducting any troubleshooting procedures, unless the procedure specifically requires the
system to operate. For troubleshooting purposes, the system may be operated with the doors open by using a pair of channel
lock pliers to turn the shaft of the main power disconnect switch to the “On” position. When the switch is turned on, high
voltage will be present inside the cabinet. Exercise caution to prevent injury. Keep hands, clothing, and tools clear of the electrical
terminals and rotating components. Ensure that your footing is stable at all times.
Symptom: Airflow too low.
Probable Cause: Dirty air filters (reduced airflow).
Recommendation: Clean/replace filters.
Symptom: EC fan(s) fail to start.
Probable Causes/Recommendations:
a. Power failure. Check main voltage power source input cable.
b. Motor starter protector tripped. Reset motor starter protector and check amperage of motor.
c. Control transformer circuit breaker tripped. Check for short circuit or ground fault; if none, reset circuit breaker.
d. Condensate overflow switch open.
1. Ensure unit is level.
2. Check that condensate pan is draining.
e. Defective contactor. Repair or replace.
f. No control signal to fan(s). Check the control I/O board for a 0-10 VDC control signal to the fan(s). Refer to the electric
drawing to determine the correct I/O board terminal numbers. This must done within 15 seconds of turning the disconnect
switch “On” or the controller will go into “Air Proving Alarm” mode.
g. EC fan’s internal overheat protection. Determine the cause of the interruption and correct. Possible causes are:
1. Blocked rotor.
2. Low supply voltage > 5 seconds.
3. Loss of phase > 5 seconds.
After causes 1, 2, and 3 are corrected, the motor will automatically reset.
After the causes below are corrected, the fan(s) must be manually reset by turning off power for 20 seconds:
4. Over temperature of electronics.
5. Over temperature of motor.