13 5/21 Rev. E 143568
OPERATION CONDITIONS AND PRESSURES
With room ambient temperature of +75
o
F and cold cabinet (unit cycling on control):
DD-66 & DD-88 with R-290
Suction pressure – 2 to 4 psig.
Head pressure – 130 to 160 psig.
DD-26 & DD-46 with R-290
Suctions pressure 1 to 5 psig
Head pressure 130 to 160 psig
SERVICE INSTRUCTIONS (Trouble Shooting Guide)
1. High head pressure and high back
pressure:
A. Condenser coil clogged or
restricted.
B. Condenser fan motor defective.
C. Air in the system.
D. Refrigeration overcharge.
2. Low back pressure and low head pressure:
A. Capillary tube restriction.
B. Refrigerant undercharged.
C. Leak in system.
D. Moisture in system.
3. Pressures normal – cabinet warm:
A. Refrigerant undercharged.
B. Thermostat set too warm.
4. Compressor starts and runs – but cycles
on overload:
A. Low voltage.
B. Overload protector defective.
C. High head pressure (see#1).
5. Compressor will not start – hums, but
cycles on overload:
A. Low voltage.
B. Relay defective.
C. Overload defective.
D. High head pressure (see #1).
6. Cabinet sweating:
A. High ambient humidity.
7. Special service situations
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