![DEFROST SEQUENCE OF OPERATION](/images/new-backgrounds/35203/3520333x1.webp)
DEFROST SEQUENCE OF OPERATION
These heat pumps have a unique “ambient modified”
The curve in the Deforst Initation Times Figure shows how defrost initiation times are automatically compensated for changes in outdoor temperature.
EXAMPLE: If the timer is factory set on pin
If the outdoor temperature drops to 10° F where ice is less likely to form, the 110 minute interval will extend to every 150 minutes.
Two requirements must be met before a defrost cycle can be initiated.
1.The defrost time cycle must be complete.
2.The liquid line temperature must be less than 28° F.
Defrost will terminate when the liquid line sensor reaches 55° F or after 10 minutes. If both or just one circuit defrosts, electric heat is energized.
The defrost time cycle will restart 10 minutes after the start of the defrost cycle even though the liquid sensor terminated defrost after 3 minutes.
During troubleshooting, the defrost time can be reduced to 20 seconds by shorting out the SW1 test pegs on the module. The pegs are 1/2" long, 3/16" apart and are mounted on a white base.
LOCKOUT CONTROL
Any one of four conditions will put the system into a
1.The discharge line temperature reaches 255° F (215° F reset) or,
2.The discharge pressure reaches 398 PSIG (310 PSIG reset) or,
3.The suction line freezestat equals 26° F (38° F reset) or,
4.The
A
NOTICE TO OWNER:
If a lockout occurs, check for the following problems before calling a serviceman:
1.Dirty filters.
2.Snow accumulation.
3.Leaf or debris blockage.
After eliminating the problem, attempt to restart the system as follows:
•turn the system switch on the thermostat to its “OFF” position for 10 seconds.
•turn it back to its original position.
If the unit doesn’t start, call a serviceman.
NOTE: Models with an
FIG. 11 - DEFROST INITIATION TIMES
Unitary Products Group | 17 |