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Defrost Systems- Described
DEFROST CYCLE (HEAT & COOL UNITS):
The microprocessor controller , in conjunction with the defrost sensor, constantly monitors the heater’s
evaporator (air-coil) temperature. Should the controller sense ice or frost has formed on the evapora-
tor, sufficient in amount as to affect the heater’s performance, an active defrost cycle (more below) is
initiated. Before initiating a defrost command, the controller defrost logic looks at both the air-coil
temperature, and the length of time the coil has remained at an ice-making temperature.
Active defrost involves using hot refrigerant gas, from the compressor, to rapidly remove ice or frost
from the evaporator coil. In practice, during a hot gas defrost cycle, valving, internal within the refriger-
ant system, reverses the flow of the refrigerant; this reversal of flow temporarily makes the air-coil the
condenser. During hot gas defrost, the air-coil warms very quickly, and accumulated ice and frost is
rapidly melted. Under most conditions the evaporator will be completely cleared in under 5-minutes.
HEAT & COOL DEFROST SEQUENCE DETAILS:
•When the controller senses air-coil temperatures conductive to making ice, the unit will enter a
50-minute defrost delay (counting) period.
•During the counting period, the fan and compressor will continue to operate, and the water will
continue to be heated. During the counting period it is normal to see a moderate amount of frost
and ice formation on the air coil.
•If, after the 50-minute counting period, the controller senses a need to defrost:
1. The refrigerant circuit reversing valve will be activated, changing the flow of hot refrigerant
gas from the pool water heat exchanger to the air-coil.
2. Fan operation will be suspended, permitting maximum heating of the air-coil.
3. The reverse cycle will continue until either:
A. The air-coil attains a predetermined temperature (indicative of total defrost), or;
B. Until 10-minutes have elapsed (regardless of total defrost having occurred).
•During hot gas defrost cycles, the compressor will not deactivate; rather, the compressor will
continue operation throughout the sequence. Upon completion of the defrost cycle (as
terminated per “A” or “B,” above), the reversing valve will be deactivated, fan operation will
recommence, and water heating will resume.
DEFROST CYCLE (HEAT ONLY UNITS):
The microprocessor controller monitors the heater ’s air-coil temperature, minimizing air-coil freeze-
up during cooler weather conditions. If the controller senses air-coil temperatures conductive to mak-
ing ice, the heater’s compressor operation is interrupted while the fan is allowed to continue in opera-
tion.
With the compressor off, the air-coil begins to warm to the surrounding air temperature. When air-coil
temperatures rise above approximately 38oF, the compressor is restarted and heating resumes.
In the event air temperatures remain below approximately 38oF, the compressor will remain off until
the air temperature rises above 38oF. The unit will not heat the water as long as the compressor
remains off.
During defrost cycles, when the controller has stopped compressor operation, the display will read:
[FS].
Controls Configuration & Adjustments...