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3. "Refrigeration" - Sequence of operation
a. Unit is in cooling if "Power" and "Refrigeration"
lights are on.
b. Power is supplied from terminal 4 on the time clock
to the motor contactor MS-1 and the 3-way valve
actuator motor driving to the closed position.
c. The motor contactor MS-1 circuit energizes when
the fan delay thermostat TDT-1 "R-B" makes.
d. The unit will continue in cooling mode until the
defrost timer triggers a defrost cycle.
4. "Defrost" - Electric defrost sequence of
operation
Note: The Electric Defrost cycle is time clock initiated
and temperature terminated. The timer settings
and the adjustable defrost termination fan
delay thermostat settings are to be
programmed per the need of each cooling coil.
a. Unit is in defrost when "Power" and "Defrost"
lights are on.
b. Upon initiation of the defrost cycle power is
supplied from terminal 3 on the time clock to the
heater contactor HC-1, control relay CR-1, and the 3-
way valve actuator motor driving to the open
position.
c. The heaters, positioned within the coil turbo
spacers in the fin pack, heat up the fins directly to
melt the accumulated frost.
d. When the coil reaches the temperature setting of
the defrost termination thermostat TDT- 1 "R-Y"
makes, triggering the time clock to terminate
defrost and return to cooling mode. The defrost
timer has a time-out setting to kick the coil out of
defrost after a fixed time interval. A 45-minute time
out is recommended as a back up to the TDT-1
termination.
CHS-SVN011C-EN
Modes of Operation
11
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