Nor-Lake Capsule Pak Refrigeration Systems - Manual (Page 18)

18 07/14 Rev. H 040086
loW tempeRatuRe (fReezeR) SyStemS
The low temperature, automatic electric defrost Capsule Pak™ Refrigeration System is the most dependable and
readily understood equipment available. It employs a basic refrigeration system with electric elements to
provide heat for defrosting.
Important: It is the installing contractor’s responsibility to check the operation upon start-up and make necessary
temperature control or thermal expansion valve adjustments as required for proper operation.
Note: Capsule Pak™ Refrigeration Systems that are designed for outdoor installation will be fitted with electric
crankcase heaters, electrically heated condensate drain tubes, automatic head pressure control valve, and the
"pump-down cycle".
Defrost Cycle
Under low temperature conditions, the air being forced through the evaporator coil is well below freezing at all
times, even during each compressor "off" cycle. Therefore, a source of heat
must be supplied to melt the accumulated frost. To achieve a complete
defrost, electric heater elements are attached to the evaporator coil and
to the drain pan. An electric time switch initiates a predetermined number
of regular defrost periods per day. When a defrost period occurs, the time
switch stops the evaporator fan(s) and the condensing unit, and energizes
the electric heaters in the evaporator coil and in the drain pan beneath it.
Note: Some models may have a programmable control used in place of
the time switch. This unit is used to control the temperature and the defrost
settings. Please see the separate instructions that are included on the
operation of this control.
Defrost Cycle Termination
As the defrost cycle progresses and the frost accumulation melts from the fins
of the evaporator coil, the temperature of the finned surfaces of the evaporator
coil will rise proportionately with the removal of the frost. When this temperature
reaches about 50°F, a point where the evaporator coil should be completely
free of frost, a defrost termination thermostat attached to the evaporator coil
will energize a solenoid coil in the defrost time switch which will revert the system to the cooling cycle. The fan(s)
in the evaporator housing will not start, however, until the fan delay cycle has expired. See the "Fan Delay" below.
Fan Delay
When a defrost cycle is terminated through the action of the defrost termination thermostat as described in the
section "Defrost Cycle Termination", the electric defrost heaters are de-energized, the compressor starts, and
evaporation resumes in the coil. The evaporator fan(s), however, will not start until the evaporator coil temperature
is reduced to about +20°F. Once this temperature is reached, the fan delay switch action of the defrost termination
thermostat energizes the evaporator fan(s) and they begin operating.
The fan delay feature is an important part of defrosting. If the fan(s) was permitted to start immediately following
a defrost period, the heat that accumulated in the evaporator housing would be circulated throughout the walk-in,
raising the temperature considerably. In addition, any droplets of moisture that remained clinging to the fins of the
evaporator coil would be blown into the storage space. The fan delay feature provides for a short refrigeration cycle
WITHOUT the evaporator fan(s) to prevent these conditions.
Note: During the initial startup of a Capsule Pak™ Refrigeration System on warm Kold Locker™ Walk-in, the
evaporator fan(s) will not start until the evaporator coil reaches and maintains +20°F. Further, the evaporator fans
may cycle "on" and "off" several times until the evaporator coil reaches and maintains +20°F.
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