Refrigeration System; Thermal Banking / Cycling; Smart Cycle / Cold Trap Dual Mode Operation; Dual Mode - AirTek SC Series Operator's Manual

sweating of pipes in the plant air system. Most important,
it increases the temperature dew point split, preventing
moisture from condensing out of the compressed air
when the air is expanded.

Refrigeration System

The major components of this system are the COMPRES-
SOR, the CONDENSER, and the EVAPORATOR. The
compressor pumps high pressure, high temperature
refrigerant to the condenser. The heat is dissipated
through finned tubes with the assistance of motor driven
fans. On water cooled units the heat is dissipated through
a water filled tube and shell condenser.
During the cooling process, the refrigerant changes from a
heat laden vapor to a liquid. This liquid refrigerant flows
from the condenser to the filter dryer, and then through the
sight glass which indicates refrigerant level. Immediately
before the inlet of the evaporator is a thermostatic expan-
sion valve which regulates the refrigerant flow to the
evaporator as low pressure cold liquid. The cold refrigerant
cools the air in the air system side of the evaporator. As the
low pressure liquid refrigerant absorbs the heat from the
air it boils and changes to a vapor. This low pressure, low
temperature vapor is then returned to the refrigerant
compressor where it is again compressed to a high
pressure, high temperature refrigerant, and the refrigera-
tion cycle repeats itself.
AIRTEK Dryers are rated to deliver full capacity (SCFM at
35ºF pressure dew point air) at 100 PSI line pressure,
receiving 100º F. water saturated inlet air, in 50 to 100º F
ambient, at 2 to 4 PSI pressure drop. Higher line pres-
sures, up to rated maximum. (higher pressure ratings are
available upon request), and cooler inlet air increases
capacity. Free liquid water, low pressures, higher air
temperatures and condensable chemical vapors, decrease
capacity. Correction figures for varying ambient tempera-
tures, heat load, and pressure ratings are located in this
manual. They can be found in the Capacity Correction
Factors, Page 12.

Smart Cycle / Cold Trap Dual Mode Operation

Smart Cycle and Cold Trap dryers are equipped with
Airtek's patented Smart Cycle Dual Mode Demand Control-
ler. It has a mounted digital dew point readout that displays
the actual dew point temperature of the compressed air.
The drain is timed and adjustable to the customers needs
or is governed by a float, demand drain.

Dual Mode

Airtek Dual Mode cycling refrigerated air dryers can operate
in either of two energy saving modes.
Load/No Load Mode / Non-Cycling Demand
The Load/No Load mode is usually selected for normal
operation. When operating in the Load /No Load mode, the
refrigeration compressor cycles from a loaded condition to
an unloaded condition. The condition is determined by the
temperature of the compressed air flowing over a special,
patented temperature probe. The probe is located in the
compressed air discharge of the evaporator. When the
temperature of the compressed air falls to a degree below
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the set point, the controller signals the unloader valve to
open. The compressor will continue to run but it will be
running in an unloaded condition. Its energy consumption
drops off to about 50%. When the temperature of the
compressed air rises to degree above the set point, the
Smart Cycle controller signals the unloader valve to close.
The compressor resumes full load operation.

Thermal Banking / Cycling

When operating in the Thermal Bank mode the refrigera-
tion compressor turns ON or OFF in response to the
temperature of the compressed air exiting the evaporator.
When the temperature of the compressed air falls to 30º F
or a degree below the set point for two minutes which ever
comes first, the sequence generates a Thermal Bank of
cold storage in the evaporator. When the compressed air
temperature rises to four degrees above the set point, the
refrigeration compressor turns back ON. The refrigerant
compressor restarts in an unloaded condition. Load is
introduced after a short time delay that allows the motor to
get up to speed. The combination of an unloaded start and
generous thermal storage prolongs compressor life while
delivering maximum performance and energy savings.
This mode is recommended for air loads at 50% or less.
4.

ADJUSTABLE CONTROLS

Separator / Coalescer Drains
All controls are preset at the factory for proper operation,
however you may need to make slight adjustments to the
following:
DEW POINT CONTROLLER: The set point of the controller
is the dew point achieved by the dryer. To raise or lower the
dew point, change the set point of the controller. The
middle and upper set points which are in 2º increments of
the lower set point adjust with the lower set point accord-
ingly.
DRAIN CONTROLOPERATION: The "DRAIN TEST" buton
when pressed will operate the Drain Relay (K1). The
"DRAIN OPEN" LED will illuminate indicating the drain valve
is open when the K1 drain relay is operated (see DRAIN
CONTROL SETTING.)
PANEL "C": This is an optional panel that displays the
ambient air and inlet gas temperatures. The display
functions as a monitor only and to alarm if above the set
point. This alarm will NOT shut down the dryer. The alarm
settings are typically at 100º F. If you choose to raise or
lower this point, you can do so by pressing the set button,
setting the alarm point and pressing set again to read
actual temperature.
NOTE: The Dew Point Controller should never be below 32º
F for long periods of time. This could result in water
freezing in the evaporator tubes which could damage the
dryer, raise the dew point and cause pressure drops
throughout the dryer. The factory setting is 36º F. Although
the dew point may be set higher, very little power savings will
be realized from a higher setting.
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