Parameter Generation and Control 9354-4250 User manual

Parameter Generation and Control, Inc.
Black Mountain, North Carolina
[phone]
500-1000 CFM Air Handler
460V, 60 Hz
Model #9354-4250
Installation and Operation Manual
Customer .
Serial # .
Ship Date .
Parameter Generation and Control, Inc.
P. O. Box 129 1054 Old US 70 West Black Mountain, NC 28711
[phone] [phone] FAX

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 2

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 3
Inspection........................................................................................................................ 4
Installation....................................................................................................................... 4
Plumbing..................................................................................................................... 4
Electrical Connections................................................................................................ 7
Electrical Connections................................................................................................ 8
Operation......................................................................................................................... 9
Turning the Chamber Off and On............................................................................... 9
Process Variable Display.......................................................................................... 10
Adjusting Set Points.................................................................................................. 10
Operation After Loss of Power................................................................................. 10
Fault Displays ........................................................................................................... 11
Control Modes .......................................................................................................... 12
Specifications, 500-1000 CFM..................................................................................... 13
Replacement Parts, 500-1000 CFM.............................................................................. 14
Appendices
Appendix A – Technical Information
Appendix B – SmartPad™ Operation Manual
Appendix C – Diagrams
Appendix D - Manuals for Accessory Equipment

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 4
Inspection
If the equipment is damaged upon receipt, immediately request the delivering carrier to
perform an inspection and prepare a report. All claims for damage must be made against
the delivering carrier. Report the nature and extent of the damage to PGC, 828-669-8717,
and include instrument serial and catalog numbers to facilitate repair or replacement.
Installation
The 500-1000 CFM Conditioner was designed to be located adjacent to or on top of the
chamber to be conditioned. Allow at least 36 inches on the right side and front of the unit
for service. The location must be convenient to an adequate process water supply, drains
and electrical power. The conditioner must be reasonably level for proper water level
control.
Electrical power and water must be connected to this unit prior to operation. The required
voltage and current are listed on the nameplate located on the unit. The sump drain may
be connected directly to a facility drain, but the condensate drain must be connected to an
open (vented) trapped drain (see Figure 3) to ensure that backpressure on the facilities’
drain does not prevent proper drainage.
Note The condensate drain has been supplied with a copper trap.
Plumbing
CAUTION To prevent damage to the water pump and water heater, the unit must not
be operated until water is supplied to the unit and the sump has filled to the
proper level.
Process Water Supply Specifications
Units Maximum Typical Minimum
Process Water Pressure PSIG (Bar) 125 (8.6) N/A 5 (0.35)
Process Water Daily
Consumption Gallons (Liters) 5.0 (19) 1.5 (5.7) 0 (0)
Condensate Production
per Day Gallons (Liters) 5.0 (19) 1.5 (5.7) 0 (0)
Sump Water Volume Gallons (Liters) 15 (57) 15 (57) 6.6 (25)
Process Water Inlet
Connect a clean water supply line through an external customer-supplied hand valve to
the Process Water Inlet connection on the rear of the conditioner; this is a ½” male NPT
connection.

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 5
Condensate Drain
Connect the condensate drain to an open (vented) trapped external drain. This drain is a
¾” female copper sweat connection on the rear of the conditioner.
Sump Drain
Connect the sump drain to a facilities
drain. This drain does not require a trap.
This drain connection is made to the ¾” ¼
turn ball valve, supplied on the rear of the
conditioner.
Coolant Water Supply and Return
If the refrigeration system is equipped
with a water-cooled condenser. Connect
coolant water to the condenser inlet
connection on the rear of the chamber
cabinet. Connect the coolant water return
line to the coolant water outlet connection.
Coolant flow requirements will vary based
on the operating conditions of condensing
units, as the temperature of the coolant fluid.
The following graph indicates the maximum
coolant flow requirements for the condenser.
500-1000 CFM
Maximum Condensor Water Flow Requirements
0.00
1.00
2.00
3.00
4.00
5.00
45 50 55 60 65 70 75 80 85 90 95 100 105
Entering Water Temperature (Degrees F)
Gallons Per Minute
Coolant Water Connections
500-1000 CFM
Coolant Water
Outlet
Coolant Water
Inlet

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 6
Filling the sump
To fill the conditioner with water, ensure
that the sump drain valve is closed and open
the customer-supplied external water inlet
valve. When the sump is filled to the proper
level, a mechanical float valve will
automatically shut off the flow and maintain
the proper water level during operation. The
float valve is preset at the factory to
maintain the proper level (1/2” above the
evaporator tubing); to change the water
level, adjust the angle of the float arm
slightly.
A low-water safety switch is located in the
front, left corner of the sump. This switch
will open when the water level is too low for
safe operation of the pump and water heater.
When the water level is correct, the float
switch will close and allow the controller to
resume operation of the unit.
NOTE The conditioner will not operate until the low water level safety is satisfied.
CAUTION The water fill valve float may be padded to prevent damage during
shipping. Remove the padding before connecting the water supply to the
inlet.
Plumbing Connections
Process Water
Inlet
Condensate
Drain
Service
Drain

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 7
CAUTION Do not connect the drain connection to an un-vented drain.
NOR
Ensure that the drain connection is vented, as shown below.
OR
“Open” (Vented) Drain Connections

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 8
Electrical Connections
CAUTION Turn all electrical switches, circuit breakers, and motor starter protectors
(MSPs) off to prevent accidental starting of equipment when power is
connected.
NOTE Determine voltage and current requirements of equipment before making
electrical connections. This information is on a data plate attached to the
machine.
Connect the air handler in accordance with all applicable codes, using a customer-
supplied disconnect device.
The SmartPad™ user interface and the optional circular chart recorder can be located
remote from the air handler. Typically, the controller is located on the front of the
chamber to be controlled. These components are usually disconnected for shipment and
must be re-connected prior to operation. Refer to the attached wiring diagrams for re-
connection information.
NOTE
The SmartPad™ user interface interconnect cable has a maximum voltage
of 24VDC. Refer to local codes to determine the proper conduit
requirements for the control cable.
The optional circular chart recorder can be powered by 24VDC or
120/230VAC. Refer to the wiring diagrams or the data plate on the
recorder for more information.
CAUTION
The compressor and blower will not
operate properly and may be damaged if
permitted to run backward. After the
Conditioner has filled with water and is
operating, observe the rotation of the
blower through the air bypass damper.
Ensure that the blower is turning as
indicated in the diagram below. If
necessary, turn off the wall disconnect and
interchanging any two phase wires at the
wall disconnect or of the line connection terminals. Exchanging
phases at this point will reverse the rotation of all 3-phase motors.

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 9
Operation
The 500-1000 CFM Conditioner is a self-contained conditioner designed to control dry-
bulb temperatures over a range of 7°C - 60°C (44.6ºF - 140ºF), dependent upon the size
and construction of the test chamber. The dry-bulb temperature is held to ± 0.2°C and
relative humidity constancy to ± 0.5% with dew points above 5°C (41°F).
The SmartPad™ may be remotely mounted; refer to the PGC SmartPad™ section at the
rear of this manual for instructions.
Turning the Chamber Off and On
When the chamber is energized and the Standby key has been pressed, the system
should begin to operate and control the temperature and humidity in the chamber at the
set points entered into the SmartPad™ user interface.
The SmartPad™ user interface is configured with a Standby key located in the lower
right corner of the keypad. Pressing this key will disable the system and place the
controller in a Standby mode. The SmartPad™ display will indicate:
Operating Range

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 10
When the system is in Standby mode, it can be energized by pressing the Standby key
Process Variable Display
The Process Variable screen is the first screen that will be displayed when the conditioner
is energized. This screen will display the measured process variables and will allow
access to the other screens in the SmartPad™.
The bottom line of the SmartPad™ display is a label for the four function keys on the key
pad. This label will vary from screen to screen to reflect the action of each of the function
keys.
Refer to the SmartPad™ manual in the appendix for a complete listing and discussion of
available screens.
Adjusting Set Points
In the Process Variable screen, pressing the SP function key will access the Set Point
screen. The Set Point screen will allow the user to enter the desired air temperature and
relative humidity set points for the chamber.
NOTE The SmartPad™ has no ENTER key. In order to enter a value in any field
all digits must be entered. For example, to enter 25.0°C air set point you
must press “2”, “5” and “0”. When the field has been filled and the data has
been entered, the cursor will jump back to the beginning of the field.
Operation After Loss of Power
If power is removed from the conditioner, the controller will resume operation in the
same mode when power is regained. For instance, if the SmartPad™ was in Standby
mode when power was lost, it will be in Standby mode when power is restored. If the
SmartPad™ was operating and controlling the chamber, it will return to that mode of
operation.
STANDBY MODE
Press the ON/OFF key
to energize the system

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 11
NOTE The SmartPad™ is not equipped with a battery backup.
All set points, tuning values and ramping profiles are stored in non-volatile
memory and will be permanently stored in the SmartPad™.
If power is removed from the controller it will resume operation when
power is restored.
In Steady State set point mode the controller will resume operation at the
previous steady state set points.
In Programmable set point mode the controller will resume operation at
exactly the same segment and time remaining in that segment if the
duration of the power loss is less than approximately 20 minutes. If the
duration of the power loss exceeds approximately 30 minutes the
controller will re-initiate the program according to the loop parameters
defined in the INIT screen.
Fault Displays
If the system encounters a temperature, low-water, remote on/off switch, or refrigerant
pressure fault, the system will shut down and the SmartPad™ will indicate the fault that
has occurred. The SmartPad™ will continue to indicate that the fault exists, and will
indicate if/when the fault has cleared.
If the fault has been cleared, the system can be re-energized by pressing the Standby key
. If the fault has not cleared, the source of the fault must be determined and corrected
before the system can be re-energized.
NOTE Some faults will clear automatically and others will require user
intervention.
Regardless of the fault clearing mechanism, the user must press the Standby
key in order for the conditioner to resume operation.

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 12
Control Modes
The PGC conditioning system offers four modes of temperature and humidity control.
1. Cascade Temperature Mode
This is the most commonly used mode because the user specifies only the desired
air temperature and relative humidity (Rh) level in the chamber. The temperature
of the water spray controls the dew point of the discharge air and the water
temperature is adjusted in order to achieve desired humidity level. The air is then
re-heated to the desired temperature before returning to the test chamber. This
allows the system to respond to load variations while retaining the basic stability
of a spray system.
2. Two-Temperature Mode
In this mode, the user establishes the desired air and water temperatures that are
required to produce the desired relative humidity level, as determined by a
psychometric chart. The Two-Temperature mode can be used when operating the
very edges of the system capabilities.
3. Slow Damper Mode
This mode is similar to Cascade mode with the difference being that the air
bypass damper control loop and the air heater control loop have been separated.
In this mode the damper is moved slowly and its final position is when the desired
percentage of air heat output is achieved. The desired percentage of air heat is
determined by the user in the tuning parameters (Manual Adjust) section of the
controller. In some situations, slow damper mode can be applied to improve
energy efficiency or extend the operating range of the system. Typically, slow
damper mode is most effective when the system is operated at a single condition
as it will often require manual tuning adjustments for proper operation at multiple
set points.
4. Dry Mode
This mode is required to control dew points below 4°C. In this mode, all water is
removed from the spray chamber and an optional desiccant dryer is used to
control humidity. Although this mode is accessible in SmartPad, it is non-
functional unless the system is equipped with a desiccant dryer.

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 13
Specifications, 500-1000 CFM
Voltage-------------------------------------------------------------------------------- 460V~
Frequency----------------------------------------------------------------------3ph, 60 hertz
Current------------------------------------------------------------------------------ 8.8 FLA
Circuit Capacity (Max / Min)--------------------------------------------------30A / 12A
Heater, Water ------------------------------------------------------------------- 1800 watts
Heater, Air (Two, 1500 watt) ------------------------------------------------- 3000 watts
Refrigerant-------------------------------------------------------------R-404a, 96 Ounces.
Process Water Pressure, (Max/Min) ------------------------------------------125/5 psig
Weight Net --------------------------------------------------------------------------1000 lb.
Weight Shipping--------------------------------------------------------------------1400 lb.
Temperature Range -------------------------------------------------------------7°to 60°C
Relative Humidity Range----------------------------------------------------10% to 95%1
Temperature Constancy (control) ------------------------------------------------ ±0.2°C
Rh Constancy (control) ----------------------------------------------------------±0.5%
1 Minimum Rh is limited by a minimum dew point of 5°C (41°F) for standard Spray
Mode. For example:
Air
Temperature Max. Rh Min. Rh
10°C (50°F) 88% 70%
25°C (77°F) 93% 32%
40°C (104°F) 95% 17%
> 50°C
(122°F) 95% 10%

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 14
Replacement Parts, 500-1000 CFM
Description Mfg. / Supplier Mfg./Supplier # PGC #
ACE Master Micro Controller PGC ACE 503g N/A
ACE4 Controller Assy. PGC OEM 6000-1559
ACE4 Power Supply Meanwell PS45-24 1607-0024
Circuit Breaker,1 Pole, 2AMP Siemens 5SX2102-8 0426-1020
Circuit Breaker,2 Pole, 2AMP Siemens 5SX2202-8 0426-2020
Compressor Copeland CS14K6E-TFD-230 1510-0298
Contactor Siemens 3RT1025-1BB40 0419-0948
Damper Drive Motor Actuator Belimo OEM 1608-
0916A
Door, Spray Chamber, Inner PGC N/A 6000-0303
Door, Spray Chamber, Outer PGC N/A 6000-0392
Evaporator Coil, 5/8 OD x .032 wall Super Radiator Co. OEM 1244-0066
Filter Bag,5 Micron, Polyester McMaster-Carr 9316T22 0215-1800
Fuse, Door Heat 5A Bussman FNM5 0409-0123
Gasket, Return Duct Transition
Box, 140” Refrig. Hardware 47-131 1604-0101
Gasket, Spray Chamber Inner
Door, 95” Refrig. Hardware 47-131 1604-0101
Gasket, Spray Chamber Outer
Door, 95” Refrig. Hardware 47-131 1604-0101
Gasket, Supply Duct Transition Box Refrig. Hardware 47-131 1604-0101
Heater, Air Vulcan OEM 0416-0508
Heater, Water Watlow OEM 0416-0599
Hour meter, UV Durant E42DIR48230 0215-2821
HygroClip Connector and Cable,
5 meters, amplified analog, 0ºC to
100ºC
PGC MOK-05-XX-005V-1-
DIO 1636-0159
HygroClip Micro Controller PGC Hygro 503 N/A
HygroClip T/Rh Transmitter,
Full-Range Calibration PGC OEM 1608-0865b
HygroClip T/Rh Transmitter,
Single-Point Calibration PGC OEM 1608-0865a
HygroClip T/Rh Transmitter, Un-
calibrated Rotronic HygroClip S 1608-0865
HygroPalm Calibration Cable PGC AC1620-modified 1609-0866
HygroPalm Calibrator Rotronic HygroPalm 2 1609-0865
Latches, Access Panel Southco 62-43-251-3 1008-0080
Latches, Inner Doors Southco OEM 1001-0082
Latches, Outer Doors McMaster-Carr 5481K19 1009-1017
Mist Eliminator PGC N/A 5000-0135
Motor Protector Siemens 3RV1021-1KA10 0427-1250
Motor Protector Siemens 3RV1021-0GA10 0427-0063

PGC Inc. Horizontal 500-1000 CFM June 2006
Parameter Generation and Control, Inc. 15
Description Mfg. / Supplier Mfg./Supplier # PGC #
Motor Protector Siemens 3RV1021-1BA10 0427-0200
Motor, Blower Continental Fan RO-TMK280-2-34 1602-0199
Pump March TE5.5CMD 1619-0091
Refrigeration Dryer, Filter Sporlan CW-165S 0215-0887
Relay , Solid State, Door Heat Omron G3NE-210T-US 0416-0414
Relay, Solid State, 4-28 VDC Continental RVDC/6V25 0416-0403
Sensor , Door Jamb Temperature JMS Southeast OEM 1607-0652
Sensor ,Water Temperature JMS Southeast 3ESCK6BZZ3120JYT
A
1619-0862
SmartPad™ controller PGC OEM 1607-1100
SmartPad™ Micro Controller PGC Spad 503D N/A
Spray Nozzle Spraying System NO. 1/4A-SS5-15. 1612-0201
Stepper Micro Controller PGC Step 503 (SDR3) N/A
Strainer, Bronze “Y” McMaster-Carr 43935K24 0215-0904
Supply Duct Transition, 10” Round PGC N/A 5000-1389
Surge Suppressor Siemens 3RT1936-1TR00 0419-0891
Switch, Float Gems LS1750-192-908 0421-0060
Switch, Hi-Lo Refrig Pressure Copeland 085-CP2M-7K 0423-0683
Thermostat, Safety Thermtrol TS-120SR 30F-240F 1636-0223
Timer, Chamber Light Intermatic FF60MC 0419-0355
Transformer Micron B100MBT713XK 0419-0326
UV Lamp Severn Trent Water 5340UD 0215-2825
UV Lamp Power Supply Severn Trent Water 20697UD 0215-2831
UV Lamp Quartz jacket Severn Trent Water 2450UD 0215-2824
UV Plastic Support PGC OEM 0215-2826
Valve, Expansion, Body Danfoss 068U2287 0215-0872
Valve, Expansion, Cartridge Danfoss 068U1037 0215-0777
Valve, Hot Gas Temp Control Sporlan SDR-3-20-S 0215-0873
Valve, Sump Float Hawkeye Steel
Products UFV600 0209-0050

Parameter Generation and Control, Inc
Precise Humidity Control
www.humiditycontrol.com [phone]
[email protected]om Fax [phone] [phone]
Black Mountain, North Carolina
Notes:
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PGC, Inc 500-1000 CFM Air Handler May 2006
Appendix A A-1
Appendix A
System Construction ................................................................................................................... 2
Theory of Operation.................................................................................................................... 3
Description of Operation............................................................................................................. 4
Measurement of Test Chamber Conditions ............................................................................ 4
Air Flow.................................................................................................................................. 4
Water Flow ............................................................................................................................. 5
Temperature Controls ............................................................................................................. 5
Description of Circuitry .............................................................................................................. 7
Safety Devices............................................................................................................................. 9
Troubleshooting ........................................................................................................................ 12
Operating Range of the System. ........................................................................................... 12
Water Temperature ...............................................................................................................12
Air Temperature.................................................................................................................... 13
Water Level .......................................................................................................................... 13
Rh Control ............................................................................................................................ 14
Maintenance .............................................................................................................................. 15
Preventive Maintenance Schedule........................................................................................ 15
Automatic Damper Motor Adjustments ............................................................................... 18
Calibration ............................................................................................................................ 18
Calibration ............................................................................................................................ 19
Calibration, Air/Rh ............................................................................................................... 19
Water Temperature Calibration ............................................................................................ 22

PGC, Inc 500-1000 CFM Air Handler May 2006
Appendix A A-2
SYSTEM CONSTRUCTION
The 500-1000 CFM Conditioner consists of four main sections:
1. Conditioning Compartment: spray bypass damper, blower, spray eliminators, spray
jets, water sump, low water level safety float switch, process water float valve, stirring
jet, evaporator coil, and particulate filter
2. Mechanical Compartment (side access panels): refrigeration condenser, compressor,
receiver, , high- and low-pressure safety switches, filter/dryer, hot gas bypass valve,
water pump, water heater, water RTD, Programmable Logic Controller (PLC), and power
panel with terminal strips, circuit breakers, motor starter, and contactors
3. Conditioner Exterior: sump drain valve, air bypass damper actuator, UV filter, and air
temperature safety thermostat.
4. Control Enclosure: SmartPad™ user interface and optional chart recorder.
The unit is sturdily constructed, with a stainless steel interior and exterior, and insulated door
with heavy refrigerator-type latches and vapor-resistant seals. Double walls separated by
insulation are used around the conditioning chamber. All internal seams are welded to preclude
saturation of the insulation.
The spray tree is a 3” stainless steel tube (spray header) with spray nozzles attached along the
sides, and a clamp on each end for sealing the tube. The clamp on the right end secures a blank
plate against an O-ring gasket. A UV lamp is inserted from the electrical compartment, through
the plate on the left end.

PGC, Inc 500-1000 CFM Air Handler May 2006
Appendix A A-3
THEORY OF OPERATION
PGC’s method of control is the
same for both reach-in
chambers and conditioning
systems. The environment to be
conditioned is controlled at a
targeted dew point temperature,
and then reheated to the desired
air temperature. This
methodology follows a proven
technique that maintaining a
constant dew point and air
temperature will produce a very
constant relative humidity. The
desired air temperature and
relative humidity or water
temperature are set via the
SmartPad™. If equipped with
an optional recorder, it can be
wired to record the actual air
temperature and relative
humidity or water temperature.
The air is cooled by means of a
water spray which constantly
sprays water across the air
stream, saturating the air. A
submerged refrigeration
evaporator coil operates 1°C-
2ºC (1.8°F-3.6°F) below the
desired dew point and cools the
water that is sprayed across the
air stream. The air is then re-
heated before it is returned to
the test chamber.
NOTE Dew point is the temperature at which the air can contain no more moisture and
some moisture begins to condense.
A portion of the air can be diverted around the water spray saturator by a bypass damper. If the
air does not pass through the water spray, it will not be cooled; if the air is not cooled, it will not
require as much (if any) air heat to be applied before it is returned to the test chamber. The
amount of air that passes through the saturator, or bypasses the saturator, is determined by the air
temperature control loop.
Mechanical
Sprayed Coil
Supply Air
Blower
Air Filter
Return Air
Dampers
Figure A-1 - Generic Conditioning Unit

PGC, Inc 500-1000 CFM Air Handler May 2006
Appendix A A-4
DESCRIPTION OF OPERATION
The 500-1000 CFM Conditioner is a self-contained conditioner designed to control dry-bulb
temperatures over a range of 7°C – 60°C (44.6ºF - 140ºF), dependent upon the size and
construction of the test chamber. The dry-bulb temperature is held to ± 0.2°C and relative
humidity constancy to ± 0.5% with dew points above 5°C (41°F).
The temperature of the water spray saturator controls the dew point of the discharge air. When in
Rh Cascade or Slow Damper mode, the water temperature in the saturator is varied slowly in
response to a humidity control system. This allows the system to respond to wide load variations
while retaining the basic stability of a spray system. When in Two-Temperature mode, the user
establishes the air and water temperatures.
MEASUREMENT OF TEST CHAMBER CONDITIONS
Precise control of temperature and humidity within the test chamber is obtained by accurately
measuring the dry-bulb temperature and the dew point temperature of the air in the test chamber
or the duct. The temperature of the water in the spray chamber controls the dew point
temperature, and is measured prior to the spray nozzles.
When operating in one of the spray modes, the dew point of the air exceeds the water temperature
by approximately 1°C for each 10°C difference between the air and water temperatures. During
the ramp portion of program cycling, the dynamic heat exchange process that takes place makes it
difficult to establish any exact relationship. When operating in the Two-Temperature mode, refer
to the air/Rh/water spray graph provided with the unit for air and water temperatures necessary
for the desired relative humidity.
AIR FLOW
As the air enters the conditioner through the round, flexible duct connection in the removable top
cover. The process blower, located beneath this cover, will force the air into the conditioning
section. Entering the conditioning section, the air first encounters the by-pass damper; the
damper determines the volume of air that enters the saturator, and the volume that is bypassed
around the saturator. When the damper is fully closed, all of the air is forced through the water
spray. As the air passes through the water spray, it is saturated and cooled, nearly to the water
temperature. This method provides a stable dew point for the air as it leaves the saturator section.
The chilled and saturated air then passes through the water droplet eliminator to remove any free
moisture that may be present. The air then continues over the dry-bulb heaters, where it is heated
to the desired chamber air temperature (without affecting the dew point) and is returned to the
chamber through the round, flexible duct connection on the left end of the conditioner.
When the damper is fully open, most of the air bypasses the water spray and travels directly to the
air heaters. The bypassed air is then mixed with any air that traveled through the saturator section
and then returns to the test chamber. The spray bypass damper will be automatically positioned
by the actuator operating on a control signal derived from the duty cycle of the air heater. The
position of the damper can range from 0% to 100% open.
The dew point of the air stream is controlled even when most of the air is bypassed around the
water spray saturator. The air bypass damper is not 100% efficient, allowing some air to enter the
water spray saturator even when closed.