model C23 / C24 pneumatic controllers
GENERAL INFORMATION
CSC–2000 Series Overview
The CSC–2000s are differential-pressure (dP), submaster controllers with adjustable minimum and maximum airflow settings. A master controller, typically a room thermostat, resets the CSC velocity setpoint.
CSC–2000s are available as direct acting for normally open VAV terminal units, and reverse acting for normal closed VAV terminal units. Each unit is equipped with separate adjustment knobs for minimum and maximum airflow settings. Calibrate all models using standard airflow measuring equipment.
The spring range of the actuator does not matter to the controller. However, sufficient main air is required to provide the actuator with enough force to operate the damper/linkage.
Any sequencing with other controllers, valves, or pneumaticelectric relays must be sequenced with the controller’s reset range, not the actuator’s spring range.
These controllers are typically used on single-duct applications but may be found in dual-duct applications. When working on dual-duct applications it may be necessary to work on one duct at a time while closing off the other.
The CSC–2000 series controllers are position sensitive. See the
Mounting section for the proper vertical/horizontal orientation for the different models.
CAUTION
Pneumatic devices must be supplied with clean, dry control air.
Any other medium (e.g., oil or moisture contamination) will cause the device to fail.
Connections Adjustments
B
B-3
model C23 / C24 pneumatic controllers
B
MODELS AND SPECIFICATIONS
O utput Sensitivity 0 to 1" range unit,
5 psig/0.02" wg (35 kPa/5 Pa)
0 to 2" range units,
5 psig/0.04"wg (35 kPa/10 Pa)
Main Air Pressure
Max. Signal Pressure
Material
15 to 30 psig (103 to 207 kPa)
6" wg (1493 Pa) applied to either port (X or Y)
ABS (beige or gray)
UL Flame Class 94 HB
0 to supply pressure
7.5 oz. (213 grams)
Output Capability
Weight
Temperature Limits
Operating 40° to 120° F (4° to 49° C)
Shipping –40° to 140° F (–40° to 60° C)
The table below illustrates the appropriate model for each application.
Direct Acting BEIGE units (C23) are designed for normally open dampers with direct-acting thermostats for cooling and reverse-acting thermostats for heating.
FLOW CHARACTERISTICS
High Setting
Low Setting
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Thermostat Pressure
Reverse Acting GRAY units (C24) are designed for normally closed dampers with reverse-acting thermostats for cooling and direct-acting thermostats for heating.
FLOW CHARACTERISTICS
High Setting
F
Low Setting
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Thermostat Pressure
Direct Acting (Beige Controllers) for Normally Open Dampers
Model
Thermostat Required
For
Cooling
For
Heating
Setpoint Range
Minimum Maximum
Reset Pressure
Band
Air Consumption
C23
Direct
Acting
Reverse
Acting
0 to 1.0" wg
(249 Pa)
Min. plus 1" wg (249 Pa)
8 ±0.5 to 13 psig
(55 ±3.5 to 90 kPa)
14.4 scim @ 20 psig
(3.93 mL/s @ 138 kPa)
Model
C24
Reverse Acting (Gray Controllers) for Normally Closed Dampers
Thermostat Required
For
Cooling
For
Heating
Setpoint Range
Minimum Maximum
Reset Pressure
Band
Air Consumption
Reverse
Acting
Direct
Acting
0 to 1.0" wg
(249 Pa)
Min. plus 1" wg (249 Pa)
3 ±0.5 to 8 psig
(21 ±3.5 to 55 kPa)
14.4 scim @ 20 psig
(3.93 mL/s @ 138 kPa)
B-4
model C23 / C24 pneumatic controllers
MOUNTING
As close to the flow sensor pickup as is feasible, fasten the mounting bracket to the mounting surface with two selfthreading screws in the two 3/16 in. (5 mm) holes. (Make sure to leave enough room to make connections.)
The CSC–2000 series are position sensitive:
• The minimum and maximum flow limits must be set
(calibrated) in the same position the controller will be mounted.
• May be mounted horizontally (preferred),with the adjustment knobs up or down, or mounted vertically (the diaphragm inside must be in a horizontal or vertical plane).
CONNECTIONS
Use 1/4 in. (6 mm) O.D. “FR” tubing for the following connections:
1. Connect the main air supply to port “M”.
2. Connect the actuator to port “B”.
3. Connect the thermostat to port “T”.
C23 Units
Use 3/8 in. O.D. “FR” tubing with a maximum length of 24 in.
to connect:
1. High pressure to port “X”.
2. Low pressure to port “Y”.
C24 Units
Use 3/8 in. O.D. “FR” tubing with a maximum length of 24 in.
to connect:
1. Low pressure to port “X”.
2. High pressure to port “Y”.
CAUTION
Pneumatic devices must be supplied with clean, dry control air.
Any other medium (e.g., oil or moisture contamination) will cause the device to fail.
B
Horizontal Mount
(Preferred, Knobs Up or Down)
Or Vertical Mount
B-5
B model C23 pneumatic controllers
ADJUSTMENTS, CALIBRATION, AND OPERATION OF
C23 CONTROLLERS
Adjustments and Calibration
1. Check that there is 0 psi at the “T” Port.
2. Use a flow hood or “tee” a Magnehelic® (or equivalent) differential pressure gauge between the controller and the dP pick-up.
3. The “LO” flow setting limit (center knob) must be set first.
Temporarily adjust the thermostat for a branch pressure lower than the 8 psig reset start point (minimum cooling); typically 6 psig or less is best. Removing the thermostat branch line would be another acceptable method. Adjust the
“LO” knob (center knob) clockwise to increase or counterclockwise to decrease dP limit. Normally one-half turn will cause a 0.1 dP change. Allow for reaction time.
Depending on actuator size and position, timing will vary. To position an actuator/damper from closed to open may take several minutes.
NOTE: If the “LO” flow setting limit must be set at“0” (zero minimum), do not turn the “LO” knob fully counterclockwise. The knob will adjust three to four full turns after a zero minimum is reached. Turning the “LO” knob fully counterclockwise will result in a negative reset condition. This means that when the controller is beginning to reset at 8 psig from the thermostat, it must first overcome the negative adjustment and will not begin to reset until a higher thermostat reset pressure is reached. This negative reset will also reduce the effective range of the controller by reducing the high end and narrowing the reset span. If a zero minimum is required, adjust the “LO” knob until the controller just begins to crack the damper open, then back-off one-fourth turn and verify zero airflow.
4. The “HI” flow setting limit (outer knob) must beset after the
“LO”. Temporarily adjust the thermostat for a branch pressure higher than the 13 psig reset stop point (maximum cooling); typically 17 psig or greater is best. Removing the thermostat branch line and teeing-in to the main air line would be another acceptable method. Adjust the “HI” knob
(outer knob) clockwise to increase or counterclockwise to decrease dP limit. Nominally one-half turn will cause a 0.1 dP change. Allow for reaction time.
5. Recheck the “LO” and the “HI” settings at least twice, verify settings, and fine tune each time if necessary. This procedure will remove internal component tensions and confirm settings.
6. Reconnect the thermostat branch line if necessary, and adjust the thermostat to the desired room temperature setpoint.
NOTE: The“HI” adjustment limits the travel of the reset mechanism. Therefore, the reset span will be less than
5 psig, the upper limit being less than 13 psig.
NOTE: Always make adjustments in the same plane/orientation as the one in which the unit will operate.
NOTE: No routine maintenance is required. Each component is designed and manufactured for reliability and performance. Careful installation and use will ensure long-term dependability.
NOTE: For information about C24 controllers see the
Adjustments, Calibration, and Operation of C24
Controllers section.
B-6
model C23 pneumatic controllers
PRESSURE INDEPENDENT OPERATION
Differential pressure is sensed via a dP pickup mounted upstream of the damper (VAV terminal inlet). The dP pickup is a dual pressure pickup sensing both high pressure and low pressure. The high pressure is connected to the “X” port and the low pressure is connected to the “Y” port. These two pressures are compared across the static diaphragm, which takes a position relative to the difference of the two pressures, the force of the LO limit adjustment spring in the upper chamber, and the force of the HI limit adjustment spring in the lower chamber.
Turning the “LO” knob clockwise (to increase) relaxes the LO limit adjustment spring, placing a lesser downward force on the diaphragm, reducing the pressure at the “B” port, and increasing airflow through the VAV terminal. Turning the “HI” knob adjustment spring counterclockwise positions the HI limit stop downward, limiting the travel of the piston cup, limiting the amount of reset, and setting the maximum airflow through the
VAV terminal.
When the “HI” knob is turned fully counterclockwise, the HI limit will equal the LO limit, and the controller will function as a constant volume controller.
An increase in airflow is sensed via the increase in dP across the static diaphragm, positioning the static diaphragm closer to the nozzle, increasing the “B” port pressure to the actuator, and decreasing airflow until the static diaphragm comes into balance at the desired dP setpoint.
A decrease in airflow is sensed via the decrease in dP across the static diaphragm, positioning the static diaphragm away from the nozzle, decreasing the “B” port pressure to the actuator, and increasing airflow until the static diaphragm comes into balance at the desired dP setpoint.
RESET OPERATION
With sufficient airflow and a thermostat signal connected to the
“T” port of less than 8 psig, the controller will position the actuator to regulate airflow at the LO limit setting. In this state, the static diaphragm is balanced over the nozzle through the forces of the opposing springs and forces of the high and low pressures.
When the thermostat signal increases above 8 psig, the piston cup will begin to position the reset lever upward, increasing the force of the HI limit spring, positioning the static diaphragm away from the nozzle, opening the damper for greater airflow, and requiring a higher dP to rebalance the static diaphragm.
The dP setpoint of the controller has been reset upwards with the increasing thermostat signal. The stroke of the piston cup is limited via the HI limit knob. Lowering the HI limit will reduce the top end of the reset span, narrowing the reset span. At each new dP setpoint, as dictated by the thermostat signal, the static diaphragm will again balance.
B
B-7
model C24 pneumatic controllers
B
ADJUSTMENTS, CALIBRATION, AND OPERATION OF
C24 CONTROLLERS
Adjustments and Calibration
1. Check that there is 0 psi at the “T” Port.
2. Use a flow hood or “tee” a Magnehelic® (or equivalent) differential pressure gauge between the controller and the dP pick-up.
3. The “HI” flow setting limit (center knob) must be set first.
Temporarily adjust the thermostat for a branch pressure lower than the 3 psig reset start point (maximum cooling); typically 1 psig or less is best. Removing the thermostat branch line would be another acceptable method. Adjust the
“HI” knob (center knob) counterclockwise to increase or clockwise to decrease dP limit. Normally one-half turn will cause a 0.1 dP change. Allow for reaction time. Depending on actuator size and position, timing will vary. To position an actuator/damper from closed to open may take several minutes.
4. The “LO” flow setting limit must be set after the“HI”.
Temporarily adjust the thermostat for a branch pressure higher than the 8 psig reset stop point (minimum cooling); typically 12 psig or greater is best. Removing the thermostat branch line and teeing-in to the main air line would be another acceptable method. Adjust the “LO” knob (outside knob) counterclockwise to increase or clockwise to decrease dP limit. Normally one-half turn will cause a 0.1 dP change.
Allow for reaction time.
5. Recheck the “HI” and the “LO” settings at least twice, verify settings, and fine tune each time if necessary. This procedure will remove internal component tensions and confirm settings.
6. Reconnect the thermostat branch line if necessary, and adjust the thermostat to the desired room temperature setpoint.
NOTE: The“LO” adjustment limits the travel of the reset mechanism. Therefore, the reset span will be less than
5 psig, the upper limit being less than 8 psig.
NOTE: Always make adjustments in the same plane/orientation as the one in which the unit will operate.
NOTE: No routine maintenance is required. Each component is designed and manufactured for reliability and performance. Careful installation and use will ensure long-term dependability.
PRESSURE INDEPENDENT OPERATION
Differential pressure is sensed via a dP pickup mounted upstream of the damper (VAV terminal inlet). The dP pickup is a dual pressure pickup sensing both high pressure and low pressure. The low pressure is connected to the “X” port and the high pressure is connected to the “Y” port. These two pressures are compared across the static diaphragm, which takes a position relative to the difference of the two pressures, the force of the HI limit adjustment spring in the upper chamber, and the force of the LO limit adjustment spring in the lower chamber.
Turning the “HI” knob counterclockwise (to increase) compresses the HI limit adjustment spring, placing a greater downward force on the diaphragm, increasing the pressure at the “B” port, and increasing air through the VAV terminal. Turning the “LO” knob adjustment spring counterclockwise positions the LO limit stop downward, limiting the travel of the piston cup, limiting the amount of reset, and setting the minimum airflow through the
VAV terminal.
When the “LO” knob is turned fully counterclockwise, the LO limit will equal the HI limit, and the controller will function as a constant volume controller.
An increase in airflow is sensed via the increase in dP across the static diaphragm, positioning the static diaphragm away from the nozzle, decreasing the “B” port pressure to the actuator, and decreasing airflow until the static diaphragm comes into balance at the desired dP setpoint.
A decrease in airflow is sensed via the decrease in dP across the static diaphragm, positioning the static diaphragm closer to the nozzle, increasing the “B” port pressure to the actuator, and increasing airflow until the static diaphragm comes into balance at the desired dP setpoint. 3.
B-8
model C24
RESET OPERATION
With sufficient airflow and a thermostat signal connected to the
“T” port of less than 3 psig, the controller will position the actuator to regulate airflow at the HI limit setting. In this state, the static diaphragm is balanced over the nozzle through the forces of the opposing springs and forces of the high and low pressures.
When the thermostat signal increases above 3 psig, the piston cup will begin to position the reset lever upward, increasing the force of the LO limit spring, positioning the static diaphragm away from the nozzle, closing the damper for less airflow, and requiring a lower dP to rebalance the static diaphragm.
The dP setpoint of the controller has been reset downwards with the increasing thermostat signal. The stroke of the piston cup is limited via the LO limit knob. Raising the LO limit will reduce the top end of the reset span, narrowing the reset span.
At each new dP setpoint, as dictated by the thermostat signal, the static diaphragm will again balance.
NOTE: For information about C23 controllers see the
Adjustments, Calibration, and Operation of C23
Controllers section. pneumatic controllers
B
B-9
