9
Single-Duct and Retrofit Terminal Units IOM
the front sensor tap (away from the valve), and the low
pressure signal is delivered from the back line (near the
valve). The pressure differential between high and low
represents the amplified velocity pressure in the inlet
duct.
7. Read the differential pressure and enter the Krueger Inlet
Airflow Sensor Chart (Figure 6) to determine the airflow
in the terminal unit. For example, a differential pressure
of 0.10 in. wg for a size 8 unit yields an airflow of 290 cfm.
BALANCING PROCEDURE
(CONTROL SEQUENCES 1102 AND 1103)
Direct Acting Thermostat:
Normally Open Damper (Control Sequence 1102)
1. Minimum Volume Setting:
b. Disconnect the thermostat line from the volume
controller.
c. Adjust the minimum volume control knob (marked
LO and located in the center of the controller) to
achieve the required minimum flow. To determine the
required pressure differential, refer to Table 1, Table
2, and the Krueger Inlet Airflow Sensor Chart that is
provided on the side of the VAV unit and in Figure 6.
d. Reconnect the thermostat line.
2. Maximum Volume Setting:
c. Disconnect the thermostat line from the volume
controller.
d. Apply 15 + psi to the thermostat port on the volume
controller (marked “T”) by tapping into the main air
pressure line.
e. Adjust the maximum volume control knob (marked
HI and located at the side of the controller) until the
desired pressure differential is registered on the
manometer. To determine the required pressure
differential, refer to Table 1, Table 2, and the Krueger
Inlet Airflow Sensor Chart that is provided on the side
of the VAV unit and in Figure 6.
f. Reconnect the thermostat line.
Reverse Acting Thermostat:
Normally Closed Damper (Control Sequence 1103)
1. Maximum Volume Setting:
b. Disconnect the thermostat line from the velocity
controller.
c. Adjust the maximum volume control knob (marked
HI and located in the center of the controller) to
achieve the required minimum flow. To determine the
required pressure differential, refer to Table 1, Table
2, and the Krueger Inlet Airflow Sensor Chart that is
provided on the side of the VAV unit and in Figure 6.
d. Reconnect the thermostat line.
2. Minimum Volume Setting:
c. Disconnect the thermostat line from the velocity
controller.
d. Apply 15 + psi to the thermostat port on the volume
controller (marked “T”) by tapping into the main air
pressure line.
e. Adjust the minimum volume control knob (marked
LO and located at the side of the controller) until
the desired pressure differential is registered on
the manometer. To determine the required pressure
differential, refer to Table 1, Table 2, and the Krueger
Inlet Airflow Sensor Chart that is provided on the side
of the VAV unit and in Figure 6.
f. Reconnect the thermostat line.
BALANCING PROCEDURE
(CONTROL SEQUENCES 1104-1110)
1. Damper action is factory set at N.O. (normally open), or
N.C. (normally closed). To change perform the following
steps:
b. Loosen the damper selection screw.
c. Turn the selection dial clockwise until the NC or NO
arrow aligns with the DAMPER arrow.
NOTE:
Accuracy in the alignment of the arrows is very
important. Make this adjustment as exact as possible.
(See Figure 8)
4. Pipe the controller: Connect port “B” to the damper
actuator. Connect port “M” to the clean, dry main air.
Connect port “T” to the thermostat output. Connect
port “H” to the total pressure tap on the airflow sensor.
Connect port “L” to the static pressure tap on the airflow
sensor. The controller can be set up for cooling or heating
applications using either a Direct Acting (DA) or Reverse
Acting (RA) thermostat signal. The two flow adjustments
are labeled LO STAT ΔP and HI STAT ΔP.
TO THERMOSTAT BRANCH SIGNAL
(RESET SIGNAL)
RESET START POINT ADJUSTMENT
(FACTORY SET @ 8PSI)
TO STATIC PRESSURE
PUSH ON NIPPLES
FOR 3/16” (5) I.D.
FR TUBING (5)
H
L
T
B
M
G
WO
NC
TO DAMPER
ACTUATOR
DAMPER
HI STAT
LO STAT
RESET START
RESET SPAN
TO MAIN AIR
SUPPLY
LOOSEN SCREW TO
CHANGE DAMPER ACTION
(SUPPLIED IN N.O. POSITION)
GAUGE TAP. LEAVE CAP ON UNLESS
CONNECTING GAUGE FOR RESET
START OR RESET SPAN ADJUSTMENT
DAMPER ACTION SELECTION
(FACTORY SET @ NORMALLY OPEN)
NOTE: SCREW MUST BE TIGHT AND ARROWA
IN PERFECT ALIGNMENT FOR DEVICE TO FUNCTION PROPERLY.
DIFFERENTIAL PRESURE (FLOW)
LIMIT ADJUSTMENT WHEN T’STAT
PRESSURE IS HIGH (HI STAT)
(FACTORY SET @ 0.65” W.C.)
- FILED ADJUSTMENT REQUIRED
DIFFERENTIAL PRESURE (FLOW)
LIMIT ADJUSTMENT WHEN T’STAT
PRESSURE IS LOW (LO STAT)
(FACTORY SET @ 0” W.C.)
ALL ADJUSTMENT CCW TO INCREASE
(1/8”-5/32” FLATBLADE SCREWDRIVER)
RESET SPAN ADJUSTMENT
(FACTORY SET @ 5 PSI)
TO TOTAL PRESSURE
(DIFFERENCE IS DIFFERENTIAL
PRESSURE, OR DEVICE
VELOCITY PRESSURE)
Figure 8 – CSC 3011