eating Coil
Aux Temperature
(Discharge Air)
(Optional)
IN-7
This application bulletin describes the sequence of operation used by the ASIC/1-
8055 to control zone temperature with a dual duct VAV system with or without
blending. The ASIC/1-8055 uses an primary airflow sensor to give pressure
independent control of the variable air volume cooling. It uses an secondary airflow
sensor to give pressure independent control of the variable air volume heating. If
the blending personality is selected, then the cooling and heating airflow are
modulated, so that a minimum total airflow is maintained. The ASIC/1-8055 is
preprogrammed with two dual duct personalities.
Dual Duct Personalities
Without
Blending
With
Blending
Dual Duct
14
15 Dual Duct VAV
Inputs
January 1999
APB 64-2 Dual Duct VAV
ASIC/1-8055 Applications
DOC-1472 (11/18/96)
Inputs
The ASIC/1-8055 controller has specific inputs for zone temperature, primary
cooling airflow, and secondary heating airflow, and optional supply air temperature,
and optional occupancy sensor. The default input types are set at the factory.
Inputs that are not required for the sequence may be used for monitoring.
Primary Airflow
The ASIC/1-8055 uses an primary airflow sensor to give pressure independent
control of the cooling air volume. The primary airflow sensor is installed on input
4 in the pin-sockets at AIR1. It is calibrated at zero airflow.
The controller measures the air velocity in feet per minute (ft./min) assuming a
standard velocity K-factor of 2338 ft/min. The velocity K-factor is the air velocity in
ft/min required to generate a velocity pressure of 1 inch water column (1 "wc =249
Pa) The velocity K-factor is provided by the VAV box manufacturer for a particular
box size and flow cross. The airflow volume Q in CFM is calculated based on the
actual K-factor in feet per minute , and duct area in square feet.
Q (CFM) = Area (ft
2
)*Velocity(ft/min)*(K-factor/2338)
Field calibration of the velocity K-factor can be done by the air balancer using the
air balance screen on the Setup software.
Note: Both airflow sensors require an airflow filter, AF-001, on the high
pressure side, to prevent dust from contaminating the sensor. The High
and Low pressure sides are opposite to that of the ASIC/1-8015 controller!
Secondary Airflow
The secondary airflow is required for dual duct personalities. The secondary airflow
sensor is used with a properly positioned airflow cross to control the heating air
volume. A secondary airflow sensor may installed on input 5 in the pin-sockets at
AIR2. It is calibrated at zero airflow and has separate K-factors and duct areas.
Wall Sensor Connections
Zone temperature sensor is normally on input 1. Typically, the zone temperature on
the WS-0xx, or WT-0XX wall sensor, is connected to the controller using a SCP-
XXX sensor cable sensor. Alternately, a zone or return air temperature sensor may
be attached on input blade, IN1. If there is no zone temperature sensor , then the
zone sensor input is in fault, all outputs are off, and it does not try to control.
The afterhours push-button on the WT-0XX, or WS-0X1 wall sensor if used, is
always on input 2. If Afterhours Enable is Yes, then shorting the input to zero will
initiate afterhours override mode for an Afterhours Time Allowed.
Input 2 may be used for the user adjust switch on the WT-0XX Wall Sensor . When
User Adjust Enable is set and input 2 is configured for user adjust switch, the zone
temperature setpoint may be adjusted up or down by the User Adjust Setpoint, based
on the condition of Input 2.
Input 3 is used for Interlock and may be used for variable user adjust with the WS-
0XX wall sensor. When User Adjust Enable is set and input 3 is configured for
Variable User adjust, 10k to 30 kohm, the zone temperature setpoint may be
adjusted up or down by the User Adjust Setpoint, based on the condition of input 3. Dual Duct VAV
Control Mode
January 1999
DOC-1472 (11/18/96)
ASIC/1-8055 Applications
Dual Duct VAV APB 64-3
Auxiliary Temperature Sensors
An optional a duct temperature sensor, TS-DO, may be placed on input 6, 7, or 8
for temperature monitoring. The auxiliary temperature sensors use the factory
provided 1.82 kohm pull-up resistor.
An optional occupancy sensor or switch may be used on input 8 to change the
control state from occupied to unoccupied. When the occupancy sensor is used in
combination with a temperature sensor, then the temperature sensor is not read
when the contacts are closed.
Control Mode
The controller determines the Control Mode, Heating, Deadband, or Cooling by
comparing the zone temperature to the Active Heating Temperature Setpoint and
Active Cooling Temperature Setpoint.
66
70
68
72
74
76
78
Deadband
Mode
Cooling Mode
Heating Mode
Active Cooling Setpoint
Active Heating Setpoint
deg. F
The controller enters the Cooling Control Mode when the zone temperature equals
or is greater than the Active Cooling Temperature Setpoint . The control reenters
the Deadband mode, when the zone temperature is 1
o
F below the Active Cooling
Temperature Setpoint and the calculated Cooling Requirement is equal to zero.
The control enters the heating mode when the zone temperature is equal to or less
than the Active Heating Temperature Setpoint. The control reenters the Deadband
mode when the zone temperature is 1
o
F greater than the Active Heating
Temperature Setpoint and the calculated Heating Requirement is equal to zero.
Active Temperature Setpoints
The controller maintains the zone temperature between Active Cooling and Heating
Temperature Setpoints. The Active Cooling and Heating Temperature Setpoints are
based on Control State, the Active User Adjust based on the position of the User
Adjust Switch or Variable User Adjust, and the Active Demand Limit Reset.
If User Adjust Enable is set, the Active Temperature Setpoints may be modified
either by the User Adjust Switch on a WT-0XX wall sensor, or by the variable user
adjust potentiometer on a WS-0XX wall sensor depending on the input
configuration. The Active Heating Temperature Setpoint is adjusted up and the
Active Cooling Temperature Setpoint is adjusted down a fraction of the User Adjust
Setpoint.
If the Active Demand Level is non-zero, the Active Temperature Setpoints are also
modified by a fraction of the Demand Reset Range as the Active Demand Level
goes from 0 to 6. The Active Cooling Temperature Setpoint is reset upwards and
the Active Heating Temperature Setpoint is reset downwards. Dual Duct VAV
Control Mode
January 1999
APB 64-4 Dual Duct VAV
ASIC/1-8055 Applications
DOC-1472 (11/18/96)
Cooling and Heating Requirement
In Deadband Control Mode, the Heating and Cooling Requirements are zero.
In the Cooling or Heating Control Mode, the Cooling or Heating Requirement is
calculated using a PI control loop.
The change in heating or cooling requirement is calculated every 30 seconds.
In heating: Error = Active HTG SP - Zone Temp Error = Previous Zone Temp - Zone Temp
or in cooling: Error = Zone Temp - Active CLG SP
Error = Zone Temp - Previous Zone Temp. Requirement = (100%/ThrottleRange)*[ Error*(CalcTime/Int Time) + Error]
The factory setting for throttle range is 4.0 degrees, and for integral time is 2.5
minutes.
Cooling Airflow Modulation
When in the cooling mode the controller modulates Primary Airflow Setpoint is
modulated between the Active Cooling Minimum and Maximum Airflow Setpoints
as the Cooling Requirement goes from zero to 100 %.
If blending is used (personality 15) in the Cooling Mode, the heating airflow is
modulated so that the total delivered airflow does not fall below the Total Minimum
Airflow Setpoint. If blending is not used (personality 14) the heating damper is
CLOSED.
66
70
68
72
74
76
78
HTG Min Airflow
Cooling Mode
Heating Mode
Active Cooling Setpoint
Active Heating Setpoint
deg. F
CLG Min Airflow
HTG Max Airflow
CLG Max Airflow
Cooling Airflow
Temperature
Heating Airflow
Without Blending
Heating Airflow Modulation
When in the heating mode the controller modulates Secondary Airflow Setpoint is
modulated between the Active Heating Minimum and Maximum Airflow Setpoints
as the Heating Requirement goes from zero to 100 %.
If blending is used (personality 15) in the heating mode the cooling airflow is
modulated so that the total delivered airflow does not fall below the Total Minimum
Airflow setpoint. If blending is not used (personality 14) the cooling damper is
CLOSED. Dual Duct VAV
Control Mode
January 1999
DOC-1472 (11/18/96)
ASIC/1-8055 Applications
Dual Duct VAV APB 64-5
66
70
68
72
74
76
78
HTG Min Airflow
Cooling Mode
Heating Mode
Active Cooling Setpoint
Active Heating Setpoint
deg. F
CLG Min Airflow
HTG Max Airflow
CLG Max Airflow
Cooling Airflow
Temperature
Heating Airflow
With Blending
Total Airflow SP
Deadband Airflow Modulation
In Deadband Control Mode, the controlling airflow is maintained at Active Cooling
Minimum Airflow Setpoint or Active Heating Minimum Airflow Setpoint
depending on the position of zone temperature with respect to Deadband midpoint
and direction of temperature change.
When entering Deadband from Cooling, cooling is the controlling airflow and the
heating is the blending airflow. The controlling Cooling airflow remains at
Cooling Minimum Setpoint until the zone temperature falls 1
o
F below the midpoint
between the Heating and Cooling Temperature Setpoints. If the zone temperature
falls 1
o
F below the midpoint between the Heating and Cooling Temperature
Setpoints, then heating air becomes the controlling airflow, and cool