York J Series - Fig. 13 - Oad Minimum Position Reset

FORM 100.50-NOM7 (808)
31
JOHNSON CONTROLS
3
100%
80%
60%
40%
20%
0%
0%
50%
100%
OUTPUT TO VFD
OAD MINIMUM POSITION
2
4
3
1
Note:
For units congured for Constant Volume Operation, the OAD
Min Position #2 setting will be ignored and only OAD Min Position
#1 will be used to set the Minimum Position of the outside air
damper.
FIG. 13 – OAD MINIMUM POSITION RESET
LD06562
OAD MIN. OAD MIN.
CURVE
POSITION #1 POSITION #2
1 10%
2
25%
25%
3 50%
4 80%
Demand Ventilation
Demand Ventilation is a control sequence that can in-
crease or decrease the amount of ventilation introduced
to the building based on ventilation demand. The de-
mand for ventilation will be determined by comparing
the level of CO
2
in the building to the Demand Venti-
lation Setpoint. The CO
2
level in the building will be
measured by an appropriate CO
2
sensor connected to
the unit.
The Demand Ventilation control sequence will only be
allowed to function if:
• The IAQ Sensor Enable setting is set to ON.
• The unit is equipped with an economizer and Econ-
omizer Enable = ON.
• The Airow Meas Cong conguration is = 0 or 1
(Minimum or 1/4-3/4 congurations not installed
or not enabled).
• Occupancy status is = Occupied.
Demand Ventilation control will operate in both heating
and cooling modes and will increase the position of the
economizer (OA Damper) from the minimum position
or the control positions of economizer or economizer
loading as required to meet the Demand Ventilation
Setpoint.
Sensor
If all conditions are met, the control will look for an
attached CO
2
sensor at the appropriate AI. The reading
at the AI will be used along with the IAQ Sensor Span
setting to determine the building CO
2
level.
If the CO
2
level indicated at the AI is out of range, the
controller will interpret the reading as a sensor failure
and generate a Trouble Fault. Demand Ventilation con-
trol sequences will not be allowed if the CO
2
sensor is
determined to be unreliable.
Algorithm
An appropriate algorithm will be used for Demand
Ventilation control. A step and wait algorithm with the
following characteristics is preferred:
• Step size is a function of the dierence between
the measured IAQ (CO2) level and the Demand
Ventilation Setpoint.
• Step time is xed.
The Demand Ventilation operation will have the fol-
lowing constraints:
The maximum OA Damper position for the Demand
Ventilation operation will be equal to the (MAX DV
MultiplIer) * (OA Damper Min Pos #1).