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DISCRETE OUTPUT/ANALOG INPUT CONTROL — The
discrete output is controlled as a function of a temperature
sensor connected to the 39L or 39NX unit. (Applicable sen-
sors are: space temperature sensor, outside-air temperature
sensor, mixed-air temperature sensor, supply-air tempera-
ture sensor, and return-air temperature sensor.) The discrete
output is turned ON/OFF as required to maintain the user
configured set point.
The controlling sensor is identified and its value is read.
The control determines which user-configurable control logic
(normal or reverse) is required.
The control compares the sensor value to the configured
set point.
If normal logic is used, the discrete output is turned ON
when the sensor value is equal to or greater than the set point.
This output is turned OFF when the sensor value is less than
the set point decreased by a user configurable hysteresis.
If reverse logic is used, the discrete output is turned ON
whenever the sensor value is less than the set point. This
output is turned OFF when the sensor value is greater than
the set point increased by a user configurable hysteresis.
DISCRETE OUTPUT, TIMECLOCK CONTROL — This
control sequence turns ON an output channel when the cur-
rent time of day is greater than or equal to the Occupied time
and less than the next Unoccupied time. This discrete output
is OFF at all other times. The output can be used for lighting
control, pump control, or to control other devices which have
to be ON during the Occupied period and OFF during the
Unoccupied period. This control sequence operates under its
own time schedule (Schedule II).
Using the local interface device or building supervisor, the
output may be overridden to extend the occupied period be-
tween 1 and 4 hours.
The control determines the output that is under time-
clock control. The current time of day is compared to the
Occupied time and to the next Unoccupied time. If the
current time of day is equal to or within the Occupied time
period, the discrete output is turned ON. If the current time
of day is equal to or within the Unoccupied time period, the
discrete output is turned OFF.
HUMIDITY (ANALOG OUTPUT) CONTROL — The hu-
midity analog output control adjusts the steam valve of the
steam grid humidifier. The valve is modulated to maintain
the desired space or desired return-air humidity set point,
depending on whether a wall-mounted or duct-mounted hu-
midity sensor is used. A duct high humidity switch is also
monitored and provides a user adjustable high limit safety.
If the supply fan is OFF, the steam valve is held closed.
If the supply fan is ON, and the unit is in the Unoccupied
mode, the valve is held closed.
If the supply fan is ON and the unit is in the Occupied
mode, the system determines the status of the duct high hu-
midity switch. If the duct humidity is above the switch set
point, the valve is held closed. If the duct humidity is less
than the switch set point, the control reads the humidity sen-
sor, compares the value to the set point and modulates the
output as required to satisfy conditions.
HUMIDITY (DISCRETE OUTPUT) CONTROL — The hu-
midity control sequentially adjusts a 2-stage humidifier. The
humidifier is controlled to maintain a desired space or return-
air humidity, depending on whether a wall-mounted or duct-
mounted humidity transmitter is used.
The first stage of humidification energizes the humidifier
spray pump (if applicable) along with the first stage of the
humidifier. The second stage of humidification energizes the
second stage of the humidifier.
A duct high humidity switch is also monitored and pro-
vides a user adjustable duct high humidity limit safety.
If the fan status is ON and the unit is in the Occupied
mode, the control reads the space or return-air humidity sen-
sor. If the humidity is 2% less than the humidity set point,
the first stage is turned ON.
If the humidity is 5% less than the humidity set point, both
stages are turned ON.
As the humidity increases, the stages are turned OFF as
follows: When the humidity is within 2% of the set point,
the second stage of the humidifier is turned OFF. When the
humidity is greater than or equal to the set point, both stages
are turned OFF. If the high humidity switch is tripped, all
stages of the humidifier are turned OFF.
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