Installation guide
1BHFt%3*45&&.7BQPSMPHJD
3
Installation and Operation Manual
VAV control
With VAV control, the system is equipped with a duct RH
transmitter. This transmitter monitors the RH in the duct
downstream from the steam dispersion unit and transmits the duct
RH to the Vapor-logic
3
controller. The controller then compares the
measured duct RH with the high limit set point (Duct High Lim
RH), which is entered through the keypad/display in the Set Up
screen. If the measured duct RH comes within 6% of the duct high
limit set point, the system output is proportionally throttled back.
If the duct RH reaches the duct high limit set point, the humidifier
is completely disabled. When any reduction in system output occurs
due to the VAV control, the “VAV Output Limit” message appears
on the Idle screen. When the measured duct RH is more than
6% below the duct high limit set point, normal system operation
is restored automatically, and the “VAV Output Limit” message
disappears from the Idle screen.
Temperature compensation control
With temperature compensation (temp comp) control, the system is
equipped with a window temperature transmitter. This transmitter
monitors interior double-pane window glass temperature and
transmits this temperature to the Vapor-logic
3
controller.
The controller
assumes a 70 °F (21 °C) room temperature and uses
the glass temperature and the RH in the space being controlled to
calculate the dew point temperature for the space.
As the window glass temperature decreases and approaches the
dew point of the room, the RH set point decreases automatically
to prevent moisture from forming on the windows. The modified
RH set point appears on the Idle screen. An asterisk (*) appears
next to the modified RH set point, denoting that temp comp has
taken control of the RH set point, and the “*Temp Comp” message
appears on the Idle screen.
Once the window temperature rises, the original RH set point is
restored. The temperature compensation option is available only
when the system is equipped with an RH transmitter. It is not
available when a remote humidistat or building automation system
is used to control the humidifier.
VAV, temp comp control operation
VL3_IOM.pdf 74 11/19/2009 9:11:16 AM