Installation guide

8
VAPOR-LOGIC
®
2
KEY PAD / DIGITAL DISPLAY OPERATION
Once in the Main Menu, use the SET key to scroll
through the items until the item you want is shown.
Use the UP and DOWN ARROW keys to change or set
the parameter.
A service timer is included as a reminder to perform
periodic maintenance and service to the humidifier. The
SERVICE timer display is included in VIEW and SCAN
displays. The SERVICE timer advances when the control
is in the AUTO mode. When the timer reaches zero, the
message SERVICE is added to the SCAN display. Once
the service timer has reached zero, it will continue to
count, but in a negative fashion to indicate how many
operating hours have elapsed since time out.
SENSING DEVICE PLACEMENT AND WIRING
Sensing Device Placement
The location of the humidity sensing devices is very
important to achieve accurate humidity control. A
drawing of a typical small air handling system is shown
below (figure 8-1). For the best control, place the
humidity sensing device in the center of room, or just
inside of the return air duct (location “A”). This will
provide the least amount of variation caused by air flow
patterns and room temperature. Placement of the duct
high limit humidity sensing device (location “D”) must be
downstream from dispersion tubes a sufficient distance to
ensure steam absorption has taken place. Accurate
control of temperatures in rooms and ducts is also very
important to improve control of relative humidity.
Control Precautions
Unsatisfactory humidifier control accuracy may involve
more than just the controller’s capability to control the
system. Other factors that may play a role in overall
system control accuracy are:
• Size of the humidification system.
• Overall system dynamics associated with mois-
ture migration time lags.
• Accuracy of humidistats and humidity transmitters
and their location.
• Dry bulb temperature accuracy in space or duct.
• Velocities and air flow patterns in ducts and space
environments.
• Electrical noise or interference.
Figure 8-1: Humidistat control or humidity and temperature transmitters recommended placement
LOCATION
A) Best
B) Fair
C) Poor
D) Best for duct high limit
humidistat
Outside Air
Relief Air
Return Air
B
AHU
Air Handling Unit
D
High limit humidistat or high limit transmitter
placement for VAV applications
Air flow switch
Steam absorption
has taken place
North or North-
East facing
window
Temperature compensation transmitter located on lower
corner of the inside surface of double pane window glass
B
A
A
B
B
C
OM-360
Point of steam
absorption