26
VAPOR-LOGIC
®
VERSION 6 INSTALLATION AND OPERATION MANUAL
mc_060508_0750
INSTALLATION
HUMIDISTAT AND SENSOR LOCATIONS ARE CRITICAL
Humidistat and sensor location have a significant impact on humidifier
performance . In most cases, do not interchange duct and room humidity
devices . Room humidity devices are calibrated with zero or little airflow;
whereas duct humidity devices require air passing across them .
Recommended sensor locations (see Figure 27):
A Ideal . Ensures the best uniform mix of dry and moist air with stable
temperature control .
B Acceptable, but room environment may affect controllability, such as when
sensor is too close to air grilles, registers, or heat radiation from room
lighting .
C Acceptable . Provides uniform mixture of dry and moist air . If extended time
lag exists between moisture generation and sensing, extend sampling time .
D Acceptable (behind wall or partition) for sampling entire room if sensor is
near an air exhaust return outlet . Typical placement for sampling a critical
area .
E Not acceptable . These locations may not represent actual overall conditions
in the space .
F Not acceptable . Do not place sensors near windows, door passageways,
or areas of stagnant airflow .
G Best sensing location for a high-limit humidistat or humidity transmitter and
airflow proving switch .
Other factors affecting humidity control
Humidity control involves more than the
controller’s ability to control the system . Other
factors that play an important role in overall
system control are:
• Size of humidification system relative to
load
• Overall system dynamics associated with
moisture migration time lags
• Accuracy of humidistats and humidity
transmitters and their location
• Dry bulb temperature accuracy in space
or duct
• Velocities and airflow patterns in ducts
and space environments
• Electrical noise or interference
Step 1 – Field wiring: Sensor placement
