Specifications

16
VAPORMIST INSTALLATION, OPERATION, AND MAINTENANCE MANUAL
INSTALLATION
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
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SENSOR LOCATION IS CRITICAL
Sensor location has a significant impact on humidifier performance. See the
recommendations below and Figure 17-1.
Note: DriSteem recommends that you do not interchange room and duct
humidity devices. Room humidity devices are calibrated with zero or
little airflow, whereas duct humidity devices require air passing across
them.
Recommended humidity control (transmitter/humidistat) locations:
A. Ideal. Ensures the best uniform mix of dry and moist air with stable
temperature control.
B. Acceptable, but room environment can 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 humidity 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 might not represent actual overall
conditions in the space.
F. Not acceptable. Do not place sensors near windows, door passageways,
or areas of stagnant airflow.
Recommended safety (airflow and high limit) sensor location:
G. Best sensing location for high limit humidistat or humidity sensor and airflow
proving switch.
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Sensor placement