Principle Of Operation - Aprilaire 300 Owner's Manual

PRINCIPLE OF OPERATION

Your new AprilAire Humidifier uses evaporation to add moisture back
to warm, dry air in the home. Evaporative humidifiers do not heat the
water themselves, but instead use the HVAC system's heat (excluding
Model 300), drawn through a water panel, to turn the water into
vapor.
The Model 300 must use hot supply water, up to 140°F (60°C), as a
heat source for evaporation to occur, independent from an HVAC
system. Hot supply water is recommended for all AprilAire Evaporative
Humidifiers to maximize their effectiveness.
Except for Model 300, the AprilAire Humidifier is designed to operate
in conjunction with the heating, ventilating, air conditioning (HVAC)
system fan. When the humidifier control calls for humidity and the
HVAC system fan is operating, water flows to the distribution tray
located inside the humidifier. The water is uniformly distributed across
the tray where it flows down through a system of outlets over the
Water Panel. Dry, hot air is moved through the moisture-laden Water
Panel where natural evaporation takes place. The now-humidified air
carries moisture in vapor form and circulates throughout the home.
With bypass Models 400, 500, and 600 Series, HVAC system air is
moved from the supply duct through the humidifier into the return
duct. 700 Series models and the Model 300 have a built-in fan which
draws air through the Water Panel.
The correct water flow is maintained by an orifice provided with
each humidifier. When the humidifier is operating (excluding 400
Series), there will be a small, steady stream of water to the drain,
which flushes away most of the trouble‑causing minerals.
Do not use the saddle valve to regulate the water flow. It is designed
to be completely open or closed.
The minerals and solid residue not trapped by the replaceable Water
Panel are flushed down the drain in the Models 300, 500, 500M, 600,
600M, 700, and 700M. This is the most effective and least expensive
method to dispose of trouble-causing minerals. The drain also
eliminates the problems caused by stagnant water.
Trouble-free performance and minimum maintenance are assured
by the design features of the AprilAire Humidifier. All humidifier
housing parts that come in contact with water are non-metal and
will never rust or corrode. Neither heat nor water will affect them
under normal operating conditions.
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