Principle Of Operation - Aprilaire 350 Safety & Operating Instructions Manual

PRINCIPLE OF OPERATION

With your purchase of this humidification system, you have invested in a humidifier
that operates on the evaporative principle – nature's own way of adding moisture
– providing optimum relative humidity (RH) throughout the heating season. It is
very possible that you have questions concerning your new humidifier – questions
on what it can do for you, and what you should do to receive maximum benefits
from it. This booklet is intended to answer these questions.
Nature, in producing an invigorating comfortable April day, combines just
the right temperature and the right amount of moisture. Aprilaire humidifiers
employ the same principle, with refinements, to give you the optimum RH for
maximum allowable comfort all winter long.
The important considerations in the evaluation of a humidifier are precise
control, sufficient capacity, trouble-free performance and minimum
maintenance. The operating principle of your Aprilaire humidifier provides
all of these advantages. Here, briefly, is the method:
Except for Models 350 and 360, the Aprilaire humidifier is installed to operate
in conjunction with the heating, ventilating, air conditioning equipment
(HVAC) blower. When the Aprilaire Humidifier Control calls for humidity and
the blower motor is operating, water flows to the distribution tray located at
the top of the humidifier. The water is uniformly distributed across the width
of the tray and through a scientifically designed system of outlets. It flows
by gravity over the Water Panel evaporator, the heart of the humidifier. Dry,
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hot air is moved through the moisture-laden Water Panel
natural evaporation takes place. The now-humidified air carrying moisture in
vapor form (nature's own way) is circulated throughout the home.
With bypass Models 400, 500 and 600 Series, HVAC system airflow is
drawn through the humidifier from the supply duct to the return duct. 700
Series models, and Models 350 and 360 have a built-in fan which draws air
through the Water Panel.
Models 350 and 360 must use service hot water (140°F maximum) for
a heat source, as heat is needed for evaporation. The other models can
work with cold or hot water, but hot water provides maximum output and
is recommended if the humidifier is to be run in fan-only mode. While the
water going to the humidifier is hot, the flushing water to the drain will be
cold. The heat is extracted during the evaporation process.
The correct water flow is determined by an orifice provided with
each drain type humidifier. When the humidifier is operating, there
will be a small, steady stream of water to drain, which flushes away
most of the trouble-causing minerals.
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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
evaporator are flushed down the drain in the Models 350, 360, 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.
There are some homes where drain facilities are not accessible or available.
Model 400 Series humidifiers are designed to satisfy these applications.
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.
The Water Panel evaporator, designed especially for uniform, high
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evaporation, and the Scale Control Insert (which encases the Water Panel)
effectively traps mineral deposits which are often the cause of damage to
working parts in ordinary humidifiers. The Water Panel
is the heart of the humidifier and must be in good condition
to assure high capacity trouble-free performance. It should be
changed at least annually with the exception of Models 400 and
400M which should be changed at least twice per heating season.
The distribution tray incorporates a synthetic fabric liner that is designed
to deliver water uniformly over the entire top surface of the Water Panel
evaporator, provided the humidifier is mounted level. It is normal for some
mineral deposits to form in the distribution tray as it dries out between
humidification cycles. These deposits can actually help distribute water in
the tray, but if they block the openings, they should be removed as described
in the "Periodic Preventative Maintenance" section of this manual.
Your Digital Humidifier Control works in conjunction with your HVAC system
to control the operation of the humidifier. The control senses indoor RH and
outdoor temperature and automatically adjusts the operation time of the
humidifier to provide the optimum humidity level in the home.
The Automatic Control can be set to turn on the HVAC blower when
humidity is required. Plumbing the humidifier to hot water is required for
this mode of operation.
The digital readout on the control displays the RH level inside the cold
air return duct. RH is a measure of the amount of moisture in the air as a
percentage of what the air can hold. Warm air can hold more moisture than
cold air can.
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