Humidifiers
Owner’s Manual
Includes Safety & Operating Instructions
and Warranty Information
Models 300, 400, 400M, 500, 500M,
600, 600M, 700 & 700M
READ AND SAVE THESE INSTRUCTIONS
TABLE OF CONTENTS
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
PRINCIPLE OF OPERATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
OPERATING INSTRUCTIONS – MODELS 400, 500, 600 & 700 . . . . . . . . . . . . . . 6
Digital Humidifier Control Indicator Lights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Blower Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Automatic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Manual Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
OPERATING INSTRUCTIONS – MODELS 400M, 500M, 600M & 700M. . . . . . . . 11
CHECK THE HUMIDIFIER OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ADDITIONAL INFORMATION FOR ALL MODELS . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
EFFECT OF WATER CHARACTERISTICS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
ANNUAL MAINTENANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
ANNUAL SUMMER SHUTDOWN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
PERIODIC PREVENTATIVE MAINTENANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
MAINTENANCE INSTRUCTIONS
Model 300. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Models 400 & 400M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Models 500, 500M, 600 & 600M. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Models 700 & 700M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
LIMITED WARRANTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
WARNING
120 volts may cause injury from electrical shock. Disconnect power and
shut o water supply before servicing.
CAUTION
Sudden operation may cause personal injury or property damage. Turn the
Aprilaire® Humidifier Control to OFF or lowest setting before servicing.
INTRODUCTION
Thank you for your recent Aprilaire® humidifier purchase. We appreciate your
business and are pleased to add your name to our growing list of customers.
You have invested in the highest quality equipment available. Aprilaire
manufactures whole-house indoor air quality products and is a recognized
leader in the heating and air conditioning industry.
Your humidifier will require periodic maintenance to assure continued fine
performance. See page 14 to obtain service parts and/or replacement Water
Panel® evaporators.
Please take a few minutes and read this booklet. This will familiarize you with
the benefits you will receive from the equipment you just purchased and help
you understand the routine maintenance that will be required.
Be sure to register your humidifier warranty online at
www.aprilaire.com/warranty
Genuine Aprilaire® Replacement
Water Panels® are available from
your installing contractor or
from most other heating and air
conditioning contractors in your
area. Use the dealer locator in our
web site www.aprilaire.com or
call 800-334-6011. Purchase only
genuine Aprilaire Water Panels to
maintain peak performance.
English 32 English
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 Model 300, 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, hot air is moved
through the moisture-laden Water Panel® evaporator where 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 Model 300 have a built-in fan which draws air through the Water Panel.
Model 300 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.
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 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.
The Water Panel® evaporator, designed especially for uniform, high 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® evaporator 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.
The control has lights which indicate humidifier operation, when the Water
Panel needs to be replaced and when service is required. See OPERATING
INSTRUCTIONS for more information.
There are many humidifiers on the market. They all add moisture… with
varying degrees of efficiency. None, however, offer the features, design, and
performance incorporated into your new Aprilaire humidifier.
English 54 English
OPERATING INSTRUCTIONS – MODELS 400, 500, 600 & 700
The Digital Humidifier Control offers two modes of operation, Automatic or
Manual. An explanation of both modes follows. (See FIGURE A on page 7 for
Automatic mode. See FIGURE B on page 8 for Manual mode.)
When in the Automatic mode, this system offers the following benefits:
• You will always receive the optimum amount of humidity so that your
home and its furnishings are always protected from the damaging effects
of excess condensation or low humidity during the heating season.
The control automatically adjusts your home’s RH based on the outdoor
temperature, increasing the time maximum comfort is maintained.
• Simple operation with few adjustments. The control eliminates the need
to manually adjust the control when outdoor temperature changes. It also
eliminates the need to turn the dial setting to OFF during the summer season.
DIGITAL HUMIDIFIER CONTROL INDICATOR LIGHTS
Call Dealer for Service: The red light indicates that the humidifier is not
operating normally and that service is required.
Change Water Panel: The yellow light indicates that it is time to change the
Water Panel in the humidifier.
Humidifier On: The green light indicates that the humidifier is operating
normally.
BLOWER ACTIVATION
The BLOWER ACTIVATION switch is set to the ON position to allow the
humidifier control to activate the HVAC fan for maximum humidification. For
this setting the Models 500, 600 and 700 must be connected to hot water.
If the HVAC system has been idle for one hour, the humidifier control will
activate the HVAC system fan to sample the air for 3 minutes. If the RH is lower
than the set point, the humidifier control will activate the humidifier and keep
the fan running. The humidifier will continue to operate for 2 hours or until the
humidification set point is reached.
If the RH set point has not been reached by the end of a call for heat, the
control will continue to operate the humidifier and the HVAC fan until the
humidification set point is reached or 2 hours have elapsed.
When the BLOWER ACTIVATION switch is in the OFF position, the humidifier
control will only operate the humidifier if humidity is required and the HVAC
system fan is operating or the HVAC system is producing heat.
Your Aprilaire Humidifier Control is installed in the cold air return duct. During
the first heating season, your humidifier control needs to be set initially to
match your home’s condition. Please follow these steps when adjusting your
control (refer to FIGURE A).
1. Turn the dial setting knob to 5, which is within the normal range. During
the next 24-48 hours it may be necessary to adjust the dial for more or less
humidity, depending on your personal comfort and home’s requirements.
Refer to TABLE 3 – Operation Guide.
2. During the coldest portion of the first heating season, minor adjustments
may be necessary. This is dependent upon your home’s construction. Refer to
TABLE 3 – Operation Guide.
The RH in your home will now be accurately controlled to meet your needs and
should not need further adjustment during future heating seasons. Make note
of the dial setting in the event you temporarily move the knob to OFF when
performing annual maintenance of your Aprilaire humidifier.
90-1235B
FIGURE A – AUTOMATIC MODE
AUTOMATIC MODE
English 76 English
MANUAL MODE
When installed in the Manual mode (see FIGURE B – internal switch in
MAN position and M in the display), it is important to anticipate a drop in
outdoor temperature and reduce the setting accordingly to avoid excessive
condensation. For example, with an outdoor temperature of 20°F the correct
setting will be 35% RH. If the temperature is expected to fall to 0°F, then merely
reduce the setting to 25% several hours prior to the temperature change.
See TABLE 1 for the recommended settings. These settings, which are based
on years of research, represent a compromise between RH levels that would
be most desirable for comfort and humidity levels that are suitable for
protection of your home and to avoid
condensation on your windows. For
example, a wintertime indoor RH of 50%
may be considered ideal for comfort, but
unfortunately, it probably would result in
condensation, which can cause damage to
your home. Observing the recommended
RH levels on your humidifier control is an
important safeguard. Condensation of
water on the inside surface of windows in
the form of fogging or frost is usually an
indication of too much humidity. This same
condensation can occur in other areas in
your home, possibly resulting in damage.
CHANGE WATER PANEL INDICATOR
The control keeps track of humidifier operation time. The yellow Change Water
Panel light flashes after a preset amount of running time has elapsed. This
running time is preset by the installer based on the humidifier model and water
hardness.
Refer to the ANNUAL MAINTENANCE section for instructions on changing the
Water Panel or call your heating and air conditioning dealer for service. After the
Water Panel is replaced, turn the control knob to the Test/Reset position until
the green Humidifier On light flashes, to reset the Water Panel change timer.
TEST/RESET
The Test/Reset feature allows the humidifier operation to be checked even if
there is no call for humidity.
Set the knob to Test/Reset, make sure that the water saddle valve is open and
that there is electricity to the humidifier. The HVAC fan must be running for the
humidifier to function. Note: Turning the knob to Test/Reset resets the Change
Water Panel timer. The humidifier will only operate for 1 minute in test mode.
(Model 400 and 400M: Floats must be down for the solenoid valve to allow
water flow.) Reduce the Humidifier Control setting to the recommended inside
RH, depending on the outside temperature. DO NOT LEAVE IN TEST MODE AS
HUMIDIFIER WILL NOT OPERATE.
ADDITIONAL INFORMATION
Your humidifier is a precision system that will accurately maintain the RH in
your home. For every 2°F change in outdoor temperature, the Digital Humidifier
Control will automatically adjust the indoor RH by 1%.
The Digital Humidifier Control will accurately control the humidity in your home
to a maximum of 45% RH.
The RH Values in TABLE 2 are targets based on outdoor temperature and the
Digital Humidifier Control setting. The actual RH may vary due to conditions in
the home (cooking, showering, etc.).
TABLE 2 – % RELATIVE HUMIDITY GUIDE
Outdoor Temperature (°F)
-10°F 0°F 10°F 20°F 30°F 40°F
Dial Setting
1 10% 10% 10% 15% 20% 25%
Relative Humidity (%)
2 10% 10% 15% 20% 25% 30%
3 10% 15% 20% 25% 30% 35%
4 15% 20% 25% 30% 35% 40%
5 20% 25% 30% 35% 40% 45%
6 25% 30% 35% 40% 45% 45%
7 30% 35% 40% 45% 45% 45%
90-1236B
FIGURE B – MANUAL MODE
TABLE 1 – OUTDOOR
TEMPERATURE/INDOOR
RELATIVE HUMIDITY
Outside
Temperature
Recommended
RH
+40°F 45%
+30°F 40%
+20°F 35%
+10°F 30%
0°F 25%
-10°F 20%
-20°F 15%
English 98 English
TABLE 3 – OPERATION GUIDE
Condition Solution
Condensation on
windows.
Reduce the setting on the control dial by
1increment.
Lack of humidity.
Increase the setting on the control dial by 1
increment. If the humidifier control is already
at the maximum setting of 7, set the BLOWER
ACTIVATION switch to ON. The humidifier
should be plumbed to hot water when using
the Blower Activation feature.
Humidifier does not
operate. (Solenoid does
not “click” when control
is moved to Test/Reset
position.)
Turn dial to Test/Reset. Make certain HVAC
blower is operating. If unit still does not
operate, consult a heating contractor.
Humidifier won’t shut off.
Turn dial to OFF. If unit continues to operate,
consult a heating contractor.
Test mode.
System operation is checked by setting the
knob to Test/Reset. Make certain HVAC blower
is operating. Humidifier will operate for one
minute. If the control knob is left in the Test/
Reset position, after 1 minute the display will
flash the software revision level e.g. r1. Note:
Placing the knob in Test/Reset resets the
Water Panel change timer.
Red Call Dealer for
Service light flashes
(FIGURE A).
Note the error code on the display (E1, E2,
E3 or E4) and call your heating and air
conditioning dealer.
Yellow Change Water
Panel light flashes
(FIGURE A).
Refer to ANNUAL MAINTENANCE on page 14
for instructions on changing the Water Panel,
or call your heating and air conditioning dealer
for service. After the Water Panel is replaced,
turn the control knob to the Test/Reset
position until the green Humidifier On light
flashes, to reset the Water Panel change timer.
OPERATING INSTRUCTIONS –
MODELS 400M, 500M, 600M & 700M
Your Aprilaire humidifier is controlled by a Manual Humidifier Control (see
FIGURE C). The Manual Humidifier Control is installed either in the cold air return
duct or on an interior wall of the home. With the Manual Humidifier Control, it
is important to anticipate a drop in outdoor temperature and reduce the setting
accordingly to avoid excessive condensation, just as with the Digital Humidifier
Control installed in Manual mode (see page 8).
To determine the indoor RH, slowly turn the knob clockwise and counterclockwise
and listen for 2 clicks. The indoor RH is within the range of the 2 clicks.
CHECK THE HUMIDIFIER OPERATION
MANUAL HUMIDIFIER CONTROL
Set the knob to the highest setting, make sure that the water saddle valve
is open and that there is electricity to the humidifier. The HVAC system must
be operating for the humidifier to function. Confirm that the solenoid valve
is energized and water is flowing into the humidifier. Return control knob to
desired setting.
90-1237
FIGURE C – MANUAL HUMIDIFIER CONTROL
English 1110 English
DIGITAL HUMIDIFIER CONTROL (INCLUDED WITH MODEL 300)
To test the function of the humidifier and the control:
Begin by pressing the ON button. ON will appear on the display. This means the
control is on, but it does not necessarily mean the humidifier is running. In order
for the control to turn on your humidifier, several conditions must be met:
1. The control and humidifier must be powered.
2. The RH level in the conditioned space must be below the set point.
Once functionality is established, set the control to the desired humidity.
ADDITIONAL INFORMATION FOR ALL MODELS
Be sure to keep fireplace dampers closed when not in use. They provide an
excellent escape route for heat, as well as humidity.
On occasion, indoor moisture producing activities such as clothes drying,
cooking, showers, etc., may raise the RH level higher than it should be, even
though the Aprilaire humidifier is not operating. Telltale indications are
condensation or frost on cold surfaces such as windows, doors, walls, etc. If
such condensation persists for several hours, your home should be ventilated to
dissipate the potentially damaging excess moisture.
EFFECT OF WATER CHARACTERISTICS
Your humidifier is designed to operate using hot, cold, hard or mechanically
softened water. (Hot water is required for Model 300 and recommended for all
models to ensure maximum performance.)
Water contains varying amounts of minerals. The residue remaining as a result of
hard water evaporation is primarily calcium and magnesium components and is
usually quite hard, scaly, and dense.
Residue from softened water tends to be soft and fluffy and has a greater
volume than hard water deposits. In either case, the service life of a Water Panel
evaporator will be the same. The Water Panel evaporator should be changed at
least once a year with the exception of Models 400 and 400M which should be
changed at least twice a heating season. In the drain-equipped models, most of
the mineral solids are flushed down the drain.
Hot supply water, 140°F maximum, is recommended with drain type humidifiers
for increasing capacity and is required for heat pump and air handler applications.
WARNING
RISK OF SCALDING. Water temperature over 125°F can cause severe burns
and scald instantly. Shut o the hot water supply before disconnecting or
tapping into any hot water supply line.
90-2495
FIGURE D – DIGITAL HUMIDIFIER CONTROL
English 1312 English
ANNUAL MAINTENANCE
For best performance, we recommend that you replace the Water Panel
evaporator in your Aprilaire humidifier at least annually with the exception
of Models 400 and 400M which should be changed at least twice per
heating season.
The Change Water Panel indicator light (Digital Control only) will blink when
it is time to change your Water Panel. See individual model instructions for
additional maintenance.
To purchase a new Water Panel:
• Call the installer of your Aprilaire humidifier. This
information is often found on your equipment.
• Call your heating and air conditioning dealer.
• Use our dealer locator at www.aprilaire.com
• Look in the Yellow Pages under Humidifying
Apparatus or Heating & Air Conditioning Contractors.
• If none of the above is successful and you still need
information, please feel free to write us.
• Purchase only Genuine Aprilaire Water Panels to
maintain performance.
If your humidifier is equipped with a Digital Humidifier Control with Change
Water Panel indicator, after replacing the Water Panel, turn the control knob to
the Test/Reset position until the Humidifier On light blinks to reset its timer.
(Blower must be operating and HVAC calling for heat.) Be sure to turn the
control knob back to it’s original setting. If the HumidifierOn light continues to
blink, your humidifier is in Test mode. DO NOT LEAVE THE CONTROL IN TEST
MODE OR HUMIDIFIER WILL NOT OPERATE.
ANNUAL SUMMER SHUTDOWN
For Models 400, 400M, 500, 500M, 600 and 600M close the bypass damper,
which is a part of the humidifier, with the small damper handle.
Humidifier Control:
• Digital Humidifier Control in Automatic mode (see FIGURE A): No adjustment
is necessary.
• Digital Humidifier Control in Manual mode (see FIGURE B): Set the knob to
the OFF position.
• Manual Humidifier Control (see FIGURE C): Set the knob to the OFF position.
PERIODIC PREVENTATIVE MAINTENANCE
Note: Periodic inspection and preventative maintenance of your total heating
system is important for efficient and safe operation. Your heating contractor can
service your humidifier when he services the HVAC system.
All models have a distribution tray above the Water Panel, which should be
inspected annually and cleaned of excess mineral deposits.
WATER LINE INSPECTION AND SERVICE INSTRUCTIONS
1. Disconnect electrical power to the HVAC
and shut off water supply.
2. Disconnect the water line at the inlet
compression nut.
3. Remove the in-line strainer from inside
the inlet side of the valve by using a small
nail or wire.
4. Flush the in-line strainer clean or replace
with a new strainer, Part No. 4004.
5. Reconnect the inlet water line. Double
wrench to prevent leaking.
6. Disconnect the water feed tube at the
outlet compression nut.
7. Inspect the water feed tube by gently
flexing it and looking for cracks or signs of
wear. Replace tube if it is cracked, brittle,
or has been damaged.
8. Inspect the orifice in the water feed tube
and make sure the small opening is unplugged.
9. Reconnect the water feed tube. Double wrench to prevent leaking.
10. Remove the drain line from the bottom of the humidifier. If applicable, flex
it to loosen any mineral deposits or blockages. Flush the drain line with
water under pressure to clear it of any debris, and slip it back onto the drain
fitting. If drain line does not flow properly, replace it. Inspect the drain line to
make sure it has a constant downward slope and is not flattened or blocked.
11. Turn on water supply and reconnect electrical power to the HVAC.
Unit
Water Panel
Part Number
300 35
400 45
500 10
600 35
700 35
INLET
COMPRESSION
NUT
INLET
SOLENOID
VALVE
ORIFICE
OUTLET
COMPRESSION
NUT
IN-LINE
STRAINER
WATER
FEED TUBE
90-1053
English 1514 English
9
12
6
11
10
3
7
8
5
2
1
4
1. Front Cover
2. Feed Tube
3. Integral Bypass Damper
4. Water Panel Evaporative Assembly
5. Distribution Tray
6. “V” Notches
7. Water Panel Evaporator
8. Scale Control Insert/Float Chamber
9. Overflow Drain Line
10. Float Cover
11. Float
12. Water Level Sensor Assembly
1. Note humidifier control setting and turn dial to the OFF position.
2. Turn off water supply. Turn the integral bypass damper (3) to the SUMMER position.
3. Press the tabs in the latches on the top and bottom of front cover (1) and pull cover off base with both hands.
4. Carefully pull the plastic feed tube (2) out of the distribution tray (5) at the top of the Water Panel
evaporative assembly (4). Tip the Water Panel evaporative assembly forward and lift it out of the
humidifier. Do not tip the Water Panel evaporative assembly more than needed to clear the housing to
avoid over-bending the water level sensor assembly (12).
5. Unsnap the distribution tray (5) from the scale control insert (8). Lightly scrape out or brush off any mineral
deposits, being careful not to stretch or loosen the synthetic fabric liner. Soaking the tray in vinegar or a
lime-removing agent is helpful when trying to remove stubborn mineral deposits.
6. Slide the used Water Panel evaporator (7) out of the scale control insert/float chamber and dispose of the
Water Panel.
7. Remove the float cover (10) and inspect the floats (11) and float chamber for mineral build-up. Remove
deposits as needed from floats, float chamber and scale control insert. Wash the parts with a disinfecting
cleaner. Reassemble the floats and float cover. Make sure stems of both floats extend through openings in
float cover and that floats move freely up and down.
8. Inspect the plastic feed tube (2) by gently flexing it and looking for cracks or signs of wear. Replace tube if
it is cracked, brittle, or has been damaged.
9. Slide a new Aprilaire No. 45 Water Panel (paper evaporator) (7) into the scale control insert/float chamber
(8). Snap the distribution tray (5) back on the scale control insert (8).
10. Reinstall the Water Panel evaporative assembly (4) into the humidifier. Take care not to over-bend the
water level sensor assembly. Push the top of the Water Panel evaporative assembly firmly back until it
snaps into place.
11. Push the end of the feed tube back firmly into the distribution tray. Replace the front cover.
12. Under normal operation the overflow drain line (9) will never have water in it. However, inspect it for
mineral deposits and replace if necessary. Make sure the drain line has a constant downward slope and is
not flattened or blocked.
13. Turn on the water supply. Return integral bypass damper to appropriate position.
14. Check system operation:
Manual Humidifier Control (Model 400M): With the HVAC blower operating, turn up humidifier control
and check system operation.
Automatic Digital Humidifier Control (Model 400): (Automatic or Manual mode) Check system operation
and reset Change Water Panel indicator by setting the knob to Test/Reset. With HVAC blower operating
and HVAC calling for heat, humidifier will operate for one minute. DO NOT LEAVE IN TEST MODE AS
HUMIDIFIER WILL NOT OPERATE.
15. Set humidifier control to its original position.
1. Turn Manual Digital Humidifier Control off.
2. Disconnect electrical power and turn off water supply.
3. Unscrew knobs to Wet Pack assembly access panel.
4. Lift the Wet Pack assembly then swing out and slide forward out of the humidifier housing.
5. To remove the distribution tray from Water Panel, push down on tray and pull out scale control insert. To
clean the “V” openings of the tray, gently pry the distribution tray cover from the tray. Lightly scrape out
or brush off any mineral deposits, being careful not to stretch or loosen the synthetic fabric liner. Soaking
the tray in vinegar or a lime-removing agent is helpful when trying to remove stubborn mineral deposits.
6. Slide the Water Panel out from the scale control insert and dispose of the Water Panel. Clean the scale
control insert of mineral deposits. Replace the Water Panel evaporator (Stock No. 35) with a Genuine
Aprilaire Water Panel. Slide the Water Panel back into the scale control insert and snap the distribution
tray cover into the distribution tray. Then snap the distribution tray back into the scale control insert.
7. Inspect the plastic feed tube by gently flexing it and looking for cracks or signs of wear. Replace tube if it
is cracked, brittle or has been damaged.
8. Remove the drain line from the bottom of the humidifier and flex it to loosen any mineral deposits or
blockage. Then flush it with water under pressure. If it does not properly clear, replace it. Slip the drain line
back onto the drain fitting. Make sure the drain line has a constant downward slope and is not flattened
or blocked.
9. Reinstall Wet Pack assembly as shown in Figure. Insert into the humidifier housing to align with guiding
flanges and ensure fit with drain spud.
10. Reconnect electrical power and turn on water supply.
11. Turn on Manual Digital Humidifier Control and check system operation.
12. Set Manual Digital Humidifier Control to its original setting.
#35 WATER
PANEL
DRAIN
TOP
WET
PACK
FLANGE
DRAIN SPUD
90-2602
90-2601
90-1077
90-2600
MODEL 300
MODEL 400 SERIES
REQUIRED MAINTENANCE INSTRUCTIONS
APRILAIRE HUMIDIFIER MODEL 300
WARNING
120 volts may cause serious injury from electrical shock. Disconnect power and shut o
water supply before servicing.
REQUIRED MAINTENANCE INSTRUCTIONS
APRILAIRE HUMIDIFIER MODELS 400 & 400M
CAUTION
Sudden operation may cause personal injury or property damage. Turn humidifier control to
OFF or lowest setting before servicing.
English 1716 English
MODEL 500 & 600 SERIES
MODEL 700 SERIES
8
2
9
3
1
4
5
6
7
1. Note humidifier control setting and turn dial to the OFF position.
2. Turn off water supply. Turn the integral bypass damper (3) to the SUMMER position.
3. Press the tabs in the latches on the top and bottom of front cover (1) and pull cover off base with both
hands. Set aside.
4. Carefully pull the plastic feed tube (2) out of the distribution tray (5) at the top of the Water Panel
evaporative assembly (4). Pull this assembly out by grasping at top and tipping out.
5. Unsnap the distribution tray (5) from the scale control insert (8). Lightly scrape out or brush off any
mineral deposits, being careful not to stretch or loosen the synthetic fabric liner. Soaking the tray in
vinegar or a lime-removing agent is helpful when trying to remove stubborn mineral deposits.
6. Slide the Water Panel evaporator (7) out from the scale control insert (8) and dispose of the Water
Panel. Clean the scale control insert of mineral deposits. Replace the Water Panel evaporator (Stock
No. 35 for Models 600 & 600M and Stock No. 10 for Models 500 & 500M) with a new Genuine
Aprilaire Water Panel. Slide the Water Panel evaporator back into the scale control insert with the
colored spot up and snap the distribution tray (5) back into place.
7. Inspect the plastic feed tube (2) by gently flexing it and looking for cracks or signs of wear. Replace
tube if it is cracked, brittle, or has been damaged.
8. Reinstall the Water Panel evaporative assembly (4) into the humidifier by fitting its drain into the
round receptacle at the base of the humidifier. Push the assembly in at the top until it snaps into place.
Push the end of the feed tube back firmly into the distribution tray and replace the front cover.
9. Remove the drain line (9) from the bottom of the humidifier. If applicable, flex it to loosen any mineral
deposits or blockage. Then flush it with water under pressure. If it does not properly clear, replace it.
Slip drain line back onto the drain fitting. Make sure the drain line has a constant downward slope and
is not flattened or blocked.
10. Turn on the water supply. Return integral bypass damper to appropriate position.
11. Check system operation:
Manual Humidifier Control (Models 500M & 600M): With the HVAC blower operating, turn up
humidifier control and check system operation.
Digital Humidifier Control (Models 500 & 600): (Automatic or Manual mode) Check system
operation and reset Change Water Panel indicator by setting the knob to Test/Reset. With HVAC
blower operating and HVAC calling for heat, humidifier will operate for one minute. DO NOT LEAVE IN
TEST MODE AS HUMIDIFIER WILL NOT OPERATE.
12. Set humidifier control to its original position.
1. Front Cover
2. Feed Tube
3. Integral Bypass Damper
4. Water Panel Evaporative Assembly
5. Distribution Tray
6. “V” Notches
7. Water Panel Evaporator
8. Scale Control Insert
9. Drain Line
3
4
5
2
8
9
1
7
6
1. Humidifier Cover Assembly
2. Base Assembly
3. Water Panel Evaporative Assembly
4. Distribution Tray
5. “V” Notches
6. Water Panel Evaporator
7. Scale Control Insert
8. Drain Line
9. Power Cord
1. Note humidifier control setting and turn dial to the OFF position.
2. Disconnect electrical power and turn off water supply.
3. Unlatch humidifier front cover assembly (1) from base assembly (2) at the bottom of the cover, lift, and
set aside.
4. Pull out the Water Panel evaporative assembly (3) by grasping at the top and tipping out.
5. Unsnap the distribution tray (4) from the scale control insert (7). Lightly scrape out or brush off any
mineral deposits, being careful not to stretch or loosen the synthetic fabric liner. Soaking the tray in
vinegar or a lime-removing agent is helpful when trying to remove stubborn mineral deposits.
6. Slide the Water Panel evaporator (6) out from the scale control insert (7) and dispose of the Water Panel.
Clean the scale control insert of mineral deposits. Replace the Water Panel evaporator (Stock No. 35) with
a new Genuine Aprilaire Water Panel. Slide the Water Panel evaporator back into the scale control insert
with the colored spot up and snap the distribution tray (4) back into place.
7. Inspect the plastic feed tube by gently flexing it and looking for cracks or signs of wear. Replace tube if it
is cracked, brittle, or has been damaged.
8. Reinstall the Water Panel evaporative assembly (3) into the humidifier by fitting its drain into the round
receptacle at the base of the humidifier. Push the assembly in at the top between the retaining ribs that
hold the assembly in place in a vertical position.
9. Remove the drain line (8) from the bottom of the humidifier. If applicable, flex it to loosen any mineral
deposits or blockage. Then flush it with water under pressure. If it does not clear, replace it. Slip drain line
back onto the drain fitting. Make sure the drain line has a constant downward slope and is not flattened
or blocked.
10. Reinstall front cover assembly (1) by hooking at the top of the base assembly (2) and latching at the
bottom.
11. Reconnect electrical power (9) and turn on the water supply.
12. Check system operation:
Manual Humidifier Control (Model 700M): With the HVAC blower operating, turn up humidifier control
and check system operation.
Digital Humidifier Control (Model 700): (Automatic or Manual mode) Check system operation and reset
Change Water Panel indicator by setting the knob to Test/Reset. With HVAC blower operating and HVAC
calling for heat, humidifier will operate for one minute. DO NOT LEAVE IN TEST MODE AS HUMIDIFIER
WILL NOT OPERATE.
13. Set humidifier control to its original position.
NOTE: The motor is permanently lubricated and does not need to be oiled.
REQUIRED MAINTENANCE INSTRUCTIONS
APRILAIRE HUMIDIFIER MODELS 500, 500M, 600 & 600M
CAUTION
Sudden operation may cause personal injury or property damage. Turn humidifier control to
OFF or lowest setting before servicing.
REQUIRED MAINTENANCE INSTRUCTIONS
APRILAIRE HUMIDIFIER MODELS 700 & 700M
WARNING
ELECTRICAL SHOCK HAZARD. Can cause injury or death. Disconnect all electrical power
supplies before servicing. Turn humidifier control to OFF or lowest setting before servicing.
90-1075
90-1076
English 1918 English
Aprilaire.com
P.O. Box 1467
Madison, WI 53701-1467
800.334.6011 F: 608.257.4357
Printed in USA
©2021 Aprilaire – Division of
Research Products Corporation
10015434 B2209190B 3.21
LIMITED WARRANTY
Your Research Products Corporation Aprilaire® humidifier unit is expressly warranted for five (5)
years from date of installation to be free from defects in materials or workmanship except, however,
for the disposable Water Panel which will have to be replaced from time to time depending upon
the amount of use.
Research Products Corporation’s exclusive obligation under this warranty shall be to supply, without
charge, a replacement for any part of the humidifier which is found to be defective within such five
(5) year period and which is returned not later than thirty (30) days after said five (5) year period by
you to either your original supplier or to Research Products Corporation, Madison, Wisconsin 53701,
together with the model number and installation date of the humidifier.
THIS WARRANTY SHALL NOT OBLIGATE RESEARCH PRODUCTS CORPORATION FOR ANY LABOR
COSTS AND SHALL NOT APPLY TO DEFECTS IN WORKMANSHIP OR MATERIALS FURNISHED BY
YOUR INSTALLER AS CONTRASTED TO DEFECTS IN THE HUMIDIFIER ITSELF.
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE SHALL
BE LIMITED IN DURATION TO THE AFORESAID FIVE YEAR PERIOD. RESEARCH PRODUCTS
CORPORATION’S LIABILITY FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES, OTHER THAN
DAMAGES FOR PERSONAL INJURIES, RESULTING FROM ANY BREACH OF THE AFORESAID IMPLIED
WARRANTIES OR THE ABOVE LIMITED WARRANTY IS EXPRESSLY EXCLUDED. THIS LIMITED
WARRANTY IS VOID IF DEFECT(S) RESULT FROM FAILURE TO HAVE THIS UNIT INSTALLED BY A
QUALIFIED HEATING AND AIR CONDITIONING CONTRACTOR. IF THE LIMITED WARRANTY IS VOID
DUE TO FAILURE TO USE A QUALIFIED CONTRACTOR, ALL DISCLAIMERS OF IMPLIED WARRANTIES
SHALL BE EFFECTIVE UPON INSTALLATION.
Some states do not allow limitations on how long an implied warranty lasts or the exclusion or
limitation of incidental or consequential damages so the above exclusion or limitations may not
apply to you.
This warranty gives you specific legal rights and you may also have other rights which vary from
state to state.
WARRANTY REGISTRATION
Visit us online at www.aprilaire.com to register your Aprilaire product. If you do not have online
access, please mail a postcard with your name, address, phone number, email address, product
purchased, model number, date of purchase, and dealer name and address to: Research Products
Corporation, P.O. Box 1467, Madison, WI 53701.
Your warranty registration information will not be sold or shared outside of this company.
20 English
