Aprilaire 550 User manual

READ AND SAVE THESE INSTRUCTIONS
Owner’s Manual
For Models 400, 550, 600 & 700
Includes Safety & Operating Instructions
and Warranty Information
Automatic Humidifiers

© Research Products Corporation 2003
TABLE OF CONTENTS
WARNING 120 volts may cause injury from electrical shock.
Disconnect power and shut off 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Principle of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Operating Instructions – Model 400, 600 & 700
• Automatic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
• Manual Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Operating Instructions – Model 550 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Effect of Water Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Annual Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Annual Summer Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Periodic Preventative Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
MAINTENANCE INSTRUCTIONS
Model 400 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Model 600 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Model 700 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Model 550 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Limited Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Replacement Record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

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Genuine Replacement Water Panel evaporators are available from your
installing contractor or from most other heating and air conditioning
contractors in your area. However, if you still have difficulty in obtaining a
replacement Water Panel evaporator, use the dealer locator in our web
site (www.aprilaire.com) or look in the Yellow Pages under Humidifying
Apparatus or Heating & Air Conditioning Contractors. Purchase only
genuine Aprilaire Water Panels to maintain performance.
Thank you for your recent Aprilaire®Humidifier purchase. We sincerely
appreciate your business and are pleased to add your name to our
growing list of customers. With this purchase, you have invested in the
highest quality equipment currently available. Research Products
Corporation is the largest manufacturer of whole house humidifiers, air
cleaners and fresh air exchangers and is a recognized leader in the
heating and air conditioning industry today.
Please be assured that in addition to product quality, we are also committed
to unit performance as well as customer satisfaction. Your unit will require
periodic maintenance to assure you of continued fine performance. Please
proceed as shown on page 9 to obtain service parts and/or replacement
Water Panel®evaporators.
Now, please take a few minutes and read the appropriate section of 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
with us for our records and your protection. You may do so by returning a
Warranty Information Card to us, or you can register online at:
www.aprilaire.com/warranty.
INTRODUCTION

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With your purchase of a humidification system, you have invested in a
humidifier that operates on the evaporative principle – nature’s own way
of adding moisture – and will provide the proper relative humidity all
during 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 help you do exactly that.
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
proper relative humidity for maximum allowable comfort all winter long.
The important considerations in the evaluation of a humidifier are Positive
Control, Sufficient Capacity, Trouble-free Performance and Minimum
Maintenance. The operating principle of your Aprilaire provides all of
these advantages. Here, briefly, is the method:
The Aprilaire Humidifier is installed to operate in conjunction with the
furnace blower motor. 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 unit. 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 unit. Dry, hot air is moved through the
moisture-laden Water Panel evaporator where the evaporation takes
place. The now humidified air carrying moisture in vapor form
(nature’s own way) is circulated throughout the home.
The correct water flow is determined by an orifice equipped with
each drain type unit. When the unit 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 opened or closed. The minerals
and solid residue not trapped by the replaceable Water Panel evaporator are
flushed down the drain. In the Models 550, 600 and 700. The drain also
eliminates the problems caused by stagnant water. This is the most effective
and least expensive method to dispose of trouble-causing minerals.
There are some homes where drain facilities are not accessible or
available. For these situations, or where high water hardness is not a
problem, the newest Aprilaire, Model 400, is designed to satisfy these
applications.
I. PRINCIPLE OF OPERATION

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Capacity is high because an average-size home (10,000 cu. ft.) requires
the addition of approximately 9 gallons of water per day to maintain 35%
relative humidity when the outside temperature is 20°. The smallest
Aprilaire Humidifier under most operating conditions, has this humidifying
capacity. Trouble-free performance and minimum maintenance are
assured by the design features of the Aprilaire Humidifier. All unit
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, along with the Scale Control Insert efficiently traps mineral
deposits which are often the cause of damage to working parts in
ordinary humidifiers. No “white dust” can be distributed throughout the
living quarters. The Water Panel evaporator is the heart of the unit and
must be in good condition to assure high capacity trouble-free
performance. It should be changed once a year with the exception of the
Model 400 where it should be changed twice a heating season.
The granular coating in the bottom of the distribution tray is designed to
provide equal distribution of water to each of the openings assuring an
even flow over the Water Panel evaporator. Do not clean the mineral
scale off the bottom of the water distribution tray at the end of the
humidification season. The scale itself provides an excellent track for the
water to follow. This is actually what we try to simulate with the
synthetic coating in the bottom of the tray. If the coating is removed, it is
not necessary to purchase a new distribution tray. You can accomplish the
same uniform performance by applying a small amount of liquid
dishwashing detergent over the entire inside surface of the water
distribution tray. This will allow the water to flow evenly through each of
the openings, provided, of course, the unit is level in order to achieve
maximum capacity.
There are many humidifiers on the market. They all add moisture… with
varying degrees of efficiency. None, however, can provide the features,
design, and performance incorporated into your Aprilaire Humidifier.

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II. OPERATING INSTRUCTIONS – 400, 600 & 700
There are 2 possible modes of operation of your Aprilaire Humidifier
Control – Automatic and Manual. An explanation of both modes follows:
Automatic Mode: (Manual Mode-see pg 6)
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 the “Operation Guide” (Table 1).
2. During the coldest portion of the first heating season, minor adjustments
may be necessary. This is dependent upon your homes’ construction,
refer to the “Operation Guide” (Table 1).
TABLE 1 – Operation Guide
Condition Solution
Condensation on windows Reduce the setting on the control dial
by 1 increment.
Lack of humidity Increase the setting on the control dial
by 1 increment.
Humidifier does not operate Turn dial to “Test/Reset.” Make certain
furnace is operating in heat mode.
If unit still doesn’t 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
furnace blower is operating and furnace
is calling for heat. Humidifier will
operate for one minute. Be sure to turn
the control knob back to the normal
setting after checking humidifier
operation.
Reset water panel change Turn the control knob to the
“Test/Reset” position until the “Change
Water Panel” light blinks to reset the
water panel change indicator timer.
(Blower must be operating and furnace
calling for heat.) Be sure to turn the
control knob back to the normal setting
after resetting the timer.
indicator

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Your Aprilaire Automatic Humidifier, is a high precision system that will
accurately maintain the relative humidity in your home. For every 1°
change in outdoor temperature, the control will automatically adjust the
indoor relative humidity (RH) by 1/2%. If you would like to determine the
RH in your home, follow these steps:
1. Determine the outdoor temperature.
2. Activate the furnace blower by setting your thermostat to a higher
temperature.
3. Turn the control dial setting to the “Off” position. Then, slowly turn the dial
clockwise until you hear the solenoid valve “click on.” Next, slowly turn the
dial counter clockwise until you hear the solenoid valve “click off”. At this
point, make note of the dial setting.
4. Locate your dial setting on Table 2. Follow the dial setting to the right
until it intersects with the current outdoor temperature. This is the
relative humidity in your home under existing conditions.
5. Return the thermostat and the Humidifier Control to their original
settings.
The Automatic Humidifier will accurately control the humidity in your
home to a maximum of 45% RH and a minimum of 10% RH. The values of
outdoor temperature and dial settings may fall in between or outside of
the listed values in Table 2. In these cases, you can only approximate your
home’s actual indoor RH.
The relative humidity 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 when
performing annual maintenance of
the Aprilaire Humidifier.
T
E
S
T
/
R
E
S
E
T
2
3
5
4
6
1
7
AUTOMATIC MODE
O
F
F
N
O
R
M
A
L
FIGURE A

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Manual Mode: (Automatic Mode – see pg 4)
Your Aprilaire Humidifier Control is installed in the cold air return. 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° the correct setting will be 35% relative humidity. If the
temperature is expected to fall to 0° that evening, then merely reduce the
setting to 25% several hours prior to the temperature change.
The recommended settings on the Humidifier Control are based on years
of research and experience (see Table 3). These settings represent a
compromise between RH levels that would be most desirable for comfort
reasons 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, but unfortunately, it probably
would result in damage to your home. Observance of the recommended
RH levels on your Humidifier Control, therefore, is an important safeguard.
Condensation of water on inside windows in the form of fogging or frost
is usually an indication of too much relative humidity. This same
condensation can take place in other areas in your home with the
possibility of damage resulting.
As an example, if the outdoor temperature is 20°F, and, following step 3,
the humidifier turns off at “5” on the dial range, then the RH in your home is 35%.
-10 0 10 20 30 40
110 10 10 15 20 25
210 10 15 20 25 30
310 15 20 25 30 35
415 20 25 30 35 40
520 25 30 35 40 45
625 30 35 40 45 45
730 35 40 45 45 45
Outdoor Temperature (°F)
Dial Setting
TABLE 2 – % Relative Humidity Guide

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Your Aprilaire Humidifier Control
is a precision instrument that can
be used to determine the RH
accurately in your home during
the winter.
To do this, follow these steps:
1. Activate the furnace blower by
setting your thermostat to a
higher temperature.
2. Turn the control dial setting to
the “Off” position. Then, slowly
turn the dial clockwise until you
hear the solenoid valve “click on.” Next, slowly turn the dial counter
clockwise until you hear the solenoid valve “click off.” At this point, read
the RH on the dial. This will be very close to the actual RH in your
home. (See Figure B)
To check the humidifier operation, set the knob to “Test/Reset”, make
sure that the water saddle valve is open and that there is electricity to the
unit. The furnace blower motor must be operating and the furnace calling
for heat for the Aprilaire Humidifier to function. Note: Turning the knob to
“Test/Reset” resets the “Change Water Panel” internal timer. After the
humidifier has operated for one minute and water is entering the unit and
coming out at the drain, reduce the humidistat setting to the
recommended inside relative humidity, depending on the outside
temperature. DO NOT LEAVE IN TEST MODE AS HUMIDIFIER WILL NOT
OPERATE. Follow the suggested settings prior to a drop in the outside
temperature.
T
E
S
T
/
R
E
S
E
T
O
F
F
MANUAL MODE
%
H
U
M
I
D
I
T
Y
2
5
%
1
5
%
3
5
%
4
5
%
O
U
T
D
O
O
R
T
E
M
P
E
R
A
T
U
R
E
0
°
F
2
0
°
F
4
0
°
F
FIGURE B
TABLE 3 – Outdoor-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%

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Your humidifier will operate effectively using either hot, cold, hard or
mechanically softened water. Whether to use available tap water, even
though it may be quite hard, or chemically softened water, is a common
concern to homeowners when installing a humidifier.
Water used in homes 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 scale. The service life of a Water Panel evaporator may
be extended by using hard water. In either case, the Water Panel evaporator
is usually changed once a year with the exception of the Model 400 which
should be changed twice a heating season. In the drain-equipped models,
most of these solids are effectively controlled by flushing them down the
drain.
Your new Aprilaire Humidifier is controlled by a manual humidistat
installed either in the living area or in the cold air return. It is important to
anticipate a drop in temperature and reduce the setting accordingly to
avoid excessive condensation. For example, with an outside temperature
of 20° the correct setting will be 35% relative humidity. If the
temperature is expected to fall to 0° that evening, then merely reduce the
setting to 25% several hours prior to the temperature change.
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 relative humidity level higher than it
should be, even though the Aprilaire Humidifier is not operating. Telltale
indications, again, 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 potential damaging
excess moisture levels.
III. OPERATING INSTRUCTIONS – 550
V. EFFECT OF WATER CHARACTERISTICS
IV. ADDITIONAL INFORMATION FOR ALL MODLES

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VI. ANNUAL MAINTENANCE
VII. ANNUAL SUMMER SHUTDOWN
For best performance, we recommend that you replace the Water Panel
evaporator in your Aprilaire Humidifier annually with the exception of
Model 400 which should be changed twice a season. If you have a
Humidifier Control equipped with a water panel timer, the “Change Water Panel”
light will be lit (during operation only) when it is time to change your Water Panel.
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 Conditioner 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.
After replacing the Water Panel, turn the control knob to the “Test/Reset” position
until the “Change Water Panel” light blinks to reset the water panel change
indicator timer. (Blower must be operating and furnace calling for heat.) Be sure to
turn the control knob back to the normal setting after resetting the timer.
1. For Models 400, and 600 close the bypass damper which is a part of the
unit, with the use of the small damper handle. For the Model 550, close
the bypass damper which is installed in the bypass pipe.
2. Shut off the water supply to the humidifier by closing the saddle valve.
Humidifier Control:
There is no adjustment to the Humidifier Control required for summer
shutdown. (Applies to both Automatic and Manual Mode.)
Service hot water, 140° maximum, is recommended with drain type units for
increasing capacity and for heat pump applications.

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1. Disconnect electrical power
to the furnace 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, Service Department,
Part No. 4004.
5. Replace the in-line strainer
and reconnect the inlet water
line. (Double Wrench To
Prevent Leaking.)
6. Disconnect the water line at the outlet compression nut.
7. Remove the orifice from the copper or plastic tube and make sure
this small opening is unplugged.
8. Replace the orifice and reconnect the outlet water line.
(Double Wrench To Prevent Leaking.)
9. Turn on water supply and reconnect electrical power to
the furnace.
OUTLET
COMPRESSION
NUT
ORIFICE
INLET
INLET
COMPRESSION
NUT
SOLENOID
VALVE
IN-LINE
STRAINER
INSPECTION AND SERVICE INSTRUCTIONS
NOTE: Periodic inspection and preventive maintenance of your total
heating system is important for efficient and safe operation. Your heating
contractor should include humidifier service at the same time.
All models are equipped with an in-line water strainer and orifice as
shown below. These parts should be inspected and cleaned periodically to
assure continued proper unit performance.
VIII. PERIODIC PREVENTATIVE MAINTENANCE

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1. Front Cover
2. Feed Tube
3. Integral Damper
4. Water Panel Evaporator
Assembly
5. Distribution Tray
6. “V” Notches
7. Water Panel
8. Scale Control Insert/Float
Chamber
9. Overflow Hose
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 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 evaporator assembly (4). Tip the Water Panel evaporator assembly forward
and lift it out of the humidifier. Do not tip the Water Panel evaporator assembly more than
needed to clear the housing to avoid over-bending the water level sensor assembly (12).
5. Unsnap the distribution tray from the scale control insert (8). Lightly scrape out any
calcium deposits and clean the “V” notches (6) but do not scrape off the granular
coating. This textured surface helps ensure even water flow for maximum performance.
See page 3 if removed.
6. Slide the used water panel (7) out of the scale control insert/float chamber and dispose
of the water panel. Inspect the overflow hose (9) to make sure it is open.
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. Slide a new Aprilaire no. 45 water panel into the scale control insert/float chamber. Snap
the distribution tray back on the scale control insert.
9. Reinstall the water panel evaporator assembly into the humidifier. Take care not to over-
bend the water level sensor assembly. Push the top of the water panel evaporator
assembly firmly back until it snaps into place.
10. Push the end of the feed tube back firmly into the distribution tray. Reset the damper to
desired position. Replace the front cover.
11. Turn on the water supply.
12. Check system operation:
Humidifier Control: (Automatic or Manual) Check system operation and reset change
water panel indicator by setting the knob to “Test/Reset”. With furnace blower operating
and furnace calling for heat, humidifier will operate for one minute. DO NOT LEAVE IN
TEST MODE AS HUMIDIFIER WILL NOT OPERATE.
13. Reset Humidifier Control to its original position. Check operation.
MAINTENANCE INSTRUCTIONS for
APRILAIRE HUMIDIFIER MODEL 400
CAUTION! Sudden operation may cause personal injury or
property damage. Turn Humidifier Control to “off” or
lowest setting before servicing.
MODEL 400
MODEL
400

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1. Note Humidifier Control setting and turn dial to the “OFF” position.
2. Turn off water supply.
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 evaporator assembly (4). Pull this assembly out by grasping at top and
tipping out.
5. Remove the distribution tray (5) from the water panel evaporator assembly by lifting
straight up from the scale control insert (8). Lightly scrape out any calcium deposits and
clean the “V” notches (6) but do not scrape off the granular coating from the bottom.
This textured surface helps ensure even water flow for maximum performance. See page
3 if removed.
6. Slide the Water Panel evaporator (7) out from the Scale Control Insert (8). Clean the
insert frame of calcium deposits with a putty knife. Inspect Water Panel evaporator
(Stock No. 35 for Model 600) and substitute a new Genuine Aprilaire Water Panel if
necessary. Slide the Water Panel back into the scale control insert with the colored spot
up and snap the distribution tray back into place.
7. Re-install the Water Panel evaporator assembly into the unit by fitting its drain into the
round receptacle at the base of the unit. Push the assembly in at the top against the
beveled tabs that will hold it in place. Push the end of the feed tube back firmly into the
distribution tray and replace the front cover.
8. Remove the drain hose (9) from the bottom of the unit and bend and flex it to loosen the
internal calcium deposits. Then flush it with water under pressure and slip it back onto
the drain fitting.
9. Turn on the water supply.
10. Check system operation:
Humidifier Control: (Automatic or Manual) Check system operation and reset change
water panel indicator by setting the knob to “Test/Reset”. With furnace blower operating
and furnace calling for heat, humidifier will operate for one minute. DO NOT LEAVE IN
TEST MODE AS HUMIDIFIER WILL NOT OPERATE.
11. Set Humidifier Control to its original position.
MAINTENANCE INSTRUCTIONS for
APRILAIRE HUMIDIFIER MODEL 600
CAUTION! Sudden operation may cause personal injury or
property damage. Turn Humidifier Control to “off” or
lowest setting before servicing.
1. Front Cover
2. Feed Tube
3. Integral Damper
4. Water Panel
Evaporator
Assembly
5. Distribution Tray
6. “V” Notches
7. Water Panel
8. Scale Control
Insert
9. Drain Hose
MODEL 600

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4
5
6
7
8
9
1
2
3
1. Note Humidifier Control setting and turn dial to the “OFF” position.
2. Disconnect electrical power and turn off water supply.
3. Unlatch humidifier cover assembly (1) from base assembly (2) at the bottom of the cover,
lift, and set aside.
4. Pull out the water panel evaporator assembly (3) by grasping at the top and tipping out.
5. Remove the distribution tray (4) from the water panel evaporator assembly (3) by
unsnapping the plastic holding strips from the tabs at the end of the tray. Lightly scrape
out any calcium deposits and clean the “V” notches (5) but do not scrape off the
granular coating from the bottom. This textured surface helps ensure even water flow for
maximum performance.
6. Slide the Water Panel evaporator (6) out from the Scale Control Insert (7). Clean the Scale
Control Insert by twisting and flexing it to loosen the calcium deposits or use a putty knife.
Inspect the Water Panel evaporator (Stock No. 35) and replace with a new Genuine
Aprilaire Water Panel if necessary. 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. Re-install the water panel evaporator assembly (3) into the base assembly (2). Push it in
at the top between the retaining ribs that hold the assembly in place in a vertical position.
8. Remove the drain hose (8) from the bottom of the unit. Bend and flex it to loosen the
internal calcium deposits. Then flush it with water under pressure and slip it back onto
the drain fitting.
9. Reinstall cover assembly (1) by hooking at the top of the base assembly (2) and
latching at the bottom.
10. Reconnect electrical power (9) and turn on the water supply.
11. Check system operation:
Humidifier Control: (Automatic or Manual) Check system operation and reset change
water panel indicator by setting the knob to “Test/Reset”. With furnace blower operating
and furnace calling for heat, humidifier will operate for one minute.
12. Set Humidifier Control to its original position.
NOTE: The motor is permanently lubricated and does not need to be oiled.
MAINTENANCE INSTRUCTIONS for
APRILAIRE HUMIDIFIER MODEL 700
WARNING! 120 volts may cause serious injury from electrical shock.
Disconnect power and shut off water supply before servicing.
MODEL 700
1. Front Cover
2. Base
3. Water Panel
Evaporator
Assembly
4. Distribution Tray
5. ”V” Notches
6. Water Panel
7. Scale Control
Insert
8. Drain Hose
9. Power Cord

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1. Note Humidistat setting and turn dial
to the “OFF” position.
2. At the side of the unit opposite the airflow duct pull front cover (1) off holding with both
hands and set aside.
3. Carefully pull the plastic feed tube (2) out of the nozzle (3) at the top of the Water Panel
evaporative assembly (4). Pull this assembly out by grasping at top and tipping out.
4. Remove the distribution tray (5) from the Water Panel evaporative assembly by
unsnapping the plastic ends of the Scale Control Insert (8), from the tabs at the end of
the tray. Lightly scrape any calcium deposits out of the “V” notches (6), but do not
scrape the granular coating from the bottom of the tray. This textured surface helps
ensure even water flow for maximum performance. If the granular coating has been
removed, place several drops of liquid dish soap on the distribution tray and clean
thoroughly. This will only need to be done once.
5. Slide the Water Panel evaporator (7) out from the Scale Control Insert (8). Clean the
insert frame by twisting and flexing it to loosen the calcium deposits, or use a putty
knife. Inspect the Water Panel evaporator (Stock No. 10 for Model 550) and substitute a
new one if necessary. Slide the pad back into the insert frame with color mark up and
snap the distributor tray back into place.
6. Re-install the Water Panel evaporative assembly into the unit by fitting its drain into the
round receptacle at the base of the unit. Push the assembly in at the top against the
beveled tabs that will hold it in place. Push the end of the feed tube back firmly into the
nozzle and replace the front cover.
7. Remove the drain hose (9) from the bottom of the unit and bend and flex it to loosen the
internal calcium deposits. Then flush it with water under pressure and slip it back onto
the drain fitting.
8. Turn up Humidistat and check unit operation.
MAINTENANCE INSTRUCTIONS for
APRILAIRE HUMIDIFIER MODEL 550
CAUTION! Sudden operation may cause personal injury or
property damage. Turn Humidistat to “off” or lowest setting
before servicing.
1. Front Cover
2. Feed Tube
3. Nozzle
4. Water Panel
Evaporative
Assembly
5. Distribution Tray
6. ”V” Notches
7. Water Panel
8. Scale Control Insert
9. Drain Hose
7
56
8
9
1
2
34
MODEL 550

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Your Research Products Corporation Aprilaire®Humidifier unit is
expressly warranted for one (1) year from date of installation to be
free from defects 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 one (1)
year period and which is returned not later than thirty (30) days after
said one (1) year period by you to either your original supplier or to
Research Products Corporation, Madison, Wisconsin 53701, together
with the model number, manufacturing code 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 ONE 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.
LIMITED WARRANTY

- 16 -
The Aprilaire®Indoor Air Comfort System is an integrated group of air
quality enhancement products designed to work with your heating and
cooling system to make your home more comfortable. For the best in
indoor air quality, ask your heating and cooling contractor about these
fine Aprilaire products, or visit us at www.aprilaire.com to solve your
Indoor Air Comfort needs.
Aprilaire®
Automatic Humidifiers
Aprilaire®
High Efficiency Air Cleaners
®
Aprilaire®
Zone Control Systems
Aprilaire®
Energy Recovery Ventilator
Aprilaire®
Electronic Thermostats
The Best in Indoor Air Comfort, The Best Cure For Dryness® , Nobody Makes Clean Air Easier® ,
Custom Comfort Throughout Your Home®
, Only The Freshest Homes Have April Air™ ,
Energy Efficiency Never Looked So Good™
The following are registered trademarks reserved by Research Products Corporation.

- 17 -
Date Dealer Name
SERVICE AND WATER PANEL REPLACEMENT RECORD

Please… Take a few minutes to visit us on-line at
www.aprilaire.com
to register your Aprilaire product.
If you do not have on-line access, please mail a postcard
with your name, address, phone number, product purchased
and date of purchase to:
Research Products Corporation
P.O. BOX 1828
Madison, WI 53701
Thank you!
Your Warranty Registration information will not be sold
or shared outside of this company.
DP #10005406 25.10.03 Printed in U.S.A.
P.O. BOX 1467 • MADISON, WI 53701-1467
WARRANTY REGISTRATION