Aprilaire Humidifier 400m User Manual

Humidifiers  
Owners Manual  
For Models 350, 360, 400, 400M, 500,  
500M, 600, 600M, 700 & 700M  
Includes Safety & Operating Instructions  
and Warranty Information  
READ AND SAVE THESE INSTRUCTIONS  

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There are some homes where drain facilities are not accessible or available.  
For these situations, or where high water hardness is not a problem, Models  
400 and 400M are designed to satisfy these applications.  
PRINCIPLE OF OPERATION  
Withyourpurchaseofthishumidificationsystem, youhaveinvestedinahumidifier  
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.  
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  
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.  
evaporation, and the Scale Control Insert (which encases the Water Panel)  
efficiently traps mineral deposits which are often the cause of damage to  
working parts in ordinary humidifiers. When properly maintained, no “white  
dust” will be distributed through the living quarters. 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 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 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 humidifier. The water is uniformly distributed across the  
width of the tray and through a scientifically designed system of outlets. It  
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.  
®
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.  
Your Digital Humidifier Control works in conjunction with your HVAC 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.  
Models 350 and 360 use service hot water (140°F maximum) for a heat  
source, as heat is needed for evaporation. 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 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. This reading will accurately indicate the RH in the living space  
when the HVAC blower is operating. Once the HVAC blower stops, the  
readout will not change.  
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 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.  
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 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.  
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- 3 -  
AUTOMATIC MODE  
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 5 for  
Automatic Mode. See Figure B on page 6 for Manual Mode.)  
FIGURE A – Automatic 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.  
90-1235  
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.  
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).  
DIGITAL HUMIDIFIER CONTROL INDICATOR LIGHTS  
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.  
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.  
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.  
Humidifier On: The green light indicates that the humidifier is operating  
normally.  
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.  
- 4 -  
- 5 -  
WATER PANEL CHANGE INDICATOR  
MANUAL MODE  
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 characteristics.  
FIGURE B – Manual Mode  
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  
Manual Mode  
The Test/Reset feature allows the humidifier operation to be checked even if  
there is no call for humidity. See “Check the Humidifier Operation” on page 9.  
Label and Resistor  
90-1236  
When installed in the Manual Mode (see Figure B), 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 that evening, then merely reduce the setting to 25% several hours  
prior to the temperature change.  
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 and a minimum of 10% RH.  
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 RH. This same condensation can occur in other areas in your  
home, possibly resulting in damage.  
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  
1
2
3
4
5
6
7
10% 10% 10% 15% 20% 25%  
10% 10% 15% 20% 25% 30%  
10% 15% 20% 25% 30% 35%  
15% 20% 25% 30% 35% 40%  
20% 25% 30% 35% 40% 45%  
25% 30% 35% 40% 45% 45%  
30% 35% 40% 45% 45% 45%  
TABLE 1 – Outdoor Temperature/Indoor Relative Humidity  
Outside Temperature  
Recommended RH  
+40°F  
+30°F  
+20°F  
+10°F  
0°F  
45%  
40%  
35%  
30%  
25%  
20%  
15%  
10°F  
20°F  
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- 7 -  
TABLE 3 – Operation Guide  
Solution  
OPERATING INSTRUCTIONS –  
MODELS 350, 360, 400M, 500M, 600M & 700M  
Condition  
Condensation on windows.  
Reduce the setting on the control dial by  
1 increment.  
FIGURE C – Manual Humidifier Control  
Lack of humidity.  
Increase the setting on the control dial by  
1 increment.  
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 and HVAC is  
calling for heat. 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.  
90-1237  
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 6).  
Test mode.  
System operation is checked by setting  
the knob to “Test/Reset”. Make certain  
HVAC blower is operating and HVAC is  
calling for heat. Humidifier will operate  
for one minute. NOTE: Placing the knob  
in “Test/Reset” resets the Water Panel  
change timer.  
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.  
Red “Call Dealer for Service” Note the error code on the display (E1, E2,  
light flashes (Figure A).  
E3 or E4) and call your heating and air  
conditioning dealer.  
CHECK THE HUMIDIFIER OPERATION  
DIGITAL HUMIDIFIER CONTROL  
Yellow “Change Water Panel” Refer to the Annual Maintenance section  
light flashes (Figure A).  
(page 11) 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.  
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 system must be  
operating 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.  
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.  
- 8 -  
- 9 -  
ADDITIONAL INFORMATION FOR ALL MODELS  
ANNUAL MAINTENANCE  
Be sure to keep fireplace dampers closed when not in use. They provide an  
excellent escape route for heat, as well as humidity.  
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.  
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.  
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.  
EFFECT OF WATER CHARACTERISTICS  
Your humidifier is designed to operate using hot, cold, hard or mechanically  
softened water. (Hot water is required for Models 350 and 360.)  
• Call your heating and air conditioning dealer.  
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.  
• 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.  
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 controlled by flushing  
them down the drain.  
• Purchase only Genuine Aprilaire Water Panels to maintain performance.  
If your humidifier is equipped with a Digital Humidifier Control with Water  
Panel change 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 “Humidifier On”  
light continues to blink, your humidifier is in Test mode. DO NOT LEAVE THE  
CONTROL IN TEST MODE OR HUMIDIFIER WILL NOT OPERATE.  
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 off the hot water supply before  
disconnecting or tapping into any hot water supply line.  
- 10 -  
- 11 -  
ANNUAL SUMMER SHUTDOWN  
PERIODIC PREVENTATIVE MAINTENANCE  
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.  
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 at the same time he services the  
HVAC system.  
Humidifier Control:  
Digital Humidifier Control in Automatic Mode (see Figure A):  
No adjustment is necessary.  
All models have a distribution tray above the Water Panel, which should be  
inspected annually and cleaned of excess mineral deposits. Older models  
have a granular coating in the distribution tray. Do not scrape the granuals  
out of the tray. Newer models have a fabric liner in the distribution tray.  
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.  
WATER LINE INSPECTION AND SERVICE INSTRUCTIONS  
1. Disconnect electrical power to the HVAC  
and shut off water supply.  
WATER  
FEED TUBE  
2. Disconnect the water line at the inlet  
compression nut.  
OUTLET  
COMPRESSION  
NUT  
3. Remove the in-line strainer from inside  
the inlet side of the valve by using a small  
nail or wire.  
ORIFICE  
4. Flush the in-line strainer clean or replace  
with a new strainer, Part No. 4004.  
SOLENOID  
VALVE  
5. Reconnect the inlet water line. Double  
Wrench to Prevent Leaking.  
INLET  
6. Disconnect the water feed tube at the  
outlet compression nut.  
IN-LINE  
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.  
STRAINER  
INLET  
COMPRESSION  
NUT  
8. Inspect the orifice in the water feed tube  
and make sure the small opening is  
unplugged.  
90-1053  
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.  
- 12 -  
- 13 -  
REQUIRED MAINTENANCE INSTRUCTIONS  
REQUIRED MAINTENANCE INSTRUCTIONS  
(APRILAIRE HUMIDIFIER MODELS 400 & 400M)  
(APRILAIRE HUMIDIFIER MODELS 350 & 360)  
WARNING  
CAUTION  
120 volts may cause serious injury from electrical shock. Disconnect  
power and shut off water supply before servicing.  
Sudden operation may cause personal injury or property damage.  
Turn Humidifier Control to “OFF” or lowest setting before servicing.  
5
1. Front Cover  
6
4
2
2. Feed Tube  
8
4
3. Integral Bypass Damper  
4. Water Panel Evaporative  
Assembly  
7
1
9
5. Distribution Tray  
6. “V” Notches  
5
7. Water Panel Evaporator  
8. Scale Control Insert/Float  
Chamber  
9. Overflow Drain Line  
10. Float Cover  
3
3
2
11  
10  
1. Inlet Grille  
2. Distribution Tray  
3. Scale Control Insert  
4. Distribution Tray Cover  
5. Water Panel Evaporator  
6. Drain Spud  
7. Power Cord  
8. Metal Housing  
9. Water Panel  
Evaporative Assembly  
12  
9
11. Float  
8
12. Water Level Sensor Assembly  
90-1077  
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.  
6
7
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).  
1
1. Note Manual Humidifier Control setting and turn dial to the “OFF” position.  
2. Disconnect electrical power and turn off water supply.  
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 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.  
3. Remove inlet grille screws (1). Remove grille from metal housing (8).  
4. Lift the Water Panel evaporative assembly (9) out of the humidifier housing (8).  
5. To remove the distribution tray (2) from Water Panel evaporative assembly (9), push down  
on tray and pull out scale control insert (3). To clean the “V” openings of the tray, gently pry  
the distribution tray cover (4) 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 evaporator (5) out from the scale control insert (3) 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 (3) and snap the distribution tray cover (4) into the distribution  
tray (2). 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 (6). Make sure the drain line has a  
constant downward slope and is not flattened or blocked.  
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:  
9. Reinstall Water Panel evaporative assembly (9) and intake grille (1).  
10. Reconnect electrical power (7) and turn on water supply.  
11. Turn up Manual Humidifier Control and check system operation.  
12. Set Manual Humidifier Control to its original position.  
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.  
- 14 -  
- 15 -  
REQUIRED MAINTENANCE INSTRUCTIONS  
(APRILAIRE HUMIDIFIER MODELS 500, 500M, 600 & 600M)  
REQUIRED MAINTENANCE INSTRUCTIONS  
(APRILAIRE HUMIDIFIER MODELS 700 & 700M)  
CAUTION  
WARNING  
Sudden operation may cause personal injury or property damage.  
Turn Humidifier Control to “OFF” or lowest setting before servicing.  
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.  
4
5
3
5
8
1. Front Cover  
4
1. Humidifier Cover  
Assembly  
6
2
2. Feed Tube  
7
7
1
1
3. Integral Bypass Damper  
2. Base Assembly  
6
4. Water Panel  
Evaporative Assembly  
3. Water Panel  
Evaporative Assembly  
5. Distribution Tray  
4. Distribution Tray  
5. ”V” Notches  
6. “V” Notches  
3
2
7. Water Panel Evaporator  
8. Scale Control Insert  
6. Water Panel Evaporator  
7. Scale Control Insert  
8. Drain Line  
9. Drain Line  
8
9
9. Power Cord  
90-1075  
90-1076  
9
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.  
1. Note Humidifier Control setting and turn dial to the “OFF” position.  
2. Disconnect electrical power and 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.  
3. Unlatch humidifier front cover assembly (1) from base assembly (2) at the bottom of the cover,  
lift, and 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.  
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  
mineraldeposits, beingcarefulnottostretchorloosenthesyntheticfabricliner. Soakingthetray  
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.  
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.  
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.  
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.  
13. Set Humidifier Control to its original position.  
NOTE: The motor is permanently lubricated and does not need to be oiled.  
12. Set Humidifier Control to its original position.  
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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 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, model number of product purchased and date of installation 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.  
Thank you!  
RESEARCH PRODUCTS CORPORATION  
PO BOX 1467 • MADISON, WI 53701-1467  
10008263 10.08  
B2204666A  
©2008 Research Products Corporation  
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