Aprilaire Essential Maintenance Instructions and Warranty Registration for Your Humidifier

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.

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	MODEL
12. Water Level Sensor Assembly		400

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.

MODEL 400

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