MAINTENANCE INSTRUCTIONS
for
APRILAIRE HUMIDIFIER MODEL
400
WARNING! 120 volts may cause serious injury from electrical shock. Disconnect power
and shut off water supply before servicing.
1. Note humidistat or 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 assem-
bly (12).
5. Unsnap the distribution tray from the scale control insert (8). Lightly scrape out any cal-
cium 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 2 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. Reset humidistat control to its original position. Check operation.
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MODEL 400
MODEL
400
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
