Aprilaire 400 Instructions

Maintenance Instructions:
Aprilaire Models 400 & 400A
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 the 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 from the scale control insert
(8). Follow the instructions below depending upon the type of distribution
tray in your humidifier:
a. For trays with a synthetic fabric liner: 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.
b. For trays with granular coating: Do not scrape off the granular
coating, but lightly scrape out any mineral deposits and clean the "V"
notches (6). This textured surface helps ensure even water flow for
maximum performance.
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).