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1. Note Humidistat setting and turn dial to the “OFF” position.
2. Turn offf water supply. Turn the integral bypass damper (10) to the SUMMER position.
3. At the side of the unit opposite the airflow duct pull front cover (1) off holding with both
hands and set aside.
4. Carefully pull the plastic feed tube (2) out of the nozzle (3) at the top of the Water Panel
evaporator assembly (4). Pull this assembly out by grasping at top and tipping out.
5. Unsnap the distribution tray from the scale control insert (8). Follow the instructions below
depending upon the type of distribution tray in your humidifier:
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.
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. See page 3 if removed.
6. 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. Replace the Water Panel
evaporator (Stock No. 10) and with a new Genuine Aprilaire Water Panel. Slide the pad
back into the insert frame with color mark up and snap the distributon tray back into place.
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. Re-install the Water Panel evaporator assembly (4) 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 (2) back firmly into the
nozzle and replace the front cover.
9. Remove the drain hose (9) from the bottom of the unit and flex it to loosen any mineral
deposits or blockage. Then flush it with water under pressure and slip it back onto the
drain fitting. Make sure the drain hose has a constant downward slope and is not flattened
or blocked.
10. Turn on the water supply.
11. Check system operation:
Humidistat: With the furnace blower operating and the furnace calling for heat, turn up
Humidistat and check system operation .
12. Set Humidistat to its original position.
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
Evaporator Assembly
5. Distribution Tray
6. ”V” Notches
7. Water Panel
8. Scale Control Insert
9. Drain Hose
10. Integral Bypass
Damper
7
5
6
8
9
1
2
3
4
10
MODEL 550
