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Maintenance Instructions for Aprilaire Models 500, 500A, & 500M

Maintenance Instructions for Aprilaire Models 500, 500A, & 500M

  1. Note Humidifier Control setting and turn dial to the "OFF" position.
  2. Turn off water supply. Move the integral bypass 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. Set aside.
  4. Pull the plastic feed tube (2) out of the distribution tray (5) 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 (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 line-removing agent is helpful when trying to remove stubborn mineral deposits.
  6. Slide the Water Panel evaporator (7) out of the scale control insert (8). Clean the scale control insert of mineral deposits. Slide the new Water Panel evaporator into the scale control insert with the colored spot up and snap the distribution tray (5) back into place.
  7. Inspect the plastic feed tube (2) by gently flexing it and looking for cracks or signs of wear. Replaces tube if it is cracked, brittle, or has been damaged.
  8. Reinstall the Water Panel evaporator 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 (2) firmly back into the distribution tray (5) and replace the front cover (1).
  9. Remove the drain line (9) from the bottom of the humidifier. If applicable, flex it to loosen any mineral deposits or blockages. 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.
  10. Turn on the water supply. Return integral bypass damper (3) to appropriate position.
  11. Check system operation:

Manual Humidifier Control: With the furnace blower operating, turn up manual humidifier control and check system operation.

Automatic Humidifier Control: (Automatic or Manual mode) Check system operation and reset Change Water Panel indicator by turning the knob to "Test/Reset". With furnace blower operating, humidifier will operate for one minute. DO NOT LEAVE IN TEST MODE AS HUMIDIFIER WILL NOT OPERATE.

  1. Set Humidifier Control to its original position.