Aprilaire 4788
Maintenance Kit For Aprilaire Model 400 400A 400M
  Aprilaire Humidifier Maintenance Kit

The Aprilaire maintenance kit 4788 includes everything you need to make your Aprilaire Model 400, 400A, 400M like new.

This 400 Series kit includes one each of the following items:

  1. 45 Water Panel ($12)
  2. 4403 Scale Control Insert ($19)
  3. 4406 Float Pair ($18)
  4. 4407 Water Distribution Tray ($18)
  5. 4405 Float Tray Cover ($17)
  6. 4004 In-Line Strainer ($5)
  7. 4231 Yellow Orifice ($3)
  8. 4335 Feed Tube with Compression Fitting ($10)
  9. Owner's Manual - Printed

The total cost of these items if purchased individually would be $96.00, save $19 by purchasing the 4788 maintenance kit.

Where is My 400 400A 400M Model Number

The Model Number on the Model 400 400A 400M is located on the side with the solenoid valve. The Aprilaire 400 Series can be configured with the bypass duct on the right or left. Thus the soleniod and label can be located on the right or left side. 
Where is my Aprilaire 400 400A 400M Model Number

Aprilaire In-Line Strainer & Orifice

Aprilaire Flow-Thru humidifiers have a solenoid with a small strainer filter in the body. These strainers should be inspected and cleaned when replacing the water panel. If the strainer becomes clogged the water pressure will tear it and pieces will jam the solenoid or loose pieces will block the orifice.

Aprilaire 24 Volt Solenoid
Aprilaire 4004 InLine Strainer Aprilaire 4231 Yellow Orifice
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NuCalgon NP24 Series Filter Housing

Aprilaire Humidifier Service Video

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