What filter/pad fits a Aprilaire 400m humidifier?
The Aprilaire 400m humidifier uses the 45 replacement furnace/whole-house water panel.
Key takeaways
- Replacement part number: 45 (Aprilaire).
- This is a furnace/whole-house water panel, not a portable-unit wick.
- Replace once per humidifying season, or sooner if it's visibly scaled or discolored.
- A cheaper aftermarket filter can fit the same slot - check reviews for real-world fit before buying.
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Also known as
The 45 replaces (and is cross-referenced under) these part numbers: P110-4545, S1-HUPAD45.
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Frequently asked
What filter/pad fits a Aprilaire 400m humidifier?
The Aprilaire 400m uses the 45 (Aprilaire #45 Water Panel Evaporator), a furnace/whole-house water panel.
Is the 45 a wick or a furnace pad?
The 45 is a furnace/whole-house humidifier water panel, not a portable-unit wick.
How often should I replace the 45?
We don't have a manufacturer-listed replacement interval for the 45 - a common default is once per humidifying season, or sooner if it's visibly scaled or discolored.
Should I buy the OEM filter or an aftermarket one?
The genuine Aprilaire 45 is the safe, exact-fit choice. A cheaper aftermarket wick or pad can fit the same slot too - check reviews for real-world fit and how well it wicks water before buying, since humidifier filters aren't independently certified the way NSF-listed water filters are.