Which Whole-House Humidifier Pad Do You Need, and How Often Should You Change It?

The right whole-house humidifier pad is matched by your humidifier's model number, not your furnace brand, so read the label on the humidifier and find it in Table 2. Most makers say to change the pad (also called a water panel) once per heating season. The AprilAire #45 and Carrier water-saver pads need changing twice per season, and steam units use a canister instead of a pad. Don't wash the pad; replace it.

Identify Your Whole-House Humidifier

To identify your whole-house humidifier, find its type (bypass, fan-powered or steam) and its model number. Type tells you what part wears out. The model number tells you which exact part to buy.

Bypass, fan-powered or steam: how to tell

Whole-house humidifiers come in three types: bypass, fan-powered and steam, and AprilAire's lineup covers all three. The AprilAire 500 is a small bypass unit, the 600 is a bypass unit, the 700 and 720 are fan-powered, and the 800 and 865 are steam. Table 1 shows what each type uses.

Table 1. Humidifier Type and What to Replace

Where the model number is

The model number of a whole-house humidifier is on the label on the humidifier itself, not on the furnace. Many HVAC brands sell humidifiers built by other makers, so the humidifier's own label decides the pad. If your unit carries the Bryant name, browse our Bryant humidifier filter replacement pads once you have the model number.

Steam humidifiers use a canister, not a pad

Steam humidifiers such as the AprilAire 800 and 865 use a steam canister instead of a pad. AprilAire's #80 canister fits the 800, 801, 865 and 866, and AprilAire says to replace it once per year. Everything else in this guide covers pad-style units.

Humidifier Pad Cross-Reference by Brand

Humidifier pads cross-reference by size class, and Table 2 lists only the fits that AprilAire, Honeywell, Lennox and GeneralAire state themselves. For other HVAC brands, such as Trane, Rheem or ICP, read the humidifier's model label and shop by that brand's collection.

AprilAire water panels #10, #12, #35 and #45

AprilAire makes four standard water panels: the #10, #12, #35 and #45, each listed for specific AprilAire models. The #10 measures 10H x 10W x 2D nominal, the #12 is 15H x 12W x 2D, and the #35 is 13H x 10W x 2D. The #45, used in the 400 series, is a paper-wicking panel with aluminum.

Honeywell HC22, HC26 and HC18 pads

Honeywell's HC22A1007, HC26A1008 and HC18P1009 pads fit Honeywell humidifiers and several AprilAire models, according to Honeywell. For example, Honeywell lists the HC26A1008 for its HE260 and HE360 and for the AprilAire 600 and 700. The HC18P1009 fits the AprilAire 112, 136, 224, 440, 445, 445A and 448.

Carrier and Bryant P110 pads

Carrier's owner's manual lists the P110-1045 pad for small bypass units, the P110-3545 for large bypass and fan-powered units, and the P110-4545 for water-saver units. These are in the same size classes as AprilAire's panels, but confirm against your humidifier's model label. If you have a Carrier small-bypass unit, check the model label before ordering.

Carrier's model names follow the same types:

• HUMCRSBP2412: small bypass.

• HUMCRLBP2417: large bypass.

• HUMCRWBP2417: water saver.

• HUMCRLFP1518: fan powered.

Lennox Healthy Climate X2660 and X2661

Lennox lists the X2660 pad for the HCWB3-12 and the X2661 pad for the HCWB3-17 and HCWP3-18. Lennox says to replace the pad at least once a year. Install it with the colored spot facing up.

GeneralAire vapor pads

The GeneralAire GA35 vapor pad fits GeneralAire 4200 and 4500 humidifiers, AprilAire models 350 through 768, and Honeywell HE260, HE265, HE360 and HE365, according to GeneralAire. GeneralAire also makes the 990-13 pad. GeneralAire warns that washing a vapor pad removes its coating.

Table 2 brings the manufacturer-stated fits together by size class. Find your humidifier model in any column, then read across.

Table 2. Find Your Pad (Manufacturer-Stated Fits)

Lennox's X2660 and X2661 are placed by the humidifier models Lennox lists, not by an AprilAire equivalence. Carrier P110 pads are listed by Carrier type in the section above.

How Often to Change a Furnace Humidifier Pad

Change a furnace humidifier pad once per heating season for most models, and twice per season for the AprilAire #45 and Carrier water-saver pads. Hard water and heavy use can shorten that. Table 3 lists each maker's interval in its own words.

Once per heating season: most pads

Most furnace humidifier pads, including AprilAire's #10, #12 and #35, should be changed once per heating season. Honeywell says to replace pads annually at the start of the heating season. Bryant says to replace the water panel at the beginning of each heating season.

Twice per season: AprilAire #45 and Carrier water-saver pads

The AprilAire #45 water panel should be changed twice per heating season, according to AprilAire. Carrier gives the same twice-per-season interval for its water-saver pad. Every other Carrier pad should be replaced at least annually.

Hard water and heavy use

Hard water can shorten a humidifier pad's life, so you may need to change it more often than once a season. Honeywell suggests a mid-season change if you have hard water, and Bryant notes hard water may need more frequent changes. For questions like whether you can use Zero Water in your humidifier, see our guide on can I use Zero Water in my humidifier.

Table 3. Replacement Interval by Manufacturer

Clean or Replace? Caring for the Pad, Tray and Frame

Replace the humidifier pad itself, but clean the parts around it: the distribution tray, the frame and any scale-control insert. Carrier and GeneralAire both say not to wash the pad. Table 4 sorts each part.

Why the pad itself should not be washed

A humidifier pad should not be washed, because Carrier recommends replacing the evaporator pad rather than cleaning a paper or mesh water panel. GeneralAire adds that washing its vapor pad removes the pad's coating. A scaled pad goes in the trash, not the sink.

Cleaning the distribution tray, frame and drain

Clean the distribution tray and pad frame when you change the pad, using vinegar or CLR for stubborn deposits, per Honeywell. AprilAire recommends an annual inspection of the distribution tray. Carrier says its scale-control insert can be cleaned with vinegar or lime remover.

Table 4. Clean or Replace

Installing the new pad the right way up

Install a new Carrier or Lennox humidifier pad with the colored spot facing up, as both makers' manuals instruct.

1. Turn off the humidifier and its water supply.

2. Remove the cover and lift out the old pad.

3. Clean the tray and frame (Table 4).

4. Fit the new pad with the colored spot up, then reassemble.

Signs the pad is spent

A spent humidifier pad shows white scaling, reduced output or odors, according to Bryant. Lennox says white dust in the home points to scale. Table 5 lists each sign and what to do.

Table 5. Symptoms of a Spent Pad

Frequently Asked Questions

Are AprilAire 35 and 45 water panels interchangeable?

No, AprilAire lists the #35 and #45 water panels for different humidifiers. The #35 fits models including the 600, 700, 760 and 768, while the #45 fits the 400 series. The #45 is a paper-wicking panel with aluminum and needs changing twice per heating season.

Can I use a Honeywell HC26 pad in an AprilAire 600?

Yes, Honeywell lists its HC26A1008 pad as fitting the AprilAire 600. Honeywell also lists the HC26A1008 for the AprilAire 350, 360, 560, 568, 700, 760 and 768, and for its own HE260 and HE360. AprilAire's own panel for the 600 is the #35.

How often should I change my AprilAire 600 water panel?

Change the water panel in an AprilAire 600 once per heating season, according to AprilAire. The 600 uses the #35 water panel. If you have hard water, you may need to change it more often; Honeywell suggests a mid-season change for hard water.

Can I soak a scaled humidifier pad in vinegar?

No, a scaled humidifier pad should be replaced, not soaked. Carrier recommends replacing the pad rather than cleaning it, and GeneralAire says washing its vapor pad removes the coating. Vinegar or CLR is for the frame and tray, per Honeywell.

Does a steam humidifier need a filter?

A steam humidifier uses a steam canister instead of a pad or filter. AprilAire's #80 canister fits the 800, 801, 865 and 866 steam humidifiers. AprilAire says to replace the canister once per year.

Should the humidifier be off in summer?

Check your humidifier's owner's manual for off-season steps, because the procedure varies by model. AprilAire, Honeywell and Bryant all schedule pad replacement for the start of the heating season. Changing the pad then means you start each winter with a fresh one.

Sources

• AprilAire: Water Panel #10, #12, #35, #45 pages; HydroCore; #80 steam canister; humidifier lineup; humidifier maintenance; "How to change your AprilAire water panel"

• Honeywell Home: HC26, HC22 and HC18 pad pages; support articles on replacement and pad-style maintenance

• Carrier: OM-HUMCRBP-01 owner's manual; humidifier maintenance page

• Bryant: humidifier maintenance page

• Lennox: WB2/WP2 manual

• GeneralAire (generalfilters.com): GA35 Vapor Pad page