What Size Pads Does My Swamp Cooler Take?

Your cooler takes the pad size listed for its model number, and the CFM class on the box is not enough to find it. A Champion 4001 takes four 27-1/2 x 27-3/4 in aspen pads in downdraft form; a MasterCool ADA70 takes 29 x 41-1/4 x 8 in rigid media. The tables below collect pad dimensions and part numbers from manufacturer spec sheets and OEM and supplier parts listings, so you can match your data plate to a size before you climb the ladder. If the plate is gone, the measuring method further down gets you to the right pad.

Why "a 4,000 CFM pad" is not a size

Two answers circulate: that pads are standard by cooler size, and that every model is different. Both are half right. Within one maker's cabinet, aspen pads are the same size every year and widely stocked. Across makers they are not. Champion's 3000 series uses a 22 x 27 in pad; Phoenix's Frigiking FD/FS 350, sold in the same 3,000 CFM class, uses 21 x 25 in. Buy by CFM and you can end up an inch short on two sides, which leaves an air gap around the pad.

The model number is not even the airflow. Champion's own table shows a 3000DD with a 1/3 hp motor moving 2,175 CFM with no duct resistance, and a 4001DD with a 1/2 hp motor moving 3,064 CFM at 0.3 in of static pressure. Phoenix rates the FD/FS 450 at 4,000 CFM by the industry standard while publishing 2,478 CFM at 0.3 in. Treat the number in the name as a family label, not a measurement; CFM explained covers why the two differ.

MasterCool rigid media sizes (Champion)

MasterCool coolers use rigid cellulose media, either 8 or 12 in deep. Champion sells the OEM media sets and lists MasterCool as the brand they fit. The model number tells you the depth: models ending in 12 (ADA7012, ASA5112) take 12 in media, the rest take 8 in.

Two cautions. First, GPAD numbers are one supplier's stock numbers, not Champion part numbers, so quote the 31xxxx or 110133 number at a parts counter. Second, the 50-series height disagrees by 1/4 in between Champion's listing (22-1/4) and the aftermarket listing (22-1/2). Rigid media does not shrink the way aspen does, so measure the old block's height before ordering an aftermarket one; a block of the wrong height either will not seat or leaves a bypass gap.

The same supplier carries larger and older MasterCool media. Models MC43, MC44, MD480 and MS480 (and Aerocool Trophy TD4800 and AD4800) take 23 x 40 x 8 in media sold as DPM100B for the 4,800 CFM cabinet, with a 23 x 40 x 12 in version also offered. The 6,500 CFM family (MC63, MC64, MD680, MS680) takes 28 x 40 x 8 in media, DPM200B, and a 28 x 40 x 12 in version exists for 12 in cabinets. The MasterCool AS/AD100 takes 36.6 x 44.75 x 12 in.

Phoenix and Aerocool sizes

Phoenix Manufacturing publishes pad sizes in its engineering data. Its Frigiking aspen coolers list both the pad frame and the pad, which is useful: the pad is up to 2 in smaller than the frame, so a pad bought to the panel size will not fit.

The same brochure states that Phoenix aspen pads are built to federal specification PP-E-911, Type 1, Class A, Grade 4, a detail worth knowing if you are comparing a bargain pad against an OEM one.

Aerocool rigid media coolers are different again. The Aerocool Pro PH6800/1/2 (6,800 industry rating, 3,500 to 4,500 delivered CFM) uses 40 in wide x 30 in high x 8 in deep media with a high density front half, Phoenix part 5-2-115. The Aerocool TD6801, TH6801, AD6800 and AH6800 take 30 x 40 x 8 in media; the original came in two pieces, and the aftermarket set sold as KP422 comes in four. For background on the brand, see the Phoenix Manufacturing guide.

Champion aspen pad sizes

Champion's spec sheet for its standard downdraft (DD) and side-draft (SD) coolers lists pad dimensions per cabinet, and OEM parts listings give the matching pad part and count.

The 110098 pad is also listed for Champion 14/21 commercial cabinets (16 pads downdraft, 12 side-draft), and 110092 for Essick Air N56/66D coolers as well as the Champion 5000; more on the two brands in the Champion and Essick Air guide. Champion's parts store also sells single aspen pads at 20-1/2 x 21, 22 x 27, 27-3/4 x 22-3/4, 27-1/2 x 27-3/4, 32-3/4 x 36-1/4 and 27 x 54 in. If your frame matches one of those within about 1/2 in, that is almost certainly your pad.

Aspen pads for 3,000 to 6,500 CFM boxes at a glance

Putting the two makers side by side shows how far apart pads in the same class can be. These are the published OEM sizes, not universal ones.

Aspen is forgiving: an oversize pad trims down with heavy scissors. So when you are between sizes, buy the larger pad and cut it, never the smaller one. Rigid media gives you no such slack; see aspen vs rigid media for why the two behave so differently, and types of evaporative cooler pads for synthetic pads that drop into aspen frames.

How to measure a cooler with no model plate

Old coolers lose their stickers, and many rooftop units have had panels swapped. Measure instead:

1. Count the pad faces. Four louvered sides means a downdraft cooler with four pads; three louvered sides plus a blower outlet on the fourth means side-draft with three. On a window unit, measure each pad separately.
2. Take one panel off and measure the opening the pad sits in. Measure height and width inside the retainer wires or lip, not the outside of the louvered panel. Phoenix's own figures show the frame running up to 2 in larger than the pad.
3. For aspen, compare against the tables and round up. Pick the listed pad within about 1/2 in of your opening, or the next size up and trim. The universal replacement parts guide covers bulk rolls if nothing listed fits.
4. For rigid media, measure the old block on all three axes. Height, width and depth (front to back, usually 8 or 12 in). Note which way the flutes slope, and photograph the block in place.
5. Take the numbers and a photo to the parts counter. Ask for the size, not the brand. A pad that fits the opening fits the cooler.

Where these sizes stop applying

The tables cover the coolers named, as listed by Champion, Phoenix and the suppliers cited. Several limits matter. Older cabinets of the same model family may have been built to slightly different dimensions, which is one reason supplier and OEM listings disagree by 1/4 in. Portable coolers (Hessaire, Portacool, Honeywell and similar) use media cut for each model and are not covered here; buy by the model number in the manual, as the portable cooler buying guide explains. Commercial and industrial cabinets use larger media in multiple blocks per face. And if your cooler uses a brand not listed, the measuring method above is the answer, not a guess from CFM.

After you have the size

Once the pads are in hand, the job is the same for every size: power off, panels off, pads out, clean the troughs and pump screen, pads in with no gaps. The step-by-step procedure, including rigid media orientation, is in how to replace swamp cooler pads. If you are not sure the old pads are done, how often to replace cooler pads gives the signs and intervals, and the water distribution system guide covers the troughs and header that decide whether new pads wet evenly.