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Another Tip to Keep AC Clean and Efficient

Here’s how the Bowins keep annoying seeds out of their Bard wall-pack air conditioners

William and Sherrie Bowin handle engineering for North American Broadcasting Company Inc., licensee of WMNI(AM), WRKZ(FM) and WJKR(FM). They read our tip about covering air inlets on wall-pack air conditioners to keep out cottonwood, dandelion and other seeds.

William and Sherrie have been doing this for their Bard wall-packs but with a twist. Bard air inlets are rather large, and the Bowins have not found an off-the-shelf filter solution like the one described in our earlier column.

Rather than fabricating a custom screen frame, they opted for a simpler approach. They cover the air intake vents with inexpensive fiberglass screens, available in rolls at most hardware or big box stores for a few dollars.

They cut the screen to size and attach it directly to the air conditioner with caulking. They are careful to use non-silicone-based caulking so that the screen can be removed easily later if necessary. (Apply the caulking to the air conditioner rather than to the screen. Trust them; installation is much easier that way, especially on a windy day.)

Cleaning is easy with a paint brush and should be performed weekly during peak cottonwood season.

Fig. 1 shows the initial screen installation. The photo was taken just five minutes after installation — before the caulking was even dry. As you can see, it was already starting to accumulate seeds.

Fig. 1: A fiberglass screen keeps cottonwood seeds out of the air conditioner.Fig. 2: After just seven days, the screen is filling up with seeds.Fig. 3: The screen is nearly completely clogged.

Fig. 4: Some of the cottonwood seeds harvested from the screen. Fig. 2 shows the same screen just seven days later. Imagine where those seeds would have ended up without the screen! Fig. 3 shows the nearly clogged screen during peak cottonwood season, and Fig. 4 show the pile of seeds that were peeled off the screen.

As William and Sherrie demonstrate, cleaning the external screen is a lot less labor-intensive and costly than removing the air conditioner cover and spray-washing the coils. If your transmitter building uses these kinds of wall-pack air conditioners, consider adding this option to extend your unit’s life.


Engineers needing to control AC loads from devices like the Raspberry PI or other micro-controllers will want to investigate the Internet of Things control relay by Digital Loggers Inc.

Contract and special projects engineer Dan Slentz, a fellow RW contributor, tips us off to this device that sells for under $20.

Fig. 5: Quick fixes like this sometimes turn into permanent installations. Inside the thermoplastic enclosure is a circuit that is surge protected, includes a de-bounce circuit and status LED, and is optically isolated. Two pairs of UL/CSA outlet plugs are provided. One pair is normally “off” and the other pair is normally “on.” The module is compact, but can control multiple AC loads up to 12 A.

Single units are available through Amazon. Search “IoT Relay Enclosed High Power Raspberry” for more information, or to order one of your own.

Dan writes that Digital Loggers manufactures a number of interesting products. See Thanks, Dan, for a neat and cost-effective problem solver.


After seeing the conduit used to route cabling into a ceiling in our Aug. 17 issue, a contract engineer who wishes to remain anonymous sent in the picture in Fig. 5.

He captioned it “Not everyone takes the time to install conduit into the ceiling.” The problem with fixes like this, he says, are that they tend to become permanent, even if they were intended as temporary.

Remember, anything you do is worth doing right.

Contribute to Workbench. You’ll help your fellow engineers and qualify for SBE recertification credit. Send Workbench tips to [email protected]. Fax to (603) 472-4944.

Author John Bisset has spent 46 years in the broadcasting industry and is still learning. He handles West Coast sales for the Telos Alliance. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award.