Air Conditioning - Evaporator Coil Cleaning

Hey all.

Just wanted to check regarding the details of cleaning an evaporator coil. We have a bit of a smell from our vents when the A/C starts and are guessing it is the coil. Although the filter is clean and new, the coil may have never been cleaned. It also appears I can gain access to our coil within our plenum easily - the side of the plenum has a panel that appears only to be taped.

So, how exactly do I clean the coils? What kind of brush/cleaner? I guess the water I use to clean it simply goes down the drain? Isn't there a chance water can get onto the heat exchanger in the furnace?

Thanks for any information, I just want to learn to do this so I can when I need to.

At most big box stores you can buy a spray can of evaporator cleaner. It works well & does not require rinsing other than by the condensate. If the coil has caked on crud, use a BBQ brush with Simple Green & water to pre-clean they follow with the evaporator cleaner. Any time you brush a coil be sure to brush in the direction of fins NOT across them.

Great info! So I guess my worry of water travelling to the heat exchanger on the furnace or something is not valid? I know what an A-coil is and does, and what it looks like, just not how the condensate pans are setup to catch the water and let air past.

The condensate runs down the fins & into the drain pan. If you use the Simple Green, rinse with either a spray bottle or a garden sprayer set for a spray rather than a stream.

I'll look for the cleaner that needs no water first, for ease of use.

So, the condensate drains on the top sides of the A into the pans? One pan for each side of the coil?

Thanks for the help. I'm trying to picture how the coil looks installed, I'm guessing with the air going through the A underneath and pans on either side.

To envision a drain pan, picture a square made of 4 troughs with the center being open.

That makes perfect sense, I understand that now. Thanks!

Oh, for the condensate pan, is a bit of bleach good for killing anything that may be growing while being safe for the unit? Our condensate tube (clear) is starting to become fouled with something.

Bleach is fine. Let it sit for 15 - 30 minutes & rinse well. If you have a gravity drain, you can get replacement tubing at any big box store. If the condensate goes into a pump before being discharged, take the pump apart, wash with hot soapy water, & reinstall. The pump top is usually held on with 2 - 4 screws.

To help prevent slime build up they sell algaeside tablets. One such brand is Actabs Jr. made by Rectorseal. Another treatment is called PanPads made by Nu-Calgon.