Don’t Clean Your Coils

With a Pressure Washer

We previously mentioned that clean evaporator and condenser coils are happy coils. Dirt and debris builds up, restricts airflow, and prevents the coils from doing their job. Recently we realized, while there is a right way and a wrong way to do everything, there is a really wrong way to clean your air conditioner.

High Powered Cleaning

Suppose you need to clean something that’s incredibly ground in. You might scrape at it, or find someway to break up its edges and get under the layer of dirt to pry it up. It’s going to take forever, require a lot of work, but eventually gets the job done. What if you could instantly apply all that force to every weak spot in the dirty build up, and just blast it apart?

This is in part, how a pressure washer works. On the one hand, we’re applying a massive amount of force in a small area. Any imperfections or weak points are going to make the substance fracture. The water will shoot through the dirt, and then blast outwards and send it to bits. On the other hand, water isn’t exactly abrasive like sand, BUT it will carry away a little more material with every drop that hits.

Detergents can be added to the mix to chemically breakdown whatever it is that’s getting sprayed. If there’s an especially solid build up, you can essentially blast and melt it apart at the same time. The nice thing with water is that it’s powerful, but fairly gentle from a consumer pressure washer. It won’t harm stone, metal, or wood most of the time.

Relaying Force

Pressure washers work because water won’t compress. No matter how much force you put into water, it won’t get appreciably smaller. There is some 0.00000001% compression, but it’s such a small amount that it doesn’t matter. What happens instead, is that all the force pushing against the water is evenly distributed around and through it.

If you put a tennis ball in a tank of water, then pressurize that tank to 100PSI, then there will be 100 pounds of force pressing on every square-inch of the ball (and on the walls of the tank). The ball is going to probably come out like a destroyed, fuzzy marble. If you puncture the tank, then the water will jet out with a force proportional to the hole size. With enough pressure, the water would slice through solid steel.

Too Much Force

In principle, the condenser and evaporator coils can withstand some force pushing against them. The earth’s atmosphere is pushing on the coils 24/7 with a force of about 14.7 PSI. Spraying water from a garden hose over the coils is going to exert some measure of pressure on them greater than atmospheric pressure (otherwise, it’d never get out of the hose). The thing is, 14.7 PSI, even 30 PSI is not a lot of force.

Our Philly-local hardware stores sell pressure washes in a variety of capacities. On the smaller end, there was 2000 PSI. The average looked to be 3800 PSI. The fins on your coils are thin, typically something like aluminum. A larger sheet could be bent in your bare hands. The little fins have a little strength because you’ve got no leverage against them and human fingers are squishy, it hurts to exert our full force on small, sharp things. The water has no such issues.

Depending on the nozzle and configuration, a pressure washer could dump all of 6000 or more pounds of force onto a tiny little fin. The overwhelming pressure at-best could bend the fin and prevent it from getting airflow. In the middle, it could slice straight through the fin like a hot knife through butter. Lastly, you could snap the fin off, and puncture the coil in the process, either by the shear pressure lancing through it or the fin tearing out a chunk of coil tubing with it.

Simply put, this ends in tears, discomfort, your repair contractor asking ‘how did you do this? I’ve been fixing air conditioners for 40 years and I’ve never seen this’, and of course, a large bill for the time consuming fix.

Do It Right

If there is any doubt about whether or not you can clean your air conditioner, just have your HVAC Contractor do it. It’s a fairly quick and painless process, it’s not labor intensive, and it’ll increase your air conditioner’s efficiency. It’s hard to find any specific downsides on this. The typical cleaning process is done either with steam cleaners or detergents that will eat away any dirt.


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