Recently, I was asked at a networking event about the practice of annual coil cleanings. An owner inquired if he should be having the mechanical contractor clean the evaporator and condenser coils at his multiple office buildings every year. My inclination was to simply say yes! However, in truth, there are some factors to be considered. Over time HVAC equipment will fall into differing levels of disrepair leading to energy waste and compromised comfort for a building’s occupants. The condenser and evaporator coils are, to a large extent, where much of the work gets done in an HVAC system. Maintaining these coils, and keeping them clean, is essential to efficient operation, but do they require cleaning every year? The condenser coil is exposed to unfiltered outdoor air, so it will accumulate dirt and debris at a fairly predictable and consistent rate from year to year. Because of this continued accumulation of dirt, annual cleaning of the condenser coils makes sense in almost all circumstances.

Studies have shown that unmaintained condenser coils can decrease overall unit efficiency by 5% in 15 years and 30% in 20 years. Monitoring the cleaning and amount of dirt/debris that is removed, will quickly tell you if it is necessary to do it on an annual basis. The evaporator coil is quite a bit different. Because the evaporator coil is only exposed to filtered indoor air (in most situations), the rate of dirt and debris build-up is far slower; however, the impact on efficiency and operation can be significant. An evaporator coil that is compromised by dirt and debris will inhibit both air flow and heat transfer causing a substantial reduction in temperature control and overall efficiency. In most situations, coil cleaning is not required annually if filters are replaced regularly. It is recommended that the coils be inspected and the results logged annually to determine the most effective schedule for cleaning. Those in favor of annual evaporator cleanings (on packaged rooftop units) suggest that as long as all of the coil cleaning labor and materials are already present for condenser cleaning, then it stands to reason that the evaporator coils should be cleaned as well.

If cost is not a factor, then there is no real downside to an annual evaporator cleaning schedule. Regardless of the schedule you settle on for your equipment, keeping your coils clean is essential to the operation of your systems to maintain optimal efficiency, as well as to keep the overall comfort of the building’s occupants.Cleaning condenser coils on your outdoor AC unit will not only help the unit cool more efficiently, but it will also cut down on the power consumption of your AC.  It is important to clean the coils early in the year, before the AC unit is needed for the summer. The outdoor condenser coil of your air conditioner performs a tough job in warm weather. It takes the concentrated heat collected from your home and dumps it into the hot outdoor air. To get rid of the collected heat, your outdoor condenser coil has to move a lot of air. If the coil is dirty or if plants or other objects are too close to the conditioner unit, the fan in the outdoor coil can’t move as much air as required for good performance and efficiency.

This raises your electricity cost for air conditioning and may shorten the life of the outdoor condensing unit.do bamboo plants purify the air Around the outdoor condensing unit of the air conditioner, remove plants and other debris from within 3 feet of the unit in all directions.fuel injector air intake cleaner Make sure the air’s upward path from the unit is unrestricted for at least 5 feet.diy air conditioning duct cleaning If your outdoor unit is installed under a deck or if someone built a trellis or some other structure above it, either move that structure or hire an air-conditioning contractor to move the outdoor unit. Most condenser coils are loaded with pollen and dust even when you can’t see it. 

If your cooling season is 4 months or more, annual cleaning is an excellent idea. Do not wait longer than 2 years before cleaning condenser coils, and if your summers are long, cleaning more than once a year may be necessary.Simply restore the power to your AC unit and you’ll have a much smoother running air conditioner. If you find that there are too many bent fins, or if the AC unit is extremely dirty, you should call a local professional to service and clean it. For more information on air conditioning see The Homeowners Handbook to Energy Efficiency. Or, for specific information about servicing air conditioners for energy efficiency, see Saturn Hydronic Systems Field Guide. Your air conditioner does two jobs: It cools down the air and it dehumidifies the air. If you live in a dry climate, you want the AC to dehumidify as little as possible because it uses extra energy and makes you spend more on lip balm and hand lotion. If you live in a humid climate, you really want it to do that second job as well as it can to keep your indoor air dry and comfortable.

But where does all that condensate go? In most homes, it goes outdoors through a pipe, like the one above. Sometimes there's a little pump that pumps it out, but most often it drains by gravity alone. Occasionally that condensate line gets clogged. This happened at my condo last week. (We live in Atlanta, Georgia, a mixed-humid climate.) Gunk in the pipe built up to the point where it was barely draining. We could run the AC for a little while and then we'd have to turn it off again. This past weekend I tackled the problem. One of the best ways to do so is with good old air pressure. If you can close off all escape routes except the one in the direction of the clog, you can shoot positive pressure into the pipe near where the indoor unit is located. That should blow the clog out the other end. In our case, that wasn't an option because our condensate line is connected to our upstairs neighbor's air conditioner, too. So I got out my little wet-dry shop vac and set it up to suck the gunk out at the end of the pipe.

The photo below shows the setup. I was hoping to avoid a trip to the hardware store, so I used red duct tape to try to make an airtight connection between the shop vac hose and the condensate line. I took the shop vac hose with me to the store and bought some fittings in the plumbing department. I hooked it all up (photo above) and got a nice, airtight connection this time. With the taped connection, I got maybe half a cup of water out of the pipe. With the airtight connection, I got the bucket full of crud you see below. If you really want to see how bad it was, watch the short video below and you can see my wife pouring it out. Yes, all that gunk was in our condensate line. One problem with condensate lines is that algae can grow in them. In our case, there's also a lot of sediment in that bucket, possibly from a corroded evaporator coil. We replaced our AC in 2009 and the condensate line hasn't been cleaned since then, so some of that crud could have been from our old unit.