The aluminum and copper fins attach to the coils to increase the surface and the rate of heat transfer. A few decades ago a typical coils had 8 to 12 fins per inch, but due to increasing energy costs and the demand for higher energy efficiency ratings, some coils today are manufactured with 16 and 18 fins per inch arranged in complex zigzag patterns. This is an excellent way to boost the energy efficiency ratings. Unfortunately, these high efficiency coils are also extremely susceptible to blockage from dust accumulation. Once dust and dirt are lodged deep within the tightly-packed fins it becomes even more difficult to get out.
The dust that accumulates is a great place for bacteria and mold to initiate growth, which not only increases the blockage problems but also gives rise to excessive operating costs, comfort control problems, and unhealthy sanitary conditions that are not conducive to good air quality.
So when green hotels are making purchasing decisions and buying the higher efficiency HVAC systems it is highly likely the EER rating on the unit is compromised in the first 18 months or less without proper preventative maintenance service.
There are a variety of methods to tackling this cleaning, all with numerous pros and cons. Selecting the most efficacious technique will come down to one’s individual situation of available funds, time, and severity of coil blockage.
Super heated steam at 600 degrees is one of the most effective and expensive methods to clean coils. It may be cost prohibitive for small coils such as PTAC units but is probably the most cost effective method for large HVAC units. Nevertheless, each situation is unique so there maybe instances when high heat steam is the right solution for PTACs. The more traditional method uses foams and sprays, which are usually less expensive, but may be less effective at dislodging deeply embedded particulates from the coils than super heated steam.
*** Above left a coil that is damaged and dirty, above right a clean well maintained coil
Both alkaline & acidic chemicals are on the market for coil cleaning. More potent solutions will have a more potent odor and fumes, proper respirator equipment will be required. These chemicals have to be disposed of properly as well. It was not uncommon for hotels to use a remote section of the parking lot or loading dock area where these chemicals were simply being rinsed into the storm water system. Additionally, using chemicals can have a degrading effect on the coils’ metals if the wrong solution is selected. Multiple reports have warned of a reaction between the cleaning chemicals and the metal parts; corrosion of the aluminum and copper fins and tubing can result. Therefore while shininess may prove appealing, it may be misleading. Over time, the degradation can damage the system and result in a costly premature coil replacement.
Some other “lower-tech” cleaning methods utilized compressed air. By blowing debris off with compressed air, this cleaning job can be the quickest method when time constraints are paramount. Drawbacks to this technique are that the dislodged debris is now airborne – required an additional step in the clean up process to recapture the blown-out particles. Adding mold into this scenario quickly highlights how much more of a problem the capturing of these particulates truly is. Also, blowing compressed air “at the dirty coils” is precisely the wrong direction towards the dirty side! Therefore using compressed air may leave a large amount of dust and dirt deep inside the unit; using a shop-vac in conjunction is recommended along with proper eye and breathing protection.
Brush cleaning is another simple easy coil cleaning method; using a small soft brush will be effective for a light amount of dust and will not be effective for extensive cleaning scenarios. For this method to be effective, one will have to clean coils more frequently – every 4 – 5 months – to ensure cleaning effectiveness.
UV light is gaining popularity as a method but it more commonly used to maintain cleanliness rather than remove large amounts of dirt and debris. I have seen an ionizer device at a show recently but I will reserve comment for now.
All in all as with any mechanical system, following the manufacturer’s recommended maintenance schedule is paramount to maintain peak performance. As with regular oil changes with your car, regular A/C coil cleaning is important, standard required service in order to promote long system life, guest comfort, and high operating efficiency. Lowering bills, increasing guest satisfaction, and decreasing unexpected repair downtimes are the direct results from coil cleaning!
EcoGreenHotel is expected to release a M&V study by the end of the 4th quarter that is currently underway. For a copy send us an email at firstname.lastname@example.org
About the Author
CHRIS LEWIS, DIRECTOR OF ENERGY SOLUTIONS EcoGreenHotel - Chris works with EGH partner owners and operators on a daily basis performing on-site mechanical evaluations, overseeing on-site project installation, executing energy audits, energy modeling to support SBA Loans and Energy Rebate Administration. Chris oversees benchmarking for several properties to insure proper reduction after project installation. Chris’s team is responsible for measuring and tracking of trends for our partner hotels adding a proactive approach to potential waste of water, electric and fossil fuels.
Prior to joining EcoGreenHotel Chris spent 17 years in the hospitality industry both in the U.S. and abroad managing and directing departments including hotel operations, food and beverage, renovation and construction. Chris previously served as Development and Construction Manager at OTO Development opening dozens of branded new development hotels.
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