Management & Operations

Proper Upkeep of Onboard Air Conditioning Systems

Posted on May 1, 2005 by Teresa Basich, Editorial Assistant

Many a bus rider will refuse to ride during the summer months if their local operation’s buses aren’t equipped with effective air conditioning units. This is especially true in warmer climates, where too much exposure to the heat is not only uncomfortable but also potentially harmful to a person’s health. Providing reliable air conditioning can be a challenge for any transit agency that depends on ridership to bring in revenue and also aims to keep its riders happy. “In serving the transportation needs of residents in a desert area, providing a cool and comfortable atmosphere for our riders is a top priority,” says C. Mikel Oglesby, general manager at SunLine Transit Agency in Thousand Palms, Calif., which lies at the southern edge of the Mojave Desert. This same principle applies at LYNX in sunny Orlando, Fla. “The agency and the riding public expect reliable service,” says Joe Cheney, interim deputy director of maintenance. “Additionally, our funding partners expect that service also be efficient and cost effective.” While having air-conditioned buses is a definite plus for an agency, additional maintenance costs can be problematic. Adequate system spec’ing and appropriate preventive maintenance programs are effective ways agencies can eliminate some of the higher costs involved with providing a cooler atmosphere in their buses. While a general list of specifications to guarantee long-lasting air conditioning systems would be a great luxury, there is no one formula. The range of weather conditions in the U.S. is too great — some areas live with minimal air conditioning throughout the year, while others require air conditioning on high most of the year. “We see ambient temperatures as high as 120 degrees or more,” says Tommy Edwards, director of maintenance for SunLine Transit. “Our average temperature in June through August is around 110 degrees, so without air conditioning we can’t even send the bus out on the road.” Cheney agrees that high temperatures during the summer create air conditioning needs that can’t be ignored. He also says that LYNX buses get warm during the winter months as well. “In the winter, the temperature may be cooler but the intense sun will still heat up the interior of the bus,” he says. With the guarantee that your vehicles will be warmer inside than out, outfitting each bus with an air conditioning unit is probably your best bet for keeping riders and drivers happy during warm spells. Below are some guidelines for spec’ing new air conditioning systems and a few other concerns maintenance directors might want to take into consideration. Heat and noise factors
Depending on the location of an agency, air conditioning units might require a stringent pull-down test or a more lenient test. In hotter areas, these tests will probably be more difficult for a unit to pass. SunLine’s Edwards uses a spec for an even warmer climate to make sure the units he receives are adequate for his area. “We need to be able to cool a hot coach down in a reasonable amount of time,” he says. Just in case, SunLine’s maintenance team always assumes that the temperature will be higher than expected because of the variance in humidity. “Even though we don’t have as much humid weather, we do see a little higher ambience,” says Edwards. To be on the safe side, he over-specs his units by about 20% to cover any potential problem areas. He also researches the capabilities of any system to make sure it will be appropriate for his buses. “We need to know the BTU factors, or the capabilities of the system. And we need to look at the fact that our area is going to need a more robust unit,” he says. Because SunLine also operates alternative-fuel vehicles, Edwards must consider noise in addition to these factors. Drive systems of alternative-fuel vehicles are much quieter than buses that use diesel fuel and consequently must be equipped with operating systems that produce much less noise. “The air conditioning becomes more predominant as a noise factor,” he says. Lifecycle costs
Another very important consideration when spec’ing new air conditioning units is the affect the systems will have on your operating costs, and more specifically, which systems will have lower lifecycle costs. Many air conditioning systems require motor brushes for their condensers and evaporators, which can wear out quickly if the unit spends most of its time running. Edwards and his maintenance staff do quarterly preventive maintenance to check the wear and tear on the motor and evaporator brushes, as opposed to annual or semi-annual maintenance. On the other side of the coin, LYNX’s Cheney feels that taking the dive and spending more on brushless motors when the unit is first purchased will save costs in the long run. “The initial cost of a brushless motor is higher, but the frequency of the required maintenance is lower, resulting in a lower lifecycle cost,” Cheney says. In addition to brushless motors, LYNX also specifies that its compressors be set on “Reheat” instead of “Cycling Clutch” to reduce maintenance on the compressor and save even more in operating costs. “It’s also important to make sure where the system is mounted — on the top of the bus or at the back of the bus — because that makes a lot of difference,” says Halsey King, president of Halsey King and Associates. “It’s much more expensive to take a 40-foot bus and put the system on top than it is to put it at the rear of the bus right over the engine.” To ensure the longest unit life, maintenance directors should ultimately adopt thorough and frequent preventive maintenance programs. Edwards and his staff follow factory standards when it comes to air conditioning upkeep. “We have our technicians factory trained and we do the suggested preventive maintenance,” he says. “We also try to keep from opening the system up.” Along with keeping a regular preventive maintenance schedule, Edwards also makes a point to keep up with the latest technology on the market. “Some of the newer technologies in air conditioning systems seem to be working well, and I look forward to that making our lives a little easier,” he says. King agrees. “Specify a system based on what’s currently available in the industry,” he says. “You don’t want to use the old system that you specified 10 or 12 years ago because modern air conditioning systems, just like bus tires and seats, have gone through generations of both accommodation, as well as technological change.” Rely on experience
As is key to spec’ing any type of equipment, it’s important to be attentive to what has and what hasn’t worked in the past. Since spec’ing new air conditioning systems is probably not a regular occurrence at your agency, talk to other people in the industry who you know have done it recently to get a feel for the systems that are on the market and make a decision that’s right for your buses. “Most specifications are built on past experience, positive and negative,” Cheney says. “Generally, if you don’t have a lot of experience, people within the transit industry will share their experiences with you.” After talking to colleagues and industry experts, turn your research inward and focus on factors in your area that might affect a new air conditioning unit. When spec’d well, the systems on your vehicles should last years. “Usually we plan on the units lasting the life of the bus, and I think with good maintenance, they do,” Edwards says.

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