(Minneapolis - October 6, 2008) - As of January 1, 2010, bus operators will be affected by two significant new EPA regulatory statutes: the 2010 engine emissions standards and the ban on R-22 refrigerant for use in new equipment. These two regulations will affect everything from new bus specifications to how fleet maintenance is done. The biggest and most dramatic change operators will see are the new EPA engines that will begin appearing on new buses sometime in 2010. The new engines must comply with lower emissions standards as set forth by the EPA, and to meet these standards bus builders and engine manufacturers will be adding Diesel Particulate Filters (DPFs) to the buses.
"While many customers are aware of this change, they may not be aware that the configuration and location of the HVAC unit could be affected," explained Steve Johnson, product manager for large bus at Thermo King. "In the United States, the most commonly used HVAC in the transit industry is mounted at the rear of the bus above the engine. As bus OEMs are forced to find space to accommodate the DPF, they are re-arranging the components in the rear of the bus. The available space for the traditional rearmount HVAC unit is being reduced or eliminated. The robust, one piece, compact design is the most reliable configuration available today and is easy to install and service. Will it go away permanently? As of now we don't know, but we do know that some type of change is inevitable."
Each bus builder will have its own approach as to how to best deal with the space issue. Fundamentally, if the space for the conventional rear-mount HVAC unit is not available, the most logical place for the unit to go is on the roof. "This is not a novel concept," continued Johnson. "Some U.S. transit properties already have experience with roof-mount HVAC, particularly on articulated buses where two cabins have to be cooled. Also, in all markets outside of the U.S., roof-mount HVAC is the standard configuration. For the most part, the rear-mount HVAC is preferred in the transit industry and in fact, more than 80 percent of what Thermo King supplies has been rear-mount over the years."
There are key differences between rear-mount and roof-mount systems. For installation of roof-mount systems, holes have to be cut into the roof for the air openings, and sealing of the HVAC unit to the roof becomes critical. The refrigerant, water lines and some harnesses have to be routed within the body of the bus to connect the roof-top unit to the compressor in the engine compartment. To realize the same capacity, the roof-mount unit will be heavier, mainly due to the configuration of the coils and the addition of covers, which are not needed on the rear-mount system. Some roof-mount configurations have separate condenser and evaporator modules that have to be connected after they are on the roof, an additional step in the installation process not required for rear-mounted units. In addition, some maintenance and repair work has to be done from the roof of the bus instead of from the ground or on a short ladder.
According to Johnson, there are several advantages of the roof-mount system as well. "The roof-mount configuration allows the operator to have a rear window if they choose, and there are more opportunities to manage air distribution, weight distribution and noise because the location of the unit can be anywhere from the back to the front of the bus."
"What all of this means for the primary stakeholders: the bus builder, the HVAC supplier and the operator is that the industry has to come up with some valid, cost-effective solutions," said Johnson. "Traditional roofand rear-mount systems are not the only options. There can be integrated solutions where the components are placed in various parts of the bus and connected, similar to what is done in some coach and small bus applications. The unit could also be integrated into the roof of the bus and eliminate the need for expensive covers."
Martin Duffy, general manager for HVAC at Thermo King, summarizes Thermo King's approach to the upcoming design challenge: "We have never been a 'one-size-fits-all supplier,' and we will work with each of our customers to provide the best custom solution for their business."
Thermo King Corporation, a business unit of diversified industrial firm Ingersoll-Rand Company Limited, was founded in 1938 and manufactures transport temperature control systems for a variety of mobile applications, including trailers, truck bodies, buses, shipboard containers and railway cars. The company operates 10 manufacturing facilities and 17 parts distribution centers worldwide. Sales and service is provided by a global dealer network of 865 independently owned companies in 75 countries. For more information, access the Thermo King web site at www.thermoking.com.
Thermo King Corporation, a business unit of diversified industrial firm Ingersoll Rand Company Limited, was founded in 1938 and manufactures transport temperature control systems for a variety of mobile applications, including trailers, truck bodies, buses, shipboard containers and railway cars. The company operates 10 manufacturing facilities and 17 parts distribution centers worldwide. Sales and service is provided by a global dealer network of 865 independently owned companies in 75 countries.
Mike O'Brien, Thermo King Corporation