Air conditioning (A/C) manufacturers report noticing an overall need for more energy-efficient and weather-resistant products, in addition to systems that allow for more bus design flexibility. As a result, rooftop systems, corrosion-resistant skirt condensers and eco-friendly options are among some of the latest air conditioning trends in transportation.
As the industry continues to grow, so does a transit agency’s ability to find a more fitting solution for their vehicles. Keep your operation at the forefront by integrating products that address new technologies, customer needs and emerging environmental standards.

American Cooling Technology
The application of rooftop A/C systems has been an industry-wide trend within the past few years. While the best option for a transit agency varies from vehicle to vehicle, there are several benefits from having an A/C installment that isn’t underneath a bus.

Condenser coils located on the roof of a vehicle access cleaner air compared to coils under a bus. The air circulated is also cooler, — because the system is physically distanced from engine and road heat — which increases overall capacity. Ground debris is also bypassed during transit, reducing inevitable maintenance costs.

Having an A/C option atop a bus gives bus manufacturers more flexibility with design as well. Even a split system, in which the condenser is roof mounted, but the evaporator remains ceiling mounted or in-wall, would allot companies more versatile use of space. More room is created for applications like wheelchair lifts and luggage compartments, which traditionally utilize space under a vehicle.

To satisfy the growing demand for skirt system alternatives, American Cooling Technology (ACT) recently introduced a line of roof-mounted condensers: CR-2, -3 and -4.

The CR-2, a two-fan condenser, has been available since 2011, and CR-4 was released last fall. However, the York, Pa.-based ACT wanted to offer a complete line, so in January, it went into production for the CR-3. In the past, ACT commonly placed two CR-2 condensers into medium size buses too large for one CR-2 and too small for a CR-4. The option to have a CR-3 application now reduces the installment complexity through fewer refrigerant connections.

“Having these different capacities available now gives us flexibility for customer requirements — they don’t have to oversize or undersize anymore,” says ACT GM Dave Oberdorff. “This fits a market niche for capacity and application in fitting the product to the bus.”

The CR-3 rooftop condenser features three high-capacity 12-inch fans, a lightweight aluminum frame, a TPO cover and O-ring connections for maximum leak protection. There are also heat rejection coils and an enhanced copper tube with aluminum coils. The CR-3 system is a single-circuit design, and the CR-4 is available in both single- and dual-circuit designs.

The line of CR Rooftop condensers currently use a split system design, but ACT has partnered with E-Climate to make a complete rooftop set available to customers.

There are also recent industry trends toward intelligent A/C controls that can operate through the bus multiplexing system, according to Oberdorff. Now becoming more of an industry standard, these controls usually increase the total cost of the A/C system, but offer operational savings over the life of the vehicle.

“We’re seeing more state and agency requests for this kind of capability overtime,” says Oberdorff. “They’re looking at it as something that’ll help with operations’ budgets down the road.”

Another trend to look out for, says Oberdorff, is the shift away from copper brush motors to brushless motors. Although more costly upfront, they require less maintenance, offer more control options and are more efficient.
“You can get as much as four to five times the life out of the brushless motors,” says Oberdorff. “And, they’re becoming more cost competitive.”[PAGEBREAK]

Rifled Air Conditioning Systems
For Rifled Air Conditioning Systems (RAC), the past year brought significant upgrades to its skirt-mounted and bulkhead (also referred to as “in-wall”) condensers.

Cheyne Rauber, RAC’s GM and sales manager, notices that the A/C industry, as a whole, has been developing a more environmentally safe standard for its products. Therefore, RAC’s skirt-mounted condensers were improved with this trend in mind.

All fan connections have been changed to weather pack connectors, which are environmentally sealed electrical connections designed to withstand exposure to extreme temperatures and moisture.

Terminals are tin-plated and have special core wings that allow crimp-only connections, eliminating the need for solder. The connector and cavity seals are triple-ribbed and made of self-lubricating silicone. Plugs are inserted into unused cavities.

In addition to industry standards, the changes on RAC’s skirt-mounted condensers also derived from the company’s experience dealing with harsh northeastern weather conditions. Some cities are using a new type of calcium chloride solvent on the roads to prevent slipperiness when it snows, according to Rauber. Bus manufacturers in this region have watched these chemicals slowly corrode equipment underneath a bus.

“The upgraded skirt condenser with weather pack connections provides a more robust system that is now environmentally sealed against tough surroundings for our clients who prefer that model,” says Rauber.

RAC also eliminated ring terminal connectors on the face of the condensers and added pigtail length options, ranging from 48 inches to 16 feet, for more variety. Ground ring terminals are now integrated into the harness.
The company’s BH-20 bulkhead style evaporators were also upgraded in November of 2011.

A multi-directional four-hole drain pan was added, which increases drainage at any angle or orientation of the bus. In the past, water could build up if a bus was parked on a slope. Now, the drain pan works to prevent overflow.

Riv-nuts have been installed on the exterior sides of the bulkhead series evaporators along with custom mounting brackets to offer additional mounting options.

Bulkhead evaporators are also available with custom covers, from metal and ABS plastic, to vinyl clad aluminum options. They can be designed to match a bus’ interior for better aesthetics.

“The bulkhead style gets the unit out of the way as it’s built into the body and more integrated into the bus itself,” says Rauber.

While the bulkhead remains a popular option for RAC customers, Rauber sees a trend toward rooftop systems as well, especially in regions facing harsh winters. It provides an additional solution to avoiding chemicals and grind on the roads.

“We’re currently reviewing and most likely going to do some redesign on our rooftop products,” says Rauber. “Customers should be able to purchase them this fall.”

Thermo King
In light of the current economy, Thermo King, a brand of Ingersoll Rand, is working to address the fact that organizations are looking for ways to save money. Simultaneously, the Minneapolis-based company is focusing its efforts on satisfying the expanding trend toward environmentally-friendly air conditioning solutions.

According to Steve Johnson, sr. product manager for Thermo King, electric A/C options are a dual solution.

In 2012, Thermo King released an all-electric heating, ventilation and air conditioning (HVAC) system. Although electric powering has been prevalent in the rail industry for many years, HVACs are a fairly new trend in the transit bus market, having made their appearance within the past two years.

Years ago, the electric A/C option was only available for all-electric buses. But now almost any type of bus can install the HVAC and have the option to go green. The system can be used on all diesel engine-driven buses in the transit and coach markets, including hybrid vehicles.

They’re a product of seven or eight years of development and were officially available in late 2010. Since then, the products have undergone upgrades to incorporate new trends as they’ve surfaced.

“We have an electric solution for each type of bus,” says Johnson. “We do what we can to help reduce maintenance for our customers and help them have more reliable buses. That’s what they’re looking for. Also, a roof-mount version is under development right now.”

High voltage power is supplied to the electric HVAC unit using an alternator driven by the bus engine. The alternator output is conditioned and stabilized before being used to power the electric compressors and fan motors, regardless of engine speed.

The unit helps save fuel by eliminating the effect of variable engine RPM on load and demand. The HVAC is also energy efficient with an R407c refrigerant. Users can expect a 5% to 10% improvement, according to Johnson.

Another cost-efficient and eco-friendly component is that the HVAC has fewer mechanical parts, such as reciprocating compressors and clutches. This improves reliability and also drives lower maintenance costs.

The product is hermetically sealed and tested at the factory, requiring no field plumbing, evacuation or charging. There is no tubing or hoses needed in the engine compartment to connect the HVAC unit and compressor. Again, this drives the overall installation costs down.

“We want to make sure we’re addressing the needs of the market, the end-user and also the OEM,” says Johnson. “We want to help customers achieve energy savings, saving on their bottom line and energy costs.” [PAGEBREAK]

Trans/Air Manufacturing

Following current trends, Dallastown, Pa.-based Trans/Air Manufacturing plans to release a new roof-mounted A/C unit, KV Ultralight, by the fourth quarter of 2012. Partnering with the German company Konvekta Thermosystems, Trans/Air aims to satisfy a growing customer demand for this type of product.

“We have a customer review that we do every year to try and benchmark our performance against our expectations,” says Rick Lehnert, president of Trans/Air.

The KV Ultralight Series, designed for heavy-duty transit applications, has an overall weight reduction of 30% compared to conventional A/C units. In addition to reducing fuel consumption, its materials aim to limit noise for passenger comfort as well as provide better insulation for increased performance.

Advanced recyclable materials are utilized in the chassis design of the product; the KV Ultralight is made from 97% recyclable components.
The unit is also available with a hermetic compressor for use in electric or hybrid vehicles.

All Ultralight products are designed to work with either high-efficiency R134a or an environmentally-friendly CO2 refrigerant. The CO2 (R-744) refrigerant provides the opportunity for customers to have a heat pump function, where heating and cooling can be done with the same unit.
The electric R134a version will be available in limited quantities in late 2012, while the heat pump version will be offered in the second quarter of 2013.

Trans/Air also offers a recently upgraded skirt-mounted condenser with stainless steel housing. This is a commonly used product for split systems in the cutaway bus market; however, many users notice gradual deterioration due to its location being so close to the ground.

“We developed a stainless steel housing option for the skirt mount option to address customer requests for something more corrosion resistant,” says Lehnert.

It features corrosion resistant all-aluminum parallel flow condenser coils and low-amperage draw condenser fans inside a stainless steel housing. The unit is comprised of materials that protect against corrosion in harsh road or weather environments.

Stainless steel condenser options are available in two- (SMC2S) and three- (SMC3L) fan configurations.

“Less product configurations and variations are better, but we understand that certain markets expect a different approach,” says Lehnert.
Corresponding stainless steel stacking kits are available for applications where skirt mounting space is limited.

Trans/Air places a large emphasis on merging its innovation with safety when addressing product trends. The company’s strong association with the school bus market has led to this priority, according to Lehnert.