A new development in air-conditioning technology could lead to significant savings for school bus operations.

Bitzer US Inc.’s latest compressor, the F400, is the first transit-style compressor to fit a conventional (Type C) school bus, the company says. Previously, air-conditioning systems on these buses were limited to automotive-style (or swash-plate) compressors.

The difference between the two is substantial, according to Matt Lish, director of transport sales for Bitzer. In warmer climates, automotive-style compressors may need to be replaced as frequently as once a year. A replacement can cost around $700 in parts and labor. Additionally, Lish says, school bus operators must bear the costs of maintaining spare buses, carrying compressor inventories and towing buses if their air-conditioning belts come loose and cause additional damage.

Air-conditioning systems using transit-style compressors generally cost a few thousand dollars more up front, but Lish says that they quickly pay for themselves since they can last 10 years if they are properly installed and maintained.

“Automotive compressors are essentially what you have in your car, but they made them a little bigger and now typically put two in buses,” Lish says. “Transit-style compressors are much larger and more robust and are designed specifically for buses and their associated complexities, such as the lengthy pipe runs, numbers of fittings, larger components and much higher refrigerant charges.”

While the transit type of compressor is already used in rear-engine school buses, earlier models have been too large to fit under the hood of a conventional school bus. Lish says that this has been a source of frustration for both the technicians who work on air-conditioned conventionals and the fleet managers who are aware of the significant maintenance costs they require. For example, a school district in northern Florida with a fleet of 142 buses reportedly had to replace 64 automotive-style compressors last year.

Lish says that unlike other transit-style compressors, Bitzer’s F400 was designed to fit under a hood. The all-aluminum unit is relatively small and light — weighing about 51 pounds — but still durable.

The project to equip a conventional bus with a transit-style compressor was initially driven by Thomas Built Buses dealer Florida Bus Unlimited and its customers’ needs. Through a joint effort, Carrier, Bitzer and TransArctic, a Carrier installer, responded by engineering an F400-powered air-conditioning system for Thomas Built’s C2 conventional. Rifled Air Conditioning Systems has also come out with a unit that uses the F400.

Lish says that similar systems are in the works for IC Corporation’s conventional, and they may also be soon for Blue Bird’s.

“This is really going to make a big splash in the industry,” Lish says.