THOUGHT LEADER
Get the Right Air Conditioning System for Your Bus
Written By Robert T. Pudlewski A
ll school bus manufacturers offer air con- ditioning options. Some install systems on the assembly line. Others offer systems that are installed by A/C manufacturer-qualified
installers or the bus sales dealer, after the bus leaves the assembly line. OEM and after-market systems vary, from system
installations that tie into existing OEM dashboard HVAC systems, to stand-alone complete air conditioning sys- tems. The components that make up an A/C system are the compressor (mounted on the engine or a separate power source), dash evaporator (driver area), controls (switches, thermostat, electronics), hanging or flush evaporators, and rooftop or skirt mounted condensers. There are so many different kinds of bus air condition- ing systems to choose from, that it can be hard to figure out which one is just right for you. Manufacturers are continually updating or adding new system configurator links through their dealer net- works, so be sure that you pick the most economical and effective cooling system. Always work with your dealer to find the cooling system that is specific to your vehi- cle’s cooling needs. Don’t compare apples to oranges, that is, “In-dash,
tie-in systems to stand-alone propriety systems.” Get the right system for your bus, and be sure to consider the power draw that the A/C system will require, so that it does not impact your vehicle’s alternator capacity to maintain its battery charge.
Level the Playing Field 1. Have your system provider reference a per-
formance pull-down test. The best and most important evaluation of a system is to measure the ability of the installed system to cool a bus interior.
2. Require BTU/hour system capacities be recorded in an industry standard format, such as the Society of Automotive Engineers (SAE).
The National Congress of School Transportation amended school bus A/C specification recommen- dations in 2015. The resulting National School Bus Specifications & Procedures document, starting on page 49, paragraph B, recommend that two performance standards be used when specifying school bus air condi- tioning systems:
• Standard Performance — The installed air condi- tioning system should cool the interior of the bus from 100 degrees to 80 degrees Fahrenheit in 30 minutes.
• High Performance — The installed air condition- ing system should cool the interior of the bus from 100 degrees to 70 degrees in 30 minutes.
The American Public Transit Association has specified
its requirements: • Capacity and Performance Requirements — The air conditioning portion of the HVAC system shall be capable of reducing the passenger compart- ment temperature from 115 degrees to 95 degrees in less than 20 minutes after engine startup.
• Hotter Ambient Conditions — The air condition- ing portion of the HVAC system shall be capable of reducing the passenger compartment temperature
Always work with your dealer to find the cooling system that is specific to your vehicle’s cooling needs.”
22 School Transportation News • MARCH 2019
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