How to Spec a Rooftop A/C Unit

When it comes to operator comfort, two key selling points for any vehicle are space and visibility. But big interiors and lots of window glass add to the demands placed on another critical comfort item: the air conditioner.

“As a trend, we’re seeing more spacious cabs and larger windows in every type of vehicle we design for,” says Gary Hansen, vice president of engineering at Red Dot Corp., a leader in heavy-duty mobile HVAC units and replacement parts. “A rooftop A/C unit is ideal for bigger cabs because it can deliver high-performance cooling without taking up valuable interior space.”

Because it’s mounted on the cab’s exterior, a rooftop A/C unit should be purpose-built to handle impact, vibration, and other demanding operating conditions, Hansen says.

R-9727: Built for Durability

No rooftop mobile A/C unit has a more proven track record than the Red Dot R-9727. It delivers 22,000 BTU/hour of cooling and airflows of 320 CFM (evaporator) and 850 CFM (condenser), and its durability and performance are best-in-class for rugged on- and off-road environments.

The R-9727’s robust components are housed in a heavy-gauge steel casing that’s gusseted and reinforced to increase its structural integrity. “Little things add up to a more durable, reliable unit,” Hansen says.

For example, Red Dot use a sealed, long-life evaporator and condenser motor with a slinger ring and hubcap for protection from weather and dust. Instead of using several small hinges for the service panel, the R-9727 has one continuous stainless steel piano hinge. The result is a stronger joint that contributes to the rigidity of the housing while ensuring accessibility to the components when service is necessary.

R-6100: Low Profile, High Performance

Red Dot’s R-6100 is the ideal rooftop A/C unit for commercial trucks and other on-highway equipment where a low profile is important. The R-6100 extends just 7.4 inches above the roofline so it won't interfere with bodies or other equipment that may protrude over the cab. 

Beneath the sleek, roto-molded housing is a tightly integrated package of components designed for long life and efficiency. The R-6100 produces a strong, steady stream of cool air—16,000 BTU/hour and airflow of 265 CFM. At that rate, the operator can work with the door open and still feel the effects of spot cooling.

Tube-and-fin coil construction ensures strong condenser performance in dusty, dirty conditions. The copper tubing is 0.022 inches thick, resulting in an effective, lightweight, rugged coil. 

The sealed motor is a permanent magnet type with a slinger ring and hubcap for weather protection. The condenser unit's fan is aluminum with a heavy-duty spider and riveted blades. 

A high-capacity, spring-loaded receiver drier helps stop moisture from compromising the performance and life of the system. 

It also saves space inside. The R-6100 ceiling plenum houses the controls for the blower and thermostat as well as a cab air filter yet protrudes barely 1.5 inches below the headliner.

Stay on Schedule

Scheduled preventive maintenance is the best way to make sure an A/C system is effective and efficient. Start by syncing your HVAC parts promotions with engine lube intervals. The accompanying chart shows you how.

“Most HVAC PM intervals involve a three-month, six-month or annual inspection,” says Hansen. “When a vehicle is in for scheduled service, follow the recommended inspection schedule for the compressor and belt-drive system, condenser, receiver-drier, expansion valve and evaporator.”

Cool, clean, reliable air is vital to operator safety as well as comfort. Promote regular preventive maintenance and quality all-makes parts and you’ll generate HVAC parts and service business all year long.