The 4 Challenges of Engineering HVAC for Military Vehicles

When you design air conditioning systems for military vehicles, the objectives and technical specifications that guide a job aren’t much different than those for piece of construction equipment or commercial truck in civilian service. The A/C system has to be effective and reliable in hot, dusty, or humid conditions. It has to fit the space limitations of the cab and be easy to maintain. And the military customer wants uptime and operator comfort, just like someone using Caterpillar equipment or Mack Trucks.

“The needs are basically the same,” says Bill Jewell, manager of aftermarket military markets for Red Dot Corporation in Seattle. “Except for the war threat.”

Indeed, military equipment operators face elements their counterparts at home do not. Their backhoe or supply truck is buttoned-up with inch-thick steel plating and bulletproof glass, so they can’t swing open the door or open a window. Climate control is a matter of personal safety.

Red Dot, which produces HVAC systems and components for commercial vehicles and heavy equipment, has supplied air conditioning for the military since early 2004. In late 2003, the U.S. Army Tank-Automotive and Armaments Command (TACOM) said it needed to protect soldiers from the effects of high heat inside High Mobility Multipurpose Wheeled Vehicles (HMMWV) with field-fitted armor kits. The steel plating and bulletproof glass shielded soldiers inside the vehicle but also prevented air from circulating into the cab, leading to temperatures in excess of 130 degrees F.

Because of Red Dot’s experience with heavy trucks, off-highway equipment, and construction vehicles, it took just one week for Red Dot to create a prototype capable of lowering the temperature inside the HMMWV cab by as much as 30 degrees F. The company entered full production less than 90 days later, and to date has shipped more than 17,000 units for HMMWVs used by the Army and Marine Corps. Red Dot also has supplied 5,900 field-fitted and factory-installed air conditioners for other military vehicles, including the M939 5-ton truck, the workhorse of the Army’s transport fleet.

These essentially were aftermarket installations—complete A/C systems installed in-theater with armor kits.

“Now we’re working with manufacturers who are competing to produce the next generation of tactical wheeled vehicles,” says Randy Grover, Red Dot military sales manager. These include Mine Resistant Ambush Protected (MRAP) vehicles and the more recent MRAP-ATV (All-Terrain Vehicle), which are designed with a raised, V-shaped underbelly that deflects the force of explosive blasts from below. “This is more like a traditional design process for original equipment, where you have stringent requirements on performance, cost, and timelines.”

Manufacturers are focused on reducing the temperature in the entire cab instead of spot-cooling the occupants like Red Dot did with the HMMWV.

“With the MRAP vehicles, we have to bring the entire cab temperature down quickly and efficiently,” Grover says, noting that a 40 F reduction from 130 F ambient is typical of the performance targets. ”You have a half dozen or so manufacturers competing for contracts to build MRAPs and M-ATVs, and each has a unique way of meeting the requirements for air conditioning. Because we have a strong track record in military markets, we’re able to efficiently engineer A/C solutions for these vehicles and the troops who use them.”

THE 4 CHALLENGES OF MILITARY APPLICATIONS

Bill Jewell says Red Dot’s experience over the past three years reveals the challenges of air conditioning military vehicles amid the heat, sand, dust, and war threat. Among them:

1. Versatility in application, commonality of components

“Like our commercial customers, the military wants commonality, and not just across one vehicle platform,” says Jewell. “The technician in the field is managing HMMWVs, armored construction equipment, armored supply trucks… It’s nice to know that a condenser is going to work on all of them.”

It’s not easy. There are more than a dozen different vehicle configurations of the HMMWV alone, each with unique weight and space limitations. There are multiple engine kits that change the pulley drive system from V-belts to serpentine, and different generations of the vehicle on the ground. Commonality and versatility go hand-in-hand.

2. The sand

Dust is a gritty problem for military equipment. The sand in Iraq is extremely fine, like talcum powder. It’s loaded with salts, carbonates, and other reactive chemicals with the potential to corrode metal parts.

“We designed components that would withstand the dust by making things waterproof,” says Jewell. “Our motors are waterproof, our compressor clutch is waterproof. If something is waterproof, it will be dustproof.”

3. Make the technician’s job easier

Perhaps the biggest difference between commercial and military vehicles is the frenetic pace of maintenance. Some vehicles have been in theater for several years, and with every troop rotation a new group of soldiers or Marines has to learn how to operate or maintain the equipment.

“Our goal from the beginning was to make it easy for the technician to do his job,” Jewell says.

When the units are to be installed in-theater, they arrive ready to go. “We provide everything except refrigerant,” said Jewell. “Crimping tools, oil for the O-rings, everything. Before the box is sealed, people check to make sure all the pieces are in there. We use color-coded bags to make it easy for people on the other end to prepare for their work.”

Other units are installed into completed cabs at factories in the United States and shipped to Iraq where they are mounted to a chassis. “We did that for the LSAC (Low Signature Armored Cab) developed by BAE Systems,” Jewell says. “It was our first opportunity to combine our success at designing for the conditions in Iraq with our experience producing rugged, factory-installed units for construction and mining vehicles.” The result was a factory-installed unit that’s durable, highly serviceable, and meets the space constraints of an in-dash installation.

Red Dot also provided HVAC technician training to more than 100 Marines and Army contractors. “They had guys who were familiar with HVAC units for buildings, but no one was familiar with mobile air conditioning,” said Jewell.

4. Smart diagnostics

To prolong component life and help technicians troubleshoot problems, TACOM specified Red Dot’s ProTecht A/C protection system. ProTecht is a compact electronic control unit that monitors high-side system pressures, compressor clutch cycles, voltage, refrigerant charge, condenser fan operation, and other key performance indicators.

“ProTecht is a system-saver,” Jewell says. It shuts the air conditioning system down if it detects excessive pressure, rapid clutch cycling, or low battery-voltage conditions. “ProTecht intervenes when there’s a risk of component failure. When you can spare the compressor clutch, you’re freeing up your technician to spend three hours on another repair.”

Blink codes on the ECU provide a simple visual indication of faults: a fast blink for low voltage, one blink for low charge, two blinks for lost charge, and so on. ProTecht also transmits A/C error and diagnostic codes to the vehicle’s SAE J1708 Data Bus using SAE J1587 protocol. A technician can hook up a laptop running Red Dot’s Windows-based A/C Technician software and see details about active faults and the A/C system’s fault history.

“One of our priorities was to keep the air conditioning operating as long as possible without damaging the system, since this would be important for the troops,” says Derek Kamemoto, lead engineer with Red Dot’s Advanced Engineering Group. “We developed a feature for the military that allows the system to continue to operate in a limited capacity rather than completely shutting it down. The blink codes would be displayed but the system would be allowed to operate right up to the point of certain catastrophic damage to A/C components before the system would disengage.”

ProTecht is used on several military-vehicle platforms, including the FMTV-LTAS, ICP-HIMARS, MEADS, LSAC, and HMMWV. It is available for commercial vehicles as well, and Red Dot is integrating it with its Automatic Temperature Control technology.

“It’s the ultimate in controls, as it offers the comfort the operator is looking for and the product reliability and diagnostic tools the vehicle owner is interested in,” says Jewell. “The diagnostics are available via a data link or the digital readout on the ATC control panel.”

Jewell says TACOM and the Defense Department are interested in high-tech solutions if they mean a more reliable, more comfortable vehicle for the troops inside. Where air conditioning was a rarity before 2004, it’s top-of-mind now. “Not every vehicle coming into service will require armor, but nearly all have the capability to add the armor if required,” he says. “And where there’s armor, there’s going to be air conditioning.”