Performance recommendations for on-board heating and air conditioning systems, including many “engine-off” products, have been finalized by a task force of the Technology & Maintenance Council of the American Trucking Associations and should be ready for general use in about a year.

Two new recommended practices, or RPs, were written by groups headed by Mike and Gail Swiger, professional truck drivers and former owner-operators from West Allis, Wis.
They also oversaw the updating of TMC’s long-standing RP on truck cab air conditioning.
Both new RPs are performance-based and very short-about a page and a half each. They use almost no engineering terms and instead inform suppliers the cab-and-sleeper temperature levels their products should provide under certain conditions, Gail Swiger explained.

“We’re going to tell you the outcome we want,” she said. “You figure out how we get there. That’s why the RPs are short and sweet.”

Truck buyers can take the RPs to truck dealers and tell salespeople to set up heating and A/C systems to achieve the desired goals. A truck’s standard heating-ventilating-air conditioning, or HVAC, should be able to meet the requirements.

So should auxiliary products, like diesel-fired interior heaters, electric or chemical coolers, and auxiliary power units. In Canada, interest in products that control cab temperature has been sparked hours-of-service changes designed to give drivers more rest (meaning more time in the sleeper each day), as well cash rebates on certain fuel-fired interior heaters, engine coolant heaters, and auxiliary power units. The program promises up to $350 back on the purchase of heaters and up to $1,400 for APUs; it is run by the FleetSmart office of Natural Resources Canada (call 613/995-7436 or go online to oee.nrcan. gc.ca).

Most suppliers in the business were members of the Swigers’ task force and were involved in writing the documents, so they know their requirements and should be able to provide test results to anyone who wants them.

Proposed RP 432, “Engine-Off HVAC Performance Requirements for Truck Cabs With Sleepers,” states:
An A/C system must maintain a temperature of no more than 78 F for 10 hours, and that a heating system maintain not less than 68 degrees for 10 hours.

Testing in both cases begins with the interior at 73 F (plus or minus 5 degrees). For the A/C, outside temperature is 100 F with 50-per-cent relative humidity and a specified solar load. For the heater, outside temp is 0 degree with no sun.

Six thermal probes in the sleeper compartment measure temperatures during the test. Two probes are on the floor in front of the bunk, two are in the rear corners at the head and foot of the bunk, and two are on the wall near the ceiling. Two additional probes monitor outside temperatures.

Proposed RP 434, “Cab & Sleeper Insulation Efficiency,” is simpler. Fibreglass, various types of fibres, urethane, polystyrene foam, and other materials can be used for insulation.

Material should be faced to reflect heat both outward and inward to help A/C and heating units do their jobs.

And the RP asks that builders offer thermal, or solar glass, as options.

A “standard” insulation package should achieve an “R” value greater than 12, and a “premium” package’s R value should be greater than 14.

“I wanted an R of 16 for the premium package, but the suppliers argued against it,” Gail Swiger said.

Many standard sleepers have little or no insulation, she asserted.

“You look in the walls and there’s nothing there. They [suppliers] talk about their so-called Arctic packages having 10 times the insulation, but 10 times nothing is not very good.”
The TMC task force believes a new RP may help change that.