Cooling Cost Control

Cooling Cost Control

If you expect the cost of diesel fuel to come down soon and your refrigerated freight can wait until it does, or if your fleet has enough money available that it doesn’t matter how much it spends on fuel to run your reefers, you can skip this article. If, however, you, like most, don’t expect fuel prices to ever come down to the levels of the recent past – or even stabilize in our lifetime – then fuel economy is likely a high priority for you.

If you expect the cost of diesel fuel to come down soon and your refrigerated freight can wait until it does, or if your fleet has enough money available that it doesn’t matter how much it spends on fuel to run your reefers, you can skip this article. If, however, you, like most, don’t expect fuel prices to ever come down to the levels of the recent past – or even stabilize in our lifetime – then fuel economy is likely a high priority for you. And fuel economy efforts should apply to reefer engines in the same way as they do to their big brothers that power your fleet trucks. A dollar saved on reefer fuel looks pretty much like the dollar you might save on the fuel used to power your trucks and tractors.

Trailer features

There’s a lot that fleets can do to control fuel costs associated with reefer operation. Like so many other things related to efficient truck operation, it begins with the right specs. Let’s first take a look at the trailer itself. Refrigerated trailers are always heavier than their dry freight counterparts, and that’s not going to change.

But since it costs money to pull weight, it makes sense to take as much weight out of the trailer in the same way as many cost-conscious dry freight fleets do for their equipment. Aluminum weighs less than steel, so aluminum cross members might make sense. How about wide base single tires? They weigh less than duals and offer better fuel economy. After they get used to the idea of single tires, drivers generally like them. But can your operation live with the perceived risk of a road delay due to a tire problem? In all cases, whether it’s extra expense for light weight components or the introduction of new technology, it always depends on a fleet’s particular application. Will a change offer an economic advantage? Only you can answer that.

Whether a fleet runs on dual tires or wide base singles, it should consider including a tire inflation system when spec’ing new equipment. Improper air pressure is the single most costly tire maintenance item when it comes to fuel economy. Inflation systems not only will improve fuel economy, but also will decrease rapid tread wear due to under inflation. These systems generate a “win-win” situation.

Since reefer fuel is used to keep freight at some predetermined low temperature, it follows that a thermally efficient trailer design will consume fuel most economically. Efficiency, however, must be balanced with practicality. Four inches of insulation and a small door might make for good thermal efficiency and, therefore, good fuel economy, but may not be practical. Tradeoffs often are required. For example, many reefer fleets carry refrigerated freight in one direction but are willing to carry dry freight on the return trip. Since loads are often packaged on skids that assume a 98-inch interior trailer width, operational efficiency might limit wall insulation to 1 5/8 inches. While this may not be the best option for fuel economy, it is often sufficient for hauling all but the most fragile products making thin wall reefers a popular design in the field.

“You’re in the business of offering a quality service, meaning that you keep product at temperature,” says Rod Ehrlich, chief technology officer and senior vice president at Wabash National. “Air movement is important.”

So is insulation. A fleet hauling produce in the upper Midwest may be able to get by with a thin wall unit. A fleet delivering ice cream in Phoenix needs upwards of four inches of insulation.

The choice of roof material also can help a fleet operating in Phoenix. Thermal ratings for trailers are determined in closed rooms that have no thermal load due to solar radiation. The surface temperature of the roof of a trailer parked in the desert sun has been measured by Wabash National engineers to be as high as 178º F. No matter where you are, ice cream needs to be held at -20º F. That makes for a delta of almost 200 degrees.

How about spec’ing a non-metallic roof? Aluminum roofs are common, but aluminum oxidizes, and when it does it becomes dark. A metal roof with a dark surface is an excellent heat absorber. Non-metallic material is available for reefer roofs. Wabash, for example, offers a product called Solar Guard, a plastic material that does not darken with age and conducts heat far less efficiently than does aluminum.

Whether you’re able to use thick insulation or must spec a thin wall reefer for operational reasons, opt for swing doors if at all possible. They simply offer better thermal efficiency than rollup doors. A swing door with its seals in good condition has an insulating capability close to that of a solid wall. That’s not the case with a rollup door. Only spec side doors if they’re absolutely necessary for your operation.

On the inside

There are a number of interior design elements that can improve overall reefer fuel efficiency depending on a fleet’s particular operation. Because much of the freight it carries will not be loaded on pallets, an over-the-road refrigerated hauler will generally want to include corrugated floors in its trailers to provide a path for air returning to the reefer unit at the front of the trailer. This will not be the case for most grocery fleets that generally carry palletized freight, which provides a return path for return air through the pallets. Again, a tradeoff between reefer fuel efficiency and the fleet’s operational requirements might be required.

There have been many advances in trailer liner material made in recent years, and fleet managers should take advantage of them. In general, they’re strong and light. Light weight materials, and these are lighter than aluminum, are desirable because they can save fuel. Strong materials are good because they can help prevent damage that allows water to enter the insulation. These new materials can be used for scuff bands as well as wall linings.

“Using new liner material is an absolute necessity,” says Chris Hammond, vice president of dealer sales at Great Dane. “Our Puncture-Guard material is strong, rigid and very thin.” Such materials make an excellent choice over aluminum or standard fiberglass for liners and scuff bands.”

Great Dane also has introduced a product it calls ThermoGuard, which contains a composite layer that the company claims seals the trailer’s insulation and reduces “out gassing” effects that cause foam insulation to degrade over time. As a result, it reduces operational costs by helping reduce reefer run-time and maintenance and thereby saves fuel. According to Great Dane, ThermoGuard can potentially reduce cooling unit run time more than 1,000 hours over five years.

“The most important aspect in the spec’ing process is for us to understand exactly what the user is going to do with the unit,” says Mike Murdock, trailer product manager at Carrier. “Knowing this we will work with the trailer supplier to deliver the best overall system. For example, the location of the evaporators and bulkheads in a multi-temp trailer will affect the cooling efficiency and therefore the fuel economy.”

But just what kind of information should a fleet manager be prepared to deliver to his reefer salesperson? Below are just a few of the information items that can make a difference:

• What kind of freight will be hauled?

• What routes will be run?

• How many daily door openings are expected?

An operation that will likely have frequent door openings will benefit by including a door switch that will shut off the reefer unit when the door is open.

This is one area in which bigger is not necessarily better. Regarding the purchase of a refrigeration unit larger than the application requires, Murdock says, “A high capacity unit will not only cost more but operate inefficiently.” Work with your dealer.”

The ultimate fuel-saving technique is simply not running an engine that drives the reefer’s cooling unit, and that’s a possibility at various times using electric standby accessories. More and more people are wanting to run their equipment on electric standby – a not too surprising because some fleets have cut their operating costs by 50 percent. That, certainly, is very application dependent. The problem is the limited availability of power drops, but even that is changing because anti-idling laws that have been on the books for years are beginning to be enforced. In addition, because of “good neighbor” policies, some receivers are supplying electric power to truckers and requiring them to shut down diesel power to their reefers as well as their trucks while making deliveries.

Technology has served transport refrigeration equipment as much as any other sector of the trucking industry. Automated temperature set points, control of reefer unit cycling as a function of product, wireless communication of reefer unit operating conditions between the truck and headquarters are only a few of the advances now available to fleets – advances that will not only offer fuel savings but also more accurate control of trailer temperatures. Fleets should take advantage of them.

There’s also a low-tech item that can go a long way in saving fuel. Install an anti-siphoning device.


It may not be number one, but high on everyone’s list of important maintenance activities is attention to door seals. Bud Rodowick, manager of fleet performance at Thermo King tells of standing inside a reefer trailer at more than one fleet that called him to help cut operating costs and being able to see light through door seals with the doors closed. He likened it to heating or cooling your house with the doors and windows open.

While most refrigerated fleet managers know that insulation deteriorates over time, too many simply don’t act on that knowledge. Remember that a reefer unit runs to keep product cold. When the trailer’s insulation deteriorates, the unit runs more and when it does it burns fuel. Rodowick says that one of the most important aspects of reefer maintenance is simply an acknowledgement that the unit is aging. A six-, seven- or eight-year-old unit should be a prime candidate for replacement.

Rodowick also stresses the importance of regular preventive maintenance for a reefer unit. He understands the desirability of fleets establishing their own PM programs, but he strongly urges that those schedules be followed. Below are additional maintenance suggestions he and others offer to keep units efficiently:

• Check for the absence of sealing drain hoses (commonly called kazoos), which too often get blown off by misguided power washers.

• Check for air chute damage. Make sure it’s attached to the unit so it can transfer air to the rear of the trailer.

• Check for any trash that might have accumulated at the bottom of the front bulkhead where air is returned to the reefer unit.

• Attend to temporary repairs made on the road. Too often such repairs are not redone properly when the truck or trailer comes into the shop, and water enters through a cut causing damage to the insulation.

• Check for the adequacy of the refrigerant charge. If it’s low, find out why, repair the problem and refill the system. Don’t simply “gas and go.”

• Finally, make sure your service technicians are adequately trained on reefer systems and trailers.


While fleet equipment managers often are not directly involved in fleet operations, they often are highly involved with fuel consumption responsibilities, so it only makes sense to understand that some operational procedures can greatly affect fuel economy. Only product at or below temperature should be loaded onto a trailer. Too often shippers present warm product and expect the trucking firm to cool it down in the trailer. That takes additional fuel for which their will be no compensation.

The doors of a trailer that are heat soaked should be opened before the reefer unit is turned on. Think of a car when it’s been sitting in a parking lot on a hot summer day. After some of the hot air escapes, Thermo King’s Rodowick suggests that you have the driver set the unit to cool to 75 or 80 degrees and turn it on with the doors open until he begins to feel cool air coming out. Then close the doors and set the correct temperature. The idea isn’t to really cool anything, just to get rid of the overheated air inside the trailer.

Routing software might help eliminate one or two door openings for a delivery operation. Anytime you do so, you’re going to save fuel. It might also help route an over-the-road truck through a desert city during night time hours when there will be less stop-and-start driving due to traffic congestion.

Some truckload carriers are not able to fill a trailer with product because of weight constraints. In such situations, install a moveable bulkhead behind the load. There’s no sense using fuel to cool an empty volume.

The engine in a refrigeration unit certainly doesn’t consume as much fuel as the truck that pulls it, but it burns enough to make a difference. With the price of fuel, it makes sense to do everything an operation will allow to operate reefers as efficiently as possible.

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