How to: Install an inverter

| December 11, 2008

Once a novelty, inverters are now mainstream over-the-road equipment.

On any given evening in America, truck stop parking lots are filled with truckers enjoying the comforts of modern domesticity, their many household appliances quietly nursing on the undulating AC current of power inverters.

Once a novelty, inverters are now mainstream over-the-road equipment. Fleets use them to recruit and retain good drivers. Truck makers offer them as factory-installed options. Anti-idling laws and the new hours-of-service rule have made them more practical.

Their appeal can be summed up in two words: convenience, economy. For many truckers, the choice is not whether to buy an inverter, but which model to choose. AC-driven appliances in all the latest colors can be found at any discount retailer, whereas their less powerful and more expensive DC counterparts generally are sold only through camping outlets and Army surplus stores.

There are two basic types of inverters: pure sine wave and modified (or quasi) sine wave. The former delivers an electric waveform as good as, and sometimes better than, the output of a utility company. The latter is less expensive but produces a waveform unsuitable for certain devices, such as microwave ovens, laser printers, some digital clocks and cordless tool chargers.

Most people base their buying decisions on power and price. The range in both categories is from 75 watts and roughly $25 to 3,000 watts and $1,000 or more. Unfortunately for many people, this simplistic approach to purchasing often leads to disappointment and frustration, usually because they undervalue quality or underestimate their AC loads.

“We’ve found that insufficient size is the biggest reason our products are returned,” says Brian Lawrence, OEM sales manager for Xantrex Technology in Arlington, Wash. “People will buy a 150-watt inverter but actually need one that’s three or four times as powerful. People commonly think that smaller electrical appliances don’t use much power. That’s not the case.”

Xantrex builds a full line of inverters and is one of the few companies offering a heavy-duty inverter-charger combination. It’s also the only approved supplier for factory-installed units. Lawrence says this segment of the business has grown steadily and rapidly since 2000, when Freightliner became the first truck maker to offer the units as options. Volvo and International soon followed suit.

Factory installs have a couple of advantages, Lawrence says. First, the inverter is covered under the truck’s bumper-to-bumper warranty. Also, the “fit and finish” is usually superior to aftermarket jobs.

“There’s nothing better than running the wires through the walls before the interior panels are mounted,” he says. “Plus, manufacturers do a good job of clearly identifying the wiring,” reducing the chance of mechanics later slicing into the system’s harness.

The number of new trucks spec’d with inverters is still relatively small, meaning that most truckers do the installation themselves. Following are the steps for mounting and connecting an inverter. This information should be used in tandem with the product-specific instructions provided by each manufacturer. The need for safety cannot be overstated in these jobs because they involve a truck’s batteries, which emit explosive gases and contain enough electrical force to instantly toast any metal they encounter, including tools and jewelry.


  1. MAP OUT THE JOB. Unpack the inverter, its cables and other parts. Figure out where to mount the unit and auxiliary switches or outlets, if they’re included. Inverters should be mounted in an area that’s well-ventilated, dry and accessible, but away from heavy objects that might slide during cornering or hard braking. The location’s distance from the truck’s battery box is also important. Closer is always better. Determine the path for routing cables between the inverter and batteries. Check under (or behind) the panels where holes will be bored, to ensure no submerged wiring or framework is damaged in the process.

  2. BORE CABLE HOLES. Following the manufacturer’s instructions, use appropriately sized hole saws to cut openings, if necessary, for the inverter’s cables and wiring. Then line each of these holes with a rubber grommet, which will protect the cable from chafing on the metal. Grommets are included with some installation kits. They’re also widely available at hardware, plumbing or auto parts stores.

    Not all holes require grommets. Xantrex, for example, uses a “pass-through” plate to route its cables from inside the cab to the great outdoors. The 4-inch weather-tight plate is designed to mount over a 31/2-inch opening. Remove carpeting, padding or rubber mats covering the mounting area before boring this hole. Later, cut the material to accommodate the plate and cables. When you’re ready to secure the plate, apply a healthy dose of silicone sealer or similar product on the mating surfaces to reduce the chance of corrosion between joined dissimilar metals.

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