THE ELECTRICIANS WHO INSTALL COMMERCIAL, industrial and residential electrical systems need electricity to do the job, but in many situations, new construction often takes place in areas where commercial power is not yet available or outlets are not easily accessible.

Cordless tools can be a short-term solution. Indeed, battery-powered products are routinely used on jobs where power isn’t available, but batteries have to be recharged, which requires electricity. Of course, power needs aren’t limited to tools. Construction sites need power for the lights, heaters in the winter, fans in hot weather, and to operate computers, printers, copy and fax machines and other equipment in field offices.

Most often needs for temporary power requirements are filled by portable generators. In addition to providing power for construction and routine repair and maintenance projects, portable generators play a critical role immediately following major disasters when they often are the only sources of power during early recovery efforts. That important role was dramatically illustrated last year as emergency crews reacted to the hurricanes and flooding that devastated the U.S. Gulf Coast, New Orleans and nearby areas.

Whatever the temporary power need, portable generator models today are smaller and lighter, more efficient, and run quieter than those available when Cool Tools last reported on them three years ago. One significant new development is inverter technology.

“Portable generators continue to change as new technology becomes available,” said Marc Leupi, pump, power and light product manager at the Wacker Corp.

“Inverter generator technology is exciting because it allows the engine to run only at the rpm needed to power the load, saving fuel and reducing sound levels. Another major innovation for the protection of personnel is a full GFCI [ground-fault circuit interruptor] sensor now available on some models. This system monitors and protects against ground faults on all outlets, not just the 120V duplex outlets like on most generators. This system is also more durable and reliable than standard GFCI outlets, which are known as high-maintenance items.”

With the wide selection of portable generators today, whether an electrical contractor needs dependable, all-purpose generators for varied power requirements or is looking for equipment with special capabilities for a project with unusual requirements, the right equipment is readily available.

The smallest generator models are powered by air-cooled gasoline engines; they are light in weight, and some of the smallest can fit in the trunk of a car. More powerful gasoline models still are very compact, and both gasoline and diesel units mounted on trailers are available for easy towing and positioning on the job. Many are available on skids for mounting on contractor vehicles or on job sites. There are also LP and natural gas models. Larger models almost always are diesel powered.

Depending on the generator model, both single- and three-phase power can be developed; some units permit the use of small tools at the same time the generator is producing three-phase power. Generator packages are designed for specific jobs such as portable light towers, including both generator and self-contained fresh air blowers and heaters.

Output of portable generators varies widely, starting at 4 kW and going up to large units producing as much as 5,000 kW and more. Units producing from 50 to 100 kW are popular choices and are available with a variety of features.

Many electrical contractors own generators and rent additional units as workloads require. Generators are readily available at general rental centers and equipment rental specialists. Because rental stores replace equipment frequently, most rental units are relatively new and are equipped with the latest features.

Representatives of four portable generator manufacturers share information about industry trends and features of today’s portable generator equipment.

Generac Power Systems, Dan Giampetroni, senior marketing manager: “Today’s models have larger power output with greater motor-starting capabilities. When evaluating generators, factors to consider are wattage rating, engine durability, electronic governor and run time that will be provided by size of the fuel tank. When operating computers off a generator, the unit should be equipped with automatic voltage regulation and electronic governor. We are seeing demand increase in larger kW sizes from 12.5 to 17.5 kW. There has been an influx of imported products to meet post-hurricane demands.

“For safe use of portable generators, engines should be allowed to cool before refueling, and equipment should be placed outside or in well-ventilated areas to protect from carbon monoxide [poisoning].”

Honda Power Equipment, Dan Sherlock, assistant manager, product planning and marketing: “The development of inverter technology allows substantial reduction in weight and noise. By eliminating the standard alternator, our new inverter models weigh less and are smaller in size than traditional generators.

“Honda’s inverter technology takes the raw power produced by the generator and passes it through a special microprocessor that provides ultra-clean power with a sine wave equal to or better than AC current from a standard household wall outlet. With availability of this clean power, contractors can now use generators to safely power delicate devices and equipment that could not have been confidently powered in the past. Computers and power-sensitive testing equipment require ‘clean power’—consistent electrical current that has a stable sine wave or signal. A computer without clean power would likely freeze, shut down or be interrupted.

“When selecting a generator for any given task, it is best to begin by answering a few basic questions: How will you use the generator? How quiet do you need it to be? How easy does the transport of the model need to be? How much power do you need to do the job? The answers to these basic questions then become the guidelines to selecting a generator. For instance, for portability, many models include standard wheel kits for easy movement of the generator from storage to the work site. Consider the options to select the right models for applications.”

Multiquip, Juan Quiros, product support manager: “Generators, per se, haven’t changed much in recent years. Generator accessories and individual unit features have improved, primarily to offer operators improved convenience and ease of operation. Government regulations concerning sound and emission levels are more stringent, and generator manufacturers have been forced to refine their products to comply. Many generators are now quieter than they were just a few years ago, permitting use in residential areas, around schools and in other noise-sensitive areas that traditionally were problematic for generator operation. Several convenience features have also been added, among them [are] additional receptacles, lifting bails and wheel kits, all of which are stronger to withstand the rigors on a job site.

“A gas-powered 6,000-watt generator is the practical power source on most jobs. It offers the convenience of 120/240-volt power, providing enough juice to operate the most common tools such as angle grinders, table saws and concrete vibrators. A 6,000-watt model is also compact enough for two operators to easily load and unload the generator into a pickup truck.

“Contractors must consider the maintenance features on any generator as this is a determining factor in maximizing productivity and minimizing downtime on the job. Brushless alternator designs are favored because they eliminate wear items such as carbon brushes and slip rings. Similarly, tighter voltage regulation keeps tools running cooler while extending both tool and generator life. When working with computers and other sensitive electronic equipment, it’s important to choose a power source with a low level of harmonic distortion. This minimizes inaccuracies and other shortcomings often caused by power sources.

“The expanding rental equipment industry has increased consumer awareness as to the benefits of renting versus buying. Combine this with increased construction activity and portable generators are one of the products realizing greater utilization. In addition, the unusually high number of hurricanes in recent years has further increased demand for portable power.”

Wacker, Marc Leupi, pump, power and light product manager: “In addition to inverter technology and full GFCI protection both previously cited, another development is the integration of electronics into the engine, which will allow more precise engine control, aiding both motor starting and frequency and voltage regulation, opening the door to new features like remote starting that are not currently cost effective.

“There are many factors to consider when selecting portable generators. The most important include motor starting capability, how long the generator must be operated, durability, quiet operation and engine quality.

“There are many makes, models and sizes of portable generators on the market. Within the same power class, there is a significant price difference between the lowest-cost economy units and the most expensive premium models. The old adage that ‘you get what you pay for’ really does apply here. Many owners of premium generators often have gone the economy generator route first only to discover that the generators cannot do what they need and end up costing more in down time, damaged power equipment, repairs and other problems.”            EC

GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or