GENERATORS: Power to the People

March 1, 2002
Generators are a necessity for most job sites and are therefore an important item for most rental fleets. Portable generators in the 3.5 to 6 kW range

Generators are a necessity for most job sites and are therefore an important item for most rental fleets. Portable generators in the 3.5 to 6 kW range are the most commonly rented sizes. This power output handles most of the smaller hand tools that a typical contractor uses.

Portable generators are mainly used in locations either where power is not yet available or where the small contractor does not have access to the line power. For example, carpenters framing houses in newly built subdivisions can utilize generators when using saws, drills and powering air compressors to supply nail guns. Generators are also used to power concrete vibrators while pouring footings, foundations and walls before power is available to the building site. Generators also power electric pumps to remove water from the excavation before the above work can take place.

It is important for rental centers to carry a generator that is of the highest quality, geared to continuous all-day operation. Many generators that are low cost are only designed for intermittent homeowner type use and cannot stand up to contractor use. Good motor starting characteristics are also desirable. This will make the unit more productive and tools will last longer.

Rental centers can help contractors by recommending the right generator for the job. A common mistake is to rent a generator that is too small. The generator needs to have enough capacity to start and run all the tools that contractors need to complete the job. If the unit is too small, it will trip the circuit breakers frequently, and this is hard on the tools being run because of high currents during start up.

Three factors play a part in sizing a generator for the job — type of load, total watts to be connected and power of the generator.

Type of load

There are two types of electrical loads — resistance and induction loads.

Electrical lights and heating units are examples of resistance loads. Most construction equipment requiring generator power has induction loads (electric motors).

There are two types of induction load motors. Universal motors, which use brushes, include power hand drills, saws and concrete flex-shaft vibrator motors. Capacitor motors include power pumps, air compressors and table saws. The main difference between these motors is that the capacitor motors need about one to three times more starting current than universal motors.

Wattage requirements

After determining the type of load, the next step is to find the total watts of the load to be connected. The most accurate method to determine wattage is to check the nameplate on the machine. However, if this information is not available, wattage can be figured by multiplying amps x volts = watts.

Load requirements to electric motors differ, but all motors require more power to start than run. Capacitor motors require up to six times more starting power for longer periods of time. Universal motors draw 1 1/2 to 2 times the running current for shorter periods of time.

What size generator?

Once you determine the wattage, you can choose your generator. The basic guide: If the generator has enough power to start up the load, it will have enough power to continually run it.

Consider this: A small contractor wishes to use a portable gasoline generator to power his temporary job shack. He needs to connect seven 100-watt light bulbs (700 watts), coffee maker (850 watts), small refrigerator (induction, 600 run watts, 2000 start watts) and a 1500-watt radiant heater.

The light bulbs, coffee maker and radiant heater would run constantly, consuming 3,050 watts. With the refrigerator cycling between off and start/run the total wattage demand on the generator will vary between 305 and 5,050, which can still be easily handled by a portable generator. A 5600-watt generator will power the job shack sufficiently.

Consider another example: A 2-inch submersible pump requires 771 running watts and a 2-hp flex-shaft vibrator runs on 2,000 watts. The pump and vibrator motor require a total of 2,771 running watts. However, the pump has a capacitor motor and will require 2,313 watts for running, while the universal motor requires 2,600 watts. You can size the generator to the largest starting and running load, which would be 4,313 watts (2,313 + 2,000). To run the pump and vibrator, again a 5,600-watt generator will be needed. This will give you plenty of room should you add another tool such as a rotary hammer, which needs 1,100 watts to run and 1,600 to start.

Mark Conrardy is sales engineering manager for Wacker Corp., Menomonee Falls, Wis.

Lincoln Electric

The new Power MIG 300 from Lincoln Electric offers a wide range of synergic multi-process capabilities in one machine including GMAW, GMAW-Pulse, FCAW, Stick and TouchStart TIG. This wire feeder welder utilizes Lincoln's Chopper technology for a smooth, stable arc, better starts and a wider sweet spot. The unit has single-phase power requirements that range from 200 to 575 input voltage and welds at 300 amps at 60 percent duty cycle. With wire feed speeds of up to 700 ipm, the welder has an optional gear change that can increase feeding torque for larger diameter wire during heavy duty welding applications.
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Terex Corp. enters the power generation industry with its new line of diesel generators. The mobile units range from 200 kW to 2,000 kW and are available in fabricated steel housings with the larger units in 20- and 40-foot ISO containers. All containerized units are designed for the engine generator to slide in and out of the container for major service. The prime features in this product line are low noise levels, 100 percent spill containment, large fuel capacity, external electrical hookup panels, full microprocessor-based instrumentation package and utility grade switchgear.
Circle 146 on reply card.

Miller Electric

The 301 G and Trailblazer DC engine driven welding generators from Miller Electric have a 300 amp output and 10,000 watt peak auxiliary power rating at 104 F. For those who do not need an AC weld output, the Trailblazer DC offers the same features as the 301 G at a lower price and with a simpler control panel. These multi-process CC/CV machines provide a 20 to 300 amp DC output for stick, TIG, MIG and flux-cored welding. Both machines now offer better DC TIG scratch starts, more dig to enhance E6010 pipe welding and smooth E7018 performance in all positions.
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Tsurumi Inc. expands its line of brushless generators with its TPG-6500HDXE. Powered by a 13-hp Honda engine, the generator has a maximum output of 6500 watts. The engine features a large muffler and spark arrestor for quiet and safe operation, a large air filter for emission control and auto-idle control for reduced fuel consumption. The brushless generator has no brushes or rings to wear out for reduced maintenance, 100 percent copper windings, condenser-type voltage regulators and electromagnetic breakers to withstand the rigors of rental applications.
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Pow'R Gard

The R30 generator from Pow'R Gard runs on a Robin/Subaru industrial grade engine. Other features include GFCI receptacles, low oil shutdown, automatic idler and fully enclosed tube frame. The product also comes with a 3-year warranty.
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MQ Power

MQ Power releases its line of industrial standby generators, which features 12 models with outputs ranging from 75 to 500 kW. Each unit is powered by a rugged 4-cycle direct injection Volvo diesel engine that meets EPA emissions standards for mobile off-highway equipment. The generators feature a brushless alternator design and an encapsulated electronic voltage regulator that precisely regulates the current into the exciter field. The products have a closed circuit cooling system with an ambient temperature rating of 40 C and a microprocessor-based, digital control panel that is vibration isolated.
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DeWalt's new generators range in output from 2,900 to 7,000 watts and are built with Honda's premium OHV GX engine. The special air intake, choke and carburetion provide easy start-up. All DeWalt generators use brushless alternators that are virtually maintenance-free. A heavy-duty frame protects the receptacles, breakers, switches and metal gas tank.
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Atlas Copco

Designated the QAS range, the 11 models of generators from Atlas Copco are intended for prime power supply on construction sites, welding plants, pump and illumination applications and as standby power in the event of main power failure. The range of sets is housed in acoustically-treated, waterproofed, steel canopies to comply with dB(A) regulations, hostile environmental conditions and to be able to withstand rough on-site handling. Skid mounted, the sets are designed for installation in confined spaces or remote locations, requiring only a firm level surface. Forklift slots and a recessed lifting rod allow easy transportation around the site.
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Wacker Corp. adds three new mobile generator models to its existing line — the G 110, G 125 and G 155 — which offer 98 kW, 109 kW and 138 kW of standby power, respectively. Each model comes equipped with a John Deere engine and a 245-gallon capacity fuel tank. The G 110 has 88 kW of prime output and offers 38.3 hours of running time under a full prime load. The G 125 has 98 kW of prime output and runs under a full prime load for 34.5 hours. The G 155 has 124 kW of prime output and runs under a full prime load for up to 26.8 hours before refueling is necessary.
Circle 150 on reply card.

John Deere

The DP 6000 generator from John Deere features a 12-horsepower Kohler engine with a cast-iron cylinder sleeve and a quiet muffler. Low-oil shutoff helps extend the life of the generator and automatic idle control is designed for better fuel economy and for preventing surges when operating power tools. Other engine characteristics include a maintenance-free, brushless alternator, GFCI protection, hour meter and overload indicator. The generator also features a welded-steel dolly kit with folding handles, making it easy to transport and protecting it from damage.
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The new line of generators from Ingersoll-Rand delivers more than seven package sizes and ranges from portable units to large back-up power generators, featuring a total of 24 different units. The new series includes 15 higher-end units with a prime output of 50kVA to 563kVA, powered by either a John Deere or Volvo engine depending on the model. Each generator is equipped with the Intellysis control panel. Some advantages of the Intellysis system include extra accurate frequency and voltage reading, multiple language readout, simultaneous information display and a memory that records up to 25 actions for easy troubleshooting.
Circle 153 on reply card.

Robin America

Generators from Robin America have automatic decompression, easy-pull recoil starters. The low-tone-designed extra large mufflers plus a sound-suppressing heavy-duty industrial air cleaner provide quiet operation. The full power switch allows 120 V full power connection to one Twist-Lock receptacle. The automatic idle control lowers engine speed when no electrical demand is needed.
Circle 154 on reply card.


Generac's GR series is a fully integrated design platform that brings dependable mobile and emergency power from 8 to 210 kVA to every kind of demanding application. The GR 25 to 210 models feature simultaneous high and low voltage, with single and three phase outputs. Every GR unit offers standard features including a large heavy-duty fuel tank, automatic start system, battery charger, jacket water heater, engine safety shutdowns and full instrumentation for engine and generator. It's all integrated in a sound-attenuated enclosure as a durable mobile package.
Circle 152 on reply card.

American Honda

The EB5000XK1 generator from Honda has a 4-stroke, 11-hp overhead valve engine. It has a full tubing frame for protection and easy transport. Other features include automatic throttle, oil alert, electronic ignition, circuit breakers and automatic voltage regulator.
Circle 155 on reply card.

kWiet Power

Besides compact size and low sound, kWiet Power generators deliver consistent output that operators can control with ease. The generators have an easy-start Isuzu diesel engine that is matched to generator size. An auto-start option is available for unattended or backup services. Every unit is test-stand-checked, and a voltage switch allows output to be matched to load while a lock on the switch protects against improper voltage change.
Circle 158 on reply card.


The SDG60S-3A2 generator from Mitsui has a frequency of 60 hz and 66 kva, 52.8 kw standby output. Prime output is 60 kva, 48 kw. Other features include 1800 rpm and an 80 percent power factor. It runs on a 4-cylinder, diesel engine and has a 40-gallon fuel tank capacity.
Circle 160 on reply card.


The NAC heavy-duty NGK Series of portable brushless generators are used wherever consistent, reliable power is needed. Durability comes from features such as the cast iron cylinder sleeve, ball bearing supported crankshaft and chrome top piston ring. These tough engines are known for their easy starting due to maintenance free electronic ignition, auto-decompression and the automatic vacuum assisted choke. Durable condenser voltage regulation provides stable voltage regulation that stands up to demanding jobs.
Circle 159 on reply card.


The W9500HE industrial portable generator from Winco is built to withstand the rigors of construction job sites and rental applications. With an 8.5 kW rated output, the generator uses heavy-duty 100 percent copper windings for superior motor starting. The control panel has receptacles for both 120- and 240-volt output, with individual circuit breakers. Powered by a Honda, 18-hp overhead valve engine with low oil protection, the generator has rugged wrap-around welded steel cradle and powder paint finish designed for extra durability.
Circle 184 on reply card.