Mobile Generator Makers Share Their Insights into the Industry

The market for mobile generators, especially the popular one-axle-trailer units that keep the lights on at festivals and run the tools at rural worksites, is juicing up. Maybe not so much this year, manufacturer reps say, but the following two years are expected to bring a surge in sales of the units. The anticipated growth in the generator market is pegged to the culmination of the Tiered engine-emissions regime. Tier 4 engines are now on the market, and the regular price increases linked to each subsequent tier have run their course. During the run-up, rental fleet owners and contractors resisted buying new gen sets because engines are a big percentage of the total expense.

“The biggest volume owners of the generators have been strategically managing the gradual addition of Tier 4 products into their fleets by leveraging TPEM [the Transition Program for Equipment Manufacturers], by extending the life of prior tier products or by utilizing remanufacturing solutions in some cases,” says Todd Howe, manager of global generator products for Doosan Portable Power. “The market’s slow adoption of Tier 4 product has impacted normal market conditions, but over the next 12 months, the industry will need to start to reinvest and replace equipment so 2017/18 should be pretty healthy years.”

That, of course, assumes a Tier 5 emissions standard won’t be imposed by the EPA. Howe doesn’t believe it will. “We believe we are done with emissions upgrades for the foreseeable future. The EPA has made no signal about additional off-highway standards which aligns with what our engine suppliers tell us — there is no Tier 5 in mind at this point. That’s good news for our users as they will have several years to get used to the technology we have now.”

By new generator technology, we are talking mostly about new diesel engines. Sometimes the new engines have ushered in a redesign of the mobile unit, but by and large the engine is what’s new. For example, Chicago Pneumatic will come out this year with a next generation of compact mobile gen sets with some new features, according to Jim Siffring, CP’s product manager for electric power and light. But the primary new feature is an Isuzu Tier 4 engine without diesel particulate filters, which translates into lower fuel consumption.

Generac/Magnum offers a mobile power solutions ranging from 6 to 2,000 kW. Their MLG Series of mobile generators offer power ranging from 8 to 19 kW in a small, compact cabinet with run times up to 43 hours. Yet Dave McAllister, director of product management for Generac Mobile Products, insists the new line is not solely about the engine. “Our mobile generators are designed with the end-user in mind,” he says. “This focus results in a better customer experience, but it also benefits our rental partners by focusing on the concept of total cost of ownership, factoring in things like fewer engine service requirements, ease-of-transport and extended run times.”

Generac-(Cut-1-B)The Tier 4 engine development is of note for one other important reason — the advanced technology has turned a mere annoyance into a much bigger problem for generator users. The issue is wet stacking, which is the incomplete burning of diesel fuel. It results in carbon buildup in injectors, exhaust valves and other engine components. In modern Tier 4 engines, the by-products of wet stacking can affect the performance of emissions aftertreatment systems.

Howe blames the ongoing problem on the tendency of operators to “underload” their engines. “Power requirements are often hard to estimate and can vary considerably so customers are quite likely to oversize machines for a particular job. But when diesel engines run with too light of a load, the engine doesn’t produce enough heat to burn all of the fuel. Wet stacking has been going on for as long as diesel engines have powered generators, but previously it was a nuisance and more of a maintenance concern. Now, with Tier 4 emissions engines, prolonged operation at light load can cause engine fault codes and shutdowns.”

The industry is wrestling with this dilemma, and Doosan has a solution it calls the “Intelligent Load Management System.” It monitors the temperature of the engine aftertreatment system, and when additional warmth is needed to “keep the aftertreatment happy,” in Howe’s words, it injects supplemental heat to ensure reliable engine performance. Siffring offers two more. One is to quit shutting off the engines on CP generators using the emergency stop button. That only causes difficulties for an operator.

“Our diesel engines are designed to purge themselves when shut down,” Siffring says. “We purge all the fuel lines to get the fuel out of the injectors and lines so that, in cold weather, they don’t freeze and break the lines and parts. When the engine is shut down normally, it goes through a purge cycle. If you hit the emergency stop button, none of that happens.”

CP-showcaseThe other bad habit that operators can’t seem to shake, according to the Chicago Pneumatic product manager, is turning the voltage selector switch while the generator is running. Not a good idea. Throwing the switch during operation changes windings and starts “all kinds of arcing” and can significantly damage the unit and possibly injure its operator.

Siffring says the mobile units have stark warning stickers alerting operators to this danger, “but people still do it.” Before sending a generator out of a rental yard, a rental agent can lock the voltage selector to a pre-set voltage for a customer’s expected use, but individual contractors must rely on operator judgment.

Most of the top-selling one-axle mobile units are marketed to rental companies — 80 percent of Doosan’s production, for example. One reason is that today’s technologically complex engines are a challenge for the average construction fleet mechanic. The generators themselves are user-friendly — “You don’t have to be a generator expert to figure out how to operate one of these,” says Siffring — but only bigger contractors and sizeable rental fleet companies have a stable of technicians capable of servicing the engines.


Generac/Magnum mobile generators can be used in a variety of settings, including emergency power applications after storm-related damage.

So what is the market for these generators? Where are the generators being cranked up? According to McCallister, Generac’s mobile generators have proven ideal in powering jobsite trailers, construction and industry sites and fuel stations in emergencies, as well as keeping critical services functioning during local storm-related power outages. As public officials and commercial interests prepare storm preparedness strategies, this segment of the market grows. A new marketing trend is entrepreneurs buying small fleets of the generators to specialize as back-up power subcontractors.

And despite the collapse of oil prices, manufacturers say the oil and gas market for the generators remains reasonably strong. Drilling of new fracking wells is not happening, but production at existing wells continues and most of the producing sites are off the grid. Onsite pumps there are pulling juice from mobile generators. Where natural gas is the fracking product or byproduct, NG-powered generators are an increasingly popular option, which eliminates the cost of transporting diesel fuel to the sites.

Future versions of today’s compact mobile generators may feature hybrid engines to conserve fuel, according to McCallister. And trailers are changing: Chicago Pneumatic is moving toward fabricating axle and tongue bolt-ons, with the rest of the trailer frame integrated into the unit. Or, if a customer prefers, a separate trailer can be purchased. These and other coming innovations, say manufacturer reps, will be predicated more on what will benefit customers instead of what will satisfy regulatory agencies.

Mobile Paralleling Box

Combining Different Size Generators with Different Fuel Types


Each contactor is rated at 1,000 amps — different sized generators can parallel as long as each unit’s output is less than 1,000 amps.

Last year, Kohler Power Systems launched a cutting-edge Mobile Paralleling Box, which delivers flexibility by allowing users to combine different sized generators with different fuel types. The new paralleling box is specifically designed for use with Kohler’s gaseous and diesel mobile generator line. Four of the new boxes can be used to parallel as many as eight generators. The Kohler Decision-Maker 3500 digital controller, which is standard on all Kohler gaseous and Tier 4 Final diesel mobile generators, provides the paralleling intelligence and network communications for remote monitoring. The digital controller along with the new Mobile Paralleling Box makes it possible to parallel generators for applications such as using multiple smaller units to replace a larger generator, providing redundancy to a primary generator in support of critical loads, meeting system capacity demands when one generator is inadequate or managing generators to be sequenced on or off in a predetermined order based on system output.

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Backup Power

Make Sure Your Offices Are Ready for the Spring Storm Season

When considering your power needs, first determine the highest power application such as an air conditioner for the job trailer.

When considering your power needs, first
determine the highest power application such as an air conditioner for the job trailer.

In addition to high temperatures this summer, many areas of the country continue to face damaging weather events, including severe thunderstorms and tornadoes. When it comes to summer storms and lengthy power outages, offices on commercial jobsites are not immune. Keeping the lights on and the computers running is an important part of construction job oversight for administrative staffs — and that means having the right portable generator at the ready. Since generators have a broad wattage output range, both a contractor and a homeowner must understand electrical requirements and estimate real emergency needs. Refrigerators or freezers operate on about 700 watts but require as much as 2,200 watts to start. A computer draws 600 to 800 watts. So, it could take a 2,500-watt generator to run a refrigerator, minimal lighting and a computer or TV.

More important, a generator must be operated outside and never be plugged into a standard outlet. A safe connection starts with a transfer switch installed by a licensed electrician. The switch cuts off the utility power while the generator operates and powers only selected appliances. When utility power is restored, the generator and transfer switch are disconnected so that the two power sources do not collide. There are a number of important things to consider when selecting a generator. How quiet does your generator need to be? Is electric start required? Do you require easy transport? How much power will you need? To determine wattage requirements, select which devices need to be powered simultaneously and what the starting requirement of the device is. Find a wattage calculator online to assist you.

Giles Lambertson is a freelance writer for Compact Equipment.

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