How to Choose and Maintain a Generator for Commercial Construction Needs

By CE Contributing Authors August 18, 2014 View Profile

By Manny Rumao
As a contractor, you know that having the right tool for the job is key to a successful end result. Choosing the right portable generator to power your equipment is no different. It’s important to make sure you have a generator powerful enough to run your equipment, but having too large of a generator just wastes fuel and costs more to maintain. In addition, you also need to be able to get it to where you need it, when you need it.

Determine Your Power Needs
First of all, you should know that all portable generators have two power ratings: continuous power (i.e., running watts) and maximum power (i.e., starting watts). Running watts are what the generator can produce continuously while running, and starting watts are what it can produce for a short time to help start motorized electrical tools like circular saws or hammer drills. Only equipment with electrical motors require this additional power at the beginning to start. For example, a circular saw takes 2,300 starting watts but 1,200 watts to run, and a hammer drill takes 3,000 watts to start but only 1,000 watts to operate. Conversely, your halogen work light takes 1,000 watts to run.

Some generators, like those from Kohler, are equipped with a built-in maintenance minder that tells you exactly what maintenance it needs.

Totaling up your power needs requires some good ‘ol grade school math. After listing the items you want to power, find the item with the most maximum power (a.k.a. starting watts). Then add that number to the continuous power (running watts) for all the other units. So if you add up the items above, it will total 5,200 watts (3,000 + 1,200 + 1,000). So you’ll need a generator with a continuous power rating of at least a 5.2 kW (5,200 W). If you can’t find the wattage amount, don’t worry. All you need to know is the volts and amps of your equipment. To calculate the wattage, just multiply volts times amps. So, your circular saw, which operates on 110 volts and consumes 20 amps, needs 2,200 watts to run and requires a generator with a power rating of at least 2.2 kW (2,200 W).

Think about Features and Brand
Next, consider how you’re going to carry and transport your generator to identify the accessories you’ll want. Will you likely be moving the generator around a worksite often, or will it more than likely stay in one place? This can help determine whether you need wheels or stabilizing feet, what kind of handles will work best and whether you need a lift bracket to connect your winch for easy loading in a truck. If you’re buying a generator, look for one from a reputable manufacturer with a commercial-grade engine and a warranty.

If you’re renting a generator, make sure you work with a rental yard you know and trust to ensure the generator has received regular maintenance and is in good condition. If the yard has a strong rental power business, a representative can also be a valuable resource in determining the type and size of generator to best meet your specific needs. Also, so you don’t spend your time focusing on your generator instead of completing the project at hand, check out the unit’s ease-of-use features. Some generators, like those from Kohler, are equipped with a built-in maintenance minder that tells you exactly what maintenance it needs, when it needs it, along with the part numbers for common maintenance for that particular model.

Using It Properly
As you probably already know, portable generators should ONLY be used OUTSIDE, never in enclosed areas, and far away from windows, doors and vents to prevent carbon monoxide poisoning. Make sure to read the owner’s manual and follow all safety labels and instructions. Make sure the area is free of debris and is compliant with all local ordinances regarding placement near a building or residence. Make sure all wires are properly grounded and insulated and all connections are secure.

When it’s time to refuel your tank or repair your unit, turn off the unit and let it cool down prior to refueling or repairing it. Refueling or repairing the unit while it is running or hot is a fire hazard and may result in serious injury. Always remember to use high-grade fuel and know what fuel is approved for use in your generator. Most generators and pumps, including Kohler’s line, can handle up to 10 percent ethanol (E10). Using fuel with higher ethanol content can cause long-term damage to the engine. And make sure you always use fresh fuel that has been properly sealed and stored, as temperature and humidity can quickly degrade fuel.

For larger diesel engines that meet the latest emissions compliance standards, like those that are in larger tow-behind generators, an additional fluid called urea needs to be refilled along with fuel. This fluid is vital to the engine’s exhaust system to help it effectively reduce nitrogen oxide emissions.

With most engines today, an oil change is recommended every 100 hours and replacing the oil filter is suggested following every other oil change.

Performing Regular Maintenance
Consult your owner’s manual for specific needs and maintenance schedules. In general, generators need the following maintenance performed:

■ Regular oil changes. With most engines today, an oil change is recommended every 100 hours and replacing the oil filter is suggested following every other oil change. Some larger towable generators can go 250 or 500 hours between oil changes. But, operators should keep their specific usage in mind and consider replacing oil filters more frequently if they’re running in severe conditions.
■ Air and fuel filter changes. Engines today often use heavy-duty filters that perform very well and last a long time, but they need to be treated with care. Don’t clean air filters with compressed air, which can easily damage the internals and cause the filter to function improperly. And don’t forget about the fuel filter, which many often overlook. If you’ve ever looked in your gas can, you know that all fuel contains some amount of debris. Just think what that does to your engine. Replace filters as recommended and you will lessen your chances of equipment failure.
■ Do an annual inspection of the alternator, including the rotor and stator, bearing condition, exciter and voltage regulator. Check your owner’s manual for details, and contact a certified service technician with any concerns.
■ For generators with trailers, ensure appropriate tire inflation pressure, tighten wheel lug nuts every three months or 3,000 miles and regularly check the tires, wheels, wheel bearings, seals, springs, suspension parts and hangers for signs of corrosion, breakage or wear.
■ You should also make sure to keep the generator clean, especially wiping off spilled fuel to reduce fire risk and ground and water contamination.
■ For long term storage, it’s best to drain all the gasoline from the unit and from the carburetor and add fresh gasoline the next time you start it. You can also add fuel stabilizer to the gas in the generator if you don’t expect to use it all up in a month or so. Fortunately, diesel fuel does not need the same preventative steps.