How to Choose the Right Mobile Generator for Construction Projects
When you’re working in the field, chances are good there won’t be any power source nearby. So you bring along a generator. As long as it can produce enough juice for the job, that’s all you need, right?
Wrong. There are differences among generators other than output capacity, and you should consider all the variables before deciding which generator to send to which job. We all know what happens when you use the wrong tool. So let’s take a closer look at how you can select the right gennie to power the work at hand.
- What is the scope of your project? Are you building a major highway? Remodeling a building?
- Will the generator need to handle surge loads?
- Will you need to switch frequencies?
- Will the generator need to run off an external fuel supply?
- Do you have to meet special noise or site contamination standards at your jobsite?
Output capacity required
Every generator has a rated output (the wattage it can produce indefinitely) and a maximum output (the highest wattage it can produce for short periods). You want a machine with outputs high enough to handle your workload but no higher. If the generator is too small to comfortably handle the load, it will shut down and so will your work. The generator could even suffer damage before it quits working, adding to your woes.
On the other hand, if the generator is too big it will eventually lose power, thanks to carbon buildup in the engine. This is called “wet stacking.” It’s most likely to occur if the generator is running at less than 50%-60% of capacity. One way to avoid this potential problem is to run two smaller generators in parallel – coupled electrically so that, combined, they function like one large generator. With this arrangement, you can shut down one of the generators onsite when demand is lower. This solution costs more up front but can give you greater flexibility and reduce the risk of downtime.
Here’s how to calculate your power requirement:
- Add up the wattage required to start each piece of equipment that will be powered by the generator. This starting power total is your maximum output requirement.
- Add up the wattage required to power each piece of equipment while it’s running. This total is your rated output.
- Add 10% to each total to give yourself a safety margin. While some leeway is good, too much can be a negative because you’ll wind up with an over-large generator.
Consider a generator with adjustable output
Some generators have multiple output settings, so you can use them in more ways onsite.
- If you have equipment than runs at both 50- and 60-Hz, a frequency switch will make it easy to accommodate both.
- An automatic voltage regulator (AVR) maintains output at a consistent level even as individual pieces of equipment are turned on or off. (It takes more power to start than to run.) If you’ll need to start large motors during the work day, that increases risk of a power surge. You may want to choose a generator with a heavy-duty, oversized alternator.
Eventually, every generator will need to be refueled. The most efficient generator is one that can handle your entire workload all day long before needing more fuel. That way, work doesn’t come to a halt while you shut down the unit to refuel. Sometimes you may need a generator that can go even longer, up to 24 hours. In this case, choose a generator that has extra-large fuel tanks or check into a generator that can switch between onboard and external fuel supplies. This can greatly extend runtime.
And speaking of fuel, although diesel-powered generators are still the most common, you may want to consider an electric portable generator for certain applications.
Still not sure which generator is best?
Whether your intention is to rent or buy, look to the experts at your equipment dealership for assistance. By first considering all the factors we’ve noted above, you’ll be able to provide maximum information to help them help you make the best decision.