Night work is a fact of life for several contractors. Take Jim Jacobs, owner of Jim’s Concrete of Bevard, Jacksonville, Florida, who uses light towers on early morning pours. “We typically use four light towers for our larger, 20,000 to 30,000 feet pours,” he comments. “Two of those will be rented, since we need light on every corner.”
“These days, people want light on a stick,” says Marc James, product marketing manager, utility equipment, Ingersoll-Rand. “They don’t need a lot of fancy bells and whistles, especially when it comes to rental units. They want something that’s easy to set up and use and will run as long as possible without refueling.”
Because of this, most light tower rental units come in a basic configuration: a 6,000-kilowatt generator powering four 1,000-kilowatt metal-halide bulbs on a 30-foot mast. There’s enough power left over – about 1,500 to 2,000 kilowatts – to run small power tools. “A 120-volt AC outlet is standard on rental units,” says Brad Dilling, light tower product manager, Genie Industries.
Although rental light towers tend not to have extras, Dilling says a number of options are available, including cold-start packages, engine warmers, heavy-duty batteries, fuel/water separators and a key ignition rather than a switch, which limits access to the unit.
The all-purpose generator
While there’s little variation in rented light towers, rented generators can offer several features, says Mark Leupi, product manager, Wacker. “This is especially true in the larger units,” he comments. One option is an electronic governor, which precisely monitors the load and engine speed, a feature required for sensitive electronics, such as computers in jobsite trailers.
Contractors usually rent one of two sizes of generators – 25 kVA and 75 kVA – although units up to 600 kVA can be found on jobsites. “Most are diesel-engine-driven units with sound-attenuated, sheet-metal enclosures,” says David Puck, product marketing manager, utility equipment, Ingersoll-Rand.
Puck has seen two approaches rental companies use to age their generator fleet. Most national rental companies put 36 months on the units, accelerating depreciation before turning them over and acquiring new products. (In recent years, however, this extended beyond 36 months as rental companies sought to lessen capital expenditures.)
Some specialty generator rental companies, though, take a different approach, and use extensive maintenance to age their units up to nine years. “And whenever they sell these units,” Puck says, “there’s always a backlog of people who want to buy them because they’ve been taken care of so well.”
Maintenance, yours and theirs
Maintenance is basic on both light towers and generators. Renters need to keep an eye on the engine oil and air filter, changing them every 300 hours. If you’ve had a rented unit for a while, resist the urge to clean it with a pressure washer, says Dale Gabrielse, training manager for Robin Subaru. Instead, use an air hose to clean it off, then wipe it down with a rag. “If you’re in a wet climate, water can sit inside the housing and cause a short,” he says.
Before you rent, determine if the unit you rent is in tip-top shape. Signs of a well-kept rental machine include a clean engine compartment, correct fluid levels and non-frayed cables. “There’s usually just a well-maintained overall appearance to the machine,” Dilling says.
On the other hand, indications a rental light tower hasn’t been properly maintained include leaks, dirty filters, faulty wiring and under-inflated tires. “Operate the light fixtures and make sure the tower mast is in good operating condition,” James says. “Most masts will run off a winch and a cable, so look for signs of wear or fraying.”
Renters need to keep an eye on the engine oil and air filter.
Respect the electrical system
Although the generators on light towers and stand-alone generators can differ in scale, the safety precautions run on parallel pathways. “You have to respect it because it’s an electrical system,” says Doug Dahlgren, product manager, Allmand Bros. “Make sure all the electrical covers are in place and do not service the electrical system unless you’re qualified to do so.”
“We always recommend renters seek qualified personnel when connecting a generator,” Puck says, “especially when you’re dealing with complex loads. If the equipment to be powered has unknown conditions that may impair operations, then a qualified person will be able to find the root cause.”
With light towers, be aware of your surroundings when setting up the masts. Watch for overhead power lines, James advises. Put the tower on level ground and use outriggers to increase its stability.
“Make sure no one is in the vicinity when you’re raising the tower mast,” Dahlgren says. “No one should stand in front of or in back of the tower when raising or lowering the mast.”
Since most light tower masts extend at least 30 feet in the air, wind can be a factor. Light towers can be rated for 60 mph gusts, but outriggers should always be extended when the mast is up. Lower the lights when you’re not using them and always be aware of the weather.
Get the right number of light towers for the job at hand and aim your lights properly. “Know how to operate the aiming features on any rental,” Dilling says. “Some can be more complicated than others especially since they need to be in the lowered position while you make adjustments.”
And don’t forget lights heat up while in use. Allow them to cool down before you put them in the transport position.
You might be used to asking for a 60-kilowatt generator for a certain application, so naturally you think you need the same thing on a similar job. With generators though, over sizing can be as much of a problem as under sizing, so renting the optimal generator becomes important. “Not only will you pay too much rental for an oversized generator,” Puck says, “the generator runs best at its rated output. Excessive underloading can cause maintenance problems and lead to poor performance.”
“We recommend running a generator on at least 50 percent load,” Leupi adds.
And save yourself some embarrassment before you call the rental company to complain about a non-working unit. Is the unit fueled? Is it wired correctly?
“In some instances people blame the generator when they had a cord wired wrong,” Gabrielse says.
“It’s not as complicated as it sounds,” says Brad Parker, operations manager for the Whitecourt, Alberta, Canada, Rental Service Corporation branch. “Some of determining what you should use is just basic math. As long as you answer some questions, we can figure it out.” These may include:
· With light towers, how much square footage needs to be lit and to what level?
· What tools do you plan to run off the generator and how many at the same time? Lights are simple, non-complex loads. Other tools, however, may require more power than the generator is rated to give.
· What are your starting loads? “We always ask our customers what they plan to run off the generator or light tower,” Parker says. “We need to figure how much start up draw they need. A pump may only run on 30 amps, but may have to draw up to three times that amount to start.”
· What is your starting sequence? If you have to fire up 15 motors all at once instead of one at a time, the load requirements will be quite different.
· Where will the unit be operated? You’ll always need to de-rate a unit for higher altitudes.
· Does your jobsite have any special requirements? If manning a generator on a remote site becomes a labor issue, check out the generators with programmable starts and stops. Many jobs have fluid containment requirements, calling for a generator with containment system. And if you’re working on U.S. Forestry Service land, any generator you use will need a spark arrestor.
Be aware of current technology, since your rental dealer may have it on hand. For example, elliptical light fixtures allow larger, more uniform coverage, says Leupi. “Most light towers have conical light fixtures,” he says, “which gives you a strong light concentration in one area; however, the light level drops off outside of that area. Elliptical lights are more even and don’t have the spotlight effect.”
“With Allmand’s parallel lamp fixture,” Dahlgren says, “half of the light produced goes directly through the lens and the other half is reflected. In a typical coaxial fixture, most of the light has to be reflected. The usable light from a coaxial fixture is considerably less.”
And be aware some new tools, such as electric jackhammers, will only work with newer inverter-type generators, Gabrielse comments. Although still rare in the rental environment, inverter generators are much quieter than standard generators, so they could be a consideration when noise is an issue.