Greenhouse Canada

Are you spending more on your LED lighting than you need to?

Inrush current, wattage, power factor and harmonics of your LED fixture could significantly change your project costs.

August 19, 2022  By Joli A. Hohenstein

Canadian Valley Growers All photos courtesy of Signify

As more growers around the world implement LED lighting in their greenhouses, project managers and light strategists are encouraging them to gather all the facts about a fixture before making an impulsive decision that could cost them more in the long run. Often, an electrical contractor details and designs a lighting project based around a specific fixture, but after the project design is completed, a grower chooses to purchase a different or less expensive fixture for the contractor to install. 

“Growers may end up paying more in total project costs because the specifications of the product purchased for the installation deviated from the product for which the project was designed. Perhaps they saw the lower price of a fixture and ran with it,” says Mark Pedersen, President/CEO, Climatrol Solutions Ltd., Surrey, British Columbia. “We want everything to run seamlessly, and it is very important with a lighting fixture that we have the complete information, just like any other component purchased for their facility. We need to be sure it is going to work for their greenhouse and not cause an issue to their electrical or hydro-electrical system.”

The first step is to ensure your electrical contractor has a detailed product specification sheet for each fixture, along with a complete application or installation guide, so that project engineers can properly design the system. Specification sheets should include: operating voltage range, full load current at common operating voltages, rated input power, power factor, total harmonic distortion, operating frequency, and inrush current on startup. Often, growers assume that engineers can assess wattage and other key factors simply based on name or by sight, which is not the case.


Knowing these details when the project is originally scoped ensures engineers specify and select the proper cables, panels, high-voltage sub feeds and transformers, among other components. Without exact specifications, small deviations from the initial plan can add up to huge expenses as electric panels may need to be reconfigured because of deviations. 

One technical detail which, if not known or identified accurately, can result in problems with the installation or operation, is inrush current. 

“Just the difference between 800 or 805 watts affects everything, and the more fixtures you have in your installation, the more it affects the design – how many circuits, how far away the fixture is from the panel,” says Pedersen.  

While a difference of five watts may not seem like much, when you are installing 5,000 or 10,000 fixtures, this creates a significant deviation and introduces complications in a system. “This is why it is very important to have all of the electrical specifications reviewed ahead of time by an electrical engineer, or the electrical contractor completing the work,” says Evann Seney, Master Electrician, Honey Electric, Chatham, Ontario. 

Put simply, the inrush current value informs the electrician about the instantaneous power demand from a light. Inrush current level has implications at the time of startup, in the event of power failure, and on the number of fixtures that can be switched on at the same time.

A fixture that has a very high inrush current can cause extensive issues in a lighting system, particularly if the circuits, cables, and transformers weren’t built to handle the load. A greenhouse system could have 100 to 200 lighting panels, all would have to be adapted – at significant expense – if the actual inrush current exceeds the provided specifications.

Certain LED fixture drivers will actively manage the fixture inrush current at startup. “All of our products are designed with our own drivers,” says Chris Strom, Application Engineer for Signify, manufacturer of Phillips LED products. “One of the things designed into the drivers was a low inrush current. Many off-the-shelf drivers have a high inrush current, and that impacts the load on the lighting system.”

It is important to consider the effect that the inrush profile will have on system protection (such as circuit breakers and fuses). A circuit breaker sized properly for a fixture with a negligible or nominal load will trip the breaker at startup if fixtures with higher inrush current are installed.

The wrong inrush current between fixture and panel also means that each time power flickers throughout the electrical grid, the controls shut off those individual panels. That in turn, blows fuses. When the fixtures all come back at once, more issues occur.

“With our fixtures for example, we install a timer in every panel,” Seney says. “If the controls are shut off in the event of a power flicker, when the power comes back on, a timer in each panel is set to turn on one panel at a time.”

Fixture Wattage
Wattage is a critical factor in LED lighting strategy design, and one that is taken only at surface value can quickly compound costs in a greenhouse. More specifically, experts say it’s important to pinpoint the optimal voltage operating range for your operation. “The specifications are going to show exactly what voltage range that fixture is good for,” Seney says. “You’re going to look for the full load current at each voltage.” 

It’s a calculation that engineers and greenhouse electricians can make specifically and accurately, given they have the proper numbers and specs up front. 

“Power or watts divided by voltage gives you current, or amps,” Seney explains. “However, you must also know the power factor of the fixtures to complete the calculation.” He adds, “Without proper specs, even a slight deviation in final numbers may require an installation redesign.”

In the same way, missing or incorrect information and specifications on fixtures could also lead to additional expenses. For example, an installation will be designed for a lighting fixture drawing 848 watts and the corresponding number of transformers. Strom commented: “Should a grower choose a cheaper fixture that draws higher wattage, say in this case, 855 watts, then additional transformers will be required, which will increase the cost of the project.” 

The cost to accommodate the need for an additional transformer is multiplied by related costs including cables, concrete pads, and electric panels. “The installation costs more. It is a heavier cable. It adds more weight, and requires more supports in the structure to carry the weight of the load on the superstructure,” Seney says.

This is where the delicate balance of voltage, fixture placement and system design come to the forefront. “The efficiency and the wattage of the fixture, makes a big difference; whether you can put five or six lights on a circuit all depends on loading,” Seney explains. While you could technically load a circuit up to 80 per cent, it is not recommended because of the potential for additional unknown loading. 

“We typically load less than the allowable Canadian standard, so there is flexibility,” Pedersen says. Factors to consider include the number of fixtures you can put on a circuit, the number of required circuits, the number and size of electrical panels, the distance from the main service and transformers to the distribution panels, and whether cables can be installed overhead or underground.

If the electrician is given the correct information, the circuit and accessories can be sized correctly so that the right voltage drop can be calculated and properly accounted.  

“Voltage drop and fixture efficiency are factors that determine the final cable size. How this plays out in the project design is that the fixtures at the walkway are typically closer to the panels. Whereas the fixtures at the gables are further away and require larger cables, which are more expensive,” Pedersen says.

Walters Gardens

Power factor
Hand in hand with voltage comes the power factor – which represents how clean the power is. Experts know a certain amount of so-called “dirty power” comes in from any power grid. The most efficient and effective systems account for that dirty power up front, using voltage regulators and other tools.

The best fixtures account for 10 per cent coming in from the grid. For example, if a lighting system is supposed to be running on 277 volts, and the power that comes in from the grid is just over 250 volts, the system will still run and function well.

“A power factor of 1.0 is perfect, and pretty much not achievable; 0.95 is still great. The closer the fixture is to a power factor of 1.0, the more efficient it is,” says Seney. 

In British Columbia, where Pedersen operates, for grid connection they are mandated to BC Hydro, the power utility. “We’ve had it at multiple locations where the spec for the main service is 600 volt, three-phase, and from phase to neutral is 347, so it’s a 600/347-volt service; however, the main power coming in is 590 or 580 volts,” he says. “BC Hydro won’t even talk to us until it’s less 10 per cent, so at that point we put in a transformer that’s tappable, or we use a fixture that can handle a little bit less power – plus or minus 10 per cent on the input power to the fixture.”

Total Harmonic Distortion
But a little-known and understood factor could potentially have the most impact, experts say. “It all comes down to the efficiency of the fixture, but also the main one for me, in our experience, is the harmonics,” says Pedersen. Total harmonic distortion (THD) indicates how much harmonic current is flowing in the power lines. Harmonics are unwanted currents at multiples of the fundamental line frequency. If there are huge spikes in harmonics from a fixture, this can result in damage to your upstream equipment, for example, high voltage transformers, lighting contactors, etc.

“If you have what we call dirty power, you have third and fifth and seventh harmonics, they are adding extra stress load onto the electrical installation, and that’s something that you have to account for. There have been a lot of people caught off guard by them,” says Pedersen. “That’s an extra load on the system, and if you’ve already loaded it to 80 per cent, and then you add a little bit more of a THD or extra resistance, your circuits overheat, and then the system fails.” 

Complicating this is that often, the harmonics are not detectable with an ammeter, which is used to measure the current in a circuit. “You get a lot of extra neutral currents, and a lot of extra current on the system itself, and it measures fine,” Pedersen says. “We put a power meter on the circuit, and that’s where we see true loading of the electrical installation. The circuits are designed to open up a certain amount of power, and if you add more load to it, the circuits can’t handle it, and this is why circuit breakers are tripping, fuses are prematurely blowing, and contactors are failing. The harmonics of a fixture is a critical factor for these reasons. 

In these situations, where high THD isn’t accounted for in the initial system design, it can be problematic. “I’ve seen THD cause all kinds of issues where electrical contractors have had to break up circuits and add additional circuits, and that affects the cost,” says Strom.

The experts emphasize that it’s critical for lighting suppliers to share complete and accurate product specifications especially on these key technical factors. For growers, their advice is to make sure contractors are aware of all of these factors, or if the project is in-house that their project team is planning around them. Rather than choosing fixtures purely based on price, they should evaluate these key factors to ensure they don’t have to retrofit or completely redo the electrical as a result of not planning for the right wattage, power factor or THD.

Otherwise, the project is at risk for serious scope creep. 

“It can literally cause a domino effect,” says Pedersen, “putting us in a situation where we must go back and reconfigure the design and installation. Not surprisingly, the costs add up fast, and any anticipated savings of choosing a less expensive fixture are quickly lost.” 

Joli A. Hohenstein is marketing specialist for Pen & Petal Inc.

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