“All of our air handlers were running flat out, trying to keep up with our set points,” said Minic, chief engineer with Jones Lang LaSalle, which manages the Harbour Centre at Aventura office complex. “Once we measured the static pressure drop across the coil, we knew that the fouled evaporator coil was responsible for our soaring cooling costs and that we could restore HVAC efficiency with the addition of ultraviolet-C (UV-C) lamps.”

In the end, a post-project audit documented a 43.7 percent increase in one air handler’s airflow levels following the UV-C installation, which also reduced energy use enough to pay for the upgrade in just five months — an impressive return on investment. The audit showed not only an increase in airflow, but also a 48.3 percent reduction in pressure drop, indicators that cooling capacity was restored to near original design specifications.

A fact that is sometimes missed, said Minic, is that when you restore cooling capacity by 43 percent, tenants will enjoy comfort 43 percent faster. In other words, the fouled coil was taking 43 percent more time to deliver the same air temperature before the UV-C retrofit than after. Moreover, the germicidal UV-C energy improved coil heat transfer efficiency — so much so that the same temperature could now be achieved using just 40 percent of the previous energy used.

THE USE OF UV LIGHTING

The UV-C wavelength has been used extensively since the 1990s to improve IAQ and, later, to improve heat exchange efficiency, boost airflow, and reduce maintenance. The germicidal wavelength eliminates microbial and organic materials buildup on HVAC cooling coils, air filters, duct surfaces, and in drain pans.

However, it is the technology’s ability to potentially slash between 10 and 25 percent of HVAC energy use that drives nine of every 10 UV-C installations, said Bruce Fontaine, then-vice president at Sustainable Management Solutions, a national energy efficiency consultancy specializing in commercial HVAC, electrical, and water use reductions, based in Pompano Beach, Florida. Fontaine’s team worked with Minic to size and specify the sustainable UV-C solution.

According to the U.S. Department of Energy (DOE), Minic is not alone in targeting HVACR as a potential source of savings, as this equipment accounts for between 30 to 50 percent of a building’s total energy use — a figure that may be even more pronounced in humid southern climates such as Florida.

“There are many benefits of UV-C,” said Minic, who was enthusiastic about the UV-C energy install. “Most important is the improvement to air quality, so tenants enjoy cleaner, healthier air. Absenteeism due to the airborne spread of unsafe microorganisms via HVAC systems is almost eliminated. Moreover, equipment life is improved, and downtime and preventive maintenance expenses like cleaning the coils, drain pans, and the purchase of coil and drain treatments, etc., are significantly reduced.”

THE HARBOUR CENTRE INSTALLATION

With one 60-ton dual-cell BAC® cooling tower, two McQuay® centrifugal chillers, and 12 AHUs (one per floor), the UV installation at the Harbour Centre presented some challenges, said Minic.

“The existing AHUs were 16 years old and offered limited access to the evaporator coils,” said Fontaine, regarding the retrofit project that began in June 2017. “Because of the tight access, we recommended the RLM Xtreme™ high-output 360 degree UV-C lamp system from UV Resources.”

The product selection was initially limited to the worst performing air handler (No. 7).

“The overall transformation in efficiency was incredible,” said Fontaine, who estimated that the project energy savings yielded a five-month ROI. “Airflow levels increased by 43.7 percent in one air handler, or roughly 6,000 cfm — nearly doubling cfm capacity. What’s even more impressive is that we drastically increased air flow levels and saw a 48 percent improvement in pressure drop across the coil, or the delta(r) P. Normally when you raise air flow, pressure drop across the coil increases. The decrease demonstrates how fouled the coil was in AHU 7.”

ROI EXCEEDED EXPECTATIONS

As with any major capital project, return on investment was a critical metric for Jones Lang LaSalle Management to share with the building’s ownership. To evaluate the success of the installation, Fontaine conducted a pre- and post-retrofit performance test.

Based on each of the 12 AHUs running 8,000 hours annually and a utility rate of $0.12 per kWh from Florida Power & Light, Minic estimated that the addition of UV-C lamps will save the Harbour Centre more than $70,000 in HVAC energy costs each year.

“The biggest surprise in the data was the significant pressure drop across the coil,” explained Fontaine. “In other words, if we did not add UV lighting and we had a 1-inch pressure drop loss at 15,000 cfm, and then increased the air flow to 20,000 cfm in an attempt to meet the building demand, the resulting pressure drop would increase to 2.25 inches. This added pressure would require a significant increase in energy consumption in order to achieve the desired temperature.”

The test AHU retrofit was such a success that UV-C lamps were retrofit on each of the Harbour Centre’s air handlers in May 2018. Minic and Jones Lang LaSalle are evaluating similar retrofits for three other office buildings it manages in Miami and Ft. Lauderdale.

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