“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.”

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. The audit showed not only an increase in airflow, but also a 48.3 percent reduction in pressure drop.

“The germicidal UV-C energy improved HVAC heat transfer efficiency so much so that the same temperature could now be achieved using just 40 percent of the previous energy used,” said Minic.

According to Minic, when cooling capacity is restored 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 UV-C wavelength has been used extensively since the 1990s. The germicidal wavelength helps to eliminate microbial and organic materials buildup on HVAC equipment; however, the technology’s ability to potentially slash 10-25 percent of HVAC energy use drives most installations, said Bruce Fontaine, vice president at Sustainable Management Solutions in Pompano Beach, Florida. Fontaine’s team worked with Minic to specify the UV-C solution.

 “There are many benefits of UV-C,” said Minic. “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.”

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.

“The existing AHUs were 16 years old and offered limited access to the evaporator coils,” said Fontaine. “Because of the tight access, we recommended the RLM Xtreme^™ high-output, 360-degree UV-C lamp system from UV Resources. This modern UV-C system installs quickly and offers flexible configurations such as those required at Harbour Centre.”

Minic had experience with the RLM Xtreme system and supported the product selection, which was initially limited to air handler No. 7, the worst performing air handler.

“The overall transformation in efficiency was incredible,” said Fontaine, who estimates 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 its capacity. What’s even more impressive is that we drastically increased airflow levels and saw a 48 percent improvement in pressure drop across the coil, or the delta P. Normally, when you raise airflow, pressure drop across the coil increases. The decrease demonstrates how fouled the coil was in AHU No. 7.”

Minic estimates that the addition of UV-C lamps will save the Harbour Centre more than $70,000 in HVAC energy costs each year. 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 Company, Minic estimates the Harbour Centre will save more than $70,000 in HVAC energy costs annually.

“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 airflow to 20,000 cfm in an attempt to meet the building demand, the resulting pressure drop would increase to 2.25-inch. 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 retrofitted on each of the Harbour Centre’s air handlers in May 2018. As for Minic and Jones Lang LaSalle, they are evaluating similar retrofits for three other office buildings it manages in Miami and Ft. Lauderdale, Florida.