February 14, 2020 - HVAC
At Harbour Centre at Aventura Office Complex in Miami, all of the air handlers were running flat out trying to keep up with the set points, says Miki Minic, chief engineer with Jones Lang LaSalle, which manages the Harbour Centre at Aventura office complex. After the static pressure drop across the coil was measured, the fouled evaporator coil was found to be responsible for the soaring cooling costs.
Minic's plan was to improve indoor air quality at the 12-story 227,000 square-foot Class A office complex, restore cooling capacity, and save enough energy in the process to pay for the upgrade in less than a year with the addition of ultraviolet-C (UV-C) lamps.
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, notes Minic. The existing AHUs were 16 years old and offered limited access to the evaporator coils.
Because of the tight access, the RLM Xtreme high-output 360 degree UV-C lamp system from UV Resources was used. The UV Resources RLM Xtreme 360 degree UV-C lamp system delivers high-output ultraviolet energy to irradiate coils and destroy mold, bacteria, and microbes in demanding, high-volume HVAC environments. The lamp system configures to fit into most any plenum.
The initial installation was limited to the worst performing air handler. In the end, a post-project audit documented a 43.7 percent increase in the test 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, indicators that cooling capacity was restored to near original design specifications. Moreover, the germicidal UV-C system improved coil heat transfer efficiency so much so that the same temperature could now be achieved using just 40 percent of the energy previously used.
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. 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 that the addition of UV-C lamps will save the Harbour Centre more than $70,000 in HVAC energy costs each year.
