Energy Saving Store Tip #1: Send Your HVAC Unit on Summer Vacation
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By Dan Parsley, EES Consulting
If scorching energy bills threaten to disrupt your relaxing summer, consider giving your HVAC unit a vacation with an RTU (roof top unit) retrofit. Unlike replacing an older unit – which comes with the sticker shock of a 15- to 20-year payback – RTU retrofits can slash 40 to 70 percent of annual HVAC energy costs and averages a one- to three-year return on investment.
This dynamic retrofit solution is designed to work with single-zone HVAC package and split units, an air-conditioning unit that has one control point (or thermostat) per unit. These single-zone units condition 60+ percent of all U.S. commercial spaces and are extremely common in furniture showrooms and manufacturing facilities. They are relatively inexpensive and simple, but they are wasting vast amounts of energy while providing marginal comfort.
It is common practice in the HVAC industry to oversize the cooling capacity of these units, often by a very large margin, to meet the comfort requirements during rare extreme weather events. By oversizing the cooling capacity of an HVAC unit, the indoor fan is proportionally oversized, which results in inefficient conditioning of the space. If lighting and demand ventilation retrofits have already been implemented, then the actual cooling load has been reduced even further, making these units even more oversized.
Using a customized set of hardware, controls, and logic, RTU retrofits dynamically scale the electrical and mechanical capacity of oversized HVAC units to increase user comfort and reduce electrical consumption. A variable frequency drive is used to continuously control the indoor fan speed to match the variable cooling and heating loads of the conditioned space, while also removing humidity from the air.
While attempts have been made to use VFDs on single zone units, this new type of solution is the first retrofit to constantly monitor the refrigeration-side and air-side of the system to “right-size” the unit for the exact indoor and outdoor conditions. This technology can be applied to any single-zone HVAC unit of at least six tons, regardless of brand; however, the larger the unit, the greater the savings and payback.
There are a number of secondary benefits as well. By reducing wear on the system’s components, RTU retrofits save on maintenance and repair costs while extending the life of your unit. The retrofit also comes equipped with a real-time diagnostic reporting tool, enabling an onsite HVAC technician to instantly see dozens of real-time, read-only control points that would normally take several hours to manually gather, allowing the technician to quickly diagnose and repair the unit.
Unlike most HVAC retrofits, RTU retrofits do not save energy at the expense of comfort. If you’re thinking about sweating it out or replacing an older HVAC unit, you may want to think twice.
Dan Parsley is President and COO of Energy Efficiency & Sustainability (EES) Consulting, a Houston-based firm with locations across the U.S. that creates customized and comprehensive solutions to fit each commercial building’s unique energy needs.
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