Improved Single Path
While conventional system designs can be used, they are not designed to produce the optimum humidity conditions needed in applications such as supermarkets and super-stores, as outdoor air is mixed with return air and then cooled and dehumidified. When forced to control humidity, their energy performance is usually poor, as they are typically run to cool all the air to a lower temperature to remove moisture. This supply air is then reheated, often using refrigeration waste heat reclaim, to avoid overcooling the store. Lower in-store humidity (about 40%) made possible by specialized air conditioning systems means lower refrigeration energy costs. Reduced humidity directly reduces this energy use by reducing frosting and thus enhances coil heat transfer. To better handle these issues, special equipment is often considered, including:
- Improved single path electric system,
- Dual path electric system (discussed in a separate segment) which combines a separate ventilation and return air path in a single unit.
The improved single path system:
- Offers reduced supply air volume, bypass, and high efficiency air handler motors that provide reduced air handler demand and energy charges throughout the year,
- Substantially increases dehumidification performance,
- Reduces or eliminates reheat requirements
- Has maintenance costs proportionately lower than conventional systems due to the equipment capacity reduction,
- Achieves both low first cost and simplicity,
The dehumidification characteristics may not match modern supermarket loads exactly.
Single path systems can be used in both retrofit and new installations, separately or integrated with additional HVAC or refrigeration equipment. They are currently available in factory packaged units for indoor and outdoor installation.
- Their excellent operating performance and design simplicity make them a natural choice for supermarket designers and operators looking for a proven and reliable technology with no special maintenance requirements,
- HVAC applications requiring good control of outdoor air quantity and humidity control of supply air,
- They are a good choice for replacing conventional rooftop units being retired.
- Schools, stores, restaurants, commercial office and other buildings where humidity is a concern and old CFC-using or inefficient equipment must be replaced.
- Process or industrial applications requiring good humidity control of supply air.
Technology types (resource)
The features that distinguish improved single path systems from conventional systems include:
A recent EPRI study examined installed costs and energy costs for a variety of supermarket HVAC systems. An improved single path system typically reduced the HVAC installed cost by up to 23% over a conventional single path system. The single path systems typically will reduce the annual operating cost between 9% and 13%. The reductions will depend on the location and the design parameters.
Contact us to receive a copy of an EPRI report on Improved Single-Path HVAC Systems or for more information.