Lunds & Byerlys HVAC Design

Challenge

The Lunds & Byerlys supermarket chain needed a modern HVAC system to optimize indoor air quality, customer comfort, and energy efficiency at their state-of-the-art store in White Bear Lake, Minnesota. The facility included a variety of zones with different cooling and heating needs, such as produce, bakery, deli, seating, and checkout areas, as well as restaurant space, loading dock, and office management spaces. Each area presented its own challenges and required specific systems designed to meet the store’s critical needs.

Solution

Lunds & Byerlys selected SEH to design a new HVAC system that consisted of multiple components: a dual path air handling unit (AHU) with humidity control, perimeter variable speed rooftop air handling units, destratification fan system, and variable refrigerant flow (VRF) system. The SEH mechanical team designed each specific system to meet the following objectives:

• Provide adequate ventilation and humidity control for the store
• Provide zone-level temperature control for the different spaces
• Reduce energy consumption and operating costs
• Improve reliability and durability of the system
• Optimize customer comfort

The dual-path AHU was installed on the store's roof, with two separate air streams: a fresh air stream and a return air stream. The fresh air stream was filtered, cooled, dehumidified, and reheated before being supplied to the store. The return air stream was filtered, cooled, and mixed with the fresh air stream before being supplied to the store. The AHU incorporated a variable-speed fan that modulated the airflow according to the facility's ventilation demand, equipped with humidity sensors that controlled the dehumidification and reheat process, maintaining the relative humidity of the supply air at 50%.

The perimeter rooftop units included variable-speed capability that helped to further control humidity in the store. Control sequences allowed the units to conserve energy by modulating to meet the store's heating and cooling demands. Rooftop units were designed with variable-speed compressors that allowed precise cooling control during the summer months with multi-stage heating sections that maintained heating setpoints while conserving energy during the winter season. 

The VRF system consisted of an outdoor unit and multiple indoor units; the outdoor unit included a variable-speed compressor that modulated the refrigerant flow according to the cooling and heating demand of the store. The outdoor unit also had a heat recovery module that allowed simultaneous cooling and heating of different zones. Indoor units were installed in the ceiling of the office wing and had variable-speed fans that modulated the airflow according to the temperature demand of the zones. Controls were installed, incorporating sensors that controlled the setpoint temperature of the zones, ranging from 68°F to 74°F depending on the zone type. Destratification fans were also installed throughout the facility to conserve energy while increasing occupant comfort.