HVAC System Detail

The HVAC System:
In a geothermal system water circulates in a closed loop system to absorb or reject heat between the office buildings via the Mitsubishi water source HVAC equipment and the Earth, providing geothermal cooling and heating at remarkably high efficiencies.  The Mitsubishi Water Source Systems consist of high efficient PQRY WR2 heat recovery systems.  These Mitsubishi heat recovery systems with highly efficient inverter driven compressors will first provide heat recovery on the refrigeration side, with the ability to simultaneously cool and heat different spaces on the same system.  Secondarily the Mitsubishi system will provide heat recovery between the water source modules that are commonly connected to the buildings geothermal closed water loop system.  The PQRY heat recovery water source units are all mounted within the building, allowing for a solar array system to be mounted on the roofs of the buildings for further energy savings.

In many cases the efficiency of these systems will exceed that of standard air-source VRF systems for the above reasons.  In addition, ground source VRF will often exceed the efficiency of traditional geothermal WSHP systems due to the aforementioned ability to recover energy more efficiently on the refrigeration side first compared to multiple distributed traditional geothermal WSHPs.

For even greater energy efficiency on the geothermal loop, each Mitsubishi water source module is equipped with a pressure independent Belimo valve (PIV).  The Belimo valve allows the water source units to vary the water flow rate through each module individually as the load is reduced on each module.  Utilizing this feature can allow for significant central station pumping savings, specifically on large buildings with several Mitsubishi water source modules located throughout the building, all served by the geothermal water loop system with central station pumps.  Each PIV is custom programmed for the Mitsubishi waters source modules, mapped to the voltage output and corresponding expected flow at each voltage output signal level.  The PIV will continuously modulate and maintain flow target by constant feedback of a built in ultrasonic flow meter to ensure efficient and stable operation at all load conditions of the water source module.  The PIV valve will also provide flow proving functionality and interface with flow proving contacts on the Mitsubishi water source module board preventing damage during operation if flow rates fall below the minimum allowed values; thus improving overall life and longevity of the water source product. Since this valve has constant pressure independent feedback of flow at all load conditions all manual hydronic balancing labor is eliminated.

Ventilation System:
The ventilation system providing outside air to the building will also be high efficient. The dedicated outside air systems (DOAS) will consist of Swegon Gold highly efficient energy recovery units and the coils in the Swegon Gold units will be paired to Mitsubishi LEV kits.  The LEV kits will be paired with Mitsubishi water source units to take advantage of inverter driven compressors for greater energy savings on the outside air system.  The Swegon Gold units also helped to reduce the foot print of the DOAS systems in the mechanical penthouse.