Chula Vista Medical Center (MOB)
Total Annual Savings:
Connected commissioning optimizes building performance, reduces operating and maintenance costs and extends equipment lifetimes. As a result of the energy audit, high priority lighting, automation/controls and heating, ventilation and air conditioning (HVAC)-related ECMs are recommended for implementation through a packaged connected commissioning project delivery. In most cases, the building automation system will be used to collect and analyze on-going performance data, identify new trends and ensure persistent savings from previously-implemented ECMs.
Perform connected commissioning with a focus on optimizing automated control sequences through programming and control device upgrades to achieve the following energy conservation measure outcomes. The connected commissioning process includes follow up investigation, controls upgrade specifications and sequences, coordination with installing contractor(s), and optimized control sequences validations. Control specifications and optimized sequences of operation will also be provided for all budgeted HVAC unit replacements.
The following measures were identified as specific opportunities to be completed as part of a connected commissioning process. These opportunities may be implemented independently or as part of a coordinated effort:
• Equipment Schedules for Air Handler Unit (AHU), Rooftop Units (RTUs), and Boiler - Reduce equipment scheduled run times. Standardize schedule by space type where possible, e.g. 5am-7am for medical offices. Schedule start time may vary based on equipment type, e.g. chiller and boilers vs AHUs. Implement optimal start where possible to enable schedules to be fully optimized to actual occupancy hours. Add after hours buttons to allow temporary override of schedule when space is needed.
• Heating & Cooling Setbacks - Establish and program standard unoccupied schedule heating and cooling zone setback setpoints , e.g. 60°F heating and 80°F cooling; ensure zones and equipment that do not need to operate with a setback are simply off when unoccupied.
• Program Air Handler/Rooftop Unit (AHU/RTU) Economizer Staging - Re-sequence supply air temperature control programming of direct expansion (DX) units so economizer dampers always open fully as the first stage of cooling prior to the chilled water (CHW) valve modulating open. This allows temperature control to take maximum advantage of outside air conditions prior to using chilled water for cooling.
• Program Air Handler/Rooftop Unit (AHU/RTU) Supply Air Temperature Reset - Program air handler unit supply air temperature resets to modulate the supply air temperature setpoint (e.g. if supply air temperature setpoint is fixed at 55°F, reset between 55-63°F) in order to maintain total zone temperature cooling error at an adjustable setpoint. Use zone feedback to reset supply air temperature for both VAV zone and single zone units.
• Program Air Handler/Rooftop Unit (AHU/RTU) Static Pressure Reset - Static pressure setpoint resets are not configured for variable volume AHU systems. Program AHU supply air static pressure reset to modulate the supply air static pressure setpoint in order to maintain the maximum (critical) zone supply air damper position at an adjustable setpoint. For example, if static pressure setpoint is fixed at 1.5" water column (W.C.), reset between 0.2 - 1.75” W.C. based on VAV zone voting as referenced in ASHRAE Guideline 36.
• Boiler Lockout – Program boiler lock out control when outside air temperature is above 80°F. Program the boiler to be disabled at this temperature with wide hysteresis (10°F typ.) to prevent constant on/off cycling.
• Program Boiler System Heating Hot Water (HHW) Reset - Program outside air temperature reset of boiler supply temperature setpoint. For conventional boilers or boilers with 3-way valves, use 180-140°F when outside air temperature varies from 20-70°F. For condensing boilers, use 180-80°F when outside air temperature varies from 20-70°F. Alternatively, use voting or hot water value (HWV) rollup based trim and respond based resets.
• Heating Hot Water (HHW) Variable Speed Pumps & Loop Differential Pressure (DP) Reset - Install variable frequency drives (VFDs) & differential pressure sensors; program HHW loop differential pressure reset by modulating pump speed based on outside air temperature or difference in temperature between supply and return loop water (delta T) to reduce pumping demand.
• Building Exhaust Fan Schedules or Interlocks - Schedule or interlock exhaust fans that do not need to operate 24/7 with the AHU/RTU which serves as makeup air for the exhaust fans, ensuring the building does not achieve negative pressure when the AHU/RTUs are off.
• Program Condenser Water (CDW) Reset - Program fans to modulate fan speed in order to maintain cooling tower leaving chilled water (CW) temperature setpoint and reset CDW temperature setpoint between 60 - 75°F. For example, if cooling tower fan speed is above 90%, increase CDW setpoint. If cooling tower fan speed is below 60%, reduce CDW setpoint.
• Program Dual Maximum Variable Air Volume (VAV) Control - Program dual maximum VAV control for VAV boxes with a single minimum CFM setpoint. Where minimum air flow setpoint requirements for heating are greater than the requirement for ventilation, minimum air flow setpoints can be reduced.
• Demand Response Sequence - Program sequences to allow non-critical loads such as common area lighting, fountains, displays, etc. to remain OFF during peak hours. Use any available load-shifting technology to delay energy use until after the peak period.
• Replace Broken Air Handler Unit Economizers - Replace damper actuators or other components needed to ensure reliable damper operation. Broken economizers should be confirmed by physically testing the automatic damper operation. Test and balance the unit to ensure minimum ventilation airflow levels and configure economizer programming per the lockout and staging control sequences above.
• Seal Air Duct Leaks - AHU-1 has a significant leak of conditioned air from the access door directly downstream of the cooling coil. The door has been bolted shut but continues to leak and is no longer easily accessible for maintenance. Replace door to seal air leaks.