Chula Vista Medical Center (Hospital)
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:
• Chilled Water (CHW) Variable Speed Pumps & Loop Differential Pressure (DP) Reset - The East Tower secondary pumping system pressure control is broken; differential pressure sensors provide no reading and both secondary pumps run at 100%. Fix differential pressure sensors, and program the system differential pressure setpoint to modulate pump speed and reset the CHW setpoint based on valve position of the air handlers.
• Replace Leaking Heating Hot Water (HHW) Valves at Air Handler/Rooftop Unit (AHU/RTU) - Multiple air handlers were observed to heat with 0% heating valve commands (notably AHU-8 and AHU-9). Test proper operation of CHW and HHW valves at by fully cycling valves; verify valves are fully closing/not leaking by observing excess in cooling or heating energy. Repair or replace leaking valves or actuators as needed and test operation using BAS control signal.
• Program Air Handler/Rooftop Unit (AHU/RTU) Economizer Lockouts - Some units were not economizing under conditions that would be expected to call the economizer. Some units have hysteresis economizer enable which will lead to simultaneous heating and cooling. Optimize control sequence where the economizer shall be enabled when outside air temperature is 1) lower than 50°F and 2) when outside air temperature is lower than the return/zone air temperature by 2°F. Economizer control should be disabled when outside air temperature is 1) higher than 70°F or 2) when the outside air temperature is greater than return/zone air temperature.
• Program Air Handler/Rooftop Unit (AHU/RTU) Economizer Staging - Multiple air handler units were not economizing under conditions that would be expected to call the economizer. Air handler units were also observed to have hysteresis economizer enable which will lead to simultaneous heating and cooling. Re-sequence supply air temperature control programming 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 - Supply air temperature setpoint has been overridden at all air handlers leading to excessive cooling and reheat. Program air handler unit supply air temperature resets to modulate the supply air temperature setpoint in order to maintain total (critical) 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 Boiler System Heating Hot Water (HHW) Reset - Boiler plant setpoint is constant; 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.
• Program Condenser Water (CDW) Reset - Condenser water temperature setpoint is constant at 78°F. 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. All connected chillers are capable of significant energy savings if condenser relief is programmed.
• Program Chilled Water (CHW) Setpoint Reset - East plant chilled water setpoint fixed at 45°F and Oceanview Tower chilled water setpoint fixed at 50°F; program reset of chiller supply temperature setpoint, (e.g. from 42 - 48°F) when outside air temperature varies from 70 - 90°F.
• Chilled Water (CHW) Variable Speed Pumps & Loop Differential Pressure (DP) Reset - In addition to programming CHW setpoint reset, program the system differential pressure setpoint to modulate pump speed and reset the CHW setpoint based on valve position of the air handlers.
• Replace Broken Air Handler Unit (AHU) Sensors - Multiple AHUs have clearly broken temperature sensors. Repair known failed sensors as part of ongoing maintenance and use analytics-based connected commissioning to identify other faulty equipment.