Seasonal Equipment Operational Considerations Joe Leichner, Daikin Applied Strategic Sales Project Developer September 9, 2014
Agenda • “Seasonal” – Means not full load heating or cooling! • Controls settings to save energy and optimize comfort • Designing/selecting new systems for replaced equipment
Seasonal = 99.9% of the Year Historical data and choosing weather criteria for a hospital: If there is a “worst-case scenario”, your hospital will see it. Seems to not account for north winds through north-facing outside air dampers! Does not account for 100 and -10 degree F. days. When designing a new building, help guide your design team. Systems and equipment degrade in performance and capacity. Bigger equipment will help handle “peak” loads, but affect efficiency at part-load. Diversity is tough to estimate, but it very important to equipment selection and operation.
Seasonal Weather and Internal Loads • Not only is the weather dynamic, your internal loads are dynamic as well. • Surgery suite loading • Emergency room usage • Patient flow and overnights • Conference rooms/meetings • Others
Seasonal Weather and Internal Loads • The use of your building affects your support systems: • Food service • Laundry • Housekeeping • Many others
Seasonal Weather, Internal Loads, and Comfort • Human comfort is both physical and mental. Physical aspects are: • Airflow • RH% • Air Temperature • Odor • CO2 • and more! • HOW DO YOU KEEP EVERY OCCUPANT AND PATIENT COMFORTABLE?
Seasonal Control Settings Controls settings for patient comfort Controls settings for medical staff comfort Controls settings for safety
Seasonal Control Settings • Controls settings for patient comfort • Patient satisfaction surveys and reimbursements • Healing rate improvement if person is comfortable? • Controls settings for medical staff comfort • Physician and nursing staff retention • Job satisfaction improved if environment of care is comfortable • Productivity enhanced if conditions are maintained
Seasonal Control Settings for Safety • Air pressurization maintenance for critical environments • Airflow for biological safety cabinets, fume hoods • Airflow for surgery suites and burn treatment areas (and others) • Food storage and food preparation areas • IT IS NOT JUST ABOUT THE TEMPERATURE; FLOWS AND PRESSURES MATTER AS WELL.
Seasonal Control Settings for Occupant Safety First Priority – Airflow and pressure maintenance In ante rooms, isolation rooms, and other specialized areas, the difference in room pressures must be maintained. How many of you fight with negative air pressure in the building especially in the winter? Load and ventilation analysis – Not expensive, but very worthwhile for comfort and energy.
Load and Ventilation Analysis • Optimizes recirculation requirements based upon space type determination • Defines exact minimum outside air requirement by zone • Defines inflow and exhaust flow for each zone • Identifies lighting, people, computer, medical equipment loads (by room or zone) • Measures current AHU peak airflow and pressure delivery
Load and Ventilation Analysis • Measures current outside air intake quantity, zone temps and settings • Identifies needs for fan/coil cleaning, damper repairs, etc. • Provides information for optimizing comfort in the occupied spaces through air/water bal. • Creates awareness of concern by your staff for patient outcomes, staff satisfaction, etc. • Can assure of proper AHU ventilation control throughout facilities
Seasonal Control Settings for Occupant Comfort Second Priority – Occupant Comfort
Seasonal Control Settings for Occupant Comfort Second Priority – Occupant Comfort
Seasonal Control Settings for Occupant Comfort • Many other considerations for occupant comfort: • Physical health of the individual • Use of clothing (sweaters, thin shirts, etc.) • Density and length of hair (traps heat from head) • Air velocity across the skin • Noise of the air and within the rooms • Lighting (% of natural lighting, color of lighting, etc.) • Wall and room aesthetics (white, shiny painted walls vs. calm colors and artwork, etc.) • Sensitivity to temperature swings (heating dead-band and cooling dead-band)
Seasonal Control Settings for Occupant Comfort • Second Priority – Occupant Comfort • Energy Policy – Temperature settings by functional space • Given all of this information, where should you set the room temperature? • 74 Degrees is the mid-point between heating and cooling. Expensive. • 76 for Cooling is most common; 78 may be too high (Dehumidification <50%) • 72 for Heating is most common; 68 may be too low (Humidity at 30%/35%)
Ventilation Quantities • Set outside air quantities as required to meet minimum volumes (periodically check the damper positions to ensure these are set in the proper position during occupancy and un-occupied conditions) • Maintain annual certifications for FHs/BSCs and space pressurization controls • Test and adjust kitchen, laundry, and other exhaust systems periodically as renovations happen (adjust sheaves as needed) – Turn on only when needed • Maintain and calibrate building static pressure controls and relief systems
Ventilation Quantities • Check economizer sequences of operation for AHUs that vary outside air quantity • Check and calibrate CO2 sensors/transmitters/controllers (Ambient air 350 ppm CO2 – adjust to control less than 800 ppm appx. – above this, people can sense the air is “stuffy” and can begin to feel tired.) (If set lower than 800 ppm, energy cost increases significantly.)
Ventilation Quantities • Normal CO2 Levels* • The effects of increased CO2 levels on adults at good health can be summarized: • normal outdoor level: 350 - 450 ppm • acceptable levels: < 600 ppm • complaints of stiffness and odors: 600 - 1000 ppm • ASHRAE and OSHA standards: 1000 ppm • general drowsiness: 1000 - 2500 ppm • adverse health effects expected: 2500 - 5000 ppm • maximum allowed concentration within a 8 hour working period: 5000 ppm • * Source: EngineeringToolbox.com
Seasonal Control Settings for AHUs • Mixed air temperature and economizer control – 55 degrees +/- with reset from OAT (Minimize chilled water cooling as much as possible.) • Supply air temperature • Low temp systems – 40 degrees (maintains fan efficiency) • Normal systems – 55 degrees (VAV systems reset from zone average to limit) • Minimize fan energy as much as possible
Seasonal Control Settings for AHUs Supply air pressure – Duct static to maintain +/- 0.5” at furthest outlet (dumping and throw/noise concerns can happen if static too low or too high) (minimize fan motor energy) Hot deck temperature – reset 180 to 120 from OAT 0 to 60 degrees (minimize hot water pump energy) Cold deck temperature – maintain at 52 to 55 degrees depending upon fan size (heat from fan motor) and duct heat absorption (long runs of duct) (minimize chilled water pump energy) Building pressure (Return air fan or relief air damper) – +0.1” normal (can vary by zone)
Seasonal Control Settings for Heating Plants Deaerator pressure – 3 to 5 psig (for aeration efficiency and feed water heating) Boiler feedwater pressure – 10 psig over generation pressure (reduce pump energy) Steam pressure – minimum pressure for loads served – distribution pressure losses (Autoclaves, sterilizers, linen presses, cooking, humidification, etc.) (Can reset pressure setting on a schedule when high pressure loads are not in operation – do not set too low as condensate volume increases drastically on large campus systems)
Seasonal Control Settings for Heating Plants Hot water supply temperature – 180 reset to 120 from outside air at 0 to 60 degrees Re-heat loop supply temperature – 140 reset to 120 from outside air at 0 to 60 degrees Perimeter heating system supply temp – 180 to 120 reset. Cycle off pump at OAT>60. Hot water pumping system pressure – minimum to maintain sufficient circulation and not below 25% flow (surging and cavitation)
Seasonal Control Settings for CHW Plants Constant flow pumping system – reset chilled water supply temperature to highest temp to satisfy all zones (one valve at 100% open) Variable flow pumping system – maintain 42/43 degree chilled water supply temp to minimize pumping energy – may reset chilled water supply temp up if chiller efficiency gain is more efficient than pumping energy spent by pumping more flow.
Seasonal Control Settings for CHW Plants Chilled water supply temperature – maintain 42 to 45 degrees for variable water pumping systems or chillers with VFDs. For constant pumping systems and chillers without VFDs, reset the chilled water supply temperature as high as possible while maintaining space temperature and relative humidity.
Seasonal Control Settings for CHW Plants Condenser water supply temperature – maintain lowest inlet temperature to chiller to reduce chiller lift requirement to minimum input temperature permitted by chiller design. Outdoor air wet-bulb temperature reset of condenser water supply temperature based upon your load and equipment. Fan speed control given constant condenser water flow. (Sorry, not a definitive answer.)
Designing New Systems for Replaced Equipment • Chiller Replacement • Evaluate chillers based upon the Integrated Part Load Value (IPLV) (This is intended to show the part load performance/efficiency and is weighted based upon some assumed capacities and hours of use.) (The IPLV is an ARI/ASHRAE Standard that all manufacturers must use and will clearly indicate which chiller is the most efficient given the stated parameters.) • Consider redundancy; low load operation needs (Mutt chillers, plant configuration, VF pumping conversion, etc.); and future load additions (remodels, additions, expansions, etc.)
Designing New Systems for Replaced Equipment • Cooling Tower Replacement • Evaluate towers based upon chiller installed capacity and free-cooling needs/wants • Consider redundancy, fan speed control type and drive, and future load additions
Designing New Systems for Replaced Equipment • Pump Replacement • If you are replacing your chiller or tower, you should also replace your pump and motor. Choosing the new pump in the highest efficiency portion of the curve can save lots of money every hour the pump runs. • Consider conversion to variable flow systems on hot water and chilled water systems; but be very cautious on condenser water and water source heat pump loops. (Requires pressure control and 3-way to 2-way control valve replacement.)
Designing New Systems for Replaced Equipment • Boiler Replacement • Consider the boiler efficiency at part load, once sizing is confirmed. • Consider redundancy, low load operation needs (Mutt boilers, etc.) • Consider future load additions (remodels, additions, expansions, etc.) • Consider redundant fuel supply (fuel oil, propane, and required storage) • Consider cost for alternative fuels
Designing New Systems for Replaced Equipment • RTU Replacement • Consider overall cost for energy, repairs and maintenance given unit life time. Much higher efficiency units are available. • AHU Replacement/Refurbish • Consider conversion of constant volume to VAV system for supply fan motors greater than 20 hp. (See table on next page.) Best seasonal performance versus constant volume.
Take Aways Ensure your design team uses seasonal weather data to properly size HVAC systems. Periodically check your controls settings to ensure they are set for the best mix of comfort and efficiency. If it has been a while since you have had a loads analysis and ventilation study, it can be money well spent as energy savings can result from minimizing and controlling ventilation rates. When equipment replacement is needed, ensure that HVAC capacities for its zone/service needs are identified, choose the most efficient equipment available, and control the equipment/system in the most efficient manner that compliments occupant comfort.