HVAC Design Conditions

HVAC Load Calculations

  • HVAC  load  calculations shall  use  HAP  (Hourly Analysis  Program)  or  Elite  (CHVAC)  load calculation software. Calculations shall be computer generated for heating and cooling space/zone calculations and hand calculated may be permitted for block load estimations in preliminary stages using ASHRAE load estimated (rule of thumb) values and past experiences.
  • For spaces or buildings housing electrical equipment, heat dissipation values shall be obtained from electrical equipment manufacturer and included in the heating and cooling load calculations considering ultimate future expansion or as specified in specific project requirement as sole decision.
  • All design parameters and input data used in the computer-developed calculations shall be supported by references and all assumptions shall be identified in details.
  • Thermal transmittance values for walls and roofs shall be selected based on recommended values in ASHRAE 90.1 Energy Standard for Buildings except Low-Rise Residential Buildings for commercial buildings and ASHRAE 90.2 for residential buildings.
  • Safety factor for load calculations shall not exceed 10 percent for cooling and 5 percent for heating or reserve capacity limitations load calculation.
  • Residential HVAC load calculation method shall only be used for residential applications as per ASHRAE recognized calculation methods.
  • HVAC load calculations shall include, but not limited to, the following:
    1. Wall, window and roof U-Factor calculations supported by manufacturing references.
    2. Wall, window and roof areas and orientations.
    3. Outside and inside design criteria.
    4. Electrical load input data, for example equipment and lighting.
    5. Outside or  ventilation  air  quantity  and  condition  of  the  air  (wet  bulb  and  dry  bulb temperatures).
    6. Exhaust air quantities for the space/zone served by the HVAC system.
    7. Entering and leaving coil conditions (wet bulb and dry bulb temperature).
    8. Total system supply air quantity.
    9. Supply air quantity to each of the rooms served by the HVAC system.
    10. Total and sensible coil load and space/zone sensible, latent and total load.
    11. Breakdown of loads (sensible, latent and total) due to solar loads, wall, roof, and glass transmission, lighting, electrical equipment, people and outside (ventilation) air.
    12. Space/zone load profile diagram comparing total load per mon The load profile is to assist in selection of refrigeration system and other energy conservation system such as thermal storage tanks.
    13. Psychometric chart for each zone/unit representing the air condition process.
    14. Results shall be summarize in an overall HVAC Load Calculation Table.



Leave a Reply