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Maximum Allowable Cooling Capacity

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					Maximum Allowable Cooling
       Capacity

  Bruce Wilcox, BSG
 Ken Nittler, Enercomp


                         Berkeley
                         Solar
                         Group

                         Enercomp, Inc.
Overview
  Air conditioners operating on peak in
  California’s hot central valley climates
  typically draw 1.7 kW/ton of rated capacity
  Field data indicates that oversizing is
  common
  The most reliable way to capture peak
  electrical demand savings from envelope
  and duct measures required under the
  standards is to ensure that air conditioners
  are appropriately sized

                                      Berkeley
                                      Solar
                                      Group

                                      Enercomp, Inc.
Proposed Changes
  Proposal expands current sizing
  requirements to include calculation of a
  Maximum Allowable Cooling Capacity
  Goal is to prevent gross oversizing
  Alternative Calculation Method software will
  be required to do calculations
  Procedures allow calculations based either
  on whole building or for each separate
  cooling system
  Tradeoff for systems with larger cooling
  capacity but same peak demand     Berkeley
                                    Solar
                                    Group

                                    Enercomp, Inc.
Proposed Language
  Standards
   – Section 150(h)3 establishing the maximum
     allowable cooling capacity
   – Two exceptions
  ACM Manual
   – Appendix L - Procedure for calculating design
     cooling capacity
   – Appendix M - Procedure for calculating
     maximum allowable cooling capacity
   – Appendix N – Procedure for calculating electrical
     input exception
                                          Berkeley
                                          Solar
                                          Group

                                          Enercomp, Inc.
Exception 1 – Systems not Covered
  No cooling system installed
  Cooling system is not an electrically driven
  compression based system




                                     Berkeley
                                     Solar
                                     Group

                                     Enercomp, Inc.
Appendix L – Design Cooling Capacity
  Follows ASHRAE 2001 Fundamentals
  Chapter 28 Residential Loads
  Using
   – Region X Design Data
   – Block Loads either whole building or by cooling
     system
   – Specific Rules to select Tables
   – Title-24 U-factors, SHGC values, Infiltration,
     Duct Efficiencies, Radiant Barriers
  Load is adjusted to rating conditions to get
  Design Cooling Capacity                  Berkeley
                                           Solar
                                           Group

                                           Enercomp, Inc.
Capacity at Standard Rated Conditions
   95 °F outdoor dry bulb
   67 °F indoor wet bulb
   Capacity = Load / (0.88 – 0.002286 x DT)
      Where:
      Capacity = Design Cooling Capacity (Btu/hr)
      Load = Sensible Design Cooling Load (Btu/hr)
      DT = Outdoor Cooling Design Temperature (°F) – 95




                                               Berkeley
                                               Solar
                                               Group

                                               Enercomp, Inc.
Appendix M – Maximum Capacity
  Uses Design Cooling Capacity from
  Appendix L
  Allows next largest size to be selected
  For buildings with more than one cooling
  system that have the design cooling
  capacity calculated for the entire building
     Maximum Allowable Cooling Capacity =
     Design Cooling Capacity + (6000 x Number of Cooling
      Systems)



                                             Berkeley
                                             Solar
                                             Group

                                             Enercomp, Inc.
Maximum Allowable Cooling Capacity
   Design Cooling    Maximum Allowable
      Capacity
                       Cooling Capacity
                           (Btu/hr)
      (Btu/hr)

      < 48000       Design Cooling Capacity
                            + 6000


    48000 - 60000   Design Cooling Capacity
                           + 12000


       >60000       Design Cooling Capacity
                           + 30000
                                  Berkeley
                                  Solar
                                  Group

                                  Enercomp, Inc.
Multiple Orientations
   Maximum Allowable is the highest of the
   four cardinal orientations
   For buildings with more than one cooling
   system, the orientation may be different for
   each system




                                      Berkeley
                                      Solar
                                      Group

                                      Enercomp, Inc.
Exception 2 – Electrical Input Exception
Appendix N
   Allowed to exceed maximum allowable cooling
   capacity if the proposed total electrical input of the
   oversized system is less than or equal to the
   standard electrical input
   Standard total electrical input is equal to 0.117 x
   Design Cooling Capacity
   Proposed electrical input includes compressor and
   fan energy
   Proposed electrical input is from CEC Directories of
   Certified Equipment
   Proposed fan energy is 0.017 W per Btu of design
   cooling capacity or may be measured as part of
   new duct measurement procedure
                                             Berkeley
                                             Solar
                                             Group

                                             Enercomp, Inc.
Standard Electrical Input




Btu/Watt Cooling Capacity for Split Air
Conditioners in the CEC Directory         Berkeley
                                          Solar
                                          Group

                                          Enercomp, Inc.

				
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