Page 197 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers
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LEED Ener gy and Atmospher e     175

             Lr          Annual refrigerant leakage rate of system i (The values range from 0.005
               i
                         to 0.02 lb refrigerant leaked per pound of refrigerant in the unit per year
                         with a default of 0.02 unless otherwise shown, such as with manufacturers’
                         test data. This is based on an annual leakage of 0.5 to 2.0 percent of the
                         total system refrigerant. Zero leakage may not be claimed.)
             Mr           End-of-life refrigerant loss of system i (The values range from 0.02 to 0.10
                i
                         lb refrigerant lost per pound of refrigerant in the unit with a default of
                         0.10 unless otherwise shown, such as with manufacturers’ test data. This
                         is based on the assumption that 2 to 10 percent of the total system
                         refrigerant will not be recovered when the system life is over, based on
                         either installation or removal losses. Zero loss may not be claimed.)
             ODP           Ozone depletion potential of refrigerant r (These are listed in Table 4.4.1
                  r
                         or can be obtained from the EPA website. For refrigerants other than the
                         CFCs, they typically range from 0 to 0.2 lb  /lb .)
                                                            CFC11  r
             Q             The gross  ARI rated cooling capacity of an individual HVAC or
               unit i
                         refrigeration unit i in ton s (A ton  of cooling capacity is based on an
                                              ac       ac
                         older system of rating refrigeration when tons of ice were delivered for
                         iceboxes. The tonnage given is actually in tons of ice melted in 24 h. One
                         ton  of cooling can be directly converted to 12,000 Btu/h.)
                            ac
             Q             The total gross ARI-rated cooling capacity of all HVAC or refrigeration in
               total
                         ton s ( Q   over all systems i)
                            ac    unit i
             Rc          Refrigerant charge of system i (This usually ranges from 0.5 to 5.0 lb of
                i
                         refrigerant per ton  of gross ARI-rated cooling capacity.)
                                        ac
             LCODP  and LCGWP , the equivalent annual life-cycle-based ozone depleting potential
                    i          i
             and the equivalent annual life-cycle-based global warming potential for system i, are
             calculated by Eqs. (4.4.1) and (4.4.2). In each equation, the variable to the left side of the
             addition sign represents the contributions from annual leakage and the variable to the
             right side of the addition sign represents an annualized contribution from installation
             of the unit and disposing of the unit at the end of its useful life.

                                 LCODP = [Lr + (Mr /Life )] (ODP × Rc )          (4.4.1)
                                       i    i     i   i      r    i
                                LCGWP = [Lr + (Mr /Life )] (GWP × Rc )           (4.4.2)
                                       i    i     i   i      r    i
             For systems with the default values of leakage and loss and a 10-year life, these equations
             simplify to Eqs. (4.4.3) and (4.4.4). Similar simplified equations can be written for the
             various default values and equipment lives.

               LCODP = 0.03(ODP × Rc )      for default leakage and loss, 10-year life   (4.4.3)
                        i         r    i
                  LCGWP = 0.03(GWP × Rc )     for default leakage and loss, 10-year life   (4.4.4)
                        i          r   i
             Finally, a weighted average of all base building level HVAC&R equipment systems
             shall be used over all systems i such that

                {∑ [LCGWP + (LCODP × 100,000 lb  /lb  )]Q   }/Q   ≤ 100 lb  /(ton · yr)
                  i       i         i         CO2  CFC11  unit i  total  CO2   ac
                                                                                 (4.4.5)
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