




Memorandum
To:		Docket EPA-HQ-OAR-2013-0748
From:		Gerald Wozniak, Margaret Sheppard, and Dave Godwin
      EPA/Stratospheric Protection Division
Subject:	Derivation of Charge Limits for Room Air Conditioners
Date:		May 27, 2014

	This document describes how EPA derived the refrigerant charge limits for room air conditioners and heat pumps proposed in "Protection of Stratospheric Ozone: Listing of Substitutes for Refrigeration and Air Conditioning and Revision of the Venting Prohibition for Certain Refrigerant Substitutes."

Source documents for calculations
      These charge limits are based upon calculations from formulas in Underwriters Laboratories (UL) standard 484, Room Air Conditioners. The formulas in Appendix F of the UL 484 standard in turn are based upon the international industry standard International Electrotechnical Commission (IEC) 60335-2-40, "Particular Requirements for Electrical Heat Pumps, Air Conditioners and Dehumidifiers" (2005). Kataoka, et al. (2000) first derived these formulas and discussed their technical basis. These formulas are empirically derived, considering molecular mass, lower flammability limit, refrigerant dispersion, leak rates, and the dimensions of the space that refrigerant leaks into. These formulas also were proposed to the IEC SC 61D and International Organization for Standardization (ISO) TC86 SC1 WG1 joint working groups to assist in setting standards for using flammable refrigerants in air conditioning equipment and dehumidifiers (Kataoka et al., 2000).
 Formula used to establish limits
      The formula from appendix F of UL 484 (section 1.6), "Requirements for Charge Limits," is for appliances with charge amounts m1 < M < m2, where M is the refrigerant charge amount in appliance in kg, m1 is 4m[3] x the lower flammability limit (LFL) in kg/m[3], and m2 is 26m[3] x LFL. The formula for the maximum allowable charge size is as follows:
      mmax=2.5 (LFL)54 hoA
      Where,
      mmax = the maximum allowable charge size allowed for the space, in kg,
      
      LFL = the lower flammability limit of the refrigerant in kg/m[3],
      h0 = the installation height of the indoor unit in m (0.6 m for an air conditioning (AC) unit on the floor, 1.0 m for an AC unit in a window, 1.8 m for a wall-mounted AC unit, and 2.2 m for a ceiling-mounted AC unit)
      A = the area of the room, in m[2]
      The formulas are based upon the conservative assumption that the ceiling of the room is 2.2 m (8 ft) high. The formulas are designed to prevent exceedance of 25% of the LFL.
      EPA used the following methodology to derive the maximum allowable charge limits by means of the aforementioned equation.  This approach included examining the charge limit with respect to the LFLs of different refrigerants, while taking into consideration variables such as the installation height (h0) of the AC unit and the area of the room.
      Source of values in the formula for maximum allowable charge size
       Lower Flammability Limit (LFL) values 
EPA used the following information in calculating the lower flammability limit on the basis of mass per unit volume (kg/m[3]), abbreviated LFLm.
Refrigerant designation
IUPAC chemical name or blend composition
                                                           Molar mass (kg/kmol)
                                                                LFLm in kg/m[3]
                                                                  LFLv in % v/v
R-290
Propane
                                                                           44.1
                                                                          0.038
                                                                           2.1%
R-32
Difluoromethane
                                                                             52
                                                                          0.306
                                                                          14.4%
R-441A
290/600/600a/170 (60/30/5/5)
                                                                          48.44
                                                                          0.041
                                                                          2.05%
For R-290 and R-32, the LFLm values are listed in Appendix B of UL 484. For R-441A, EPA used the LFL as a percentage of volume per volume from A.S. Trust & Holdings' SNAP submission (2.05%) and calculated the LFLm from the LFLv using the following formula:
                        LFLm = (MM/24.4) x LFLv x 1000
      Where, 
      LFLm = lower flammability limit in kg/m[3] (0.041),
      MM = molecular mass in kg/mol (0.04844),
      LFLv = lower flammability limit as a percentage volume (0.0205),
      24.4 = conversion factor, 1 mole of a gas per 24.4 liters at standard temperature (32ºF, 0ºC) and pressure (1 atmosphere, 101.325 kPa), based on the ideal gas law,
      1000 = conversion factor, 1000 liters per m[3]
      
       Installation Height (h0) values  
      Appendix F in the UL 484 standard sets four installation heights for a unit:  0.6 m for an AC unit on the floor, 1.0 m for an AC unit in a window, 1.8 m for a wall-mounted AC unit, and 2.2 m for a ceiling-mounted AC unit. In terms of determining if concentrations are small enough to remain below the LFL if the refrigerant is released, a greater compressor height h0 corresponds with better mixing of the refrigerant throughout a room. For example, a release of refrigerant near the ceiling will be more thoroughly mixed and there will be lower concentrations than if the same refrigerant charge is released close to the floor.
      EPA established the tables of proposed charge limits with h0 values that correspond to the following room air conditioner types:
         * h0=0.6 m:  packaged terminal air conditioners (PTACs), packaged terminal heat pumps (PTHPs), and portable air conditioners (all units on or near floor)
         * h0=1.0 m:  window AC units
         * h0=1.8 m:  wall-mounted AC units
         * h0=2.2 m:  ceiling-mounted AC units

 Correlation of AC unit capacity and room area 
      After determining the LFLm and installation heights the EPA used approximation of appropriate capacities for cooling a given area. The capacities for cooling a given area of a room is based upon the following table from EnergyStar 2014:
Area To Be Cooled (ft[2]) 
Capacity Needed (BTUs/hour) 
100 up to 150
5,000
150 up to 250
6,000
250 up to 300
7,000
300 up to 350
8,000
350 up to 400
9,000
400 up to 450
10,000
450 up to 550
12,000
550 up to 700
14,000
700 up to 1,000
18,000
1,000 up to 1,200
21,000
1,200 up to 1,400
23,000
1,400 up to 1,500
24,000
1,500 up to 2,000
30,000
2,000 up to 2,500
34,000
      
      EPA used the correlations below in associating capacity with room area. We used a conversion factor of 0.092903 m[2]/ft[2]. EPA established the tables of proposed charge limits with respect to the minimum area required for a maximum charge that correspond to the room air conditioner type. 
                               Area To Be Cooled
                                 range (ft[2])
min (ft[2])
max (ft[2])
min (m[2])
max (m[2])
Capacity (BTU/hr)
                                 100 up to 150
                                      100
                                      150
                                      9.3
                                     13.9
                                     5,000
                                 150 up to 250
                                      150
                                      250
                                     13.9
                                     23.2
                                     6,000
                                 250 up to 300
                                      250
                                      300
                                     23.2
                                     27.9
                                     7,000
                                 300 up to 350
                                      300
                                      350
                                     27.9
                                     32.5
                                     8,000
                                 350 up to 400
                                      350
                                      400
                                     32.5
                                     37.2
                                     9,000
                                 400 up to 450
                                      400
                                      450
                                     37.2
                                     41.8
                                    10,000
                                 450 up to 550
                                      450
                                      550
                                     41.8
                                     51.1
                                    12,000
                                 550 up to 700
                                      550
                                      700
                                     51.1
                                     65.0
                                    14,000
                                700 up to 1,000
                                      700
                                     1,000
                                     65.0
                                     92.9
                                    18,000
                               1,000 up to 1,200
                                     1000
                                     1,200
                                     92.9
                                     111.4
                                    21,000
                               1,200 up to 1,400
                                     1200
                                     1,400
                                     111.5
                                     130.1
                                    23,000
                               1,400 up to 1,500
                                     1400
                                     1,500
                                     130.1
                                     139.4
                                    24,000
                               1,500 up to 2,000
                                     1500
                                     2,000
                                     139.4
                                     185.8
                                    30,000
                               2,000 up to 2,500
                                     2000
                                     2,500
                                     185.8
                                     232.3
                                    34,000
      
       Sources of uncertainty in capacity value 
        EPA's EnergyStar program website also suggests some adjustments to capacity to address additional factors that may increase or decrease cooling capacity needed for a room:
         o      If the room is heavily shaded, reduce capacity by 10 percent.
         o      If the room is very sunny, increase capacity by 10 percent.
         o      If more than two people regularly occupy the room, add 600 BTUs for each additional person.
         o      If the unit is used in a kitchen, increase capacity by 4,000 BTUs.
The calculations used to derive the charge sizes in EPA's proposed rule do not adjust for these additional factors.
 Proposed charge limits 
 Table A below illustrates the maximum design charge sizes (kg) for window air conditioners with an installation height equal to 1m for different cooling capacities. Table B illustrates the maximum design charge sizes (kg) for PTACs, PTHPs and portable air conditioning units with an installation height equal to 0.6 m. Table C illustrates the maximum design charge sizes (kg) for wall mounted AC units with an installation height equal to 1.8 m. Table D illustrates the maximum design charge sizes (kg) for ceiling-mounted AC units with an installation height equal to 2.2m. These tables clearly indicate that charge sizes will slightly increase as a result of the installation height of the unit. For example, the charge size of 1.73 kg for R-32 in Table A (the lowest installation height) is much smaller than the charge size of 3.82 kg for R-32 in Table D (the highest installation height). It is also important to note that these charge sizes were derived with respect to the minimum room area for a given capacity and thus these calculations are based on a conservative analysis. For example, if the maximum room area was considered, it would yield a slightly higher maximum design charge size.
 The UL standard indicates that the formula used above is for appliances with charge sizes in a given range of m1 and m2. As indicated on page 1 of this memo, m2 is 26 m3 x LFL. Therefore, the calculations of allowable charge size, shown in Tables A through D, must be checked to ensure the values remain below m2. Although this limit is not reached in Tables A and B, it is reached in Tables C and D; those values are marked with an asterisk (*). Specifically, these maximum charge limits will apply and supersede those in the Tables C and D:
   * In Table E, for R-32, for capacities >= 18,000 BTU/hr: 7.956 kg.
   * In Table E, for R-290, for capacities = 34,000 BTU/hr: 0.988 kg.
   * In Table E, for R-441A, for capacities = 34,000 BTU/hr: 1.066 kg.
   * In Table F, for R-32, for capacities >= 12,000 BTU/hr: 7.956 kg.
   * In Table F, for R-290, for capacities >= 24,000 BTU/hr: 0.988 kg.
   * In Table F, for R-441A, for capacities >= 23,000 BTU/hr: 1.066 kg.
       
 Incorporating these results, Tables E and F present the maximum charge size limits for wall-mounted and ceiling-mounted room air conditioners, respectively.

The proposed charge limits are stated below in Tables A, B, E and F. (Values published in the notice of proposed rulemaking are rounded to the nearest tenth of a kilogram, rather than the nearest gram.)
       Table A. Maximum Design Charge Sizes for Window Air Conditioners

Refrigerant
                        Maximum design charge size (kg)

                     Associated cooling capacity (BTU/hr)

                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         10,000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         30,000
                                                                         34,000
R-32
                                                                          1.734
                                                                          2.124
                                                                          2.742
                                                                          3.004
                                                                          3.244
                                                                          3.468
                                                                          3.679
                                                                          4.067
                                                                          4.588
                                                                          5.484
                                                                          6.008
                                                                          6.489
                                                                          6.717
                                                                          7.756
R-290
                                                                          0.128
                                                                          0.157
                                                                          0.202
                                                                          0.221
                                                                          0.239
                                                                          0.256
                                                                          0.271
                                                                          0.300
                                                                          0.338
                                                                          0.404
                                                                          0.443
                                                                          0.478
                                                                          0.495
                                                                          0.572
R-441A
                                                                          0.141
                                                                          0.172
                                                                          0.222
                                                                          0.243
                                                                          0.263
                                                                          0.281
                                                                          0.298
                                                                          0.330
                                                                          0.372
                                                                          0.445
                                                                          0.487
                                                                          0.526
                                                                          0.544
                                                                          0.629

      Note: For use with self-contained air conditioning units or heat pumps with an evaporator at least 0.6 and no more than 1.0 m above the floor. (Assumes h0=1.0 m) 
      Cooling capacities between those in the table are to be linearly interpolated between the next smaller and larger capacities listed in the table.
                                       
 Table B. Maximum Design Charge Sizes for Packaged Terminal Air Conditioners, 
       Packaged Terminal Heat Pumps, and Portable Air Conditioning Units

Refrigerant
                        Maximum design charge size (kg)

                     Associated cooling capacity (BTU/hr)

                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         10,000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         30,000
                                                                         34,000
R-32
                                                                          1.041
                                                                          1.274
                                                                          1.645
                                                                          1.802
                                                                          1.947
                                                                          2.081
                                                                          2.207
                                                                          2.440
                                                                          2.753
                                                                          3.290
                                                                          3.605
                                                                          3.893
                                                                          4.030
                                                                          4.653
R-290
                                                                          0.077
                                                                          0.094
                                                                          0.121
                                                                          0.133
                                                                          0.144
                                                                          0.153
                                                                          0.163
                                                                          0.180
                                                                          0.203
                                                                          0.243
                                                                          0.266
                                                                          0.287
                                                                          0.297
                                                                          0.343
R-441A
                                                                          0.084
                                                                          0.103
                                                                          0.133
                                                                          0.146
                                                                          0.158
                                                                          0.169
                                                                          0.179
                                                                          0.198
                                                                          0.223
                                                                          0.267
                                                                          0.292
                                                                          0.316
                                                                          0.327
                                                                          0.377

      Note: For use with self-contained air conditioning units or heat pumps with an evaporator no more than 0.6 m above the floor. (Assumes h0=0.6 m) 
      Cooling capacities between those in the table are to be linearly interpolated between the next smaller and larger capacities listed in the table.

   Table C. Derived Maximum Design Charge Sizes for Wall-Mounted AC Units  
Refrigerant
                        Maximum design charge size (kg)

                     Associated cooling capacity (BTU/hr)

                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         10,000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         30,000
                                                                         34,000
R-32
                                                                          3.122
                                                                          3.823
                                                                          4.936
                                                                          5.407
                                                                          5.840
                                                                          6.243
                                                                          6.622
                                                                          7.321
                                                                         8.259*
                                                                         9.871*
                                                                        10.814*
                                                                        11.680*
                                                                        12.090*
                                                                        13.960*
R-290
                                                                          0.230
                                                                          0.282
                                                                          0.364
                                                                          0.399
                                                                          0.431
                                                                          0.460
                                                                          0.488
                                                                          0.540
                                                                          0.609
                                                                          0.728
                                                                          0.797
                                                                          0.861
                                                                          0.891
                                                                         1.029*
R-441A
                                                                          0.253
                                                                          0.310
                                                                          0.400
                                                                          0.438
                                                                          0.473
                                                                          0.506
                                                                          0.537
                                                                          0.593
                                                                          0.670
                                                                          0.800
                                                                          0.877
                                                                          0.947
                                                                          0.980
                                                                         1.132*

      Note: For use with self-contained air conditioners or heat pumps with an evaporator at least 1.0 and no more than 1.8 m above the floor. (Assumes h0=1.8 m) 
      Cooling capacities between those in the table are to be linearly interpolated between the next smaller and larger capacities listed in the table. 
      See Table E for maximum charge sizes for those above marked with an asterisk (*).
                  
  Table D. Derived Maximum Design Charge Sizes for Ceiling-Mounted AC Units: 
                                       
                                 Refrigerant 

                        Maximum Design Charge Size (kg)
                                       
                         Associated capacity (BTU/hr)

                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         10,000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         30,000
                                                                         34,000
R-32
                                                                          3.815
                                                                          4.673
                                                                          6.033
                                                                          6.608
                                                                          7.138
                                                                          7.631
                                                                         8.093*
                                                                         8.948*
                                                                        10.094*
                                                                        12.065*
                                                                        13.217*
                                                                        14.276*
                                                                        14.777*
                                                                        17.063*
R-290
                                                                          0.281
                                                                          0.344
                                                                          0.445
                                                                          0.487
                                                                          0.526
                                                                          0.563
                                                                          0.597
                                                                          0.660
                                                                          0.744
                                                                          0.889
                                                                          0.974
                                                                         1.052*
                                                                         1.089*
                                                                         1.258*
R-441A
                                                                          0.309
                                                                          0.379
                                                                          0.489
                                                                          0.536
                                                                          0.579
                                                                          0.619
                                                                          0.656
                                                                          0.725
                                                                          0.818
                                                                          0.978
                                                                         1.071*
                                                                         1.157*
                                                                         1.198*
                                                                         1.383*
      Note: For use with self-contained air conditioners or heat pumps with an evaporator more than 1.8 m above the floor. (Assumes h0=2.2 m) 
      Cooling capacities between those in the table are to be linearly interpolated between the next smaller and larger capacities listed in the table. 
      See Table F for maximum charge sizes for those above marked with an asterisk (*).

        Table E. Maximum Design Charge Sizes for Wall-Mounted AC Units
Refrigerant
                        Maximum design charge size (kg)

                     Associated cooling capacity (BTU/hr)

                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         10,000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         30,000
                                                                         34,000
R-32
                                                                          3.122
                                                                          3.823
                                                                          4.936
                                                                          5.407
                                                                          5.840
                                                                          6.243
                                                                          6.622
                                                                          7.321
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
R-290
                                                                          0.230
                                                                          0.282
                                                                          0.364
                                                                          0.399
                                                                          0.431
                                                                          0.460
                                                                          0.488
                                                                          0.540
                                                                          0.609
                                                                          0.728
                                                                          0.797
                                                                          0.861
                                                                          0.891
                                                                          0.988
R-441A
                                                                          0.253
                                                                          0.310
                                                                          0.400
                                                                          0.438
                                                                          0.473
                                                                          0.506
                                                                          0.537
                                                                          0.593
                                                                          0.670
                                                                          0.800
                                                                          0.877
                                                                          0.947
                                                                          0.980
                                                                          1.066

                                        
      Note: For use with self-contained air conditioners or heat pumps with an evaporator at least 1.0 and no more than 1.8 m above the floor. (Assumes h0=1.8 m) 
      Cooling capacities between those in the table are to be linearly interpolated between the next smaller and larger capacities listed in the table.
                  
       Table F. Maximum Design Charge Sizes for Ceiling-Mounted AC Unit
                                       
                                 Refrigerant 

                        Maximum Design Charge Size (kg)
                                       
                         Associated capacity (BTU/hr)

                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         10,000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         30,000
                                                                         34,000
R-32
                                                                          3.815
                                                                          4.673
                                                                          6.033
                                                                          6.608
                                                                          7.138
                                                                          7.631
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
                                                                          7.956
R-290
                                                                          0.281
                                                                          0.344
                                                                          0.445
                                                                          0.487
                                                                          0.526
                                                                          0.563
                                                                          0.597
                                                                          0.660
                                                                          0.744
                                                                          0.889
                                                                          0.974
                                                                          0.988
                                                                          0.988
                                                                          0.988
R-441A
                                                                          0.309
                                                                          0.379
                                                                          0.489
                                                                          0.536
                                                                          0.579
                                                                          0.619
                                                                          0.656
                                                                          0.725
                                                                          0.818
                                                                          0.978
                                                                          1.066
                                                                          1.066
                                                                          1.066
                                                                          1.066
                                        
      Note: For use with self-contained air conditioners or heat pumps with an evaporator more than 1.8 m above the floor. (Assumes h0=2.2 m) 
      Cooling capacities between those in the table are to be linearly interpolated between the next smaller and larger capacities listed in the table.
 Conversion to English units of measure
For the readers' information, we provide the same maximum design charge sizes as above converted to ounces, using the conversion factor 35.274 oz/kg.
            Maximum Design Charge Sizes in Ounces for Window Units

                               Capacity (BTU/hr)
Refrigerant
                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         1,0000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         3,0000
                                                                         34,000
R-32
                                                                          61.17
                                                                          74.92
                                                                          96.72
                                                                         105.96
                                                                         114.44
                                                                         122.35
                                                                         129.77
                                                                         143.46
                                                                         161.85
                                                                         193.45
                                                                         211.91
                                                                         228.89
                                                                         236.92
                                                                         273.57
R-290
                                                                           4.51
                                                                           5.52
                                                                           7.13
                                                                           7.81
                                                                           8.44
                                                                           9.02
                                                                           9.57
                                                                          10.58
                                                                          11.93
                                                                          14.26
                                                                          15.62
                                                                          16.87
                                                                          17.47
                                                                          20.17
R-441A
                                                                           5.26
                                                                           6.45
                                                                           8.32
                                                                           9.12
                                                                           9.85
                                                                          10.53
                                                                          11.16
                                                                          12.34
                                                                          13.92
                                                                          16.64
                                                                          18.23
                                                                          19.69
                                                                          20.38
                                                                          23.54

             Maximum Design Charge Sizes in Ounces for PTACs/PTHPs

                               Capacity (BTU/hr)
Refrigerant
                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         1,0000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         3,0000
                                                                         34,000
R-32
                                                                          36.70
                                                                          44.95
                                                                          58.03
                                                                          63.57
                                                                          68.67
                                                                          73.41
                                                                          77.86
                                                                          86.08
                                                                          97.11
                                                                         116.07
                                                                         127.15
                                                                         137.33
                                                                         142.15
                                                                         164.14
R-290
                                                                           2.71
                                                                           3.31
                                                                           4.28
                                                                           4.69
                                                                           5.06
                                                                           5.41
                                                                           5.74
                                                                           6.35
                                                                           7.16
                                                                           8.56
                                                                           9.37
                                                                          10.12
                                                                          10.48
                                                                          12.10
R-441A
                                                                           3.16
                                                                           3.87
                                                                           4.99
                                                                           5.47
                                                                           5.91
                                                                           6.32
                                                                           6.70
                                                                           7.41
                                                                           8.35
                                                                           9.99
                                                                          10.94
                                                                          11.82
                                                                          12.23
                                                                          14.12



          Maximum Design Charge Sizes in Ounces for Wall-Mounted Units
Refrigerant
                               Capacity (BTU/hr)

                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         1,0000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         3,0000
                                                                         34,000
R-32
                                                                         110.11
                                                                         134.86
                                                                         174.10
                                                                         190.72
                                                                         206.00
                                                                         220.22
                                                                         233.58
                                                                         258.23
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
R-290
                                                                           8.12
                                                                           9.94
                                                                          12.83
                                                                          14.06
                                                                          15.19
                                                                          16.23
                                                                          17.22
                                                                          19.04
                                                                          21.48
                                                                          25.67
                                                                          28.12
                                                                          30.37
                                                                          31.44
                                                                          34.85
R-441A
                                                                           8.93
                                                                          10.93
                                                                          14.11
                                                                          15.46
                                                                          16.70
                                                                          17.85
                                                                          18.94
                                                                          20.93
                                                                          23.62
                                                                          28.23
                                                                          30.92
                                                                          33.40
                                                                          34.57
                                                                          37.60

        Maximum Design Charge Sizes in Ounces for Ceiling Mounted Units

                               Capacity (BTU/hr)
Refrigerant
                                                                          5,000
                                                                          6,000
                                                                          7,000
                                                                          8,000
                                                                          9,000
                                                                         1,0000
                                                                         12,000
                                                                         14,000
                                                                         18,000
                                                                         21,000
                                                                         23,000
                                                                         24,000
                                                                         3,0000
                                                                         34,000
R-32
                                                                         134.58
                                                                         164.83
                                                                         212.79
                                                                         233.10
                                                                         251.78
                                                                         269.16
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
                                                                         280.64
R-290
                                                                           9.92
                                                                          12.15
                                                                          15.69
                                                                          17.18
                                                                          18.56
                                                                          19.84
                                                                          21.05
                                                                          23.27
                                                                          26.25
                                                                          31.37
                                                                          34.37
                                                                          34.85
                                                                          34.85
                                                                          34.85
R-441A
                                                                          10.91
                                                                          13.36
                                                                          17.25
                                                                          18.90
                                                                          20.41
                                                                          21.82
                                                                          23.14
                                                                          25.59
                                                                          28.86
                                                                          34.50
                                                                          37.60
                                                                          37.60
                                                                          37.60
                                                                          37.60
 

 
 References

      Energy Star, "Properly Sized Room Air Conditioners." Available at http://www.energystar.gov/?c=roomac.pr_properly_sized; accessed May 8, 2014.
      IEC 60335-2-40, "Particular Requirements for Electrical Heat Pumps, Air Conditioners and Dehumidifiers." 2005.
      Kataoka, O., Yoshizawa, M. and Hirakawa, T. 2000. Allowable charge calculation method for flammable refrigerants. International Refrigeration and Air Conditioning Conference, Purdue University, West Lafayette IN, USA. 2000. Available online at http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1505&context=iracc
       UL 484, Room Air Conditioners. Appendix F, "Requirements for Charge Limits."  8[th] Edition. August 2012.
      
      

            








