In a commercial building, the heating load at winter design conditions is 211 400 Btu/hr (with pick-up allowance) and the cooling load at summer design conditions is 232 800 Btu/hr. From the performance specifications for commercial, gas-electric, heating and cooling, packaged rooftop units provided in Table 6.9, select an RTU that can efficiently meet these loads.

Table 6.9

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Nominal Tons of Cooling 55662222 15 15 18 18 20 20 Nominal Tons of Cooling 15 18 20 25 Net Cooling (Btu/hr) 176 000 176 000 202 000 202 000 236 000 236 000 278 000 277 000 Net Cooling (Btu/hr) 178 000 204 000 236 000 278 000 Number of Cooling Stages NNNNNNNN 2 2 2 2 2 2 2 2 Number of Cooling Stages 2 2 2 2 Gas-Electric, Heating and Cooling Units Heating Input (Btu/hr) EER 9.5 9.7 9.7 9.7 9.5 9.5 9.7 9.5 EER 9.7 10.0 9.7 IPLV 9.8 9.5 9.5 10.2 10.1 10.1 10.0 10.4 10.0 Electric-Electric Heating and Capacity Cooling Units Heating Capacity (kW) IPLV 9.9 10.5 10.4 230 000 300 000 275 000 360 000 275 000 360 000 275 000 360 000 10.5 30 50 73 30 50 73 30 50 73 Heating Output (Btu/hr) 30 50 73 186 000 243 000 223 000 292 000 223 000 292 000 223 000 292 000 Heating Output (Btu/hr) 102 390 170 650 249 149 102 390 170 650 249 149 102 390 170 650 249 149 102 390 170 650 249 149 Steady State Heating Efficiency 81 81 81 81 81 81 81 81 Steady State Heating Efficiency 100 100 100 100 Number of Heating Stages 22222222 Number of Heating Stages 3 3 3 3