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Table 501.4.2 <br /> Makeup Air Opening Sizing Table for New and Existing Dwelling Units <br /> One or multiple power One or multiple fan- One atmospherically vented Multiple atmospherically Duct di- <br /> vent,direct vent ap- assisted appliances and gas or oil ap- vented gas or oil ap- ameter <br /> pliances,or no combus- power vent or direct vent pliance or one solid fuel pliances or solid fuel <br /> tion appliances appliances Column B appliance appliances <br /> Passive opening 1-36 1-22 1-15 1-9 3 <br /> Passive opening 37-66 23-41 16-28 10-17 4 <br /> Passive opening 67-109 42-66 29-46 18-28 5 <br /> Passive opening 110-163 67-100 47-69 29-42 6 <br /> Passive opening 164-232 101-143 70-99 43-61 7 <br /> Passive opening 233-317 144-195 100-135 62-83 8 <br /> Passive opening 318-419 196-258 136-179 84-110 9 <br /> w/motorized damper <br /> Passive opening 420—539 259—332 180—230 111-142 10 <br /> w/motorized dam_per <br /> Passive opening 540-679 333-419 231-290 143-179 11 <br /> w/motorized damper <br /> Powered makeup air >679 >419 >290 >179 NA <br /> Notes: <br /> A.An equivalent length of 100 feet of round smooth metal duct is assumed.Subtract 40 feet for the exterior hood and ten feet for each 90-degree elbow to <br /> determine the remaining length of straight duct allowable. <br /> B.If flexible duct is used,increase the duct diameter by one inch.Flexible duct shall be stretched with minimal sags.Compressed duct shall not be accepted. <br /> C.Barometric dampers are prohibited in passive makeup air openings when any atmospherically vented appliance is installed. <br /> D.Powered makeup air shall be electrically interlocked with the largest exhaust system. <br /> Combustion air <br /> Not required per mechanical code(No atmospheric or power vented appliances) <br /> ✓ Passive(see IFGC Appendix E,Worksheet E-1) Size and type 3 inch ridged,4 inch flex <br /> Other,describe: <br /> Explanation-If no atmospheric or power vented appliances are installed,check the appropriate box,not required.If a power vented <br /> or atmospherically vented appliance installed,use IFGC Appendix E,Worksheet E-1(see below).Please enter size and type.Combustion <br /> air vent supplies must communicate with the appliance or appliances that require the combustion air. <br /> Section F calculations follow on the next 2 pages. <br />