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Directions-The Minnesota Fuel Gas Code method to calculate to sire of a required combustion air opening,is called the Known Air <br /> Infiltration Rate Method. For new construction,4b of step 41s required to be filled out. <br /> IFGC Appendix E,Worksheet E-1 <br /> Residential Combustion Air Calculation Method <br /> for Furnace,Boiler,and/or Water Heater in the Same ace <br /> Step 1:Complete vented combustion appliance information. <br /> Fumam/8otlar. <br /> _Draft Hood _Fan AssistedOirect Vent Input: Btu/hr <br /> or Power Vent <br /> Water Heater. <br /> _Draft Hood Fan Assisted _Direct Vent Input 8tu/hr <br /> or Power Vent <br /> Step 2:Calculate th volume of the Combustion Appliance Space(CAS)containing combu:Zon <br /> Cgs. / <br /> The CAS includes all spaces connected to one another by code compliant op Ings. CAS volume: Z 7 h <br /> LXWxH L <br /> Step 3:Determine Air Changes per Hour(ACH)i <br /> Default ACH values haw been Incorporated Into Table E-1 for use with Method 4b(KAIR Method). <br /> N the year of construction or ACH is not known,use method 4a(Standard Method). <br /> Step 4:Determine Required Volume for Combustion Air.(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> 4a.Standard Method <br /> Total Btu/hr Input of all combustion appliances Input Btu/hr <br /> Use Standard Method column In Table E-1 to find Total Required TRV: W <br /> Volume(TRV) <br /> If CAS Volume(from Step 2)is greater than TRV then no outdoor openings are needed. <br /> N CAS Volume(from Step 2)B kis than TRV then go to STEP S. <br /> 4b.Known Air Infiltration Rate(KAIR)Method(DO NOT COUNT DIRECT VENT <br /> APPLIA <br /> Total Btu/hr Input of all fan-assisted and power went appliances Input: Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA. 6 ft' <br /> Required Volume Fan Assisted(RVFA) t, <br /> Total Btu/hr Input of all Natural draft appliances Input: v Btu/hr <br /> Use Natural draft Appliances column In Table E-1 to find RVNFA: ,V y"4t--ft' <br /> Required Volume Natural draft appliances(RVNDA) <br /> Total Required Volume(TRV)=RVFA+RVNDA TRV- + <br /> N CAS Volume(from Step 2)Is greater than TRV then no outdoor openings are needed. <br /> H CAS Volume from Ste 2 is less than TRV then 'o to STEP S. <br /> Step S:Calculate the ratio of available interior volume to the total required volume. <br /> Ratio■CAS Volume(from Step 2)dhdded by TRV(from Step 4a or Step 4b) Ratio_ / <br /> Step 6:Calculate Reduction Factor(RF). <br /> RF=1 minus Ratio RF=1- • / _ / *� / <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside. <br /> Total Btu/hr Input of all Combustion Appliances In the same CAS Input: Btu/hr <br /> (EXCEPT DIRER VENT) 51 <br /> Combustion Air Opening Area(CAOA): <br /> Total Btu/hr dlWded by 3000 ku/hr per In' CAOA= /3000 Btu/hr per in'_ �� in' <br /> Step B:Calculate Minimum CAOA. <br /> Minimum CAOAuCAOAmu1dp1kdbyRF Minimum CAOA= Z x = <br /> Step S:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAO0=1.13 muftipfled by the square root of Minimum CAOA CAOD=1.13 V Minimum CAOA Z= dVIYiameter <br /> o up one Inch In size If using flax duct <br /> I If desired,ACH an be determined using ASHRAE calculation or blower door test.Follow procedures in Section <br /> G304. <br /> G:\Forms\VentMakupCombAtrCals041Sll.do« Page 5 of 6 <br />