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Directions-The Minnesota Fuel Gas Code method to calculate to size of a required combustion air opening,is called the Known Air <br /> Infiltration Rate Method.For new construction,4b of step 4 is 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 Space) <br /> Step 1:Complete vented combustion appliance information. <br /> Furnace/Boiler: <br /> reft Hood �an Assisted �irect Vent Input: Btu/hr or Power Vent <br /> Water Heater: <br /> reft Hood �Fan Assisted �Direct Vent Input: Btu/hr or Power Vent <br /> Step 2:Calculate the volume of the Combustion Appliance Space(CAS)containing combustion appliances. <br /> The CAS includes all spaces connected to one another by code compliant openings. CAS volume: � fta <br /> LxWxH �L�WaH <br /> Step 3:Determine Air Changes per Hour(ACH)1 <br /> Default ACH values have been incorporated into Table E-1 for use with Method 4b(KAIR Method�.If the year of construction or ACH is not known,use <br /> 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: ft3 <br /> Volume(TRV) <br /> if CAS Volume(from Step 2)!s gre a t er th a n TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)!s less th an TRV then go to STEP 5. <br /> 4b.Known Air Infiltretion Rate(KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> Total Btu/hr input of all fan-assisted and power vent appliances Input: � Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA: ft3 <br /> Required Volume Fan Assisted(RVfA) <br /> Total Btu/hr input of all Natural dreft appliances Input: Btu/hr <br /> Use Natural draft Appliances column in Table E-1 to find RVNFA: fta <br /> Required Volume Naturel dreft appliances(RVNDA) <br /> Total Re uired Volume RV =RVFA+RVNDA TRV= 0 + 0 - O TRV fta <br /> Step 5:Calculate the ratio of available interior volume to the total required volume. <br /> Ratio=CAS Volume(from Step 2)di vided by 7RV(from Step 4a or Step 4b) <br /> Ratio= Q / Q = <br /> Step 6:Calculate Reduction Factor(RF). <br /> RF=lminus Ratio RF=1- �.�� _ � .�0 <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside. <br /> Total etu/hr input of all Combustion Appliances in the same CAS Input: � Btu/hr <br /> (EXCEPT DIRECT VENT) <br /> Combustion Air Opening Area(CAOA): <br /> Total Btu/hr d iW d ed by 3000 Btu/hr per inz CAOA= 0 /3000 Btu/hr per inz= �.0� in: <br /> Step 8:Calculate Minimum CAOA. <br /> MinimumCAOA=CAOAmu/tiplled by RF MinimumCAOA= �.00 x 1 .QQ = O.QO inz <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAOD=1.13 m ultiplled by the squ ore root of Minimum CAOA CAOD=1.13 J Minimum CAOA= in.diameter go up one inch in size <br /> if using flex duct <br /> 1 If desired,ACH can be determined using ASHRAE calculation or blower door test.Follow procedures in Section <br /> G304. <br />