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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 filed out. <br /> IFGC Appendix E Worksheet E-1—Residential Combustion Air Calculation Method for FurnaceBoiler,and/or Water Heater in the Same Space) <br /> Step 1:Complete vented combustion appliance information. <br /> Furnace/Boiler <br /> raft Hood QFan Assisted [DDirect Vent Input: 40,000 Btu/hr <br /> or Power Vent <br /> Water Heater: <br /> raft Hood [Z]Fan Assisted []0iirect Vent Input: 30,000 <br /> Btu/hr <br /> or Power Vent <br /> Step 2:Calculate the volume of the Combustion Appliance Space(CAS)containing combustion appliances.The CAS includes all <br /> spaces connected to one another by code compliant openings. <br /> CAS volume: 700 ftZ L x W x H L W H <br /> Step 3:Determine Air Changes per Hour(ACH)l <br /> Default ACH values have been incorporated into Table E-1 for use with Method 4b(KAIR Method). <br /> If the year of construction or ACH is not known,use method 4a(Standard Method). <br /> Step 4:Deternine Required Volume for Combustion Air.(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> 48.Standard Method <br /> Total Btulhr input of all combustion appliances Input:P BtuAnr <br /> Use Standard Method column in Table E-1 to find Total Required TRV: fe <br /> Volume(TRV)If CAS Volume(from Step 2)is greater than TRV then no outdoor openings are needed.If CAS Volume(from Step 2)is leas than <br /> TRV then go to STEP 5. <br /> 4b.Knowi Air InMmbon Rate(KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> Total Btulhr input of all fan-assisted and power vent appliances Input: 30000 Btulhr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA. 2250 le <br /> Volume Fan Assisted(RVFA) <br /> Total Btulhr input ut of a1 Natural draft appliances input: 0 _BbAr <br /> Use Natural draft Appliances colcunn in Table E-1 to find RVNFA: 0 fta <br /> Required Vokune Natural draft appliances(RVNDA) <br /> Total Required Volume(TRV)=RVFA+RVNDA TRV= 2250 + 0 = 2250 TRV ft <br /> If CAS Volume from Step 2 is greaterOwn TRV than no outdoor openings are needed.If CAS Volume 2 is lass than TRV than no to STEP 5. <br /> Stop S.Calculate the ratio of available interior volume to the total rem volume. <br /> Ratio=CAS Volume(from Step 2)divided by TRV(from Step 4a or Step 4b) <br /> Ratio=700 /2250 =.31 <br /> Step 6:Calculate Reduction Factor(RF). RF=1 minus Ratio <br /> RF=1 - .31 -.69 <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside.Total BhAr input of all Combustion Appliances in the some CAS <br /> Input: 30000 <br /> Btuft(EXCEPT DIRECT VENT) <br /> Combustion Air Opening Area(CAOA):Total Btulhr divided by 3000 Btulhr per inZ <br /> CAOA=30000 /3000 Btwbr per inZ=10 int <br /> Step 8:Calculate Minimum CAOA: Minimum CAOA=CAOA muNp/led by RF <br /> Minimum CAOA=10 x.69 _6.9 in <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD): CAOD=1.13 muitipifed by the square root of Minimum CAOA <br /> CAOD=1.13 d Minimum CAOA= 2.94 in.diameter go up one inch in size if using flex dud <br /> 1 if desired,ACH can be determined using ASHRAE calculation or blower door test.Follow procedures in Section G304. <br /> 5 <br />