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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-1,1346.6012 <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: 100,000 <br /> Draft Hood Fan Assisted Direct Vent Input: ' Btu/hr <br /> or Power Vent <br /> Water Heater: 75,000 <br /> _Draft Hood Fan Assisted _Direct Vent Input: ' Btu/hr <br /> r Power Vent <br /> Step 2:Calculate the volume of the Combustion Appliance Space(CAS)containing combustion appliances. 1 290 <br /> The CAS includes all spaces connected to one another by code compliant openings. CAS volume: ft3 <br /> Lx W x H 1200 L 12.00 W s.o0 H <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). <br /> If 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 El to find Total Required TRV: ft3 <br /> Volume(TRV) <br /> If CAS Volume(from Step 2)is greater than TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)is less than TRV then go to STEP 5. <br /> 4b.Known Air Infiltration Rate(KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> Total Btu/hr input of all fan-assisted and power vent appliances Input: 75000 Btu/hr <br /> Use Fan-Assisted Appliances column in Table El to find RVFA: 5625 ft3 <br /> Required Volume Fan Assisted(RVFA) <br /> Total Btu/hr input of all Natural draft appliances Input: 0 Btu/hr <br /> Use Natural draft Appliances column in Table E-1 to find RVNFA: 0 ft3 <br /> Required Volume Natural draft appliances(RVNDA) <br /> Total Required Volume(TRV)=RVFA+RVNDA TRV= 5625 + 0 = 5,625.00 TRV ft3 <br /> If CAS Volume(from Step 2)is greater than TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)is less than TRV then go to STEP S. <br /> Step 5:Calculate the ratio of available interior volume to the total required volume. <br /> Ratio=CAS Volume(from Step 2)divided by TRV(from Step 4a or Step 4b) Ratio= 1290 / 25.00 = 23 <br /> Step 6:Calculate Reduction Factor(RF). <br /> RF=1 minus Ratio RF=1- •23 = .77 <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside. 75000 <br /> Total Btu/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 divided by 3000 Btu/hr per int CAOA= 75,00(I /3000 Btu/hr per int= 25.00 <br /> Step 8:Calculate Minimum CAOA. <br /> Minimum CAOA=CAOA multiplied by RF Minimum CAOA=25.00 x 0.77 = 19.25 in2 <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAOD=1.13 multiplied by the square root of Minimum CAOA CAOD=1.13 V Minimum CAOA= 5.00 in.diameter <br /> go up one inch in size if using flex duct <br /> 1 If desired,ACH can be determined using ASHRAE calculation or blower door test.Follow procedures in Section G304. <br /> I:\Building\SafetyPolicieslnformation\Current\2016\VentMakupCombAirCals2016.docx Page 5 of 6 <br />