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' � . <br /> , Directions -The Minnesota Fue/Gas Code method to�alculate to size of a required combustion air opening, is called fhe{1Cnown Air <br /> Infiltration Rafe Method. For new construction,4b of step 4 is required to be�lled out. <br /> IFGC A endix E,Worksheet E-1--Residential Combustion'Air Calculation Method for Furnace, Boiler,and/or Water Heater in the Same S ace <br /> Step 1: Complete vented combustion appliance information. <br /> Furnace/Boiler: <br /> �raft Hood QFan Assisted ✓QDirect Vent �nput: 1 OOOOO Btu/hr <br /> or Power Vent <br /> Water Heater: <br /> �raft Hood Q✓ Fan Assisted �irect Vent Input: 55000 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: 2128 ft3 L x W x H L W 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 E-1 to find Total Required TRV: - ft3 <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/ess than <br /> 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: 55,��� Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA: 4�Z5 ft3 <br /> Required Volume Fan Assisted(RVFA) <br /> -------------------- <br /> Total Btu/hr input of all Natural draft appliances Input: Btu/hr <br /> Use Natural draft Appliances column in Table E-1 to find RVNFA: ft3 <br /> Required Volume Naturat draft appliances(RVNDA) <br /> Total Required Volume(TRV)=RVFA+RVNDA TRv= 4125 + ----------- _ 4125 TRV ft3 <br /> If CAS Volume from Ste 2 is reater than TRV then no outdoor o enin s are needed. If CAS Volume from Ste 2 is less than TRV then o to STEP 5. <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) <br /> Ratio=2128 �4125 _.51 <br /> Step 6:Calculate Reduction Factor(RF). RF=1 minus Ratio <br /> RF=� - •51 _.49 <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside.Total Btu/hr input of all Combustion Appliances in the same CAS <br /> �nput: 55000 Btu/hr(EXCEPT DIRECT VENT) <br /> Combustion Air Opening Area(CAOA):Total Btu/hr divided by 3000 Btu/hr per in2 <br /> cAoa=55000 /3000 Btu/hr per in2=1$•3 in2 <br /> Step 8:Calculate Minimum CAOA: Minimum CAOA=CAOA multiplied by RF <br /> Minimum CAOA=18•3 X•49 -8•9 in2 <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD): CAOD=1.13 multiplied by the square root of Minimum CAOA <br /> CAOD= 1.13� Minimum CAOA= 3•3 in.diameter 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 /> 1 I 5 � <br />