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� Diredions-The Minnesota Fuel Gas Code method to calculate to size of a required combustfon 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 /> Resident(al Combustion Air Calculation Method <br /> (for furnace,Boiler,and/or Water Heater in the Same Space) <br /> Step i:Complete vented combustion appliance information. <br /> Furnace/Boiler: $0000 <br /> raft Hood �an Assisted �irect Vent Input: etu/hr or Power Vent <br /> water Heater: 40000 <br /> raft Hood �fan Assisted �ired Vent Input: Btu/hr or Power Vent <br /> Step 2:Calculate the volume of the Combustion Appliance Space(CAS)containing combustfon appliances. <br /> The CAS includes a►I spaces connected to one another by code compliant openings. CAS volume: 64O ft3 <br /> LxWxH 10 l 8 W�H <br /> Step 3:Determine Air Changes per Hour(ACH)1 <br /> Detault 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 /> 5tep 4:Determine Requlred Volume for Combustion Air.(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> 4a.Standard Method <br /> Tota)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)1s qr e a t er th a n TRV then no outdoor openings are needed. <br /> If CA5 Volume(from Step 2)1s kss th an TRV then go to STEP 5. <br /> 4b.Known Air Infihration Rate�KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> Total Btu/hr input of all fan-assisled and power vent appliances Input: � Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA: 3000 � <br /> Required Volume Fan Auisted(RVFA) <br /> Total Btu/hr input of all Naturel dreR appliances Input: � Btu/hr <br /> Use Naturai draft Appliances column in Table E-1 to find RVNFA: � fta <br /> Required Vdume Natural draft appliances(RVNDA) <br /> Total Re ufred Volume RV =RVFA+RVNDA TRV= �OOO + � _ 300� TRV ft3 <br /> Step 5:Calculate the ratio of ava(lable interior volume to the total required volume. <br /> Ratio=CAS Volume(from Step 2)d!vlded by TRV{from Step 4a or Step 4b) <br /> rtat�o= 640 � 3000 = 0.21 <br /> Step 6:Calculate Reduction Factor(RF). <br /> RF=1 In!e ut Retlo (tF a 1_ O.2� = 0.7�7 <br /> Step 7:Calculate single outdoor opening as ff all combustion air is from ouuide. 40000 <br /> Total Btu/hr input of all Combustion AppUances in the same CAS Input: Btu/hr <br /> (EXCEPT DIRECT VENT) <br /> Combustion Air Opening Area{CAOA): A <br /> Total Btu/hr d!�d ed by 3000 Btu/hr per inz CAOA= "�'OOOO /3ppp gtu/hr per inx= �3.33 inz <br /> Step 8:Calculate Minimum CAOA. <br /> Minimum CAOA=CAOA muklp►led by RF Minimum CAOA= �3.33 x Q.79 = 10.49 ��� <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD► <br /> CAOD=1.13 m ukipllsd by t he sq u a re root of Minimum CAOA CAOD=1.13 V Minimum CAOA= 3.66 in.diameter go up one inch in size <br /> if using flex dutt <br /> 1 If desfred,ACH can be determined using ASHRAE calculation or biower door test.Follow procedures fn Section <br /> G304. <br />