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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 /> Draft Hood ❑Fan Assisted �Direct Vent Input: Btu/hr or Power Vent <br /> Water Heater: 7C000 <br /> Draft 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. �296 <br /> The CAS includes all spaces connected to one another by code compliant openings. CAS volume: ft3 <br /> 9x16x9 LxWxH � 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).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)is g�ea t er th an TRV then no outdoor openings are needed. <br /> �f CAS Volume(from Step 2)is less th an 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: ��o� Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find R„FA: 5625 ft3 <br /> Required Volume Fan Assisted(RVFA) <br /> Total Btu/hr input of all Naturel draft appliances Input: O 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 /> TotalRe uiredVolume TRV =RVFA+RVNDA TR�- 5625 + 0 _ 5625 TRVft3 <br /> Step 5:Calculate the ratio of available interior volume to the totai required volume. <br /> Ratio=CAS Volume(from Step 2)di vided by TRV(from Step 4a or Step 4b) <br /> Rat'°_ �296 / 5625 = .23 <br /> Step 6:Calculate Reduction Factor(RF). <br /> RF=1 mi n us Ratio RF=1- •`� _ •/ 7 <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside. 75��� <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 di vid ed by 3000 8tu/hr per in� CAOA= 75000 /3000 Btu/hr per inz= �� inz <br /> Step 8:Calculate Minimum CAOA. <br /> Minimum CAOA=CAOA mulfip/ied by RF Minimum CAOA= 25 x .77 - �9,25 inz <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAOD=1.13 m u/tiplied by t he sq u are root of Minimum CAOA CAOD=1.13 d Minimum CAOA= �'�V 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 Sec[ion <br /> G 304. <br />