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� Direc'ions- The Minnesota Fuel Gas Code method to calculate to size of a required combustion air opening, is called the Known Air <br /> Infil[ratron Rate Method. For new construction,4b of siep 4 is required to be filled out. <br /> 2 ; -�-z %�-�-#= i`� = % c,(,c-r� <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 appiiance information. <br /> Furnace/Boiler: <br /> _Draft Hood _ Fan Assisted ?�Direct Vent Input: U� Btu/hr <br /> or Power Vent <br /> Water Heater: <br /> _Draft Hood X� fan Assisted _Direct Vent Input:��� `'�� Btu/hr <br /> or Power Vent <br /> Step 2:Calculate the volume of the Combustion Appliance Space(CAS)containing combustion appliances. (,/ <br /> The CAS includes all spaces connected to one another by code compliant openings. CAS volume: ! Y� ft3 <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 NGT COUNT DIRECT VENTAPPLIANCES) <br /> 4a.Standard Method <br /> Total etu/hr input of all combustion appliances Input: Btu/hr <br /> Use Standard Method column in 7able E-1 to tind Total Required TRV: ft' <br /> Volume(TRV) <br /> If CAS Vo�ume(from Step 2)is greoYer thon TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)is/ess 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 famassisted and power vent appliances Input SU� 0� Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA: �, � �J ft3 <br /> Required Volume Fan Assisted(RVFA) <br /> Total Btu/hr input of all Natural draft appliances Input: U Btu/hr. <br /> Use Natural draft Appliances column in Table E-1 to find RVNFA: ��Y`-� ft' <br /> Required Volume Natural draft appliances(RVNDA) <br /> Total Required Volume(TRV)=RVFA+RVNDA TRV= �3 � � �=� + ��-'4"`� _ ` � �=� TRV ft' <br /> If CAS Volume(from Step 2)is greoter 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 /> 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= � � / f t �t,� = i <br /> Step 6:Calwlate Reduction Factor(RF). <br /> RF=1 minus Ratio RF=1- , I = -!' "� <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside. <br /> �- <br /> Total Btu/hr input of ali Combustion Appliances in the same CAS Input: = �; J�� Btu/hr <br /> (EXCEPT DIRECT VENT) <br /> Combustion Air Opening Area(CAOA): <br /> Total Btu/hr divided by 3000 Btu/hr per in2 CAOA= r� t„t.) /3000 Btu/hr per in�= t (,�, {,� in2 <br /> Step 8:Calculate Minimum CAOA. <br /> Minimum CAOA=CAOA multiplied by RF Minimum CAOA= (� x = � �� inZ <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAOD=1.13 multiplied by the squore root of Minimum CAOA CAOD=1.13 d Minimum CAOA= �� ��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 <br /> G304. <br /> Page 5 of 6 <br />