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Directions-The Minnesota Fue/Gas Code method to calculate to size of a requlred combustion a!r opening, Is called the Known Air <br /> In�ltration Rate Method. for new canstruction,46 of step 4 is requlred to be filled out, <br /> IFGC Appendlx E,Worksheet E-1 <br /> Resldential Comhustfon Air Calculatlon Method <br /> (for Furnace,Boiler,and/or Water Heater In the Same S ace) <br /> 5tep 1:Camplete vented combustlon appllance information. � <br /> Furnace/Boiler: �/� <br /> _Draft Hood _ Fan Assisted �Qjrect Vent Input: ��Btu/hr <br /> or Power Vent T 7 <br /> Water Heater: <br /> _Draft Hood Fan Assisted _Dlrect Vent Input: �b{�, Btu/hr <br /> or Power Vent ' � <br /> Step 2:Ca(culate the volume of the Combustfon Appiiance Space�CAS)containfng combustion app ances. �"' <br /> The CAS includes all spaces connected to one another by code compllant open! gs. CAS volume: J �� ft3 <br /> LxWxH H <br /> Step 3:Oetermine Alr Changes per Hour(ACH)1 <br /> Default ACH values have been incorporated Into Table E-1 for use wlth Method 4b(KAIR Method). <br /> If the year of constructlon or ACH Is not known,use method 4a(Standard Method). <br /> Step 4:Determine Required Volume for Combustion Air.(DO NOT COUNT DIRECT VENT APPLlANCES) <br /> 4a.Standard Method <br /> Total Btu/hr Input of ali combustion appllances tnput; etu/hr <br /> Use Standard Methad column in Table E-1 to find Total Requlred TRV: ft' <br /> Volume�TRV) <br /> If CAS Volume(from Step 2)!s greater thon TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)!s less thatt TRV then go ta STEP 5. <br /> 4b.Known Alr Inflftration Rate(KAIR)Method(DO NOT COUNT DIRECT'VENT APPLIANC ,/� <br /> Total etu/hr input of all fan-asststed and power vent appliances input; d�/�/ Btu/hr <br /> �- <br /> Use Fan-Assisted Appliances column In Ta61e E-1 to flnd RVFp; 2 ft' <br /> Requfred Volume Fan Assisted(RVFA) <br /> Totaf Btu/hr input of all Natural draft appllances Input: �_Btu/hr <br /> Use Natural draft Appllances column In Ta61e E-1 to flnd RVNFA: bh�� {�' <br /> Required Volume Natural draft appliances(RYNDA) <br /> Tatal Requlred Volume(TRV)=RVFA+RVNDA TRV= �i + � _ _ / .�TRV R3 <br /> If CAS 4olume(from Step 2)ls 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 af avallable Interior volume to the total required voiume. <br /> Ratio=CAS Volume(from Step 2)dJvided by TRV(from Step 4a or Step 46) <br /> Rado= � / �� _ . <br /> Slep 6;Calculate ReducUon Factor(RF). <br /> RF=1 minus Ratio RF=1• - � ' " <br /> Step 7;Caitulate sfngle outdoor opening as if all combustion air Is from outside. <br /> Total 6tu/hr Input af aU Combustion Appliances in the same CA5 Input:����/��tu/hr <br /> (EXCEPT DIRECT VENT) <br /> Combustion Air Opening Area(CAOA): <br /> Total etu/hr dfWded by 3000 Btu/hr per in' CAOA= � 3000 Btu/hr per in2= �j�� Inl <br /> Step 8:Calculate Minlmum CAOA. <br /> Mintmum CAOA=CADA multl lled 6 RF Minimum CAOA= x % = UJ r ] int <br /> Step 9:Calculate Combustion Air Opening Oiameter(CAOD) <br /> CA00=1.13 multlplled by the square root of Mi�imum CAOA CAOD=1.13� Minimum CAOA=��in.diameter <br /> go up one Inch in size If using flex duct <br /> l lf desired,ACH can he determined using ASHRAE calculation or biower door test.Follow procedures in Section <br /> G304. <br /> 6:\Forms\VentMakupCombAirCaIs041511.docx Page 5 of 6 . <br />