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Directions-The Minnesota Fuel Gas Cade 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 /> (far 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 Ubirect Vent Input: Btu/hr <br /> or Power Vent (7� <br /> Water Heater: +1r <br /> _Draft Hood Fan Assisted _Direct Vent Input: /r4-15 ° Btu/hr <br /> r Power Vent <br /> Step 2:Calculate t e 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: (e.O ft3 <br /> LxWxH LZOH <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: ft' <br /> Volume(TRV) <br /> If CAS Volume(from Step 2)is greater than TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)is less than TRV then go to STEPS. <br /> 4b.Known Air Infiltration Rate(KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANC S <br /> Total Btu/hr Input of all fan-assisted and power vent appliances Input: 69'c'b Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA: 562-5 ft3 <br /> Required Volume Fan Assisted(RVFA) <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: it"4-4'3E'�i}t' <br /> Required Volume Natural draft appliances(RVNDA) / q_ / <br /> Total Required Volume(TRV)=RVFA+RVNDA TRV= 7�/e / + _ �fc�G > TRV ft' <br /> If CAS Volume(from Step 2)is greater than TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)is less than TRV then go to STEP S. <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 4h) �,( <r- <br /> Ratio= "/ d4� / J � = I 7/ <br /> Step 6:Calculate Reduction Factor(RF). (((( <br /> RF=1minus Ratio RF=1- 7/ _ <br /> Zp <br /> Step 7:Calculate single outdoor opening as if all combustion air is from outside. <br /> Total Btu/hr input of all Combustion Appliances in the same CAS Input: 7 �� Btu/hr <br /> (EXCEPT DIRECT VENT) / <br /> Combustion Air Opening Area(CAOA): � <br /> Total Btu/hr divided by 3000 Btu/hr per in? CAOA75.-v P/3000 Btu/hr per int= int <br /> Step 8:Calculate Minimum CAOA. <br /> V '7 <br /> Minimum CAOA=CAOA multiplied by RF Minimum CAOA= x , Z b _ / ,��, int <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAOD=1.13 multiplied by the square root of Minimum CAOA CAOD=1.13 V Minimum CAOA=3/05 <br /> 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 /> G:\Forms\VentMakupCombAirCals041511.docx Page 5 of 6 <br />