Laserfiche WebLink
� i • . � <br /> Directlons-The Minnesota Fuel Gas Code method to calculate to size of a required combustion air opening,is called the Known Air <br /> Inflltretion Rate Method.For new constructfon,4b of step 4 is required to be fllled out. <br /> IFGC Appendix E,Worksheet E-1 <br /> Residential Combustion Air Calculation Method <br /> (for Furnace,Bofler,and/or Water Heater in the Same Space) <br /> Step i:Complete vented rnmbustion appliance information. <br /> Furnace/Boiler: 200000 <br /> reft Hood �an Assisted �irecc Vent Input: Btu/hr or Power Vent <br /> water Heater: 40000 <br /> reft Hood �Fan Assisted �irect Vent Input: Btu/hr or Power Vent <br /> Step 2:Calculate the volume of the Combustion Appliance Space(CAS)containing combustion appliances. <br /> The CAS includes all spaces rnnnected to one another by code mmplfant openings. CAS volume: 640 � <br /> LxWxH 10 L 8 W 8 H <br /> Step 3:Determine Air Changes per Hour(ACH)1 <br /> Defauk 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 rnmbustion apptlances Input: Btu/hr <br /> Use Standard Method column in Table E-1 to flnd Total Required TRV: ft� <br /> Volume(TRV) <br /> If CAS Volume(from Step 2)is prea t er th an TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)/s less tfi on TRV then go to STEP 5. <br /> 46.Known Air Infiltration Rate(KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> Total Btu/hr input of all fan-suisted and power vent appliances Input: 4��� Btu/hr <br /> Use Fan-Assisted Appifances column in Table E-1 to flnd RVFA: `�OOO ft� <br /> Required Volume Fan Assisted(RVFA) <br /> Total Btu/hr input of all Natural drak appliances Input: � Btu/hr <br /> Use Natural draft Appliances column in Table E-1 to find RVNFA: � ft, <br /> Required Volume Natural draft appliances(RVNDA) <br /> Total Re uired Volume TR =RVFA+RVNDA TRV= �OOO + 0 _ 300Q �v� <br /> Step 5:Calculate the ratio of available interior volume to the total required volume. <br /> Ratio=CAS Volume(from Step 2)dl vided by TRV(from Step 4a or Step 4b) <br /> rtatio= 640 � 3000 = 0.21 <br /> Step 6:Calculate Reduction Factor(RF). <br /> RF=lminus Ratb RF=1-0.�� = O.�v <br /> Step 7:Calculate single outdoor opening as if all combustion air is from ouuide. 40000 <br /> Total Btu/hr input of all Combustion Appliances in the same CAS Input: Btu/hr <br /> (EXCEPT DIRECT VEN� <br /> Combustion Air Opening Area(CAOA): <br /> Total Btu/hr d I vl d ed by 3000 Btu/hr per in: CAOA= 40000 /3ppp gtu/hr per in:_ �3.33 in� <br /> Step 8:Calculate Minimum CAOA. <br /> Minimum CAOA=CAOA mulNplied by RF Minimum CAOA= 1 J.33 x o.79 = 10.49 ��_ <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAOD=1.13 m uhipqed by the sq u a re root of Minimum CAOA CAOD=1.13�Minimum CAOA= 3.66 in.diameter go up one inch in size <br /> ff using flex duct <br /> 1 If desired,ACH can be determined using ASHRAE calculation or blower door test.Follow procedures in Sectfon <br /> G304. <br />