Laserfiche WebLink
Directions-The Minnesota Fuel Gas Code method to caiculate to size of a required combustion air opening,is called the Known Air <br /> InfiRration Rate Method.For�ew construction,4b of step 4 is required to be filled out. <br /> IFGC Appendix E,Worksheet E-1 <br /> Residential Combustion Air Calculatfon Method <br /> (for Furnace,Boiler,and/or Water Heater in the Same Space) <br /> Step 1:Complete vented combustion appliance information. <br /> Furnace/Boiler: 80000 <br /> raft Hood �an Assisted �irett Vent Input: Btu/h�or Power Vent <br /> water Heater: 40000 <br /> raft 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. �792 <br /> The CAS includes all spaces tonnected to one another by code comp►iant openings. CAS volume: ft3 <br /> LxWxH 16 l 14 W 8�H <br /> Step 3:Determine Air Changes per Hour(ACH)1 <br /> Default ACH values have been incorporated into Table E-i 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 VEIYT APPLIANCES) <br /> 4a.Standard Method <br /> Total Btu/hr input of a�l combustion appliances Input: Btu/hr <br /> Use Standard Method column in Table E-i to ftnd Total Required TRV: ft9 <br /> Volume(TRV) <br /> If CAS Volume(from Step 2)is pre a fe� th a n TRV then no outdoor openings are needed. <br /> If CAS Volume(from Step 2)1s ►ess th an TRV then go to STEP S. <br /> 4b.Known A(r lnfiltration Rate(KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANCES) <br /> Total Btu/hr input of all fan-assisted and power vent appliances Input: � Btu/hr <br /> Use Fan-Assisted Appliances column in Table E-1 to find RVFA: `�OOO � <br /> Required Yolume Fan Assisted(RVFA) <br /> Totai Btu/hr input of all Naturai dreR appliances Input: � Btu/hr <br /> Use Natural dreft Appliances column in Table E-1 to find RVNFA: � fta <br /> Required Volume Natural draft appliances{RVNDA) <br /> TotalRe uiredVolume RV =RVFA+RVNDA TRV= �OOO + � _ 300� TRVfts <br /> Step 5:Calculate the ratio of available intertor volume to the total required volume. <br /> Ratio=CAS Volume(from Step 2)dl vided by TRV(from Step 4a or Step 4b) <br /> Ratio= 1792 � 3000 = 0.60 <br /> Step 6:Calculate Reduction factor(RF). <br /> RF=lminus Ratio RF=1- O.�O = �.�0 <br /> Step 7:Calculate single outdoor opening as if all combustion afr is from outside. L�OOOO <br /> Total Btu/hr input of all Combustion Appliances in the same CAS Input: Btu/hr <br /> (EXCEPT DIRECT VENT) <br /> Gombustion Air Opening Area(CAOA): ,1 ��.�� <br /> Total Btu/hr d ivld ed by 3000 Btu/hr per in: CAOA= `f'OOOO /3ppp gtu/hr per inx= inz <br /> Step 8:Calculate Minimum CAOA. <br /> Minimum CAOA=CAOA multlpUed by RF Minimum CAOA= 13.33 x Q.40 = 5.37 ��� <br /> Step 9:Calculate Combustion Air Opening Diameter(CAOD) <br /> CAOD=1.13 m uk/plled by t he sq u o re root of Minimum CAOA CAOD=1.13 V Minimum CAOA= 2'62 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 Sectfon <br /> G304. <br />