Building Permit Application - Laserfiche WebLink

Home Browse Search

Directions-The Minnesota Fuel Gas Code method to calculate to size of a required combustion air opening,is called the Known Air Infiltration Rate Method.For new construction,4b of step 4 is required to be filled out. IFGC Appendix E,Worksheet E-1 Residential Combustion Air Calculation Method (for Furnace,Boiler,and/or Water Heater in the Same Space) Step 1:Complete vented combustion appliance information. Furnace/Boiler: $DODO raft Hood Dan Assisted i� rirect Vent Input: Btu/hr or Power Vent Water Heater: 40000 raft Hood Z Fan Assisted Direct Vent Input: Btu/hr or Power Vent Step 2:Calculate the volume of the Combustion Appliance Space(CAS)containing combustion appliances. The CAS includes all spaces connected to one another by code compliant openings. CAS volume: 640 ft3 LXWXH ®L 10 W8JH Step 3:Determine Air Changes per Hour(ACH)1 Default 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 method 4a(Standard Method). Step 4:Determine Required Volume for Combustion Air.(DO NOT COUNT DIRECT VENT APPLIANCES) 4a.Standard Method Total Btu/hr input of all combustion appliances Input: Btu/hr Use Standard Method column in Table E-1 to find Total Required TRV: ft3 Volume(TRV) If CAS Volume(from Step 2)is gre a ter th a n TRV then no outdoor openings are needed. If CAS Volume(from Step 2)is less than TRV then go to STEP 5. 4b.Known Air Infiltration Rate(KAIR)Method(DO NOT COUNT DIRECT VENT APPLIANCES) Total Btu/hr input of all fan-assisted and power vent appliances Input: 400000 Btu/hr Use Fan-Assisted Appliances column in Table E-1 to find RVFA: 3000 ft3 Required Volume Fan Assisted(RVFA) Total Btu/hr input of all Natural draft appliances Input: 0 Btu/hr Use Natural draft Appliances column in Table E-1 to find RVNFA: 0 ft3 Required Volume Natural draft appliances(RVNDA) Total Required Volume TRV =RVFA+RVNDA TRV= 3000 + 0 3000 TRV ft3 Step 5:Calculate the ratio of available interior volume to the total required volume. Ratio=CAS Volume(from Step 2)divided by TRV(from Step 4a or Step 4b) Ratio= 640 / 3000 = 0.21 Step 6:Calculate Reduction Factor(RF). RF=lminus Ratio RF=1- 0.21 — 0.79 Step 7:Calculate single outdoor opening as if all combustion air is from outside. 40000 Total Btu/hr input of all Combustion Appliances in the same CAS Input: Btu/hr (EXCEPT DIRECT VENT) Combustion Air Opening Area(CAOA): Total Btu/hr di vi d ed by 3000 Btu/hr per inz CAOA= 40000 /3000 Btu/hr per inz= 13.33 int Step 8:Calculate Minimum CAOA. Minimum CAOA=CAOA multiplied by RF Minimum CAOA= 13.33 x 0.79 = 10.49 in, Step 9:Calculate Combustion Air Opening Diameter(CAOD) CAOD=1.13 m ultiplied by the square root of Minimum CAOA CAOD=1.13 V Minimum CAOA= 3.65 in.diameter go up one inch in size if using flex duct 1 If desired,ACH can be determined using ASHRAE calculation or blower door test.Follow procedures in Section G304.