Presentation on theme: "Proper Vent Sizing 4 Natural Draft Furnaces 4 Fan Assisted Furnace 4 Common Vent Systems."— Presentation transcript:
Proper Vent Sizing 4 Natural Draft Furnaces 4 Fan Assisted Furnace 4 Common Vent Systems
Natural Draft Furnaces 4 Note the furnace vent connector DIAMETER. 4 Note the furnace input BTU/H rating 4 Note the vent HEIGHT [vertical length] 4 Note the vent LATERAL [horizontal length]
Natural Draft Vent Chart Furnace Input Rating in Thousands of BTU Per Hour
Fan Assisted Furnace Chart Appliance Input Rating in Thousands of BTU Per Hour
Fan Assisted Furnace Chart 4 As the vent diameter increases in size, more heat is required to keep the vent dry. 4 Fan assisted appliances must keep the btu/h input rating between the fan minimum AND fan maximum. –If the btu input rating is less than the FAN MIN, condensation may occur. –If the btu input rating is more than the FAN MAX, the flu gas may backup and cause the vent to become pressurized.
Single Wall vs Double Wall 4 Single wall connectors permit greater heat loss. –Must restrict the use of single wall vent connectors due to rapid condensation development. –Building / vent damage will occur due to corrosive condensation.
Common Vent Systems 4 The installation of two or more gas appliances. –One the same floor level. –Are connected to one common vent system.
Common Vent Systems 4 Use the ‘common vented appliance tables.’ 4 Use the vent height measured from the taller appliance. –The taller appliance will have least total height. 4 Use the vertical height of the connector rise.
4 Common venting with a natural draft appliance is allowed. –Follow Min/Max range in the common vent connector table. –Use double wall for the ‘fan assisted’ appliance. 4 May use single wall vent for the natural draft appliance. –Must use double wall vent for the ‘common’ vent.
Common Vent Systems 4 The common vent uses the ‘common vent table’ –Must use NAT / FAN column when using Natural Draft combined with Fan Assist. –Must use FAN / FAN column when using Fan Assist combined with Fan Assist.
Common Vent Systems Combined Appliance input rating in thousands of btu/hour
Common Vent Systems 4 Vent tables take into account for two 90º elbows for the entire vent system –When more than two 90º elbows are used, the maximum capacity listed must be reduced by 10% for each additional elbow or equivalent. –Two 45º equal one elbow –Using 45º elbows instead of 90º is preferred Less restriction the better
Common Vent Systems 4 Always maintain 1/4” rise per foot of LATERIAL [horizontal] run-out. 4 Always maintain 75% less horizontal run- out of vertical height. 4 Terminate 2 feet higher than any structure with 10 feet of the vent.