Venting Furnace And Water Heater Together

Another potential problem with newer category i vents involves furnace and water heater flues that are connected to masonry chimneys.

Venting furnace and water heater together.

I know that irc g2427 3 3 4 allows these two appliances to join into a common vent connector. Two appliances connected into single vent. This practice is common with standard efficiency 80 furnaces. 6 flue 28 27 square inches 8 flue 50 27 square inches total 78 54 square inches.

Let s say you have a job where you combine a furnace or boiler 8 flue with a water heater 6 flue. Lowering the btu rating of the furnace by even half would not require a change in the size of venting. They are connected at the wye. The water heater vent is located below the furnace vent at the wye.

I would venture to say that the vast majority of installs in this area use 6 b vent for a combination furnace water heater. Many homes are built with the water heater and furnace sharing the same combustion gases exhaust vent. If you re replacing natural draft furnace no motor assistance for exhaust gases removal with an induced forced draft motor equipped appliance and your natural draft water heater remains connected to the same chimney flue pipe make sure that water heater vent pipe connection is y and not t type. The solution is to use the masonry chimney as a chase for a b vent.

Water heater ducts may lead directly outdoors or they may tie into a larger vent duct that also serves a gas or propane furnace or boiler in the home. Take a look at the two pics then. The duct may be metal or plastic depending on the type of vent system. In those cases the cold masonry cools the exhaust gases causing loss of draft as well as moisture condensation.

The difference is that a power vent water heater pulls in combustion air from the space around the appliance then uses a fan to propel the exhaust through the vent. To determine the main flue size refer to figure 3 and locate the square inch area of each individual flue size. When installed correctly this venting arrangement works with an 80 gas furnace or lower than 80 gas water heater.