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.

Venting furnace and water heater together.

When installed correctly this venting arrangement works with an 80 gas furnace or lower than 80 gas water heater. Lowering the btu rating of the furnace by even half would not require a change in the size of venting. The solution is to use the masonry chimney as a chase for a b 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.

This practice is common with standard efficiency 80 furnaces. 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. In those cases the cold masonry cools the exhaust gases causing loss of draft as well as moisture condensation. The duct may be metal or plastic depending on the type of vent system.

I would venture to say that the vast majority of installs in this area use 6 b vent for a combination furnace water heater. A direct vent system pulls in. Another potential problem with newer category i vents involves furnace and water heater flues that are connected to masonry chimneys. Take a look at the two pics then.

Two appliances connected into single vent. They are connected at the wye. The water heater vent is located below the furnace vent at the wye. The furnace is induced draft the water heater natural.

6 flue 28 27 square inches 8 flue 50 27 square inches total 78 54 square inches. All water heater venting systems use a vent duct or pipe also called a chimney or flue to bring exhaust gases from the water heater to the outdoors. Let s say you have a job where you combine a furnace or boiler 8 flue with a water heater 6 flue.