What is a Conventional Storage Direct Vent Water Heater?

Conventional storage direct vent water heaters are still the most popular of all the water heater types.  These water heaters heat water before you need it, and store it in a tank.  This is unlike the on demand/instantaneous/tankless water heaters that produce water as it is needed.

These types of water heaters have been around for many years and come in a variety of sizes, measured in gallons.  Smaller homes and mobile homes may only have a 20 gallon water heater, where mid to larger size homes that require more hot water may have tanks that range from 40-120 gallons or more.  For businesses and commercial applications, the size of the hot water storage tank can be much larger with sizes of up to 10000 gallons.

conventional direct vent water heater

Gas Fired Conventional Water Heater -- DOE's Office of Energy Efficiency and Renewable Energy

The majority of homes currently utilize some type of conventional storage type water heater.  In this type of heater,  water is heated and stored within the tank for later use.   When hot water is needed, it travels out the top of the storage tank and to wherever it’s needed in the home.  Cold water is fed into the bottom of the tank to replace the hot water that was removed, and it is then heated via the burner to the desired temperature.

As can be seen from the diagram above, the exhaust gases from the burner are directed up through the flue where they leave the hot water heater, and are vented directly to the outside.

What isn’t show in that diagram is that the combustion air for the burner is brought in through the same vent and fed directly to the burner.  This has the added benefit of preheating the combustion air, which in turn raises the combustion efficiency which in turn helps to lower the energy costs.

There are few differences in conventional storage direct vent water heaters.  Most notably are the types of fuel used to fire the burner.   Natural gas and propane are two of the most common fuel choices.  Fuel oil is also a possibility, and a good choice for those in the northeast, or wherever natural gas isn’t readily available.

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