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What is the difference between a regular water heater and a power vent water heater?
Friday, August 17, 2018
The most common gas water heater is technically called an “atmospheric vent” type. Because warm air rises, the hot gases created by combustion are pulled by natural convection up a vertical metal flue through the roof to the outside. It’s a tried-and-true, simple system, that does not require electric power or moving parts.
But what if the location of a water heater makes it impossible to run a vent through the roof? Then a power vent water heater is the solution. It uses an electric blower to push the combustion gases, along with added air to cool the exhaust down, through PVC pipe to an exterior wall or soffit that can be be dozens of feet away.
There are both advantages and disadvantages to choosing a power vent hot water heater:
• Can be installed almost anywhere in a home, but best located outside the conditioned living area.
• Exhaust vent can be run horizontally for a long distance.
- Often less expensive to install for new construction, because the vent can run horizontally and terminate at an exterior wall, it does not require flashing of a roof penetration, and PVC pipe is cheaper and easier to install than metal vent pipe.
- Costs at least 50% more than a regular water heater.
Requires more “make up” air (the air added to the exhaust flow).
The sound of the exhaust fan may be noticeable if near or in a living area.
120-volt power (regular wall outlet) must be nearby for fan.
Needs more maintenance because it has a motor and moving parts.
A power vent water heater is recognizable by the rounded blower fan housing at the top of the tank connected to PVC pipe, like in the photo above, and below is the vent termination at a side wall. This particular water heater has more pipes connected to it than usual because it is part of a hydronic heating system—the hot water it produces is also used to heat the home. To learn more about hydronic heating, go to our blog “How does a hydronic heating system work?”
There are also direct vent water heaters available, which utilize a sealed system that draws air for combustion from the exterior of a home. Learn more at our blog “What is the difference between a regular water heater and a direct vent water heater?”
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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
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