Hot Water Heater, The Basics
The average hot water heater accounts for 25% of the home's total energy use.
With rising energy prices, it just makes sense to learn a little more about these units. There are
various types available but the most common is the storage type water heater. This is where a tank of
water is heated by a built in burner or electric element to a set temperature and maintained at that
temperature until hot water is required at a tap.
These units have an energy efficiency rating that is referred to as the energy
factor (EF). This is a relative rating of the efficiency and ranges from about .5 to 1.0. In simple
terms, the higher the EF the less it will cost to operate.
Another rating of these units is their first hour rating. This is a measure of
how much hot water the unit can provide in the first hour you turn it on. It takes into account the
amount of water stored and how fast it can heat it.
A hot water heater is also rated according to its storage capacity. This is the
number of gallons of water the units can hold.
Standard units can use gas, electric, oil, geothermal, or the sun to heat the
water. The energy source you choose should be based on the price and availability of the energy source
as well as up front cost.
They all operate in the same basic way. A thermostat senses the temperature of
the water inside the tank. It turns the fuel on and off as required to maintain a set temperature. That
temperature is adjustable to suit the tastes of the customer.
These units have some added components for safety and to make them last longer.
First, they have a safety feature that is called a temperature/pressure relief valve. This is a valve
that opens to relieve the pressure in the tank in case of a malfunction. The outlet of the valve is
piped down to within a few inches of the floor. This is to prevent injury and damage if the valve opens.
The water released when the valve opens will be extremely hot and may flash to steam.
Another safety feature that has been implemented in the United States is called
flammable vapor ignition resistant (FVIR) technology. This is basically design features that are
integrated into a hot water heater to prevent flammable vapors such as gasoline in a garage from
entering the unit and igniting. The technology usually includes three parts. The first part is called
the flame arrestor plate and allows combustion air to enter the unit while preventing flames from
escaping downward and igniting vapors. The second part is typically called a thermal cutoff switch. This
is a temperature sensor located near the burner that opens to shut the gas off. This will usually occur
when adequate combustion air is not available. this will cause the burner flames to droop and the cutout
to open. The final part is usually a LDO screen. This is basically an air filter that is installed to
prevent the combustion air openings from becoming clogged by lint, dust, and oil.
**HOT TIP** If your unit has this feature, the screen will require periodical
Most storage units have what is called a sacrificial anode. This is a metal rod
that is suspended in the tank. Minerals that are naturally in the water interact with metal and can eat
away the metal. This anode provides a place for the reaction to occur without damaging the tank.
One big disadvantage of this type of hot water heater is that, as the tank of
water sits in your home, it cools off. This is referred to as stand by heat loss. Then the heater has to
turn on to heat the water back to temperature. This wastes energy dollars!
If the insulation value on your tank is less than R-24, it is a good idea to
install a water heater blanket. This will help to minimize the standby losses and therefore save you
money. Water heater blankets are available in many stores or you can even make your own. If you purchase
one, get one with at least an R-8 insulation rating.
If you have an electric unit, you can also install a timer that will help to
lower the standby losses. The timer is set to only maintain the water temperature at specific times
during the day. They are available at many hardware and home improvement stores for less than $50. The
timers can save you 5-10% on your water heating costs which will pay for the timer very quickly.
You can increase the efficiency of your water heating system by adding a solar water
heater or a drain water heat recovery