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LOWER YOUR WATER HEATER'S
TEMPERATURE... AND SAVE SOME BUCKS!
Let the Natural Handyman take the mystery out
of adjusting your water heater
nothing like a hot shower to wash away the worries of the day. And despite
the proliferation of low-temperature detergents, hot or warm water really does
clean clothes better!
But you can have too much of a good thing. That storage tank in your
basement... the good old water heater... can be a real energy glutton. Lowering the temperature even a little can bring you big energy savings... from
3% to 5% for every 10 degrees!
Each type of water heater has a different adjustment method. The
descriptions below will apply to most heaters. If your water heater is
significantly different from the ones depicted here, we suggest you obtain a
manual from the manufacturer.
First things first...
test your water temperature
You don't need a special thermometer for this... a cooking thermometer will
work just fine! The gauge on the one shown at left starts at 130 degrees.
No brain surgery here... put the thermometer in a deep glass (keep the gauge
dry) and fill it with hot water direct from the tap. Be sure to run the water till it is
How hot should your hot water be?
According to the US Department of Energy, a temperature of 120 degrees at
is adequate for most household chores with a minimal danger of scalding and
maximal energy efficiency. However, that is the temperature at the tap,
not in the tank. Tank temperature should be no less than 130 degrees to
prevent bacterial growth, such as Legionnaires disease.
The only appliance that requires a hotter water is the dishwasher, with
a recommended temperature of 140 degrees or higher for proper disinfection and
cleaning. Since most dishwashers pre-heat the water to the proper
temperature, lowering the setting of your water heater will have no
effect. However, if you have turned the pre-heating function of your
dishwasher off, you should turn it back on!
Lowering the temperature too much can have unintended consequences. You
will need to use more heated water to obtain the same temperature at the faucet
or shower. Thus, if your tank currently gives your family three showers in
the morning, you might find the last person screaming!!
Adjusting tank-type electric water heaters...
The temperature of an tank-type electric water heater is controlled by a
thermostat. The thermostat has a visible scale and is adjustable by
turning the control to the desired temperature. The typical thermostat
control is adjusted by using a screwdriver. Remember...
the recommended minimum temperature is 130 degrees!
The thermostat is concealed behind a metal plate and may also be covered with
insulation. TURN OFF THE POWER BEFORE REMOVING THE PLATE. This is
important... there may be exposed high voltage wires under the cover.
IMPORTANT NOTE: Most electric water heaters have two
thermostats... one near the top of the tank and one near the bottom. It is
important that these both be adjusted to the same temperature. Otherwise,
one element may never go on causing premature wear to the other. Also, the
usable output of hot water or the time it takes to heat the tank may decrease...
depending on which thermostat is set higher!
GOING ON VACATION? Turn off the power to your water heater to save even
Adjusting gas water heaters...
Unlike electric water heaters, gas water heaters have one heat source and one
temperature control... near the bottom of the tank. Some gas water heaters
have an exposed thermostat control which can be set to the desired temperature
by rotating it. A few have the control concealed under a plate that can be
moved aside to make the adjustment.
GOING ON VACATION? Lowering the temperature will save energy and
money. Turning the water heater off will save even more.
if you don't want to or don't know how to relight the pilot light, don't turn
the heater off!
Adjusting oil water heater temperature...
Oil water heaters have a simple temperature adjustment knob located on the
side of the tank. If you haven't noticed this adjustment, add more
lighting in the basement!
About furnace-fired oil water heaters...
Many homes have oil-fired furnaces which double as tankless water heaters. No
separate tank is needed. There are some
obvious advantages to this arrangement. First, you only have one appliance to be concerned
with... the furnace. These integrated water heaters are very efficient and
produce a continuous supply of hot water without the heat loss associated with
nice as this "demand" system is, the picture isn't completely
rosey. Furnace-fired water heaters do not produce a large volume of hot
water per minute. Because of this inherent limitation, the outlet pipe is
only 1/2" as opposed to the typical 3/4" outlet pipe from a tank-type
water heater. If two hot water taps are opened at the same time, the
temperature drop is sudden and unforgiving. For example, if
you are in the shower and someone turns on the washing machine, you will be in
for a chilly surprise!
This problem can be solved, but it requires the addition of a supplemental
heating tank that provides additional storage capacity. Amtrol's
Hot WaterMate (at left) has an internal heat exchanger that uses your
furnace's hot water output to preheat water in the tank. By incorporating
a separate thermostat, you have precise control over the water temperature.
A second drawback is that the hot water temperature is the same as the furnace
temperature. The typical furnace temperature 140 to 160 degrees. At
these temperatures the
risk of severe scalding is high!
Though your first impulse might be to lower the temperature of the furnace,
DON'T! Lowering the temperature of the furnace will radically change the built-in
efficiency of your furnace and of your heating system as a whole.
Think about it… if you lower the temperature of the furnace, the
temperature of the water circulating through your radiators will likewise be
lowered. This will in turn increase the amount of time it will take for your
home to be
heated. All things being equal, it takes the same amount of oil to
keep your home at a certain temperature regardless of how hot the water is.
Therefore, your oil burner will have to cycle on and off more often to maintain
this lower temperature because it will take longer for the temperature to rise.
This will cause increased wear and tear on the furnace without any gain (or even
a loss) in efficiency. The most inefficient moment in your furnace's operation
is when it first starts up!
So instead of focusing on the furnace as the culprit, you can take measures
to lower the faucet hot water temperature AFTER it leaves the furnace.
This is done through the installation of a "mixing valve". A mixing
valve is a simple thermostatically-controlled mechanism that mixes a little cold
water with the hot water to lower the temperature. Mixing valves are adjustable
to produce the desired water temperature, but it is wise to use a thermometer to
verify the temperature at the tap. Installation does require some plumbing
skills such as pipe cutting and soldering, but the end result is worth it!
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