Tankless water
heaters
also called instantaneous, inline,
on-demand or instant-on water heaters, are gaining in popularity.
These water heaters heat the water as the water flows through the
device, and do not retain any water internally except for what is in
the Heat Exchanger Coil.
A Tankless
Water Heater may be installed at the faucet or in your
bathroom far from the central water heater or larger (whole house)
models can be used to provide all the hot water requirements for an
entire house.
Tankless
water heaters can be broken down into two categories; "full
on/full off" and "modulated". Full on/full off units do not change the
power output at all. |
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| The unit is
either on or off. Modulated tankless water heaters base the BTU output
on the flow of water running through the unit. This is usually done
through the use of a 'flow sensor', modulating gas valve, inlet water
temperature sensor and a outlet water temperature sensor/choke valve
and means that you will receive the same output temperature of water
at differing velocities.
Usually within a close range of +/- 2
degrees Tankless water heaters can be far more efficient than storage
water heaters. In both kinds of installation, the absence of a tank
saves energy as conventional water heaters have to reheat the water in
the tank as it cools off (called standby loss). With a central water
heater of any type, water is wasted waiting for water to heat up
because of the cold water in the pipes between the faucet and the
water heater.
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Point of use
tankless water heaters
are located right where the water is
being used, so the water is almost instantly hot, which saves water.
They also save even more energy than centrally installed tankless
water heaters because no hot water is left in the pipes after the
water is shut off. However, point of use tankless water heaters are
usually used in combination with a central water heater since they are
usually limited to under 1.5 GPM, as the expense of buying a heater
for every kitchen, laundry room, bathroom or sink, often outweighs the
money saved in water and energy bills. In addition, point of use water
heaters until recently were almost always electrical, and electricity
is far more expensive than propane and natural gas.
Under current US conditions, the most cost effective configuration
from an operating viewpoint is usually to use a
central tankless water heater for the most of the house,
and install a point of use tankless water heater at any distant
faucets or bathrooms. However, this may vary according to how much
electricity, gas and water costs in the area, the layout of the house,
and how much hot water is used.
Only electric
tankless water heaters were available at first and they are
still used for almost all point of use heaters, but natural gas and
propane heaters are now common. When considering a whole house gas
tankless unit remember the unit functions on a 75-77F rise in water
temperature so if you live in a cold weather climate look at the
unit's capacity with 38-50F inlet water temperatures.
Through 2007 tankless water heaters of
80%+ efficiency carry and Energy Tax Credit of $300.00. Common,
reputable Mfrs for gas are Takagi, Noritz, Bosch and Rinnai.
Electrical units are good from Steibel, Eemax, Seisco.
(Source: Wikipedia)
A Tankless Water
Heater requires a skilled, knowledgeable installers.
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