Tankless Hot Water Heaters
~ Energy Efficiency ~
Hot Water - On Demand
In my quest
for
achieving not merely energy efficiency… but instead,
actually reducing energy
consumption, I have taken the next big step in trying to get my
combined monthly utility
bills below $50.
This is
something simple that everyone should do:
Install an on-demand hot water heater. Most American households
spend $10-$25
per/month in heating hot water. Virtually
all American homes have a hot water heater.
Typically, they come in sizes of 40 to
65
gallons. We spend
money on energy (utilities) to
keep all that water hot… all the time!
Why?
This would be akin to
putting a full tea kettle on the stove at medium heat, and then leaving
it on
day and night, forever, just in case we might want to make a cup of tea. This is insane, and of
course, none of us
would ever do such a thing. But
most of us
are in fact doing just such a thing.
We
waste energy 24-7-365 just trying to keep our 40+ gallons of water hot
all of the
time. This, too, is
just insane.
 The solution?
A
“tankless”, or “on-demand” hot
water system. This
is a pretty new technology for North
America. I
have been inspecting homes for years, and
have yet to see one of these units in operation in any of the homes I
inspect. However,
tankless systems have
been used in Europe and in Japan
for decades. The American concept of having 40 to 60 gallons
of hot water
ready at all times… just sitting around and consuming energy
24 hours a day is a
totally foreign concept to the Japanese and the Europeans. It made no sense to me
either, as to why I
should spend money to heat all that water, and spend even more money to
keep it
heated all the time… just in case I might want some hot
water for a few minutes
during the course of a day. So,
I
purchased a new all electric tankless on-demand unit for my home from a
German
company called Stiebel. It
took about 4
hours to install. It
sits on the wall
and is not much bigger than a shoe box.
The
cost was the same as for another traditional, 50 gallon water heater. So,
I removed the 50 gallon water tank I was
using… and now I have all that space freed up for use as a
closet that before,
had only room for 50 gallons of hot water. When I compare our
home electric bill last year (July 2007) against our home electric bill
for the same month this year (July 2008)... we went from 82.8 kilowatt
hours per day in July 2007 to only 54.6 kilowatt hours in July 2008.
In August, we went from using 60.1 kilowatt hours per day in
2007, to using only 51.4 kilowatt hours per day in August 2008.
By this one act: switching to a tankless system... we have
reduced our electric consumption by more than 30%. Now, we are spending
$20 less every month on our electric bill.
Our tankless
unit will pay for itself in less than two years.
Now, there is no requirement for hot water
while I am away from
home, so my new water heater heats no water at all, resulting in
immediate
energy savings. When
I am home, this
little wonder only heats water when I turn on the hot valve on a faucet
for a
shower etc… There is a considerable energy savings as there
is no longer a huge
hot water tank working 24 hours a day just to keep reservoir of hot
water. Output
varies with different models, ranging
from the very small units designed for just one sink or one dishwasher,
to the
much larger units designed for the entire house.
Mine is a whole house unit, and still is
not
much bigger than a shoe box. Fuel
savings (electric/propane/natural gas)
from my new on-demand system is estimated to be between 30% to 50% per
year (they can be 8% – 14% more
energy efficient
for homes that use a lot of hot water, "a lot" is 86 gallons or more
per day). And,
unlike my old water tank which could run
out of hot water… the supply of hot water in my tankless
system is endless,
with flow rates high enough to run a bathtub, two sinks, and a
dishwasher… all
at the same time, with whisper quiet operation.
This type of system is not be suited to
every American household. Homes
with large families who use their hot
water on and off all day long are generally not
satisfied with the tankless
systems. Using hot water continually throughout the
day would
negate any possible monetary savings realized by not having hot water
tank. Evaluate your own needs and consumption habits before
plunging into
purchasing this type of system. Some people have found the
need to add a
small hot water tank to make their system viable for their
use. Generally,
if nobody is home for much of the day, and nobody is awake for most of
the
night, then there is simply no need to spend money on energy to keep a
reservoir of hot water for roughly half of each day.
Most families in America
would find this system
ideally suited to their lifestyle and would enjoy a considerable energy
savings
with its use.
What
is a Tankless
Water Heater?
Tankless water heaters, also called “Instantaneous”
or “On-Demand”
water heaters, provide hot water only as it is needed.
The
traditional tank-type water heaters produce and store hot water all the
time which creates
standby energy losses that cost you money, all day, every day, all the
time.
How
do Tankless Water Heaters work?
Tankless water heaters heat water directly
without the use
of a storage tank. Therefore,
they avoid
the standby heat losses associated with the traditional tank type water
heaters. When a hot
water valve is turned on, cold
water travels through a pipe into the tankless unit. In
an electric tankless water heater (like the
one I installed in my home)
an electric element heats the water. In
a gas-fired tankless water heater a gas burner heats the water. As a result, tankless water
heaters deliver a
constant supply of hot water. How
many
times has someone in your home “used
all
the hot water”?
That no longer
happens with a tankless system. You
don't
need to wait for a large storage tank to fill up with enough hot water.
Tankless
systems make hot water for as long as
there is a demand (valve turned on). Typically, tankless water
heaters provide hot
water at a rate of between 2 to 5 gallons per minute. Typically,
gas-fired (propane or natural gas)
tankless water heaters will produce higher
flow rates than the electric tankless water heaters will. Some of the smaller tankless
systems cannot
supply enough hot water for simultaneous, multiple uses in large
households. For
example: taking a shower and running the
dishwasher at the same time can stretch a smaller tankless system to
its limit. To
overcome this problem, you can install
a “whole house” type tankless water heater or
install two or more tankless systems,
connected in parallel for simultaneous demands of hot water. You can also install
separate tankless water heaters
for appliances, such as a clothes washer or dishwater, as these can
consume a
large volume of hot water in a short time.
Selecting
a
Tankless
Water Heater
Before buying a
tankless water heater, you must consider the
following three things:
- Fuel
Type
- Location,
Size and Demand
- Application
1.
Fuel Type
The first thing that you'll need to
decide when selecting a tankless
water heater
is the fuel type. You
will need to select
between an electric tankless water heater or a gas fired unit that
operates on
propane or natural gas. Lets
discuss the
electric operated models first. In
my
home, I have no natural gas or propane, and the utility company does
not offer
such in my area. My
home is all electric,
so my choice was pretty well made for me. If you plan to
purchase an
Electric
Tankless Water Heater, you must consider the electrical
requirements of such a system. These
requirements are:
Voltage, Amperage,
and Circuit Breaker
Voltage:
Many of
the tankless system retailers sell units that will accommodate
110V,
120V,
208V, 220V, 240V, and 277V.
Amperage:
Different electric tankless
water heaters will have various requirements in amp draw.
You will
want to ensure that
your electrical
distribution panel (breaker box)
can
support the electrical demands of your electric tankless water heater.
Circuit Breaker:
You must ensure
that you have a circuit that will support your electric
tankless water
heater.
It may be
necessary to put your
electric tankless system on its own circuit.
You
should consult
with a qualified, licensed electrician
for more information.
If
you plan to purchase a gas-fired
tankless
water heater, one must consider these two things: the
Gas-Type and
the Venting Requirements. This is a bit more
complicated than
installing an electric system. If
you
are uncertain about any of these steps, it would be prudent to consult
with a
certified plumber or electrician:
Gas-Type:
You
will first need to identify whether your type of gas is natural gas or
propane.
It is
crucial that you examine your
current gas line to ensure that it will meet
the requirements of your
new gas-fired
tankless water heater.
The
requirements
of the tankless water heater may exceed that
of your existing
conventional tank-style
water heater.
Venting
Requirements:
Next,
you will need to consider the venting
requirements
for your specific installation scenario, since gas fired
systems
do require proper venting.
There
are a
few important things to keep in mind when purchasing
the gas venting
accessories for your gas-fired tankless water heater.
First, be sure
that you purchase only Category III
stainless steel (UL1738 certified) venting for your gas-fired tankless
water heater. "Type
B" venting accessories
are not acceptable. Also,
be sure to
check local building codes to ensure that your specific needs will be
completely
met.
Additionally, many
tankless water heater manufacturers
offer complete venting "kits". Customers
should evaluate the needs of their own
specific installation to ensure that they will be getting all of the
necessary
gas venting accessories. Depending
on
where you will be installing the tankless water heater, a pre-made kit
will
probably not meet all of your needs. Ensure
that you measure out the route your vent will take, and consider where
the
discharge will go through the wall or ceiling.
Then consider the necessary clearances
and also consider ample access to
air for combustion, only then purchasing the appropriate gas venting
pieces. *Note:
gas-fired tankless water heaters may
still require a minimal electrical connection. Be
sure to review your installation
requirements for the unit you are considering for purchase. Next for consideration:
2.
Location,
Size, and Demand
When deciding
which system to purchase, you will need to consider just
where
you will need the hot water. Are
you
looking for a system that will just heat the water at one bathroom sink
(called a single point application),
an
entire bathroom (called a multipoint
application), or an entire house, apartment, or condo (called a whole house application)? It is
very important to
recognize the number of fixtures that require hot water. Each fixture has its own
demands. The chart
below illustrates the typical flow
rates (demand) for some standard
fixtures:
Bathtub:
Flow rates average between 2 - 4 gallons
per minute
Shower:
Flow rates average between 1.5 - 3
gallons per minute
Kitchen Sink: Flow
rates average between 1 - 1.5
gallons
per minute
Laundry Sink: Flow rates
average between 2.5 - 3
gallons
per minute
Dishwasher: Flow
rates average between 1 - 3 gallons
per minute
The flow rate is
especially important, since tankless water heaters
generate a specific temperature rise based on the flow rate demanded. For example, a Stiebel
Tempra 12 model,
running on 240 Volt power, will raise the water temperature by
54°F above the
ambient incoming water temperature at 1.5 gpm, or it will raise the
water
temperature by 36°F above the ambient incoming water
temperature at 2.25 gpm,
and by 27°F above the ambient incoming water temperature at 3.0
gpm, up to a
high of about 125°F.
A larger unit, like the Stiebel Tempra 36
model, running on 240 Volt
power,
will raise the water temperature by 92°F at 1.5 gpm,
92°F at 2.25 gpm, and 82°F
at 3.0 gpm, above the ambient incoming water temperature, up to about
125°F.
This means that if you are using a 1.5 gpm shower and a 1.5 gpm kitchen
sink
simultaneously, a total demand of 3.0 gpm, the Stiebel Tempra 12 model
will
raise the temperature 27°F, whereas the Stiebel Tempra 36 model
will raise the
temperature 82°F.
Next, you should look at your incoming water
temperature. If you
live in a colder
climate like Idaho
or Ohio, your
incoming water temperature will likely be much lower than if you live
in a warmer
climate like Oklahoma
or New
Mexico. Your
best bet is to find out how much
temperature rise you will need in order for your hot water to reach the
desired
heat. For example: if the normal incoming
water temperature for
your shower is 65°F, and you are using a 2.0 gpm shower, and
you want to raise
that temperature to 115°F, you will want to look for a Tankless
Water Heater
that will provide at least a 50°F temperature rise at 2.0 gpm
(115°F - 65°F =
50°F). However,
if you anticipate
additional simultaneous demand, such as the hot water from the
dishwasher being
used while someone is showering, you will need to add the
dishwasher’s gpm to
the shower's gpm in order to determine your overall gpm demand and then
find
the temperature rise necessary to meet your overall needs. All this may seem
complicated… but it is not
really hard if you take a notepad and tackle one paragraph at a time. And now, for the final
consideration:
3.
Application
You may have a specific application or
purpose in mind for your
tankless water
heater. Here are a few examples of the different models and their
functionality
for a specific application:
Single Point Application
A single point application is one where only one fixture,
such as a
dishwasher
or a shower, will require a tankless water heater.
These
units can be quite small. Some
of them are about the size of a shoe.
Multi Point Application
The "Flow Controlled" range of water heaters from Eemax are ideally
suited to serve two points, like two sinks in close proximity. Eemax Series Two units are
ideally suited for
residential showers, entire bathrooms, smaller houses, condos, summer
cabins
and apartments.
Whole House Indoor Use
Larger Whole House units are designed to serve an entire house,
apartment,
condo, or cabin, where multiple points of use will exist. This is what I purchased for
my own home,
and
is about the size of a shoe box.
Tankless
Water Heater
Installation and Maintenance
Proper installation
and maintenance of your tankless water heater
can optimize its energy efficiency. Proper
installation depends on many factors. These
factors include your climate as well as your local building code
requirements. You
should have a qualified, licensed plumbing
and heating contractor install your tankless water heater. Be sure your contractor
first consults the
manufacturer’s installation instructions.
Manufacturers usually provide the
necessary installation and instruction
manuals with the product. Your
contractor should also contact your municipality for information about
obtaining a permit, if necessary, and also about any state or local
water
heater installation codes.
Many tankless water heaters have a life expectancy of more than 20 - 25
years. They also
have easily replaceable parts that
extend their life by many more years. In
contrast, the traditional storage tank water heaters last only 10 - 15
years.
Periodic water heater maintenance can significantly extend your
tankless water
heater's life and minimize any reduction of its incredible efficiency. Read your owner's manual for
specific
maintenance recommendations.
Tankless
Water Heater Manufacturers
There are many
manufacturers of tankless water heaters,,,,,,,,,,:
Eemax, Stiebel, Chronomite, Rheem, and Bosch just to name a few.
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• PO Box 4296 Boise, ID 83711 • 208.781.0605
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