Tankless Electric Water Heaters,
The rest of the story
Tankless (aka instantaneous) water heaters are a hot topic
these days. Modern tankless water heaters incorporate computer
chips, an array of sensors and high-powered inputs. These
briefcase sized tankless units only heat when the hot water
tap is open. The water is heated very rapidly as it flows
through a heat exchange coil. The manufacturers of these units
are making claims about big savings from energy efficiency,
etc. “Why would anyone even consider an old-fashioned
tank type water heater these days?” Unfortunately, they
neglect to tell you the “down side” of the product.
Most Americans are unfamiliar with this type of equipment
and they might not be prepared to handle the special demands
of this complicated device.
Proper sizing is critical with tankless equipment. Tankless
water heaters are sized by flow rate as measured in gallons
per minute (GPM). Typically, a bathtub needs 4 GPM, showers
2.5 GPM, washing machines 3 GPM, dishwasher 3 GPM and each
sink 2 GPM. Flow rates from older faucets and showerheads
may be much higher. The size of unit needed is determined
from your highest demand for hot water at any one time. Because
tankless water heaters must heat water very fast, they have
limited capacity and have difficulty supplying multiple hot
water needs simultaneously. Adoption of this new technology
has been slow because busy American households often require
several hot water appliances to operate at the same time.
Want to run the dishwasher or wash machine while showering?
You may not be able to. If your demand is too great, a second
tankless unit may be required or an energy efficient storage
tank water heater may be a better solution. Also keep in mind
that northern climates, the incoming ground water temperature
is colder and tankless units are not recommended.
Water quality is also an important issue with tankless heaters.
The ads talk about long life, but in reality, unless the water
is very pure, few will have longevity. Because of the extremely
high temperatures needed to heat the water in the short trip
through the heat exchange unit, many minerals precipitate
out of the water and deposit on the coils of the unit shortening
its life. This applies to both gas and electric units. Most
warranties are voided if water hardness is too high, others
provide de-liming instructions when a warning light illuminates.
Moderately high dissolved solids (above 500 PPM) or moderately
low pH are also problems. You may also need to have your water
analyzed for carbon dioxide, chlorides, copper, iron and more.
Read the warranty and to be sure hard water is covered. Traditional
electric tank-type units are much more capable of handling
diverse water conditions across the country.
One of the issues that has implications for your utility
is the untimely load these units place on the system. Family
sized models require 240 volts and up to 150 amps
capacity to operate! This level of demand almost always exceeds
that of most residential service. In addition to the cost
of the heater, significant wiring upgrades are usually required
as well. Unfortunately, all of that demand (14 to 30kw) is
pure uncontrollable peak load. Residential
users also face the possibility of having to upgrade their
existing transformer.
These are not do-it-yourself installations and definitely
not fix-it yourself products. One major brand is sold and
serviced only by ‘factory-trained’ technicians
who carry 60+ page troubleshooting manuals and a treasure
trove of electronic meters, pressure meters and thermometers
due to the sensors and electronics aboard. Traditional electric
tank-type water heaters have only four (4) service parts made
up of only two (2) elements and two (2) thermostats. Service
calls are relatively easy and straightforward. Parts are a
lot cheaper than labor costs these days. Wonder what a service
diagnosis and an electronic circuit board on a tankless unit
costs? Can you even find a qualified technician to work on
one?
Tank-type water heaters are more ‘forgiving’.
The stored water acts like a buffer. This is how commercial
applications, like hotels, can service large groups of guests
who are taking showers at the same time. The same occurs in
your customers’ homes during family visits, holidays
and other times of high usage.
How about all those promised energy cost savings? True, these
microprocessor-controlled wonders do not loose much heat to
‘standby’ heat loss, however, unlike traditional
electric elements, their efficiency drops with scale buildup.
Their savings figures also come from comparisons to “low
end”, traditional steel heaters. A full size Marathon
water heater loses only about 5 degrees in 24 hours! Not much
more savings to squeeze out there!
Next time you hear someone wanting a tankless water heater,
tell them the “Rest Of The Story.” Twice the installed
cost of a Marathon water heater, more service (if you can
find it), short life, and no savings over a Marathon - some
deal! Wouldn’t you prefer a cost effective and hassle
free water heating, with a Lifetime Warranty Marathon. Better
for you and better for your utility. |
