REVOLUTIONARY
WATER HEATING TECHNOLOGY
FOR THE 21ST
CENTURY
It is no wonder that humans have
recognized the soothing, therapeutic benefits of a warm bath since the
beginning of time, considering that it is from this very environment that
we each begin life. Whether a primordial cause or simply an instinct,
all mammals gravitate towards the relaxing environment provided by warm
water. However, humans are the only species that have learned to provide
themselves with the means for enjoying these benefits at will.
The Challenge to SEISCO
and all mankind is to produce this hot water comfort in the very best
way. The road to ultimate hot-water comfort has been lined with many attempts
at improvement, including channeling hot springs, heating tanks of water,
and heating water instantaneously. All have been precursor to what now
is proving to become the water heating system of the 21st century,
the SEISCO Continuous Hot-Water Heating System.
- A BRIEF HISTORY OF WATER
HEATING
Hot Springs
The earliest families enjoyed warm baths in rare, but valued, natural
hot springs. As civilizations advanced, so did mankind’s development
of the technology for providing hot water wherever families lived.
Hot Water in the Victorian Age
At first, people heated water in vessels. Later, the affluent used gas-fired,
coil-type, "flow-through" water heaters to heat the water in
their Victorian homes. These heaters consisted of copper water pipe formed
in a coil which acted as a heat exchanger and a gas burner. After a hot
water fixture was opened, the gas burner would then be lit, heating water
as it flowed through the coil. Unfortunately, this type of heater had
no water temperature control. Instead the ultimate output temperature
depended upon the heating capacity of the burner size and the volume of
water sent through the coil. It was critical to maintain enough water
flowing through the heater, while the heater was in operation, in order
to avoid dangerously overheating it. Since this system provided a constant
heating capacity, the ultimate ability of the system to provide the desired
water temperature depended upon both the temperature of the incoming water
as well as the volume or flow rate.
The Beginnings of the Hot Water
Tank
Later, with the introduction of public, pressurized, water systems
came fixtures such as showerheads and spray faucets, which produced increasingly
higher, flow rates of water. With the higher flow fixtures also came a
higher demand for hot water and the need for a better way of heating water.
The danger involved with improper venting of the earlier gas "flow-through"
water heater limited heating capacity design. At high water flow rates,
the user often could not achieve sufficient heating for the water to accommodate
a single shower. These conditions gave rise to innovation that led to
the development of storage-tank water heaters.
During the l920’s, some of the earliest of the storage-tank water
heaters in the U.S. were actually a combination of the "flow-through"
heat exchanger with a holding tank for storage. One such device built
by the "Holyoke Heater Company" and fueled it with kerosene.
Electric Tank Water Heaters
After Westinghouse introduced the alternating current to the U.S.,
water heaters began consisting of an insulated tank and a heating source
that was either electricity or gas. The heating source, either electric
immersion elements or gas burner, heated the water until the water temperature
in the tank rose high enough to trip an automatic resetting thermostat.
When tripped, the thermostat would turn off the heat source. As hot water
was drawn out of the tank during use, the water temperature dropped below
the thermostat setting. At a preset temperature, the thermostat would
reset, activating the heating source to heat the new water. Over the past
70 years few changes have be made to either storage-tank or tankless water
heaters–that is until SEISCO.
- BENEFITS DERIVED FROM SEISCO’S IMPROVED TANKLESS WATER HEATING
TECHNOLOGY
Considering the long, distinguished history of storage-tank heaters,
a suitable question is why try and develop an improved "flow-through"
water heater that has no tank? With all the water heating technologies
today including solar, heat recovery, and heat pump water heaters, why
bother trying SEISCO?
Before going any further with the discussion of the SEISCO System,
let us use the following passages to address these questions of "why".
Ultra High Energy Efficiency
Not now, or ever, will an electric storage-tank water-heater equal
the 99+% efficiency of the tankless SEISCO. This is because the inherent
design of storage-tanks limits how well the tank can be insulated to reduce
heat (energy) loss when it is not in use. Contrarily, when the SEISCO
is not in use it shuts off.
A Lifestyle of Continuous Hot Water
Consider the value of being able to fill large spa tubs–which
are becoming increasingly more common in new homes–keeping the water
hot for as long as you wish to bathe, while knowing that you will have
hot water to shower and rinse off even after your bath is finished.
Consider the value of continuous hot water to a working mother, arriving
home around six p.m., who will be able to do load after load of wash,
while simultaneously preparing dinner or watching TV. She no longer needs
to worry about having hot water for her family’s night time showers.
Consider also, the value to the entire family, teenagers, visiting
friends or grandchildren, who all will be able to bathe and shower, getting
ready as fast as they can with out a thought of using up all the hot water.
It is hard to completely measure the lifestyle benefits of having a source
for endless hot water, on demand, for as long as you need it.
Safety
Issue 1. Thousands of people each year suffer serious injury
or death, from fire, explosions, and severe scalding from storage-tank
water heaters. All too often, the ones who suffer are the ones with the
least defense: the very young and the disabled. Ponder the value of providing
a water heating system that virtually eliminates the potential for explosion,
scalding and water damage?
Issue 2. Annually, thousands of people are injured, some very
seriously, while attempting to install or remove heavy, tank water heaters
from basement or attic locations. Consider the relief of a system that
provides more benefits than a heavy, tank water heater, but weighs only
20 lbs. and can be carried by most single-handedly.
Environment
Issue 1. What’s the value of an electrical water
heating system that is competitive to the cost of heating water by gas?
For decades we have been concerned about the impact of air quality resulting
from burning fossil fuels. Stringent requirements have been placed on
emissions from automobiles and major plants burning fossil fuels. We ignore
the fact, however, that an estimated 60 million gas water heaters, in
the U.S. today, are pumping out carbon monoxide, carbon dioxide, and unburned
residues hourly from each of their 3-inch diameter vents. When one tries
to envision the size of a hole equal to 60 million 3-inch holes, the size
becomes overwhelming.
Which is cleaner, the emissions from gas water heaters in our home
or those that come from the stack of a gas fired electric generating plant?
Unfortunately, we’ve accepted hazards resulting from the residential
burning of fossil fuel, not because it is more efficient, but because
it has been CHEAPER. SEISCO provides cheap heat without including excessive
emissions.
Issue 2. What’s it worth to produce an alternative water
heating system that could reduce the enormous volume of landfill space
currently occupied by old tank heaters? Each year we dispose of over 7,000,000
worn out storage-tank water heaters into landfills. Because of its small
size, the SEISCO reduces this disposal requirement by a factor of approximately
10. In addition, the SEISCO system is at least 85% recyclable. Finally,
the SEISCO system can last two to three times longer than the normal storage-tank
heaters of today, reducing the frequency of water heater disposal. The
use of SEISCO can significantly reduce landfill waste and harmful gas
heater emissions.
Design Options
What’s it worth to a homeowner, architect or builder to be able
to do away with the concern about where to put the bulky, ugly, storage-tank
water heater?
What about the homeowners who,
because of limitations to their existing electrical service, can’t
replace their existing water heater with a tankless electric system like
the SEISCO? It’s worth a great deal to these homeowners to be able
to convert their existing water heating system to a system of endless
hot water. They can now do so by simply installing a smaller "Extender"
model of SEISCO in line with a "tank type" water heater? They
no longer need to add a second or larger "tank" heater, wasting
energy cooking water when the extra hot water isn’t needed.
This arrangement also satisfies the customer who asks what do I do
for hot water if the electricity goes off? One can simply buy the smallest
storage-tank gas water heater available and add a SEISCO "Extender"
model in line with it.
Systems and Maintenance Cost Reduction
What would a flow-through tankless
hot water heater be worth, whose size was only slightly larger than a
brief case, yet had the capacity, in a single heater, to take care of
four hotel rooms or eight hospital rooms? Consider the value of a system
that only uses energy when hot water is actually being used. How about
the hospital, hotel or resort condominium in which there no longer exists
the need to install a two pipe re-circulating system pumping hot water
24 hours a day to rooms at times when the occupants obviously do not need
hot water, or that aren’t even occupied? What does it mean to eliminate
the need to purchase and maintain a very expensive boiler system, which
requires expensive specially trained people just to do the maintenance?
What’s the space alone worth to these types of buildings, or for
that matter, to the local fast food restaurant, beauty/barber shop, retail
space, medical office building and many, many more business and commercial
applications?
An Intelligent Appliance for the New Millennium
What would it be worth to have a water heating system that periodically
checks itself and provides a full diagnostic code with visual flashing
LED lights, digital sound alerts or a numerical readout. All of which
provide you with information of failing elements long before they actually
failed?
What if that same water heater could detect leaks, and when it did,
not only turns off the power to its heating elements, but also turns off
the water supply, protecting your home from electrical AND water damage?
Enabling Technology for Passive
Systems
The SEISCO provides all these benefits and more. There are endless
additional reasons for a SEISCO improved water heating system including
the following:
A fully automatic "flow-through" water heater such as the
SEISCO not only increases the efficiency of, but also acts as an enabling
technology to passive hot water systems, such as solar, heat pump, and
heat recovery. Most passive water heating systems require a back up water
heater.
Normally, to insure an adequate supply of hot water, storage-tank
heaters are used to back up these systems. The passive system, in conjunction
with the tank heater, produces the initial tank full of hot water. As
this hot water is being drawn off in use, the water temperature will drop
since the passive system cannot heat the flow of incoming cold water fast
enough. Once the water temperature has dropped below the tank heater’s
preset thermostat setting, say 130° F,
the storage-tank’s heating source, electric or gas, is activated.
This causes the back up electric or gas heat source to heat up the total
volume of water in the tank and not just the water that had been used.
This design actually defeats, in part, the efficiency and cost effectiveness
of the passive system. Since the total volume of stored water is generally
heated by the back up, the passive system is deprived the opportunity
to fully reheat the water.
The SEISCO works much more efficiently in combination with the passive
system’s storage tank because it allows the passive system to do
what it was designed to do, to reheat the water in the tank. This can
be accomplished by first, installing a SEISCO in line down stream from
the storage tank and second, by simply disconnecting the elements on the
storage tank from the power supply.
The SEISCO will only be activated after the water temperature drops
below a predetermined set point, say 115°
F, then heating ONLY the water actually used, and only for the temperature
difference required. For instance, if 10 to 20 gallons of heated water
were actually used from the storage tank, then the SEISCO may only be
required to raise the temperature of this water by just 10 or 20 degrees.
The passive system would thus be allowed the opportunity to provide
all, and not just part, of the heat required to reheat the balance of
the water in the tank.
In addition, the SEISCO not only improves the overall efficiency
and cost effectiveness of the passive system, it insures an endless and
continuous supply of hot water whether the passive system is providing
heat or not.
- REASONS others have failed to successfully produce and market a
tankless water heater
Insufficient Residential Electrical
Service
Until recently, homes have not had sufficient electrical service to
make tankless water heaters practical, a first requirement for the electric
"flow through" water heating system. The electric "flow-through"
heater can draw as much power (current/amps, not kWh*), for the short
time it is used, as does the space heater for the house, when it is being
used.
Most homes until recently were provided with minimal electrical service
(your home’s electric panel) most often rated at 100-125 amps. In
a retrofit situation, there is often not sufficient service to provide
for a whole house "flow-through" electric water heating system,
except in areas that enjoy relatively warm water year round.
Today, with so many new appliances and electric technologies, including
the heat pump, electrical services have steadily increased for new homes.
It is now very common for the builder to install 150-200+ amp services.
Now, even manufactured homes are using the Seisco whole house electric
"flow through" water heating system.
Lack of Adequate Devices to Control the Required Power
The technology for properly controlling the power supply to a whole-house
water heating system hasn’t existed in "flow through" water
heaters until the SEISCO. The reasons are covered in detail in the following
sections.
* Remember in residential services, you pay for kilowatt-hours
not amps. To use kilowatt-hours you have to use kilowatts (power) for
hours. The very thing you don’t do with an electric "flow-through"
water heating system as it is on only when you use it and off the rest
of the time.
IV. PAST DEFICIENCIES OF TANKLESS
WATER HEATERS
Because of very high-energy costs and limited water supply, most
of the world, other than the U.S., uses some form of the flow-through
water heater, now referred to as a tankless water heater. The electric
versions of these tankless water heaters are often very rudimentary, consisting
only of a heating element inserted in a pipe or tube in the water flow.
They are activated either automatically by a flow switch, or manually
with an external switch. Typically, these versions are used at the "point
of use" (near the sink or shower), thus reducing water wasted running
out the fixture, waiting for the delivery of hot water. In many homes
in the world, even today, the only hot water available in the whole house
is provided in the bathroom by this type of tankless water heater for
showers or warm baths.
Primitive Temperature Control
Until the 1970’s, most tankless water heaters’ only
means of temperature control was a thermostat located in the flow of water
within the device. This type of control is slow to respond, often allowing
the water to be heated dangerously hot before the thermostat trips and
shuts off the supply of heat. For this reason, the design of the heating
capacity for these type heaters is limited to a heating capacity (BTU
output- power) that is generally safe for the nominal flow rates of water
typically experienced at the faucet or shower. In addition to the limitations
for heating capacity, the heaters utilize a flow switch that will not
allow the heater to turn on until a minimum flow of water is achieved.
This design is a further attempt to prevent overheating the water, reducing
the potential for dangerous scalding. These tankless heaters are referred
to as "fixed input" heaters because when activated, they turn
on at their full heating capacity and remain at that level unless turned
off by the thermostat or the flow switch. The absence of suitable temperature
and power control for the electric tankless water heater have, prior to
the Seisco, greatly reduced its suitability for residential, whole house,
use.
Temperature Control Improves Slightly
Redesign efforts in the ‘70’s introduced new technology
that attempted to better control the power to the heating elements for
electric tankless water heaters. These controls used temperature
comparisons for determining the required power level, instead of the old
and slow thermostat. The heating elements would be turned "on"
or "off" depending upon the difference in the water temperature
measured at different locations within the water heater, using the outlet
temperature as the principal controlling reference-temperature.
The purpose of these control schemes was to provide a more rapid response
to turning on, turning off or varying the power input to the heating elements.
These control schemes were essentially based on the same type control
theory that is utilized in electric ovens. As the temperature increases,
the power is reduced or cycled in order to attempt to maintain a fixed
water temperature. This type control works well when the flow rate is
constant and the speed of heating is relatively slow. The water is heated
at a rate slow enough , by design, to avoid over-temperature and then
maintained at a steady flow rate.
- THE
CURRENT DEFIENCIES OF OTHER TANKLESS WATER HEATERS
The current deficiencies experienced in most electric tankless
heaters today are outlined in the subsequent passages.
Inadequate Control Technology–Application
Dynamics Require Highly Responsive, Power Controls
Water heaters or ovens typically use commodity type temperature
sensors. These sensors for temperature measurement do not provide an
immediate indication of the full change in temperature, but rather take
seconds to provide a reliable measurement of the total temperature change.
This means that the control is always sensing the full temperature change
seconds after it has been experienced. Tankless water heater control
systems respond to temperature change, i.e., water temperature dropping,
by adding additional power. In other high wattage tankless heaters,
because of the delay in sensing temperature change, when power is applied
the water is overheated before the control senses it. When the temperature
sensor senses overheating, the reverse occurs with the control turning
off the power and again for too long. The water cools below the desired
temperature before the sensors indicate the change to the control system.
These conditions will continue with the water temperature continuing
to oscillate, first in large temperature swings, then reducing to ever
smaller swings, assuming the water flow has now stabilized, until the
temperature stabilizes at the desired water temperature.
This settling out process takes, in best case scenarios, about one
minute with the previous tankless water heater control technology and
is characteristic in what we experienced in classic "proportional
integral control", (PID). These temperature fluctuation conditions
re-occur when water flow rates are just modestly changed. One can imagine
what happens in the scenario described. When one has set the shower
temperature, and then someone else turns a hot water faucet on or off,
–it’s not a pleasant experience.
The problem that exists in the reality of the application is very
basic. When someone is showering, using the previous "flow-through"
or tankless water heater technology, there is nothing smooth about the
temperature changes resulting from changes in water flow. As mentioned
earlier, tankless heaters of the past have worked best when they have
a constant flow of water passing through them.
Water heating for domestic use, however, is relatively dynamic.
Rarely can one depend on a fixed or constant rate of water flow. For
example when most of us prepare to take a shower, we turn the hot water
on full blast, to speed up the delivery of hot water to the fixture.
Then, as the water reaches the fixture, we rapidly reduce the hot water
flow and adjust the hot to cold water ratio, in order to establish a
comfortable steady-state temperature. While we are in the shower, it’s
not uncommon for someone else to turn on hot water for other use. This
results in a higher flow and greater hot water requirement. From a fixed
temperature source, like the tank type heater, the temperature of the
water delivered to the faucet declines slowly during use. There are,
however, no rapid fluctuations in temperature except from a pressure
drop resulting in flow changes in the ratio of either the hot or cold
water of the tempered water supply. With the use of a storage-tank heater,
one can quickly adjust the fixture to smoothly compensate for temperature
changes resulting from flow changes. Again this is because, with a tank
heater, we are using a supply of hot water with a fixed temperature,
albeit not constant and not trying to control its instantaneous heating.
Without going into a dissertation of advanced PID control theory,
it is sufficient to note that, when applied to the dynamics of domestic
water heating applications, the classic "PID" control schemes,
most commonly used, inherently produce the same unacceptable results.
One might argue that with the use of flow measurement devices and
faster response temperature sensors, these problems could be relatively
easily overcome. True, but for two problems. The first is that the typical
flow measurement devices, which provide immediate indication of changes
in flow rate, such as turbines, are installed in the water flow of the
heater. As anyone knows, water is a very aggressive environment leading
to reliability and maintenance issues from the use of such devices.
The second and equally important issue is cost. These type of devices
add unacceptable expense to an appliance which is already cost sensitive.
The same cost issue exists with rapid response temperature sensors.
Finally, the classic methods of control used in "PID" are
simply not adequate, in such dynamic applications, to maintain the desired
temperature control.
High Mineral Deposit Accumulation Caused by Inherent Over-boiling
Further complicating the difficulty of producing an acceptable
tankless electric water heating system, for "flow-through"
water heating, are the scaling and minerals issues. All typical electric
tankless heaters used today contain and control one or more heating
elements. The elements produce a high heat output within a heating chamber(s)
which only contain a very small quantity of stored water.
In the case of the single element "point of use" heater,
the one element is always turned on to a preset full power level. Heaters
with multiple heating elements turn on at least one of the elements
to full power, regardless of the control schemes ability to modulate
the level of power. The individual wattage (heating capacity) of the
single element will require at least the first element to turn on full,
just to heat the minimum flow of water. As the flow increases, additional
elements are turned on, partially or fully, as required to heat the
water.
When the flow of water stops, the electric tankless water heater
is turned off. In most designs, there is a very small amount of water,
partially heated, with which to absorb the remaining heat (called latent
heat) from the heating element. This latent heat saturates the water,
resulting in the water, within the heating chamber being overheated,
(over-boiled at shut down), to temperatures reaching 160°
- 180° F. These high water temperatures
cause the minerals in the water to be constantly boiled out. These deposits
are then discharged, with new flow, into the showerheads or appliance
screens, clogging them up, and creating a maintenance nightmare. Considering
the estimated 40 or more times a day that a family turns on and off
a hot water fixture, the cumulative amount of mineral residue becomes
significant.
These very conditions are exacerbated by the existing design and
control schemes utilized by tankless technology, other than the SEISCO.
Small "point of use" heaters generally are quite susceptible
to overboiling as they have less than a pint of hot water contained
in the heating chamber. Larger heaters with multiple elements have similar
small volumes of water within each individual heating chamber.
In order to develop a system, which has sufficient power to
heat flowing water, to satisfy the normal water heating requirements
for a household, one needs sufficient heating capacity (power). Therefore,
this inherent "over-boil" design issue is further complicated
as you increase the wattage (heating capacity) of the elements to provide
sufficient power for whole house use.
Unreliable, High-Maintenance,
Difficult to Service
The very problems discussed above have given rise to the characteristically
high maintenance requirements for the typical electric tankless water
heaters. High temperature over-boiling results in excessive scaling
and mineral deposit accumulation in the heating chamber and on the elements.
As a result of the type of sequential power control scheme that is used,
multi-chamber heaters work the first two elements disproportionally
more than the remaining elements. Both these conditions cause early
failures of the heating elements. In addition, as previously discussed,
most typical electric tankless water heaters use mechanical flow switches,
which are exposed to the water. These flow switches are susceptible
to failure in a relatively short period of time.
The heating elements in a very large percentage of these heaters
are not the standard "screw-in" type of water heating elements.
Often, the consumer must buy a special element and sometimes even replace
the entire heating chamber in order to repair his heater. This is particularly
true with most point of use type electric tankless water heaters.
Finally, some electric tankless water heaters can be activated when
there is no water in the heater itself. Such activation will destroy
the heating elements and can damage the heater itself.
In general then, most problems, for other existing electric tankless
technology result from early failure of the heating elements, and excessive
mineral deposits which in part are purged from the heater accumulating
in faucet aerators, and appliance screens. The users of such systems
either have to install filters downstream of the water heater or constantly
clean their aerators and appliance screens.
Power Quality Problems
When one is controlling 28,000 watts of energy and modulating
power from multiple heating elements with very high wattage, it is no
wonder that power quality issues will result. Modulating even two heating
elements of 5,000 watts or a total 10 kW can have the same effect on
lighting as if you were standing at your air-conditioning thermostat
flipping the switch on and off rapidly. Other than the SEISCO, no high
wattage electric tankless water heaters have addressed this problem
successfully,.
- SEISCO SOLUTIONS
The myriad of deficiencies in existing tankless water heaters presented
a challenge to SEISCO. Produce a "flow-through" tankless
water heater employing a control scheme that allowed the use of sufficient
power to satisfy the water heating lifestyle requirements for a family
in the United States. In doing so we not only had to make sure that
the consumer did not have to compromise any lifestyle benefits but we
also had to insure a system that provided an unlimited supply of hot
water, space savings, reduced scaling, and energy savings.
Over the years, based on the magnitude of these issues, we had
been told by many experts, involved in control theory, that what we
wanted to achieve was nearly impossible. Our effort has been compared
to balancing a bowling ball on the head of a pin.
After twelve years of research and development, we did, in fact,
accomplish the seemingly impossible. The following addresses the manner
in which we overcame each of the obstacles.
SEISCO Provides Highly Responsive
Power Control
Conventional temperature-based control-schemes principally use
the outlet water temperature from the heater for the control reference
temperature. As previously discussed, by the time the water temperature
at the outlet has exceeded or dropped from the desired temperature,
and that temperature measurement has been transferred by the temperature
sensing circuit to the control, the water in the rest of the chamber
has already been heated or cooled too much. The reason for these conditions
is the lag time required for the temperature sensor to sense the full
temperature change.
To minimize this problem, many control systems employ additional
control circuitry that allows the heater to respond to increasing/decreasing
temperatures, depending upon the speed of the temperature rise or fall
("rate"). The purpose of this control circuitry is to allow
for the anticipation of power requirements and make corrections as the
measured water temperature approaches or is dropping from the desired
temperature. This type circuitry is commonly referred to as "anticipation"
as it looks at the rate of temperature changes and attempts to anticipate
the power response needed.
"Anticipation" control circuitry is absolutely necessary
to minimize temperature swings as the system attempts to reach or maintain
a steady state temperature. A major challenge exists, however, in heaters
that have multiple heating chambers and heating elements with high heating
capacity. The most typical control schemes employing anticipation use
the outlet temperature as the reference water temperature. In such control
schemes, the normal delay in monitoring temperature is increased by
the additional time it takes for water to pass through the extra heating
chambers before reaching the outlet. Because of the additional volume
of water, in the multi-chamber heater designs, this additional delay,
in obtaining temperature information, is accompanied with a longer corrective
period. Even when utilizing the best anticipation schemes with standard
PID controls, there exists an unacceptable delay in reaching and maintaining
steady temperatures in applications such as domestic water heating.
Given the problem, one might assume that adding extra temperature
sensors in each chamber will automatically provide sufficient additional
information to monitor heating conditions all along the water’s
heating path. If one thought that, he would be wrong. In a design employing
a serpentine-heating path, water flow conditions around temperature
sensors change rapidly with just the slightest change in flow. With
these flow changes, what you expect with respect to your ability to
accurately monitor the temperature changes, resulting from heat added
(or reduced) in each chamber, just doesn’t occur. Furthermore from
one heater to another, orientation of the heating element within individual
heating chambers changes the flow characteristics of the water around
the temperature sensor.
The SEISCO’s patented continuous venting system further adds
to the complexity of obtaining accurate temperature measurements. SEISCO
utilizes a unique and patented continuous venting system of small holes
that provide passageway from the top of each chamber to the outlet pipe.
This passageway allows air to pass across the top of each heating chamber
directly to the outlet pipe. This is very important, otherwise air would
become entrapped in the top of the chambers and finally partially expose
the heating element and or temperature sensors. As the heater is operated,
a small amount of water flows across and through this passageway, instead
of the normal flow path of the water. As this small amount of hot water
flows from the outlet pipe, any air generated during the heating operation
flows out with it.
As the water flows through each heating chamber, heat is transferred
to the water from the heating elements,. A certain amount of heat, however,
will rise or remain at the top of the chamber maintaining a slightly
higher temperature gradient in the water at the very top of the chamber,
than in the water flowing just below it. This gradient will differ depending
upon flow conditions. In low flow conditions, a substantial part of
the heat is carried out in the water flowing through the vent passageway.
Thus this heat never gets added to the water flowing through the bottom
of the chambers nor measured by the temperature sensors at the bottom.
The final outlet temperature is made up from the combination of hot
water flowing out the vent mixing with that from the lower outlet of
the final chamber. Therefore with different flow rates, while the final
outlet temperature may be exactly what you want, the temperature profile
throughout the heater, as indicated by each of the sensors, will differ
from one flow rate to another.
When you combine all these variables affecting temperature measurements,
with the lag times we have been discussing, as well as the dynamics
of the application, you began to realize the complexity of problems
that exist in attempting to precisely control temperatures.
Those familiar with computer modeling would appreciate the difficulty
in trying to develop a model that allows one to generate control formulas
that appropriately deal with all the variables we have been discussing.
To overcome these problems we realized that we had to reduce them
to a manageable component. To do this, after almost 12 years of development,
we developed a very complex algorithm that calculates a reference temperature
based on the average temperature rise we want to obtain. This calculated
reference temperature represents a temperature that is compared to the
average of all the water temperature measurements within the SEISCO.
When the temperature average of all the temperature sensors equals the
calculated reference temperature, then the SEISCO has added or reduced
the heat sufficiently to achieve and maintain the desired temperature
at the outlet pipe. With this algorithm, we are able to determine long
before the water reaches the outlet, whether we need to add or reduce
power. We have calculated the time that we have gained, through the
use of the algorithm, to be almost equal to the lag time of the system.
This means that we can respond to flow changes almost as fast as if
we had real-time temperature and flow measurements.
The SEISCO control technology distributes equal amounts of power
to each element during operations ("Power Sharing" is explained
below in the solution to problem 2). This power distribution method
enhances the utilization of such an algorithm. Theoretically, each temperature
sensor, at the outlet of each heating chamber should indicate a measurement,
in a four-chamber unit, equal to the effect of 1/4th of the
heat being added or reduced. This is not the case in actual practice,
because of the differing temperature profiles previously discussed.
The algorithm provides us the tool to deal with these deviations in
temperature profiles.
This left us with only one
remaining major issue, that being the problem of the time it takes for
the heating elements to transfer the heat to the water once the system
recognizes it needs to add or reduce power.
To minimize the impact of this delay, the SEISCO’s control
scheme uses the components of P.(proportional), I. (integral) and D.
(derivative) in a highly modified manner. A great many special parameters
were developed, having been empirically determined to be necessary for
proper water temperature control. Further we developed a unique anticipation
algorithm and utilize it much differently than in most "PID"
control. In addition to our extraordinary engineering staff, we have
the pleasure of utilizing the services of two very well known Ph.D.s
who have spent many years practicing, teaching at major universities,
and authoring papers and text books on control theory. Some of their
work involves technology developed for NASA. Each of them confirmed
the absence of the control theory, developed for the SEISCO, in any
textbook on control theory with which they are familiar.
SEISCO Eliminates Over-Boiling and Disbursement of Excessive Mineral
Deposits
We recognized that mineral deposits occur exponentially for every
degree F that you heat water over 120°
F. We knew that the only way that we could overcome overboiling and
the resultant mineral deposit conditions was to make sure that, during
operations, we did not allow the heat in any heating chamber to exceed
120° F. Furthermore, we wanted to keep
the hottest chambers average water temperature, at shutdown, from rising
above 125° F, and then for only a very
short period of time. This goal led us to a complete rethinking of the
methods for power distribution to the heating elements.
SEISCO Uses Power Sharing
A very unique and patented control scheme was developed which delivered
power to each element equally. If we needed the power of only one element,
we turned on each of our elements to a precise power level such that
the sum of the total power to all the elements equaled that of one.
This control of the power level is achieved in a manner similar to adjusting
the level of multiple light bulbs controlled by a rheostat. We then
designed a residential flow-through water heater having four heating
chambers with a heating element in each chamber. We conducted lifestyle
studies with a major U. S. homebuilder and determined that 120°
F continuous water temperature was required for consumer satisfaction.
During the course of these studies, we also determined the typical
peak hot water flow rate requirements from the water heater,
in the normal household use, is 2.2 gpm.
We then designed the heating capacity for the system such that
at approximately 40-60% total power, the system, even in the colder
U.S. climates, would provide sufficient heat to properly satisfy the
hot water requirements for showering. We also designed the chambers
so that they contained sufficient water to absorb the latent heat from
the designed wattage elements, when shut down. This control scheme,
referred to as "Power Sharing", is the subject of one issued
and one U.S. Patent pending, as well as many foreign patents issued
and/or pending, This "Power Sharing" control scheme provided
us with the opportunity to heat water equally in each chamber, adding
only 1/4th the total heat as it passed through each chamber.
This method insures that the final temperature of the water is reached
only as it flows out of the outlet of the heater from the very last
chamber.
In illustration, assume we wanted to deliver 120°
F water and the inlet water temperature is 52°
F. We would have to raise the water temperature a total of 68°
F. Unlike the other existing technology, the water in our first chamber
would come in at 50° F and leave it,
heated 1/4th of the total 68°
F required or 17° F. The temperature
of the water leaving the first chamber, then would only be 69°
F. The water in the second chamber would be heated to 86°
F, the third chamber to 102° . Only
as the water left the outlet pipe connected to the final chamber is
the water finally heated to the full 120°
F. (Remember the final outlet temperature is the combination of hot
water from the vent mixed with the hot water from the last heating chamber)
At shut down, no chamber has water temperatures exceeding an average
of over 110° -112°
F. The first three chambers average water temperature would be less
than 100° F.
This most significant improvement results from the fact that
at shutdown, when the flow and power are shut off, all the heating elements
are turned off from a typical operating power level of only 60%
or less. This insures the latent heat in any chamber is reduced significantly.
The chamber’s water capacity design allows this reduced heat to
be absorbed without over-boiling conditions.
One might ask, what conditions occur that result in the heater
turning on to full power, and when that occurs, what keeps us then from
the same over-boiling problem? The heater as discussed is designed to
take care of a single shower application utilizing only 40-60% power.
Often, while one person is using hot water another will began a competitive
hot water use. Depending upon the combined flow, the heater during this
period may operate at 100%. It is important, however, to note that,
within the heating capacity of the Seisco model used, when the desired
temperature is met, the water temperatures in the individual chambers
will be the same as they were in lower flow. At some point, one
of the users will turn off their faucet and the power level will almost
instantly drop accordingly. When the final user turns off the hot water,
the power level at shut down will have dropped to the lower 50-60% level.
The only time when this may be different is when a person is filling
a tub using a high flow fixture and then shuts it off. Even then because
of the SEISCO’s chamber design the affect of latent heat in the
elements is minimized. .
These are reasons that the patented "Power Sharing"
control is one of the single most important technical advancements utilized
in the SEISCO. This method allows water to be gently heated in stages
as it passes through each heating chamber. Thus by eliminating the very
conditions, which result in the excessive mineral deposits, we overcame
the problem. The result of the elimination of the characteristic scaling
and excessive mineral deposits has astounded designers, not only in
the U.S. but also in Europe.
SEISCO Uses Microprocessor
(Computer) Control
All the control theory, which has been discussed here in generality,
was developed within extremely complex control algorithms and incorporated
into a microprocessor (computer) controlled system. The microprocessor
control actually performs up to 3 million calculations per second. The
result of all this work is a tankless water heater that, when used,
has virtually no perceptible difference in use from that of a storage-tank
heater, except for not running out of hot water.
The SEISCO control system, that safely and properly controls sufficient
power, has enabled the development of an exciting "flow-through"
tankless water heater for the whole house, restaurant, boiler replacement
etc.
SEISCO Solves the Problems
of Reliability and Maintenance
Throughout the design evolution of the SEISCO, over the last twelve
years, we have had to address all of these problems. The structural
design was based on a modular heater design allowing parts that fail
in service to be easily replaced without the need of replacing the whole
heater. The heating elements are standard screw-type immersion-heating
elements supplied by Chromalox, a subsidiary of Emerson Electric.
A unique and patented method of flow detection was developed for
the SEISCO. This method works by monitoring changes in a very slight
temperature difference between the water at the top of a heating chamber
and water at the bottom of the adjacent heating chamber. There are no
moving parts and the SEISCO method for flow detection is inherently
reliable.
Engineering plastics are used structurally to reduce scale
and provide an economical heat exchanger with long service life. The
selection of the proper engineering plastic was, in itself, an extraordinary
challenge. Most engineering plastics become brittle with time and exposure
to chlorinated water, in particular, hot water. Even with a suitable
material, the biggest stresses to the water heater structure are those
that are thermally induced. For example water may enter at 50°F,
leaving heated to 120° F and then at shut down rises to 130°
F. Shortly after shutdown and before the temperature can drop, someone
turns on the faucet and the heater body containing the 130° F water
is purged very quickly with 50° F water. This environment is extremely
destructive to many engineering resins causing cracks that would result
in a leaking water heater.
After many years and extensive testing through the cooperation
of DuPont’s Engineering Polymer Division, it was discovered that
certain nylons demonstrated unusually good properties for this environment.
In fact the DuPont’s "Zytel" that is used in the SEISCO
actually becomes tougher and more elastic over time and exposure to
hot water. Most people do not realize that these are the very properties
that have made the DuPont’s "Zytel" such good material
for the headers of radiators for automobiles.
Seisco Solves Power Quality Problems
Of all the achievements made during the development of the SEISCO,
however, perhaps the single most important technical achievement, utilized
in the SEISCO, is the, Patent Pending, power modulation design. This
very unique control technology eliminates light flicker and power quality
issues related to the use of SEISCO. The power modulation scheme (turning
the elements on or off or adjusting their power level as you would a
light with a rheostat) is computer controlled. An extremely sophisticated
algorithm allows the microprocessor to monitor and regulate the SEISCO’s
heating elements at less than full power, in a manner complimentary
to the line frequency (AC), eliminating light flicker and other power
quality issues.
Seisco Provides Unprecedented Safety Features
The SEISCO also provides within its control, redundant water
level detection. Not just one, but two level detection devices are located
near the top of the heating chambers. This feature prevents the heating
elements from turning on or remaining on in the event there isn’t
a sufficient level of water within the heater. Also, redundant high
temperature limit switches are provided within the control of the SEISCO.
When a low water level condition or a high temperature condition is
detected by these devices, the control will open the relay contacts
and shut the power off to the elements automatically. The manner in
which the control opens the relay contacts is equivalent to pulling
the plug out of an electrical outlet, completely disconnecting the power
supply to the elements. These are only some of the safety and reliability
features that the SEISCO utilizes.
The SEISCO will also, in the near future, provide options for remote
control of water temperature, as well as remote monitoring of operating
conditions. Other future options will include valves that will automatically
turn off the water supply and power in the event of a leak in the system
or the plumbing above it and shed excessive power demand during the
short-term water heating use without inconveniencing the consumer.
Seisco Provides Intelligence in Control, Self-Diagnostics
The SEISCO control is an intelligent control that actually verifies
its systems integrity including the heating elements on a regular basis.
If the microprocessor detects a problem including a water leak in the
system, a light will flash red and audible beeps will sound. The frequency
of light flashes and beeps provides a code that can be interpreted by
a technician over the phone. This self-diagnostic feature can provide
warning of failing heating circuits long before they have actually failed.
The control technologies that were developed to achieve the foregoing
accomplishments, which include power quality issues, are monumental,
and far too complex to give proper discussion in this report.
- Tankless Water Heater Cost Comparisons NOTES AND ASSUMPTIONS
We continue to be asked to provide a broad
range of Tankless Water Heater Cost Comparisons between the SEISCO, storage-tank electric and
gas water heaters. Often the consumer asks us to relate our statements
to the "Estimated Energy Cost" as shown on the storage-tank
water heater labels.
The Label and the Real World
Sometimes Differ
It’s important that the reader understand that labeling is
required for certain appliances to conform to the Energy Policy and Conservation
Act. Tests have been developed to estimate the energy efficiency and cost
of operations for certain classes of water heaters. While the test protocol
is intended to provide a method for a fair means of energy Tankless Water Heater Cost Comparisons,
the parameters and protocol for these tests have forever been questioned
or challenged. The problem in using such comparisons is that the testing
has been established under specific laboratory conditions most of which
can and do vary substantially in actual applications. Most important is
the fact that some variations in actual application will effect the energy
efficiency and operating costs of one class of water heater more than
another. Very often the type heater and its location result in substantial
increase in the air-conditioning or heating costs for the home. The following
segments serve as examples.
- Unlike the laboratory test conditions, the BTU content for a therm
(100,000 BTUs) of natural gas will vary from area to area. Areas whose
natural gas has a lower BTU content than used in the laboratory testing
will consume more gas thus cost more money heating water.
- The incoming water temperature, from which the DOE test calculations
are being made, has been established at 57°
F. In many parts of the U.S. one does not normally experience inlet
water temperatures (delivered to the fixture) this cold year round.
- The ambient air temperature in which the water heater is tested
is 68° F. Again, there are many Tankless Water Heater Installations,
varying widely geographically, such as in a crawl space, basement, or
attic where this temperature does not represent a genuine average ambient
temperature.
- The storage-tank gas heater has to be vented. So long as the heater
is placed outside the living area of the home, venting doesn’t
have a negative effect on other energy costs. In a very large percentage
of the homes in the U.S., however, gas heaters are located in the living
area and, as such, allow conditioned air, air that one has paid to heat
or cool, to be forced out of the home. The conditioned air, that is
lost, is replaced by infiltration of air drawn into the home from the
outside, requiring additional heat or air-conditioning to heat or cool
this outside replacement air. Furthermore, a fuel burning water heater
will give off considerable heat to the inside of a home by virtue of
the pilot and the hot vent. The vent itself reaches temperatures of
300° F above the inside temperature
of the home. The effect of these conditions adds to the heating or air-conditioning
cost. These costs are not added or even estimated in the energy label
on a gas fired water heater. Imagine putting a 3" hole in your
roof, and periodically heating a six-foot pipe to 375°
F for the 2.5-3 hours per day your water heater is heating, in use or
recovery. This hole in the roof is approximately equivalent to a 12"
window left open one half inch 24 hours a day, 365 days a year.
Additional Energy Cost Estimates
and Issues.
One very reliable source in the Energy Conservation Department of
the California Energy Commission prepared a paper on gas water-heating
costs. He developed a spreadsheet program for estimating the operating
costs for gas storage-tank water heaters located outside the home and
not in a conditioned space. The program assumes a household using
64.5 gallons of hot water daily, (DOE daily estimated hot water usage
per household). With natural gas cost currently at $1.20 per therm of
gas, the estimated operating costs for a 50-gallon gas tank heater is
over $400 per year.
SEISCO HAS NO HIDDEN COSTS!
In reality, depending upon the climate and water temperatures, actual
water heating costs for a 50-gallon gas heater could be less than $350
or more than $400 per year, even without including the impact of vent
and stack loss on space heating and air-conditioning. Conservative calculations
for the additional cost related to the loss of conditioned air to exceed
an additional $100 per year.
The energy efficiency (AFUE),
as the consumer understands the term, for most commonly installed electric
storage-tank heaters is approximately 88%. The same efficiency for a comparable
standard gas fired water heater is 54%. The efficiency for a SEISCO "flow-through"
water heating system is over 99%. In 1997, a study was done by an independent
consulting firm in College Station, Texas to compare the operating costs
of a new 40gallon storage-tank electric water heater against the SEISCO.
The test was done in January of l997. The results of this winter test
indicated a monthly cost for heating water with the SEISCO, in this city
during the month of January, to be less than $15.00 and a 26% savings
over the 40 gal. electric storage tank water heater.
Gas water heaters become less
efficient with use, particularly in areas of
hard water. Scale builds up
on the walls of the tanks and mineral deposits collect at the bottom of
the tank, both acting as insulation, reducing the efficiency for the transfer
of heat from the burner to the water.
SEISCO ALLOWS YOU TO SAVE ENERGY AND WATER TOO!
Studies have indicated a normal household will draw varying amounts
of hot water, turning the faucet off and on over 40 times daily. The normal
flow rate from a faucet drawing hot water is estimated at 1.50 gallons
per minute. There are obviously times and uses, such as the washing machine,
when this draw is higher. At this nominal flow rate, assuming a wait for
the hot water of an average of only 20 seconds, one half a (1/2) gallon
of water is wasted. The total hot water wasted daily for 40 such draws
would be at least 20 gallons. A great many households people experience
much longer waits, and therefore more hot water is wasted, particularly
in the winter.
It has been determined by independent sources that an average home
will waste approximately 10,000 gallons of water per year running it down
the drain waiting for hot water. Keep in mind that the water you draw
out of the hot water faucet was originally delivered from the water heater.
At one time this same water had been heated only to later cool down in
a long run of pipes. By locating the SEISCO central to the major points
of use, the estimated reduction in wasted hot water is 40% being 4,000
gallons per year and almost 11 gallons per day. The cost to heat this
4,000 gallons of water from 65° F. to
135° F., in an electric storage-tank heater
(88% efficient) at $.084/kWh, is $65.00. The savings which are estimated
in the following comparisons between the estimated cost of various types
of water heaters includes an estimate of only 10 gallons saved as a result
of one’s ability to locate the SEISCO central to the major points
of hot water usage.
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