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TANKLESS Tankless Water Heater Product Guide Tankless Water Heater Applications Tankless Water Heater Electrical Guide Tankless Water Heater Installation Tankless Water Heater Cost Comparisons Tankless Water Heaters Service Guide
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SEISCO TANKLESS WATER HEATER SOLUTIONS EXPLAINED IN SEISCO’S TECHNOLOGY PATENTS The myriad of deficiencies in existing tankless water heaters presented a challenge to SEISCO. Produce a tankless water heater employing a control scheme that allowed the use of sufficient power to satisfy the HOT water 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 tankless water heater 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 for its Tankless Water Heater Conventional temperature-based control-schemes principally use the outlet water temperature from the water heater for the control reference temperature. As previously discussed, by the time the hot 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 hot water’s full temperature change. To minimize this problem, many control systems employ additional control circuitry that allows the water 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 the tankless water heater that has multiple heating chambers and water heating elements with high heating capacity. The most typical control schemes employing anticipation use the outlet temperature as the reference hot water temperature. In such control schemes, the normal delay in monitoring temperature is increased by the additional time it takes for hot 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 water 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, hot 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 water temperature changes, resulting from heat added (or reduced) in each chamber, just doesn’t occur. Furthermore from one water heater to another, orientation of the water heating element within individual heating chambers changes the flow characteristics of the hot water around the temperature sensor. The SEISCO’s tankless water heater’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 water heating element and or temperature sensors. As the water heater is operated, a small amount of hot 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 of the water heater’s heating chambers, 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 hot water at the very top of the chamber, than in the water flowing just below it. This gradient will differ depending upon hot water flow conditions. In low water 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 hot water flowing through the bottom of the chambers nor measured by the temperature sensors at the bottom. The final outlet hot water 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 water temperature profile throughout the water 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 for tankless water heaters.
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 14 years of development, we developed a very complex algorithm that calculates a reference temperature based on the average water temperature rise we want to obtain. This calculated reference water temperature represents a hot water temperature that is compared to the average of all the water temperature measurements within the SEISCO. When the water temperature average of all the temperature sensors equals the calculated hot water reference temperature, then the SEISCO has added or reduced the heat sufficiently to achieve and maintain the desired water temperature at the outlet pipe. With this algorithm, we are able to determine long before the hot 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 water heater’s system. This means that we can respond to flow changes almost as fast as if we had real-time hot water temperature and flow measurements. The SEISCO tankless water heater control technology distributes equal amounts of power to each water heating 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 water 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 hot water profiles previously discussed. The algorithm provides us the tool to deal with these deviations in water 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 water heater’s 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 four very well known Ph.D.s who have spent many years practicing, teaching at four 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 tankless water heater, in any textbook on control theory with which they are familiar. SEISCO Eliminates Over-Boiling and Disbursement of Excessive Mineral Deposits for Electric Tankless Water Heaters 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 hot water temperature in any heating chamber to exceed 120° F. Furthermore, we wanted to keep the hottest chambers average water temperature, at shutdown, from rising above an average 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’s Tankless Water Heater Uses Patented Power Sharing
A very unique and patented control scheme was developed which delivered power to each water heater element equally. If we needed the power of only one element, we turned on each of our heating elements to a precise power level such that the sum of the total power to all the water heater’s 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 tankless water heater having four heating chambers with a water 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 water heating capacity for the system such that at approximately 40-60% total power, the tankless water heater, even in the colder U.S. climates, would provide sufficient heat to properly satisfy the hot water requirements for showering. We also designed the water heating chambers so that they contained sufficient water to absorb the latent heat from the designed wattage elements, when the water heater was turned off. 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 hot water is reached only as it flows out of the outlet of the heater from the very last water-heating chamber.
In illustration, assume we wanted to deliver 120° F hot 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 tankless water heater 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 hot 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 hot water left the outlet pipe connected to the final chamber, the water was only then 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 water heater’s 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 water heater turning on to full power, and when that occurs, what keeps us then from the same over-boiling problem? The tankless water heater as discussed is designed to utilize only 30-60% power in order to take care of a single shower application. Often, while one person is using hot water another will began a competitive hot water use. Depending upon the combined flow, the tankless water heater during this period may operate at 100%. It is important, however, to note that, within the water 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 hot water faucet and the power level will almost instantly drop accordingly. When the final user turns off the hot water, the power level of the water heater at shut down will have dropped to the lower 30-60% 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 water heating 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 tankless water heaters. This method allows water to be gently heated in stages as it passes through each water 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 for Tankless Water Heaters 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 water 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 tankless water heater for the whole house, restaurant, boiler replacement etc. SEISCO Solves Problems of Reliability and Maintenance for Tankless Water Heaters. 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 water heater design allowing parts that fail in service to be easily replaced without the need of replacing the whole water heater. The water 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 SEISCO’s line of tankless water heaters. This method works by monitoring changes in a very slight temperature difference between the hot 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 water flow detection is inherently reliable. Engineering plastics are used structurally to reduce scale and provide an economical heat exchanger for a tankless water heater 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 tankless water heater structure are those that are thermally induced. For example water may enter the water heater 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 hot water faucet and the water 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 tankless 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 dynamic hot water environment. In fact the DuPont’s "Zytel" that is used in SEISCO’s tankless water heaters 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 Inherent in Other High Power Electric Tankless Water Heaters. Of all the achievements made during the development of SEISCO’s Tankless Water Heater, 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 electric tankless water heater. The power modulation scheme (turning the water heating 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 water heater’s elements at less than full power, in a manner complimentary to the line frequency (AC), eliminating light flicker and other power quality issues. Seisco Bring Unprecedented Safety Features To The Tankless Water Heater.
SEISCO’S tankless water heater also provides within its control, redundant water level detection. Not just one, but two level detection devices are located near the top of the water heating chambers. This feature prevents the water heating elements from turning on or remaining on in the event there isn’t a sufficient level of water within the water heater. Also, redundant high temperature limit switches are provided within the control of this unique water heater. 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 water heating 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’s water heaters utilizes. SEISCO’s tankless water heaters 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 Brings Intelligence in Control, Self-Diagnostics to Tankless Water Heaters. The SEISCO’s water heater control is an intelligent system that actually verifies its operating integrity including that of the water 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 from the water heater that can be interpreted by a technician over the phone. This self-diagnostic feature can provide warning of failing water 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. |
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