Team 17-3



Dr. Giuseppe Palmese Team 17-3

Center for Automation Technology 283 Vincent Tancredi, Captain

3101 Ludlow Street Antonio DiCianni

Philadelphia, PA 19104 Christopher Kaskoun

Daniel Taurone

Dung Truong

Re: On Demand Water Heater May 30, 2007

Dear Dr. Palmese:

We have enclosed a copy of our Freshman Design Report entitled “On Demand Heating System.” The report concludes that the “On Demand Heating System” will be the most efficient solution to the energy loss and wasted water caused by the standard mixer valve, hot water tank, and distance between shower and tank. The other alternative solutions were not chosen because each solution only solves one of these problems and do not maximize energy and water savings. The report continues to further examine and design the final “On Demand Heating System.”

Sincerely,

Team 17-3

|(signature) | |(signature) |

|Vincent Tancredi, Captain | |Antonio DiCianni |

|(signature) | |(signature) |

|Christopher Kaskoun | |Daniel Taurone |

|(signature) | | |

|Dung Truong | | |

ENGR 103

Freshman Engineering Design

Final Project

| |17-3 | |

|Design Team No. | | |

| | |

|Submitted to: |Giuseppe Palmese |

| |{name of advisor} |

AND THE

ENGR 103 PROJECT DESIGN FACULTY OF DREXEL UNIVERSITY

|ENTITLED: |On Demand Water Heater |

TEAM MEMBERS (include email addresses)

|Vincent Tancredi vat26@drexel.edu |

|Antonio DiCianni ad453@drexel.edu |

|Daniel Taurone dmt52@drexel.edu |

|Chris Kaskoun cdk33@drexel.edu |

|Dung Truong dt88@drexel.edu |

Submitted in partial fulfillment of the requirements for

Freshman Engineering Design, ENGR 103, Design Project

Submitted on ____________________

{date}

ABSTRACT

Currently, a major source of energy consumption in the common household stems from heating water. We have improved the efficiency of heating water by implementing an On Demand Water Heater into homes. This device is placed inside pipes that lie directly before applications that use hot water such as a shower or sink. Ground water travels through the pipes in a house and passes through the On Demand Water Heater. The device that is placed inside the water pipe is a long cylinder with fins on the outside. This cylinder houses electric cartridges that emit heat. As the water flows over the electric cartridges and the accompanying fins it is heated to a desired temperature. This device contains a safety design that includes sensors that lie in between each cartridge. If the sensor detects that any cartridge is malfunctioning or emitting excess heat it will shut all cartridges off.

EXECUTIVE SUMMARY

The design flaws of today’s existing water heaters affect all members of society; safety, efficiency and comfort control are all compromised by traditional shower water heating systems. Our team’s research has proven there is a much more efficient method to heating water. Our design project focuses on designing and developing an accurate yet efficient hot water heating system, primarily for the bathroom. The parameters of our design include safety, economics and precision. The ideal hot water heating system incorporates all these aspects into its design. It is essential that such a device meet the needs and demands of both the consumer and the government’s efficiency standards. These improvements are targeted to reduce consumer costs and injuries. The primary purpose of our improved hot water heating system is to increase efficiency and decrease monthly water and energy bills. Our research team estimates this product will cost almost slightly more than a traditional instantaneous block heater. However, the benefits of this device include lower monthly heating and water bills, precise water temperature and pressure control, and optimal safety features.

TABLE OF CONTENTS

ABSTRACT i

EXECUTIVE SUMMARY ii

TABLE OF CONTENTS 1

1. INTRODUCTION 2

1.1. Problem Background 2

1.2. Survey of Literature 3

1.4. Constraints 4

1.5. Criteria 6

2. SOLUTION 6

2.1. Statement of Work 6

2.2. Results 9

3. DISCUSSION 12

4. RECOMMENDATIONS FOR FUTURE WORK 13

5. REFERENCES 15

6. ACKNOWLEDGMENTS 18

APPENDIX A 19

APPENDIX B 21

APPENDIX C…………………………………………………………………………....24

On Demand Water Heater

1. INTRODUCTION

1.1. Problem Statement

Every morning when people get in the shower they face the problem of unwanted cold water, pressure fluctuation, and water wastage. Also, the use of hot water in a household results in the consumption of valuable energy. We are investigating ways of solving these problems with a simple yet efficient and cost effective system.

1.2. Problem Background

The average shower in America lasts seven and one half minutes. This means the average water consumption of a shower is anywhere from fifteen to fifty-two and one half gallons of water (“Water Usage”). This large range is due to the fact that there are several types of shower heads. Shower heads are normally broken into two groups: low flow shower heads and high flow shower heads. Low flow shower heads range anywhere from two to five gallons per minute; while high flow shower heads range from five to seven gallons per minute. Based on a family of four and assuming that everyone takes just one shower a day this can cost the family up to $306.60 (per year) considering water costs on the average $0.004 a gallon. For many families, the cost for water usage in a house can be a financial burden (“Water Usage”).

In addition to water and energy consumption due to shower heads, there exists another area of concern. Currently, the water flowing into shower heads and sinks is heated by a number of means. One way is to use a standard hot water tank. With this method, a hot water tank maintains the temperature of water until it is needed by an application in the house such as a shower or sink. While water sits in this tank, energy is wasted to maintain the temperature of the water. Energy is thus wasted all day and night as the temperature in the tank is maintained. If this thermal energy loss was eliminated, energy consumption would be reduced by 20% to 30% (“Electric Tankless Water Heaters”). Once hot water is drawn from the tank, ground water is then pumped in to replace the hot water. This subsequently reduces the temperature of the remaining hot water in the tank. The temperature that a household application can now draw from the tank is reduced. As more cold water enters, more energy is required to heat the water.

Another option to heat water in a home is a tankless water heater. The idea behind this concept is that water is only heated when it is needed. Ground water is pumped into a house and through the pipes that lead to a shower or sink. Right before the water reaches one of these applications, it passes through a heater in the pipes. This heater will then instantly warm the water in the pipes to a desired temperature. One of the drawbacks to the tankless water heater is that efficiency decreases with a larger workload such as multiple showers and sinks (“Top-Rated Water Heaters”). The objectives stated previously are the main concern for this group and each will be factored into a final solution.

1.3. Survey of Literature

To begin this project we began to research the methods by which water is heated in a home. Water is heated either by a hot water tank or by a tankless water heater. First we researched the ways in which a hot water tank works. This research involved exploring the positives and negatives of a water tank heater. Research for this method involved examining current patents and descriptions by companies that produce water heater tanks. Next, we investigated the tankless water heater. Researching the tankless water heater revealed that it was a better method of heating water than a water tank. For this research, we looked at patents and information provided by manufacturers. Once we had picked the tankless water heater to modify, we began to research scholarly articles that explained heater transfer and thermal energy concepts. Also, we utilized our advisor, Giuseppe Palmese, to determine the energy needed to heat specified water flow rates at specific temperatures. Our advisor provided valuable information needed to complete the research. Group research of the tankless water heater also focused on efficiency, cost and energy usage. With this information from the scholarly articles, patents, and our advisor we were able to gain a great deal of knowledge regarding water heating. This information enabled us to choose a path to the best solution.

1.4. Constraints

The solution to this problem would require the installation of a new system or component to heat water and/ or control the temperature more efficiently. Installing such a system would require a current water regulation device to be replaced with one that is specifically designed to optimize hot water usage. Ideally, this new fixture could be incorporated into the design of the new home. Otherwise, fixing an existing hot water flow issue would require equipment to be removed or altered allowing access to the pipes or devices for controlling water flow. Another issue to be aware of is space constraints. Depending on solution choices, space may be required to house this new water heating system. Also, to incorporate a new heating system, pipes may need to be diverted to and from the system to the bathroom area. This would require maintenance on the house and some level of cost to install and operate the device.

The cost of the installation would depend completely on the method chosen to control the temperature. The cost, in this case, would be the price of the new device. If the solution was more complicated and required construction and the installation of expensive devices than the cost would be much higher. If the solution chosen involved construction around existing pipes and fixtures, then the supplies for the installation and the price for a professional to install the system must be factored into the decision. In addition to the installation cost, the cost of operation must be considered. The best solution would essentially reduce energy wastage and decrease monthly expenditures. To make the purchase worth while, the cost of the system versus future savings should be considered.

Such an installation would have to follow current building codes and safety regulations. Proper scalding safeguards must be added to avoid burning or overheating. Also, there must be sufficient room for the device to operate properly. This means that proper ventilation and airflow requirements must be taken into account. In addition, the solution must respect the household’s current energy regulations. This means that the system can not cause a short circuit in the house.

Our solution addresses temperature changes in the bathroom as a result of poor water heating and loss of energy in the water. With a conventional water heating system, water sits in the pipes throughout the house, loses energy, and becomes cold. Also, when running the shower, energy is lost because the bathroom is too far away from the hot water heater and water decreases in temperature as it makes its way to the bathroom. A solution to this problem must solve these temperature issues. An effective system must heat the water right before it enters the bathroom fixture, or the water must be kept hot as it travels to the bathroom. Another alternative is to regulate the water so that only the hot water is sent to the bathroom.

1.5. Criteria for Success

For the design for an On Demand Water Heater to be a success it must improve upon the flaws of the already existing tank water heater. The space that it takes up must be reasonable for the average home. Also, it should be simple to install and operate. In addition, the strain of this device on the energy of a common household must be taken into consideration. This device also must be economical and provide the user with a reason to choose it over common existing solutions. For this design to be considered an improvement on existing options it must reduce heat loss and have a low electrical strain on the household. In addition, testing must be completed to verify the calculations for how much energy is required to heat a given amount of water. Once these calculations are verified, material for the piping and casing must be selected to maximize efficiency and cost benefits. The selection of these materials will again center on limiting heat loss. Overall, this device must be energy efficient, cost effective and durable.

2. SOLUTION

2.1. Statement of Work

Researching and innovative thinking and analyzing are the most important actions that an engineer can take in order to find a solution within several weeks. There were three alternative solutions to research and test, the insulated pipe, a new mixer valve, and an onsite heating device. By researching, analyzing and comparing the solutions according to the previously stated criteria, we were able to determine the best solution of the three possibilities.

The first solution is to replace all the hot water pipes with new insulated pipes. In order to make this work, the home has to be gutted wherever the hot water pipes ran; that may include the walls and floors in the bathroom, kitchen and most likely any other adjoining rooms or spaces. There is too much interior work to be done and it is impractical when compared to the energy savings after the installation of new pipes. Within our research, we have found the cost of a professional drywall installer to tear down and re-do the wall to be at least $9.98 per hour (U.S. Department of Labor). The pipes would cost anywhere from $2.00 and up depending on the material, make, durability and installation style. If the cost of renovation was not a factor, the most common materials that are currently used include polyethylene, neoprene foam, polyurethane, and fiberglass (U.S. Department of Energy). The best insulator of these common materials is polyurethane (“Results…” 32). However the easiest to install and the least costing would be polyethylene. About two to four degrees Fahrenheit is retained in most insulated pipes (U.S. Department of Energy). After just researching the cost and materials and analyzing the information, it can be concluded that pipe insulation is impractical for already built homes so this would not be the best solution.

Another solution is to design a mixer valve. We found that the mixer valve, commonly used in most baths today, work in such a way as to combine hot and cold water proportional in order to create a satisfying temperature of water. We decided that a good solution is to simply modify the mixer valve. A modified mixer valve could simply replace the current valve without renovation or change to the shower or bathroom. To create a device that monitors the flow rate we had to become familiar and adapt or design a laser system to detect the change of water flow. A software or program could be created to command the laser system in its detection and adjust the valve to maintain the temperature. This system would most likely be powered through electrical wiring within the walls. The device is waterproof to prevent any mishaps. The effectiveness of the new mixer valve depends upon the laser’s sensor and software. However after carrying out some research, we have found that there is already a thermostatic blending valve (Patent 06851440) which does not use any laser detection and monitor software, but simply a modified thermostat. This new valve is already becoming the new standard in most showers today. With this discovery, our new mixing valve seemed overly complicated and would cost more than the thermostatic blending valve we found.

The last solution would be an on-site heating device that would heat the water inside the pipes almost instantaneously. There are several ways the water can be heated. One is by running a pipe through a heating block. However, a heating block would take too long to heat up and heat the water and to cool down. Another is a heating coil made of the same type of material. The coil is would heat up faster; however the heat of transfer from the coil through the pipe and then the water would take too long. The last resort would to put a heating element inside the pipe to heat the water more efficiently. We found the best way to do this is to put en electric cartridge inside the pipe so that it may be in contact with the water as much as possible. The electric cartridge is best because it would be relatively easy to replace without having to remove the pipes, while the others would have to be worked around the pipes and require more space. The electric cartridge would be the least expensive to replace and it does not have to be designed from scratch. The power of each electric cartridge would be electrically wired inside the walls of a home and, of course, be waterproofed by enclosing any hazardous elements in a waterproof material.

After regarding and analyzing the different solutions, their effectiveness, and practicality, the best solution is an on site heating device using electric heating cartridges. Heating cartridges are already in use, although not specifically to heat water. Although the mixer valve as well as the electric cartridges would both be easily replaced, the electric cartridge would be more effective in directly heating the water to a desired temperature, whereas the mixer valve only monitors and changes the water flow of hot and cold water. The cost effectiveness of each solution is different with the insulated piping being the least and the heating device being the most effective.

2.2. Results

After coming up with multiple designs for the water heater, we feel that the On Demand Water Heater is the optimum solution to fit our initial criteria. This design was the most efficient in satisfying the conditions desired. The other proposed solutions did not meet one or more of the main goals, which were quick heating and cooling of the water, pressure regulation, and safety. Other goals included ease of installation into an existing house and low production cost to make it more profitable for marketing to general consumers. Not only does On Demand Water Heater meet most of the primary objectives, it also meets the secondary goals.

The On Demand Water Heater heats the water via an electric cartridge, which has fins to more effectively transfer heat to the water. The electric cartridge heats up quickly, and is extremely efficient in transferring heat to the water, so the water gets heated quickly as well. This lessens the amount of water used at the beginning of a shower. Secondly, the electric cartridge also cools almost instantaneously after being turned down or off, which means the water will cool very quickly. Also, since the heating system is surrounded by water, the pipe is not being heated, so the risk of fire is reduced. There is also little to no risk of scalding from water that is too hot, because the system will not heat above a certain temperature. The cost of constructing a section of pipe with a electric cartridge in it is also reasonable enough to be profitable for commercial production. Finally, this solution does not require the water to be heated when not in use, which would save in overall energy costs for a house.

The most common existing solution has a few shortcomings when compared to the On Demand Water Heater. Most showers currently use the mixer valve, which mixes hot and cold water in varying ratios to change the temperature. This method does not allow the water temperature to rise and fall very quickly, and some water must be preheated while the water is not in use. Because of this, the mixer valve method is less energy efficient. Also, if the input temperature is changed, the output temperature will also be changed. Therefore, if water must be redirected to another area of the house, the water temperature in the shower will change. This will also change the water pressure of the shower. Its advantages, however, are its safety and marketability, although this system does not prevent scalding. The disadvantages of this system, though, make the On Demand Water Heater a more beneficial option.

Another method of heating without a heating tank is via gas instead of electric. This method would use a gas hater to heat the pipe leading to the shower. This design poses a few problems, however. First, the heat transfer from the heating source to the water is not very efficient. Second, the pipe takes a long amount of time to heat up and cool down, so the temperature cannot be changed rapidly. Finally, this method is not very safe. The gas heater uses an open flame, which is obviously unsuitable to install inside the walls of a house. Because it does not meet all of the criteria desired and poses an extreme safety hazard, the gas heater is not an acceptable solution.

Insulation of pipes is another alternative. However, this also has many disadvantages. The insulation would not make a large difference in the water temperature, so another heating source would have to be used anyway. Also, this solution is highly impractical for a preexisting house, because all of the pipes would have to be accessed and either replaced or covered with an insulating material. The cost of this would offset any money saved by the insulation, so it would not be worth it, except in a house being built, and even then, the benefits would be slim.

The tankless heaters, while better in comparison to the other solutions, have their own down sides. The block heater, which uses a heating block around the pipe to heat the water indirectly, is inefficient. The block transfers heat to the pipe, which then transfers heat to the water. In this process, some of the heat can be lost. Therefore, the heating block must be heated hotter to increase the water temperature. The cartridge heater is a better solution, because it transfers the heat more effectively. Another option would be to use a coil to heat the water by twisting the pipe around the heating source, but again, the heat transfer is inefficient. The drawbacks of these solutions are the reason why the cartridge heater with fins is the ideal option.

Once we had determined that the tankless heater with electric cartridges was the best option we needed to perform a few specific calculations to find out more about this method of heating. To determine the wattage needed for our system we used the equation P = (m/t)*c*∆T. P is equal to power in joules, m is equal to mass in grams, t is equal to time in seconds, and c is the specific heat of water measured in J*g-1*C◦(appendix ). This is a very important part of our project because if the system draws to much electricity, it is not feasible. To calculate the amount of Amps that our system would require we used the equation P = I^2*R. We used the P from the previous equation and for resistance R we selected a sample electric cartridge heater to meet our required power output. Based on our calculations we determined that we needed about 70 A to heat water from 12° C to 45° C (Figure 3 in Appendix C). This is a fairly large amount of electricity considering the main breaker in the average house is between 200A and 300A.

The cartridge heater with fins was the design that our team determined was the most effective design. It saves energy by not heating a tank constantly, as it is only in use when the water is needed. The mixer valve and insulation do not have this benefit. Also, it is fairly easy and inexpensive to install, unlike the insulation. The water will also always stay at the desired temperature, while the mixer valve may not if water is diverted to other areas of the house. This design also saves water, because the user does not have to wait for the water to heat up at the beginning of the shower. The cartridge heater with fins is the most effective of the tankless designs because it is safer than the gas heater and more efficient with heat transfer than the heating block or the coiled heater. All of these benefits make the cartridge heater with fins the optimal design for the criteria desired.

3. DISCUSSION

Our team’s design project focuses on designing and developing an accurate yet efficient hot water heating system. The parameters of our design include safety, economics and precision control. The ideal hot water heating system incorporates all these aspects into its design. It is essential that such a device meets the needs and demands of both the consumer and the government’s efficiency standards.

There are many issues regarding household shower systems. Safety, efficiency and control are compromised by traditional shower water heating systems. When the standard shower system is turn.ed on, the home’s hot water heater uses energy to heat the water and send it through the pipes to the shower head. Ultimately, water is wasted because it does not reach the consumer’s desired temperature at a quick enough rate. In this case water and energy are lost due to this heating system’s poor design. By incorporating a digital control device with an instantaneous hot water heater, the temperature of the water can be manipulated precisely to the consumer’s discretion. Our improved heating system also includes an internal temperature monitor. This safety feature is projected to reduce the number of scalding incidents due to extreme hot water conditions. The temperature gauge restricts the system from heating water above 45◦ Celsius. These improvements are targeted to reduce consumer costs and injuries.

The primary purpose of our improved hot water heating system is to decrease energy loss as much as possible. While instantaneous hot water heaters reduce energy loss in comparison to traditional storage tanks, their designs are flawed. Our team’s research has proven there is a much more efficient method to heating water instantaneously. Figure 3 in Appendix A compares the energy efficiencies of a previously existing block water heater with our improved heating design. Our newly designed hot water heater incorporates key safety and control features with an enhanced heating system. Figure 2 of Appendix C is a schematic of our proposed heating system. Our research team estimates this product will cost almost slightly more than a traditional instantaneous block heater. However, the benefits of this device include lower monthly heating and water bills, precise water temperature and pressure control, and optimal safety features.

4. RECOMMENDATIONS FOR FUTURE WORK

Currently, the on demand tankless water heater exists in research and drawing. To continue work on this project one would need to construct a prototype from existing drawings and calculations. To test the tankless water heater the first prototype should contain the following controls: water temperature in, desired water temperature out, water flow, and standard piping material. This first experiment would be preformed to ensure that the energy calculated can actually heat the incoming water to the desired output temperature. This would test the electric cartridges that were selected. After, the heater’s cooling abilities need to be investigated. More tests would need to be preformed to evaluate the systems response to altered water flow rates. One way to ensure that the device will be able to handle different flow rates is to select the correct material. After this is done, the specific area that the device covers can be determined. The following equation can be used in which area is the only variable:

[pic]

In this equation hplate represents the coefficient of heat transfer dependent on the material; A is the area of the device; and the ΔT is the difference between the temperature of the heater and the water. In this equation the rate of heat transfer depends on A because hplate is constant and ΔT is pre-determined.

Another variable that will have an effect on the efficiency and safety of the heater is the placement and arrangement of the electric cartridges. Different options for this include less distance that the cartridges cover and more energy per cartridge or more distance and less energy for each cartridge.

5. REFERENCES

“Bureau of Labor Statistics, U.S. Department of Labor: Drywall Installers, Ceiling Tile.” Occupational Outlook Handbook, 2006-07 Edition. 4 Aug 2006. .

"EERE Consumer's Guide: Insulate Hot Water Pipes for Energy Savings." U.S. Department of Energy: Energy Efficiency and Renewable Energy. 12 September 2005. 25 Feb 2007 .

"Electric Tankless Water Heaters." Tankless Water Heaters. 2007. American Tankless Water Heaters. 28 Apr 2007 .

“Estimating Water Usage Guidelines.” Wholly Water. 2003. 1 Mar 2007 .

Ground Water & Drinking Water. 28 Nov 2006. U.S. Environmental Protection Agency. 6 Mar 2007 .

Images

“Thermostatic Mixing Valves – TMV.” . n.d. .

“Insulate Hot Water Pipes for Energy Savings. ” U.S. Department of Energy: Energy Efficiency and Renewable Energy. 12 Sept 2005 .

Klenck, T. Hot-water heating system. Popular Mechanics v. 173 (October 1996) p. 98+

Kline, Kevin B., “Method of Mixing Fluids Using a Valve.” American Patent 06851440. 08 Feb 2005.

“Results and Methodology of the Engineering Analysis for Residential Water Heater Efficiency Standards.” U.S. Department of Energy: Office of Codes and Standards (OCS). Oct 1998. .

Penn, Cyril. "Where Water Heating Energy Really Goes." Home Energy Magazine Online 08 03 2007 .

"PowerStar AE12 Point-of-Use Electric Tankless Water Heater." Bosch Water Heaters. Bosch . 8 Mar 2007 .

Lord, N. Hot Tips on Water Heaters [Tankless variety]. Old House Journal v. 33 no. 6 (November/December 2005) p. 29-30

"Tankless Water Heaters." Tool Base Services . 25 Feb 2007 .

"Top-Rated Water Heaters." Consumer Guide to Home Energy Savings: Condensed Online Version. December, 2006. American Council for an Energy-Efficient Ecconomy. 28 Apr 2007 .

"Water Heating." Energy Efficiancy and Renewable Energy. U.S. Department of Energy. 1 Feb. 2007 .

"Water Heating." Minnesota Propane Gas Association. 2003. 4 Feb. 2007 .

6. ACKNOWLEDGMENTS

We would like to thank our advisor Giuseppe Palmese for his guidance throughout the project. He aided our group in important decision making during the preliminary phases of the project. As the project progressed he helped to focus our groups’ research. His guidance and support throughout the project are greatly appreciated. Also, we would like to thank Jay Bhatt for his assistance in the research portion of our project. Finally we would like to thank all of the Writing Intensive Tutors who helped us throughout the project. With their previous knowledge of this project, they helped focus each of our assignments. In addition they provided valuable grammar help.

APPENDIX A: Hot Water Usage

Figure 1.

[pic]



This figure displays the hot water energy use for a home with a natural gas heater and the standby loses that occur. The standby loses are a very significant percent of wasted energy.

Figure 2.

[pic]



This figure shows the hot water energy use of a home with an electric heater. The shower in the house hold accounts for 37% of hot water usage.

Figure 3.

[pic]

This chart compares attributes of different heating methods. It shows the electric heater versus other, more conventional methods such as oil and electric tank heaters.

APPENDIX B: Hot Water Heating Methods

Figure 1.

[pic]



This is diagram of a typical water tank. The tank on the left uses electricity to generate heat. The tank of the right uses gas for power. These two designs are typical methods of heating water in homes. They are inefficient and leave appliances lacking water pressure.

Figure 2.

[pic]

This is an example of a tankless water heater. The red sections in the diagram represent the heating coils. As the coils give off energy, the water that flows by is heated to a desired temperature.

Figure 3.

[pic]



This is an electric cartridge that would be used as a heating mechanism. The coil would be placed inside our fin design and as the water flows by, it would instantly be heated.

Appendix C: Our Design

Figure 1.

[pic]

This is our final design. The On Demand Water Heater uses fins to maximize the surface area that is in contact with the water. This fins house the electric coils that heat the water.

Figure 2.

[pic]

This is a diagram our On Demand Water Heater along with the pipes and safety system. As water travels through the pipes there are many checkpoints to make sure that the electric cartridges are working properly. The electric cartridges are in constant conversation with the power control. If any malfunction is detected, the system is immediately shut off.

Figure 3.

|  |  |  |Temperature Out |Max Energy needed |Minimum |

|Specific Heat |Flow Rate |Temperature ◦C |Min |Max ◦C |J/sec |J/sec |

|H2O |(gram/sec) | |(ground water ◦C) | | | |

|J/g◦C | | | | | | |

|4.148 |63.0902 |12.7 |12.7 |45 |8452.850232 |0 |

|4.148 |126.1804 |12.7 |12.7 |45 |16905.70046 |0 |

|4.148 |189.2706 |12.7 |12.7 |45 |25358.5507 |0 |

|4.148 |252.3608 |12.7 |12.7 |45 |33811.40093 |0 |

|4.148 |315.451 |12.7 |12.7 |45 |42264.25116 |0 |

|4.148 |378.5412 |12.7 |12.7 |45 |50717.10139 |0 |

|4.148 |441.6314 |12.7 |12.7 |45 |59169.95162 |0 |

This is a chart of the calculations we preformed to find the wattage output of the On Demand Water Heater. We determined that the best flow rate to use would be 2.5 gallons per minute which, in this table, would require about 20 kJ to be heated to the desired temperature.

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