Residential Energy Audit - Chapter 9

Thermosiphoning solar heaters use the principle of natural convection to circulate water from the collector to a storage tank. As the water in the collector heats up, it becomes less dense and rises to the top of the tank, while cooler water from the bottom of the tank flows into the collector to be heated. This process continues as long as there is a temperature difference between the collector and the tank. Therefore, the statement that thermosiphoning solar heaters move water from the collector to a storage tank using the buoyancy of hot water is true.

Hot water has a tendency to rise due to its lower density compared to cold water. As a result, when the water heater is not in use, hot water will naturally flow upwards through the pipes. However, since the pipes are not insulated, the heat from the water will be lost to the surrounding environment, causing the water to cool down. Eventually, the cooled water will flow back down into the tank. This process of heat loss and circulation explains why the pipes near the water heater lose heat even when water is not flowing.

A draft inducer is necessary for an oil-fired water heater in a fairly airtight residential structure because it helps minimize the amount of indoor air that the water heater consumes. This is important because airtight structures can have limited air supply, and using a draft inducer ensures that the water heater does not deplete the indoor air. Additionally, a draft inducer provides a more reliable draft compared to a barometric draft control, ensuring efficient and consistent operation of the water heater. Therefore, the statement is true.

The explanation for the given correct answer is that integrated space and water heaters are more efficient compared to having separate units for space and water heating. By combining both functions into a single heater, energy is saved and the overall efficiency is increased. This makes integrated space and water heaters a potential choice for the future.

The statement suggests that the temperature of the water affects the amount of scale that can be deposited. It states that hard water at 160 deg F can deposit 8 to 10 times more scale than hard water at 120 deg F. Therefore, it implies that higher temperatures lead to a greater deposition of scale.

The statement is true because standby energy refers to the energy consumed by a water heating system when it is not actively heating water. This includes energy used to maintain the temperature of the water in the tank. Studies have shown that standby energy can account for a significant portion of the total energy used for water heating, ranging from 20% to 60%.

Pressure reducing valves are designed to reduce the pressure of water flowing through a system. When the pressure is reduced, the flow rate of hot water also decreases. This is because the reduced pressure restricts the flow of water, resulting in a lower flow rate. Therefore, it is true that pressure reducing valves reduce hot water flow rate.

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A sacrificial anode is a metal rod that is intentionally made more reactive than the steel parts of a tank. When submerged in an electrolyte, such as water, the sacrificial anode corrodes instead of the steel, effectively sacrificing itself to protect the tank's steel parts from corrosion. Therefore, the statement that a sacrificial anode protects the tank's steel parts against corrosion is true.

This statement is true because any weatherization, heating, and air conditioning work in a building involves testing for drafts and carbon monoxide (CO). Weatherization work aims to improve energy efficiency by sealing any drafts or air leaks in a building. Heating and air conditioning systems can produce CO if not properly maintained, so testing for this gas is crucial to ensure the safety of occupants. Therefore, it is accurate to say that any work related to weatherization, heating, and air conditioning in a building includes draft and CO testing.

Solar water heaters rely on sunlight to heat water, so they may not be as effective during cloudy weather. In order to ensure a continuous supply of hot water, solar water heaters are typically connected to backup water heaters. These backup heaters can be powered by electricity, gas, or another conventional energy source, and they kick in when the solar system is unable to generate enough heat. Therefore, it is true that solar water heaters are normally connected to backup water heaters in case of cloudy weather.

Placing electric storage heaters on top of an insulated platform can help save energy because the insulation prevents heat loss through the floor. This means that more heat is retained within the room, resulting in less energy being required to maintain a comfortable temperature. By reducing heat loss, the insulated platform allows the heaters to operate more efficiently, thereby saving energy and reducing heating costs.

Tankless coils waste energy because they require a large boiler to operate even during the summer months when the demand for hot water is low. This means that the boiler is constantly running and consuming energy unnecessarily, leading to energy wastage.

If the pipes are within 8 inches of the flue, using fiberglass pipe wrap without facing and securing it with wires is the safest choice. This is because the fiberglass insulation helps to prevent heat transfer and protect the pipes from the high temperatures of the flue. The lack of facing on the wrap allows for better airflow and prevents moisture buildup. Securing the wrap with wires ensures that it stays in place and does not unravel or become loose. Therefore, the statement is true.

Standby losses refer to the heat loss that occurs when hot water is stored in a tank and is not being used. To minimize standby losses, several measures can be taken. Pipe insulation helps to prevent heat loss through the pipes, ensuring that the hot water remains hot until it reaches the tap. Heat traps are devices installed in the pipe connections of the water heater, which prevent the heated water from flowing back into the tank and losing heat. Reducing water temperature can also minimize standby losses by lowering the temperature difference between the stored water and the surroundings. Tank insulation helps to insulate the water heater, reducing heat loss to the surrounding environment.

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Water heating systems in multi-family homes are designed for recovery capacities of 3 to 10 gallons per hour per resident. This means that the system is capable of heating and providing a continuous supply of hot water at a rate of 3 to 10 gallons per hour for each resident in the building. This range takes into consideration the varying hot water usage patterns and demands of different households, ensuring that there is enough hot water available for everyone's needs.

The measures mentioned, low flow shower heads and pressure reducing valves, are effective in reducing hot water waste. Low flow shower heads limit the amount of water flowing through the shower, reducing the amount of hot water used. Pressure reducing valves help to regulate the water pressure, preventing excessive water flow and reducing hot water waste. By implementing both of these measures, less hot water is wasted, leading to increased energy efficiency and cost savings.

Minimizing pipe diameter and minimizing pipe length can help in minimizing distribution losses. When the diameter of the pipe is reduced, there is less surface area for frictional losses to occur, resulting in lower energy losses. Similarly, by minimizing the length of the pipe, the distance over which the energy is lost is reduced, leading to lower distribution losses. Therefore, both actions contribute to minimizing distribution losses in a system.

Water heating systems in single family homes are designed to have recovery capacities of 3 to 20 gallons per hour per resident. This means that the system is capable of heating and providing hot water at a rate of 3 to 20 gallons per hour, per person living in the home. The range allows for different household sizes and water usage patterns, ensuring that there is enough hot water available for everyone's needs.

Technicians do not insulate the tops of gas-fired storage tanks because the vinyl facing used as insulation is combustible and it might interfere with the draft diverter. Insulating the tops of the tanks with a combustible material like vinyl facing can pose a fire hazard. Additionally, the insulation might obstruct the proper functioning of the draft diverter, which is responsible for ensuring the safe venting of exhaust gases. Therefore, it is best to avoid insulating the tops of gas-fired storage tanks to prevent potential safety risks.

The sacrificial anode is a device that is installed in a water heater to protect the tank from corrosion. It works by attracting corrosive elements in the water, which causes the anode to corrode instead of the tank. Softened water contains less minerals and is therefore less corrosive, which means that the sacrificial anode will corrode at a slower rate. As a result, it will need to be replaced less frequently, typically every 2-3 years. By replacing the anode regularly, the life of the tank can be extended by another 10 years, in addition to the normal 8-10 year lifespan of a water heater.

Storage water heaters with better warranties incorporate features such as improved tank coatings, auxiliary sacrificial anodes, and curved dip tubes. These features contribute to making the flushing of sediment more efficient. Improved tank coatings help to prevent corrosion and extend the lifespan of the water heater. Auxiliary sacrificial anodes attract corrosive elements, protecting the tank from damage. Curved dip tubes enhance the flushing process by efficiently removing sediment buildup. Overall, these features improve the performance and durability of the storage water heater.

The given answer correctly identifies the true statements about the energy usage in water heaters. Demand refers to the energy used for heating incoming cold water, standby refers to heat loss through storage tank walls, and distribution losses consist of heat losses through the pipes and fixtures.

The correct answer is 1 because fiberglass insulation is required to be at least 1 inch thick around pipes that are at least 8 inches from the flue. This thickness helps to prevent heat loss and maintain the temperature of the pipes.

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Increasing water heating efficiency to existing water heating systems can be achieved by implementing multiple strategies. One of the strategies is reducing the use and waste of hot water, which can be done by encouraging water conservation practices such as shorter showers or using low-flow fixtures. Another strategy is reducing standby losses from storage tank and pipes, which involves insulating the tank and pipes to minimize heat loss. Additionally, reducing distribution losses through pipes and fittings can also contribute to improving water heating efficiency by ensuring that hot water reaches its destination without unnecessary heat loss.

Aerating low flow shower heads mix water and air to create a misty spray, while laminar-flow shower heads do not mix water and air at the nozzle, but instead, form individual streams of water.

The draft fan in an induced-draft water heater serves multiple purposes. It regulates the air that passes through the burner, ensuring that the combustion process is efficient and controlled. It also minimizes the amount of excess air during combustion, which improves the overall efficiency of the water heater. Additionally, the draft fan limits airflow through the flue during combustion during the off cycle, preventing any potential backdrafts. This feature makes induced-draft water heaters safer, as it reduces the risk of combustion gases leaking into the indoor environment. Finally, the draft fan provides a more reliable draft, ensuring consistent and efficient operation of the water heater.

Tankless water heaters, also known as instantaneous water heaters or on-demand water heaters, heat water as it flows through the heater. They eliminate standby losses, which means they do not waste energy by continuously heating and storing water like traditional water heaters. Tankless water heaters are available with recovery efficiency ranging from 78% to 95%, making them energy-efficient. However, they have a limitation in terms of capacity, as running multiple water-consuming appliances simultaneously, such as taking a shower and running a dishwasher, may overload the heater and reduce its performance.

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This answer is correct because sealed combustion water heaters are designed to have a separate combustion and venting system, which makes them ideal for tightly sealed homes. The separate system ensures that the combustion process is isolated from the indoor air, reducing the risk of pollutants entering the home. Additionally, this type of water heater is commonly used in mobile homes when installed in the living space, as it provides a safe and efficient heating solution for these structures.

The energy factor in water heating takes into account the energy losses associated with the water heating process, the pilot light, and the storage tank. The water heating process itself involves energy losses due to heat transfer and inefficiencies in the heating system. The pilot light, which is constantly burning to ignite the main burner, also contributes to energy losses. Additionally, the storage tank losses refer to the heat lost from the stored hot water to the surrounding environment. Overall, the energy factor considers these various sources of energy losses to determine the efficiency of the water heating system.

Softened water contains higher levels of sodium due to the addition of salt during the softening process. This increased sodium content can pose a risk to individuals with high blood pressure, as it can further elevate their sodium intake and potentially worsen their condition. Additionally, the salt in softened water can accelerate the corrosion of anodes in water heaters, causing them to deteriorate at a faster rate and potentially leading to costly repairs or replacements.

An indirect water heater derives its heat from various sources such as solar collectors, a boiler, a heat pump, and an air conditioner. These sources provide the necessary heat to warm up the water indirectly, without direct contact between the heating source and the water. This allows for efficient heating and ensures that the water remains clean and free from any contaminants that may be present in the heating source.

Tankless water heaters should not be installed with a draft diverter as it can cause improper venting and potential safety hazards. The 89+ and 90+ units of tankless water heaters come with draft-assisting fans, which help in proper venting. Sealed combustion or direct vent units are recommended for tankless water heaters as they provide better efficiency and safety. Additionally, tankless water heaters can be problematic for utility companies due to their high power consumption.

The design of water heating systems is determined by factors such as occupancy, number of plumbing fixtures, and per capita use. Occupancy refers to the number of people using the system, which affects the demand for hot water. The number of plumbing fixtures, such as sinks and showers, also influences the demand. Additionally, per capita use considers the average amount of hot water used by each individual. These factors are interlaced and need to be taken into account when designing water heating systems to ensure that the recovery capacity, energy input, and storage capacity are sufficient to meet the demand.

Indirect water heaters have the advantage of eliminating the need for a chimney with heat losses. This means that they do not require a chimney to vent combustion gases, resulting in reduced heat loss. Additionally, they are safer because they do not burn fuel or require combustion air. Finally, if an indirect water heater is well insulated and coupled to a boiler that provides space heating, it can achieve higher efficiency compared to a direct water heater.

Sediment buildup in water heaters can cause various signs and issues. One sign is noise in gas water heaters, which can be caused by the sediment interfering with the burner's efficiency. Another sign is odors in both gas and electric water heaters, as the sediment can create a breeding ground for bacteria that produce foul smells. Lastly, sediment buildup can lead to bottom-element burnout in electric water heaters, as the sediment can insulate the heating element and cause it to overheat.