What Is an Indirect Water Heater and How Does It Work?

What Is an Indirect Water Heater?

An indirect water heater is a device used to provide domestic hot water for a household or commercial water heating system.

It is typically connected to a boiler or a space heating system and uses a heat exchanger to transfer heat from the heating system to a separate hot water tank.

The hot water in the tank is then distributed to faucets and fixtures in the building.

Indirect water heaters can be fired by natural gas, oil, propane, or electricity, and they are known for their efficiency and insulation.

They can come in different configurations such as coil, storage tank systems, tankless systems, or hybrid tank-tankless systems, depending on the size and demand for hot water.

In general, the hot water output of an indirect water heater is determined by a formula based on the specific heat of water, system efficiency, and heat input.

They may require additional components like an expansion tank and are often compatible with large boilers.

Indirect water heaters provide a cost-effective and durable solution for water heating, offer redundancy in case of boiler failure, and can be operated during the summer months.

However, they may require extra piping and pumps, and it is always recommended to seek professional advice to properly size the system based on the heating loads of the building.

Key Points:

An indirect water heater is used to provide hot water for a household or commercial water heating system.

It is connected to a boiler or space heating system and uses a heat exchanger to transfer heat to a separate hot water tank.
The hot water in the tank is distributed to faucets and fixtures in the building.
Indirect water heaters can be fueled by natural gas, oil, propane, or electricity and are known for their efficiency and insulation.

They come in different configurations depending on the size and demand for hot water.
Additional components like an expansion tank may be required and it is recommended to seek professional advice for proper sizing.

Did You Know?

1. An indirect water heater is a device that uses heat transfer to provide hot water for domestic use.

2. The majority of indirect water heaters are connected to a separate boiler or a central heating system, utilizing the heat generated by these sources to indirectly heat the water in the tank.

3. Unlike traditional water heaters, indirect water heaters do not have their own built-in heating elements, relying instead on the heat generated from external sources to warm the water.

4. Indirect water heaters are often more energy-efficient than other types of water heaters, as the heat transfer process reduces energy loss and helps maintain a steady supply of hot water.

5. Indirect water heaters are commonly used in homes with boilers and radiant heating systems, as they can utilize the excess heat from the boiler to efficiently provide hot water while reducing energy consumption.

Types Of Indirect Water Heaters

Indirect water heaters are an efficient and effective way to provide hot water for various purposes, such as domestic water heating or space heating. These systems utilize a heat exchanger that transfers heat from a primary heat source, typically a boiler, to the water stored in a separate tank.

There are three main types of indirect water heaters:

Storage Tank Systems: These are the most common type of indirect water heaters. They consist of a storage tank that holds a certain volume of water and a coil or heat exchanger inside the tank. The heat exchanger is connected to the primary heat source, usually a boiler. When the boiler is engaged, hot water from the boiler flows through the heat exchanger and transfers its heat to the water inside the tank. This heated water can then be used for domestic hot water or space heating purposes.

Tankless Systems: In contrast to storage tank systems, tankless indirect water heaters do not have a storage tank. Instead, they heat water instantaneously as it passes through the heat exchanger. When there is a demand for hot water, cold water flows through the heat exchanger, where it is quickly heated by the primary heat source. This type of system is particularly useful for situations where there is a limited amount of space or when there is a higher demand for hot water.
Hybrid Tank-Tankless Systems: As the name suggests, hybrid tank-tankless systems combine the advantages of both storage tank and tankless systems. They have a small storage tank that holds a certain volume of water for immediate use, allowing for quick hot water availability. If the demand exceeds the capacity of the storage tank, the tankless component kicks in to provide continuous hot water. This hybrid design provides the best of both worlds, ensuring a constant supply of hot water while maximizing overall efficiency.

Factors Affecting Efficiency Of Indirect Water Heaters

The efficiency of an indirect water heating system depends on several factors. These include insulation, heat output, heat input, and proper sizing.

Insulation: The storage tank of an indirect water heater should be well-insulated to minimize heat loss. Adequate insulation reduces energy consumption and ensures that the hot water stored in the tank remains hot for longer periods.
Heat Output: The heat output of the primary heat source, such as the boiler, affects the efficiency of the system. If the heat output is too low for the demand, the hot water production may be insufficient.

Heat Input: The heat input refers to the energy transferred from the primary heat source to the water in the heat exchanger. A more efficient heat exchanger will allow for better heat transfer and increase overall system efficiency.
Sizing: Choosing the right size indirect water heater is crucial. If the system is undersized, it may struggle to meet the demand for hot water, resulting in inadequate hot water availability. Conversely, an oversized system will waste energy and may lead to temperature fluctuations.

Choosing The Right Size Indirect Water Heater

Selecting the proper size indirect water heater is essential to ensure sufficient hot water supply and optimal efficiency. Several factors determine the size requirements, including the demand for hot water, the formula for calculating heat load requirements, and the specific heat needs of the user.

Determining the demand for hot water involves considering the number of faucets, fixtures, and appliances that will require hot water simultaneously. A formula based on the specific heat requirements of each item is then used to calculate the heat load, which represents the amount of heat energy needed to meet the demand.

It is recommended to consult with a professional to accurately determine the correct size for an indirect water heater. A professional can assess the specific needs of the user and consider factors such as the size of the space to be heated, the type and efficiency of the primary heat source, and any future expansions or changes in hot water demand.

Consult with a professional to accurately determine the correct size.
Consider factors such as the size of the space to be heated, the type and efficiency of the primary heat source, and any future expansions or changes in hot water demand.

Benefits And Drawbacks Of Indirect Water Heating Systems

Indirect water heating systems offer several benefits, including:

High Efficiency: Indirect water heaters are highly efficient because they utilize the waste heat generated by a primary heat source, such as a boiler. This reduces energy consumption and lowers utility bills.

Durability: Indirect water heaters are known for their durability. The absence of direct contact between the primary heat source and the water storage tank prolongs the lifespan of the system.
Redundancy: Indirect water heaters provide redundancy by being compatible with large boilers. If the primary heat source fails, the system can be easily switched to another heat source, ensuring a continuous supply of hot water.

However, there are a few drawbacks to consider:

Initial Cost: Indirect water heating systems can be more expensive to install compared to other types of water heating systems due to the additional components required, such as the heat exchanger and storage tank.
Extra Piping and Pumps: Indirect water heaters require additional piping and pumps to connect the primary heat source to the storage tank or heat exchanger. This may require modifications to existing plumbing systems.

Electricity Requirement: Indirect water heaters often require electricity to power the pumps and controls, adding to the overall energy consumption of the system.

Important Considerations For Installing An Indirect Water Heater

When installing an indirect water heater, there are several important considerations to take into account:

Heating Loads: Accurately assessing the heating loads of the space and hot water demands is crucial. This will determine the appropriate size and specifications for the indirect water heating system.
Professional Advice: It is highly recommended to consult with a professional. They can ensure proper installation and address any technical or compatibility issues with the existing heating system.
Summer Operation: Some indirect water heating systems have a summer operation mode. This allows the primary heat source to be disconnected or switched to a lower setting. This conserves energy during periods of low hot water demand.

Expansion Tank: An expansion tank may be required. It accommodates the expansion of water as it heats up. This prevents pressure buildup and potential damage to the system.

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Frequently Asked Questions

What is the difference between a direct and indirect water heater?

The primary difference between a direct and indirect water heater lies in their method of heating. In a direct water heater, the flame and air have direct contact, enabling the heat to transfer directly to the water. However, in an indirect water heater, the flame remains enclosed within a sealed combustion chamber. The heat generated in this chamber is then transferred to the water indirectly, as it passes through a heat exchanger. This indirect method ensures that the flame never comes into contact with the exhaust air, enhancing safety and efficiency.

What is direct water heater?

A direct water heater is a type of system that includes a storage tank with its own burner, specifically designed to heat water directly within the tank. This option is particularly ideal for households that have a significant demand for hot water. These direct fired water heaters come in different configurations, such as baffled and center flue designs, providing homeowners with various options based on their specific needs. With its efficient and direct heating mechanism, this type of water heater offers an effective solution for delivering hot water consistently.

Is indirect water heater same as tankless?

While both indirect water heaters and tankless coil systems provide hot water, they are not the same. An indirect water heater uses a separate storage tank to heat water indirectly through a heat exchanger, typically using a boiler. This allows for consistent hot water supply and is more suitable for larger homes with higher hot water demands. On the other hand, a tankless coil system heats water directly as it flows through a heat exchanger within the boiler. It is a cost-effective option for smaller homes with lower hot water demands. However, it may struggle to maintain a consistent supply of hot water for larger households. Therefore, the choice between an indirect water heater and a tankless coil would depend on the size of the home and its hot water demands.

Do indirect water heaters last longer?

Yes, indirect water heaters have a longer lifespan compared to standard tank-type gas-fired water heaters. This is primarily due to the fact that indirect tanks do not require an additional source of fuel, such as gas or electricity, to heat the water. By utilizing the existing heating system in the house, indirect tanks avoid the wear and tear associated with combustion processes, resulting in a longer lifespan. Additionally, indirect tanks are typically made of high-quality materials that are more durable, further contributing to their longevity. Thus, if you are looking for a water heating solution that offers a longer lifespan, an indirect water heater would be a suitable choice.

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