What is the minimum feedwater temperature recommended for a system without a deaerating heater?

The minimum feedwater temperature recommended for a hydronic system without a deaerating heater is typically 120 degrees Fahrenheit. This temperature is important for several reasons, primarily related to the prevention of corrosion and the enhancement of system efficiency.

When water is introduced into a system at too low a temperature, it may contain a higher concentration of dissolved gases, such as oxygen, which can lead to corrosion within the piping and boiler components. By ensuring that the feedwater is at least 120 degrees Fahrenheit, the solubility of these gases is reduced, minimizing their potential for causing damage.

Additionally, starting with warmer feedwater can improve the thermal efficiency of the heating system, as less energy will be required to bring the water up to the desired operating temperature. This can result in better performance and energy savings over time.

While options that suggest temperatures lower than 120 degrees, such as 100 degrees Fahrenheit, may seem viable at first glance, they do not provide adequate protection against corrosion and could lead to inefficiencies. Higher temperatures, like 140 degrees and 180 degrees Fahrenheit, are typically above the minimum requirements and may not be necessary for all systems without a deaerating heater, making 120 degrees Fahrenheit the recommended minimum standard.