Thermostatic balancing valves have been around for a while now, but I had not given them any consideration for domestic hot water systems. Not understanding how thermostatic balancing valves work and how the system functions was my primary reason for holding off on using them.

Reading several manufacturers’ literature on how they function caused me to pause and consider how they impact flow and the scouring effect in hot water and hot water return systems for hospitals. 

The flow rate in health-care hot water systems is an important aspect to keep in mind as we consider scouring the piping to reduce or eliminate the biofilm that the bacteria (Legionella) feed on.

Hot water systems rely on proper flow balancing to ensure efficient operation and freedom from biofilm. Two commonly used methods for achieving flow balancing are thermostatic and flow-rate balancing valves. 

This column will explore the characteristics, operation and benefits of these two valve types. We will provide a comparative analysis to help readers understand their differences and make informed decisions when selecting the most suitable option for their domestic hot water system.

Maintaining a Constant Temperature

Thermostatic balancing valves are designed to maintain a consistent temperature throughout a water heating system by adjusting the water flow. These valves use a temperature-sensitive element, often a wax or liquid-filled bulb, which expands or contracts in response to a fluctuation in temperature.

The operation of thermostatic balancing valves is relatively straightforward. When the temperature-sensitive element detects a temperature variation, it expands or contracts, thereby activating the actuator connected to the valve mechanism. This actuation adjusts the valve opening, allowing for precise control over the water flow. 

By modulating the flow rate, thermostatic balancing valves ensure that each circuit or branch within the system receives the appropriate amount of hot water, resulting in a uniform temperature distribution.

Thermostatic balancing valves offer several advantages. First, they provide automatic temperature regulation, maintaining consistent temperatures throughout the building. This feature is particularly beneficial in multistory or large-scale installations where temperature variations are more likely to occur and immune-compromised patients are not a concern. 

Additionally, thermostatic balancing valves can help improve energy efficiency by minimizing overheating, leading to reduced energy consumption. They are relatively easy to install and require minimal maintenance.

Promoting Consistent Flow

Flow-rate balancing valves, on the other hand, regulate water flow within a water heating system based on the desired flow rate. These valves typically feature a flow measurement device, such as an orifice plate or flow meter, to monitor and control the volume of water passing through.

Flow-rate balancing valves operate by adjusting the valve opening to achieve the target flow rate. By controlling the water flow, these valves ensure that each circuit or branch within the system receives an appropriate and balanced amount of water, preventing underflow or overflow conditions. This balancing promotes consistent flow and enhances the overall performance of the system.

The benefits of flow-rate balancing valves are notable. Firstly, they offer precise flow control, allowing for accurate adjustment of flow rates to meet specific requirements. This feature is especially advantageous in applications where flow variations can affect the system’s performance, such as in hot water return. 

Secondly, these valves provide stability and consistency, eliminating the risk of uneven temperature distribution. This aspect is crucial for maintaining hot water temperatures and preventing localized temperature extremes. Lastly, flow-rate balancing valves can aid in system diagnostics and troubleshooting by providing valuable flow-rate data that helps identify potential issues.

Consider the Application

When comparing thermostatic and flow-rate balancing valves, it is essential to consider their respective advantages and applications. Thermostatic balancing valves excel in systems where temperature control is critical, ensuring consistent temperature while optimizing energy efficiency. They are commonly used for water heating systems in residential, commercial and industrial buildings.

On the other hand, flow-rate balancing valves are more suitable for applications where precise flow control is required, such as health-care water heating systems. These valves focus on achieving balanced flow rates throughout the system and providing stable temperature distribution at a calculated velocity and flow rate.

Thermostatic and flow-rate balancing valves offer distinct advantages for flow balancing in water heating systems. While thermostatic balancing valves prioritize temperature regulation and energy efficiency, flow-rate balancing valves prioritize precise flow control (feet per second) and stability. 

By understanding the characteristics and operation of these valves, individuals can make informed choices when selecting the most appropriate option for their specific water heating system requirements, ensuring optimal performance, comfort and energy efficiency.

If you are considering a thermostatic balancing valve in a hospital setting, you should pause to reconsider its use.

The hot water system will be designed to about 4 feet/second (fps) to scour the piping and remove the biofilm that Legionella bacteria feed on. The hot water return line will use around 3 fps for the design of the system. 

Something else to consider is the wax sensor element if superheating the hot water system will be performed. This wax substance can be damaged or melted away during such an event.

Thermostatic balancing valves or flow-rate balancing valves; which is best for your project?