IN THE NEWS: Balancing Hot Water Recirculation Systems with PHCP Pros
Balancing Hot Water Recirculation Systems
In multistory buildings, hot water distribution presents challenges due to heat loss and varying distances between fixtures. In theory, recirculating (pumping) hot water continuously ensures delivery to all fixtures in the building and reduces water waste. However, it doesn’t guarantee uniform hot water throughout a building because water follows the path of least resistance.
Balancing ensures that flow is distributed adequately across all branches of a hot water system and is accomplished using balancing valves. These valves regulate flow to compensate for heat loss, with closer branches requiring less flow and farther branches needing more, providing consistent performance throughout the system.
A Brief History of Balancing Valves
Initially, domestic hot water (DHW) circulation relied on gravity-fed systems without pumps, depending solely on natural convection. Hot water rose due to its lower density, while cooler water returned to the heater.
Manual balancing valves were introduced in the mid-20th century as HVAC and hydronic systems became more common in large commercial buildings. These valves allowed technicians to adjust manually and balance water flow, improving efficiency and comfort in buildings with complex piping networks.
Pressure-independent balancing valves, also known as automatic or fixed flow valves, emerged in the late 1990s to early 2000s. They were developed to address challenges in maintaining efficient water flow in HVAC systems, particularly in variable-flow systems where traditional valves struggle to adapt to fluctuating pressures. PIBVs automatically adjust to changing pressure conditions, providing a more efficient and balanced distribution of heating or cooling without requiring manual adjustments.
Thermostatic balancing valves (TBVs) were introduced in 2012. TBVs utilize thermal actuators to provide precise temperature control in DHW systems, offering a way to balance water flow based on temperature without manual intervention.
CircuitSolver, developed by ThermOmegaTech, is often cited as one of the first thermostatic balancing valves specifically designed for DHW recirculation systems in the U.S. market.
How Thermostatic Balancing Valves (TBVs) Work
At the heart of the thermostatic valves is a thermal actuator, commonly using a paraffin wax which will phase change to produce motion. As the temperature rises, the wax melts, expanding in volume and pushing a diaphragm that extends the actuator’s piston, adjusting the valve position. When the temperature decreases, the wax solidifies, reversing the process.
TBVs use a phase change (solid to liquid) paraffin wax actuator to modulate flow based on fluid temperature going through the valve.
The Advantages and Disadvantages of TBVs
Advantages:
- Self-actuated and maintenance-free
- Automatically adjusts flow based on temperature
- Improves energy efficiency and system performance
- eliminates manual balancing and associated labor
- It is a temperature device directly addressing a temperature problem.
Disadvantages:
- Higher upfront cost compared to manual valves and PIBVs
Types of Thermostatic Balancing Valves
At present, there are two types of TBVs in the market:
Fixed TBVs are factory-calibrated to a single return temperature and tamper-proof. They have a larger design Cv (5 F below-set point), resulting in lower pressure drop due to a narrower open-to-close temperature range (10 F).
Adjustable TBVs allow field-adjustable temperature settings but require proper calibration to prevent system imbalances. They are typically adjustable over a 50 F span, resulting in a lower design Cv and higher pressure drop (>4:1 versus fixed in some cases), and are contractor-dependent for correct setup. Any startup issues often lead to revalidating temperature settings across the DHW system. Field adjustments can be made by unqualified personnel, posing a risk to system performance.
See the comparison here.
This feature originally ran on PHCP Pros on June 2, 2025. Read the full feature here.