Balancing DHWS Return with CircuitSolver®

To download the printable PDF version of this application, click here.

The Trouble In The Return

During periods of no use, domestic hot water recirculation systems(DHWS) function as a closed loop. The mixing valve will utilize the water from only the return line and water heater since no additional cold water can enter the system.

When an excess of return flow is directed to the water heater, the system’s water temperature will gradually rise until it equals the storage tank temperature. Conversely, if too much return flow is directed to the mixing valve, the temperature throughout the system will decrease to ambient temperature.

Traditional Solution

Conventionally the way to solve this issue involves installing a manual balancing valve between the water heater and the return flow into the water heater. However, the flow requirement is typically set based on estimation rather than automatic adjustment to accommodate the evolving dynamics of a recirculating hot water system. Consequently, this design can result in gradual temperature increases or decreases over time. ater system.

Thermostatic Solution

A more effective approach to balancing a DHWS return is to use a thermostatic valve, such as CircuitSolver®, instead of the manual balancing valve. The set-point of the CircuitSolver® should match the desired return temperature. When installed on the supply inlet of the return piping to the water heater, the CircuitSolver® will regulate the flow of water back to the water heater in proportion to how cool the return water temperature is relative to the mixing valve output temperature.

When the water temperature at the return valve equals the desired return temperature, the CircuitSolver® would be closed, except for a small bypass, allowing minimal flow back to the water heater. However, as the return water temperature drops below the desired temperature, the CircuitSolver® opens, providing increased flow to the water heater. This effectively mitigates both positive and negative temperature creep.

CircuitSolver® valves will ensure that significant temperature variations, either higher or lower than the mixing valve output temperature, are avoided. It is a temperature solution to a temperature problem.

Example System:

CircuitSolver DHWS Diagram 01 827x1024 - Balancing DHWS Return Line

The master mixing valve output temperature is 125°F with a desired return temperature of 115°F, 10°F ∆T.

The set-point of the CircuitSolver® in the return line to the water heater should be the same as the CircuitSolver valves at the end of each branch/riser.

How To Select The Correct CircuitSolver®:

  • Select the set-point temperature equal to the desired return temperature.
  • Select the size of the CircuitSolver® equivalent to the return to the water heater line size.
  • Choose applicable options – union, check valve, ball valves, Viega ProPress® ends, etc.
  • Build the appropriate model number based on these selections.