Demand-Driven Hot Water Recirculation with Flow Switching Module
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Solution Overview
Problem
Conventional hot water recirculation systems in buildings are inefficient, leading to significant water and energy wastage as they require continuous pumping and heating of the entire hot water loop, which results in energy loss and increased greenhouse gas emissions.
Innovation Solution
A demand-driven hot water recirculation system with a flow switching module that selectively diverts water back to the water heater when the temperature is below a set-point, using a pump only when a fixture is in use, and integrating an ergonomic mixing valve for intuitive operation, reducing energy consumption and water loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If continuous recirculation pumping is used to maintain hot water availability, then hot water delivery speed is improved, but energy consumption and water waste increase significantly
Solution Approach 1:
The system uses periodic recirculation cycles instead of continuous pumping. A controller activates the recirculation pump at predetermined intervals to circulate hot water through the distribution pipes, then shuts it off. This periodic operation maintains adequate hot water temperature in the pipes while dramatically reducing energy consumption compared to continuous operation.
Solution Approach 2:
The system performs preliminary heating of the recirculated water by routing it through the water heater before distribution. This ensures that the pipes are pre-filled with hot water in advance of when it is needed at fixtures, eliminating the wait time for hot water arrival without requiring continuous pumping.
2Reliability
If the entire hot water loop is continuously heated, then hot water availability is improved, but energy waste increases due to radiating heat into the house
Solution Approach 1:
The system heats water in the recirculation loop periodically rather than continuously. The controller activates heating only during scheduled recirculation cycles when hot water is actually being distributed to fixtures, preventing unnecessary heat radiation into the house while maintaining reliable hot water availability when needed.
Solution Approach 2:
The system maintains hot water temperature locally in the distribution pipes only when and where it is needed, rather than heating the entire loop continuously. By targeting specific zones during recirculation cycles, the system ensures hot water availability at fixtures while minimizing unnecessary heating and energy waste in unoccupied areas.
3Stability of the object's composition
If recirculation pump operates continuously, then hot water temperature consistency is improved, but pump wear and tear increases
Solution Approach 1:
The recirculation pump operates periodically at scheduled intervals rather than continuously. This reduces the total operating time and mechanical wear on the pump, extending its service life. The periodic operation is sufficient to maintain adequate temperature consistency in the hot water loop by circulating water through the heater at regular intervals.
4Speed
If hot water is pumped through long pipe runs, then hot water availability at distant fixtures is improved, but water waste increases during the wait time
Solution Approach 1:
The system performs preliminary circulation of hot water through the entire distribution system, including long pipe runs to distant fixtures, before hot water is actually needed. This pre-fills the pipes with hot water, so when fixtures are activated, hot water arrives immediately without the usual cold water flush, eliminating water waste while maintaining speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system minimizes water and energy wastage by only heating the necessary portions of the piping, reducing wear on the pump and lowering energy consumption, while maintaining efficient hot water delivery.
Implementation Method 1
a water heater (4) installed in a house or other building
Implementation Method 2
a pump (9) connected to the return piping for returning water from one or more hot water plumbing fixtures to the water heater
Implementation Method 3
a flow switching module (20) associated with the hot water plumbing fixture and fluidly connected to the hot water supply piping and the return piping. The flow switching module can selectively supply water from the hot water supply piping either to the hot water plumbing fixture or divert water to the return piping
Data Source
AI summary
A hot water recirculation system for a house or other building causes water to be recirculated to a water heater for reheating until the water is above a set-point temperature at which time the heated water is made available for use at a faucet or other hot water plumbing fixture. Recirculation of hot water takes place only when there is demand for hot water at a hot water plumbing fixture. A flow switching module for use in the hot water recirculation system can selectively direct water supplied to the flow switching module from a water heater either to a hot water plumbing fixture or to return piping for returning the water to the water heater. The flow switching module may be operated manually, automatically, or semi-automatically.