Sabbath controller for a hot water tank
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Solution Overview
Problem
Existing Sabbath-compliant hot water systems waste energy by maintaining water at a constant temperature below 40°C and allow temperature drops during use due to continuous cold water replenishment, as they either randomize heating or shut off the water inlet completely, leading to inefficiencies and temperature fluctuations.
Innovation Solution
A water heating control system with a control unit that periodically activates and deactivates the heater, closes the water inlet valve during heating, and optionally uses a circulation pump to maintain an average water temperature below 40°C, while preventing cold water from entering the tank during use, thus optimizing energy usage and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the water inlet valve remains open during Sabbath mode, then the tank can be continuously replenished with cold water, but the incoming cold water mixes with hot water and causes temperature fluctuations that may drop below the permitted threshold
Solution Approach 1:
The control unit closes the water inlet valve before the Sabbath begins, preventing cold water from entering the tank during Sabbath mode. This preliminary action ensures that the hot water volume is fixed and will not be diluted by incoming cold water, thereby maintaining temperature stability above the 40°C threshold throughout the Sabbath period.
2Temperature
If the heater operates continuously at low power during Sabbath mode, then the water temperature is maintained above 40°C, but energy is wasted heating water that may not be needed and heating occurs even when the tank is full
Solution Approach 1:
The control unit receives signals from a temperature sensor to determine the actual water temperature in the tank. Based on this feedback, the control unit intelligently activates or deactivates the heater during Sabbath mode, ensuring the temperature remains above 40°C only when necessary. This feedback mechanism prevents unnecessary energy consumption by avoiding heating when the temperature threshold is already satisfied.
Solution Approach 2:
The system transitions from static continuous heating to dynamic intermittent heating during Sabbath mode. The heater operates in variable cycles, being activated only when the temperature drops toward the 40°C threshold and deactivated when the threshold is maintained, optimizing energy usage while ensuring compliance with Sabbath requirements.
3Temperature
If the heater is activated by a thermostat in response to hot water being drawn, then the water temperature is maintained, but the heater operation is triggered by user action which is prohibited on Sabbath
Solution Approach 1:
The control unit is programmed to automatically activate the heater at predetermined intervals or based on predicted usage patterns before Sabbath begins, rather than reacting to actual user draws during Sabbath. This preliminary and predictive heating strategy ensures temperature maintenance without requiring real-time thermostat response to user actions, thereby maintaining Sabbath compliance.
4Temperature
If the water inlet valve is closed during Sabbath mode, then temperature stability is improved, but the tank cannot be replenished and may run out of hot water
Solution Approach 1:
The control unit closes the water inlet valve before Sabbath begins, but ensures the tank is sufficiently filled with hot water in advance. This preliminary filling action provides a sufficient reserve of hot water that will last throughout the Sabbath period without requiring replenishment, thereby maintaining both temperature stability and adequate water volume.
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 efficiently maintains hot water at a permissible temperature, reducing energy waste and temperature fluctuations, ensuring continuous availability of hot water while adhering to Sabbath restrictions, and allowing for timely adjustment to prevent overheating before the Sabbath.
Implementation Method 1
Water in the tank 11 is heated by a heater 15
Implementation Method 2
water temperature is controlled by a control unit 16 in response to a temperature signal indicative of water temperature generated by a temperature sensor 17
Data Source
AI summary
A water heating control system has a tank for holding a volume of water heated by a heater and having a hot water outlet and a cold water inlet connected to a main water supply whereby hot water removed from the hot water outlet is replenished with cold water. A temperature sensor provides a temperature signal indicative of water temperature in the tank, and a control unit monitors the water temperature based on the temperature signal and is responsive to selection of a Sabbath mode of operation for periodically actuating and de-actuating the heater while maintaining an average water temperature to less than a permitted preset threshold. In Sabbath mode the control unit closes a shut off valve connected to the water inlet when the heater is actuated and opens the shut off valve when the heater is not actuated.