Control of an electric water heater as per a load shedding request signal and a salubrity index
AssigneeHydro-Quebec
InventorsAlain Moreau, André Laperrière, François Laurencelle
Life of this patent
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Abstract
An electrical water heater that receives a load shedding request signal uses a temperature sensor that is positioned so as to measure a water temperature in a lower area of a tank of the water heater. A controller continuously determines a salubrity index of the water heater as a function of the temperature measured by the sensor and a time measurement The controller decides to interrupt an electrical power supply of the water heater through a switch so as to interrupt or not interrupt an operation of the water heater upon receipt of the load shedding request signal and only if the salubrity index meets a preestablished criterion.
Claims19
A system for controlling an electric water heater as per a load shedding request signal, the system comprising:
- a temperature sensor positioned in order to measure a temperature of water in a lower area of a tank of the water heater;
- a switch coupled to an electrical power supply circuit of the water heater, an opening and a closing of the switch being controllable by a control signal in order to interrupt or not interrupt an operation of the water heater;
- and
- a controller connected to the temperature sensor and to the switch, the controller being configured to:
- continuously determine a salubrity index of the water heater as a function of the temperature measured by the temperature sensor and a time measurement;
- and
- producing the control signal of the switch so that the switch causes an interruption of the operation of the water heater upon the load shedding request signal only if the salubrity index meets a preestablished criterion, wherein the salubrity index is determined by ratios between a time length during which the temperature measured by the temperature sensor is at a specific temperature degree and a reference time length for the specific degree, the preestablished criterion being a salubrity index having a value of at least one in order to prevent a proliferation of Legionella in the water heater.
A method for controlling an electric water heater as per a load shedding request signal, the method comprising the steps of:
- positioning a temperature sensor in order to measure a temperature of water in a lower area of a tank of the water heater;
- coupling a switch to an electrical power supply of the water heater, an opening and a closing of the switch being controllable by a control signal in order to interrupt or not interrupt an operation of the water heater;
- and
- connecting a controller to the temperature sensor and to the switch, the controller being configured to:
- continuously determine a salubrity index of the water heater as a function of the temperature measured by the temperature sensor and a time measurement;
- and
- producing the control signal of the switch so that the switch causes an interruption of the operation of the water heater upon the load shedding request signal only if the salubrity index meets a preestablished criterion, wherein the salubrity index is determined by ratios between a time length during which the temperature measured by the temperature sensor is at a specific temperature degree and a reference time length for the specific degree, the preestablished criterion being a salubrity index having a value of at least one in order to prevent a proliferation of Legionella in the water heater.
Dependencies are inferred from the claim text.