Electric water heater having dry fire protection capability

Patent metadata

Field	Value
Publication number	US-2016363347-A1
Application number	US-201514735972-A
Country	US
Kind code	A1
Filing date	Jun 10, 2015
Priority date	Jun 10, 2015
Publication date	Dec 15, 2016
Grant date	—

Abstract

A water heater has a tank defining an interior volume, a heating element disposed within the interior volume, and a temperature sensor disposed with respect to the heating element so that the temperature sensor detects temperature of an area ambient to the heating element in the interior volume. The heating element is actuated at a predetermined actuation rate and for a cumulative actuation period so that the predetermined actuation rate maintains the heating element below a predetermined maximum temperature in air and so that the actuation period contributes a predetermined amount of energy to the ambient area when the heating element is immersed in water.

First claim

What is claimed is:

1 . A water heater, comprising:
a tank defining an interior volume; a heating element disposed within the interior volume; a temperature sensor disposed with respect to the heating element so that the temperature sensor detects temperature of an area ambient to the heating element in the interior volume; and a controller in communication with the temperature sensor and configured to actuate the heating element at a predetermined actuation rate and for a cumulative actuation period so that the predetermined actuation rate maintains the heating element below a predetermined maximum temperature in air and so that upon conclusion of the cumulative actuation period, the heating element contributes at least a predetermined amount of energy to the area that is measurable by the temperature sensor when the heating element is immersed in water.

2 . The water heater as in claim 1 , wherein the controller is configured to
receive a first signal from the temperature sensor indicating temperature of the ambient area and determine a first temperature based on the first signal, after determining the first temperature, intermittently actuate the heating element for the predetermined cumulative actuation period, after the predetermined cumulative actuation period, receive a second signal from the temperature sensor indicating temperature of the ambient area and determine a second temperature based on the second signal, and disable the heating element if the second temperature exceeds the first temperature beyond a first predetermined increment.

3 . The water heater as in claim 2 , wherein, at the intermittently actuate step, the controller is configured to intermittently actuate the heating element for a plurality of actuation periods, the actuation periods being of a same duration.

4 . The water heater as in claim 2 , wherein, at the intermittently actuate step, the controller is configured to intermittently actuate the heating element for a plurality of actuation periods, and wherein a cumulative duration of the actuation periods is a period of actuation sufficient to heat water ambient to the heating element by at least a second predetermined increment.

5 . The water heater as in claim 4 , wherein the first predetermined increment defines a temperature threshold that corresponds to the second predetermined threshold.

6 . The water heater as in claim 4 , wherein respective inactive periods of the heating element separating the actuation periods are of duration and frequency sufficient to maintain the heating element below a predetermined maximum temperature.

7 . The water heater as in claim 1 , wherein the heating element and the temperature sensor are housed in the same harness, and wherein the harness is secured to a wall of the tank.

8 . A water heater, comprising:
a tank defining an interior volume; a heating element disposed within the interior volume; a temperature sensor disposed with respect to the heating element so that the temperature sensor detects temperature of an area ambient to the heating element in the interior volume; and a controller in communication with the temperature sensor and configured to
upon detecting a condition for activating the heating element, receive a first signal from the temperature sensor indicating temperature of the ambient area and determine a first temperature based on the first signal,
after determining the first temperature, actuate the heating element for a cumulative actuation period sufficient to heat water ambient to the heating element by at least a predetermined increment and separate periods of actuation of the heating element within the cumulative actuation period by respective inactive periods of the heating element sufficient to maintain the heating element below a predetermined maximum temperature,
after the predetermined cumulative actuation period, receive a second signal from the temperature sensor indicating temperature of the ambient area and determine a second temperature based on the second signal,
disable the heating element if the second temperature exceeds the first temperature beyond a threshold corresponding to the predetermined increment, and
actuate the heating element in response to the condition, if the second temperature does not exceed the first temperature beyond a threshold corresponding to the predetermined increment.

9 . A method of detecting a dry fire event in a water heater having a tank defining an interior volume, a heating element disposed within the interior volume, and a temperature sensor disposed with respect to the heating element so that the temperature sensor detects temperature of an area ambient to the heating element in the interior volume, the method comprising the step of actuating the heating element at a predetermined actuation rate and for a cumulative actuation period so that the predetermined actuation rate maintains the heating element below a predetermined maximum temperature in air and so that upon conclusion of the cumulative actuation period, the heating element contributes at least a predetermined amount of energy to the area that is measurable by the temperature sensor when the heating element is immersed in water.

10 . The method as in claim 9 , wherein the actuating step comprises:
detecting a first temperature of the ambient area; after detecting the first temperature, intermittently actuating the heating element for a predetermined cumulative actuation period; after the predetermined cumulative actuation period, determining a second temperature of the ambient area; and disabling the heating element if the second temperature exceeds the first temperature beyond a first predetermined increment.

11 . The method as in claim 10 , wherein the intermittently actuating step comprises intermittently actuating the heating element for a plurality of actuation periods, the actuation periods being of a same duration.

12 . The method as in claim 10 , wherein the intermittently actuating step comprises intermittently actuating the heating element for a plurality of actuation periods, and wherein a cumulative duration of the actuation periods is a period of actuation sufficient to heat water ambient to the heating element by at least a second predetermined increment.

13 . The water heater as in claim 12 , wherein the first predetermined increment defines a temperature threshold that corresponds to the second predetermined threshold.

14 . The water heater as in claim 12 , wherein respective inactive periods of the heating element separating the actuation periods are of duration and frequency sufficient to maintain the heating element below a predetermined maximum temperature.

15 . A method of detecting a dry fire event in a water heater having a tank defining an interior volume, a heating element disposed within the interior volume, and a temperature sensor disposed with respect to the heating element so that the temperature sensor detects temperature of an area ambient to the heating element in the interior volume, the method comprising the steps of:
upon occurrence of a condition for actuating the heating element, detecting a first temperature of the ambient area; after detecting the first temperature, actuating the heating element for a cumulative actuation period sufficient to heat water ambient to the heating element by at least a predetermined increment, wherein periods of actuation of the heating element within the cumulative actuation period are separated by respective inactive periods of the heating element sufficient to maintain the heating element below a predet

Assignees

• Rheem Mfg Co

Inventors

• Chaudhry Raheel A
• Hinton Arthur Y

Classifications

• F24H1/0018

  using electric energy supply · CPC title

• F24H9/2021 Primary

  Storage heaters · CPC title

• F24H2250/02

  Resistances · CPC title

• F24H9/1818

  Arrangement or mounting of electric heating means · CPC title

• F24H1/202 Primary

  with resistances · CPC title