Water heater and a method of preventing the water heater from empty boiling

Abstract

A water heater, which includes a water pipe, a combustor, and a dry-boiling protector. The dry-boiling protector includes a first sensor, a second sensor, and a controller. The first sensor senses a resistance of water in the water pipe, and the second sensor senses a flow rate of the water in the water pipe. The controller is electrically connected to the first sensor and the second sensor to stop the combustor to heat water when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period, and a flow rate sensed by the second sensor is not zero.

What is claimed is: 
     
         1 . A dry-boiling protector of a water heater, which the water heater has a water pipe, the dry-boiling protector comprising:
 a first sensor provided on the water pipe to sense a resistance of a fluid in the water pipe; and   a controller, which is electrically connected to the first sensor, stopping the water heater to heat water when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.   
     
     
         2 . The dry-boiling protector of the water heater of  claim 1 , further comprising a second sensor provided on the water heater to sense a flow rate of the fluid in the water pipe, wherein the controller stops the water heater to heat water when a flow rate sensed by the second sensor is not zero, and a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period. 
     
     
         3 . The dry-boiling protector of the water heater of  claim 2 , wherein the water pipe has an input section where cold water enters the water pipe, and both the first sensor and the second sensor are provided on the input section. 
     
     
         4 . The dry-boiling protector of the water heater of  claim 1 , wherein the first sensor has two electrodes, both of which are electrically connected to the controller and are suspended in the water pipe to sense a resistance between the electrodes. 
     
     
         5 . The dry-boiling protector of the water heater of  claim 1 , wherein the first sensor has an electrodes, which is electrically connected to the controller and is suspended in the water pipe, and the water pipe is a metal pipe electrically connected to the controller to sense a resistance between the electrode and the water pipe. 
     
     
         6 . The dry-boiling protector of the water heater of  claim 1 , wherein the water heater further has a gas pipe, a burner, and a gas valve; the gas pipe supplies gas to the burner; the gas valve, which is on the gas pipe, is electrically connected to the controller to cut off the gas in the gas pipe by a command of the controller. 
     
     
         7 . A water heater, comprising:
 a water pipe;   a combustor for heating the water pipe;   a first sensor provided on the water pipe to sense a resistance of a fluid in the water pipe; and   a controller, which is electrically connected to the first sensor, stopping the combustor when a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period.   
     
     
         8 . The water heater of  claim 7 , further comprising a second sensor provided on the water heater to sense a flow rate of the fluid in the water pipe, wherein the controller stops the combustor when a flow rate sensed by the second sensor is not zero, and a resistance sensed by the first sensor is higher than a critical resistance for a predetermined period. 
     
     
         9 . The water heater of  claim 8 , wherein the water pipe has an input section and a heat section connected to the input section; cold water enters the water pipe via the input section; the first sensor and the second sensor are provided on the input section; and the combustor heats the heat section. 
     
     
         10 . The water heater of  claim 7 , wherein the combustor has a gas pipe, a burner, and a gas valve; the gas pipe supplies gas to the burner; the gas valve, which is on the gas pipe, is electrically connected to the controller to cut off the gas in the gas pipe by a command of the controller. 
     
     
         11 . The water heater of  claim 7 , wherein the first sensor has two electrodes, both of which are electrically connected to the controller and are suspended in the water pipe to sense a resistance between the electrodes. 
     
     
         12 . The water heater of  claim 7 , wherein the first sensor has an electrodes, which is electrically connected to the controller and is suspended in the water pipe, and the water pipe is a metal pipe electrically connected to the controller to sense a resistance between the electrode and the water pipe. 
     
     
         13 . A method of preventing a water heater from boiling dry, wherein the water heater has a water pipe, the method comprising the steps of:
 sensing a resistance of a fluid in the water pipe; and   stopping heating the fluid when the resistance is higher than a critical resistance for a predetermined period.   
     
     
         14 . The method of  claim 13 , further comprising the step of sensing a flow rate of the fluid in the water pipe, wherein the step of stopping heating the fluid is performed when the flow rate is not zero, and the resistance is higher than a critical resistance for a predetermined period. 
     
     
         15 . The method of  claim 14 , wherein the water pipe has an input section where cold water enters the water pipe; and the resistance and the flow rate are sensed in the input section. 
     
     
         16 . The light acupuncture module of  claim 13 , wherein the water heater further includes a combustor, which burns gas to heat the water pipe; and the step of stopping heating the fluid is cutting off the gas to the combustor.