Gas Heater for Water and a Gas Water Heater

Abstract

A method of operating a gas heater for water including the steps of restricting a water flow to the gas heater; determining a first rate of a first gas heating for the restricted water flow; adjusting the gas heating to the restricted water flow; repeating the previous steps until a heated water has a temperature above a temperature threshold; removing the restriction to the water flow to increase the water flow; and determining a second rate of a second gas heating for the increased water flow.

That which is claimed is: 
     
         1 . A method of operating a gas heater for water, the method comprising:
 restricting a water flow to the gas heater;   determining a first rate of a first gas heating for the restricted water flow;   adjusting the gas heating to the restricted water flow;   repeating the steps of restriction, determining, and adjusting until a heated water has a temperature above a temperature threshold;   removing the restriction to the water flow to increase the water flow; and   determining a second rate of a second gas heating for the increased water flow.   
     
     
         2 . The method of  claim 1 , wherein the step of removing of the restriction to the water flow includes electronically controlling a by-pass valve to the water flow to the gas heater. 
     
     
         3 . The method of  claim 2 , further comprising opening the by-pass valve to increase the water flow. 
     
     
         4 . The method of  claim 1 , wherein the step of removing of the restriction to the water flow includes using a temperature dependent shape memory alloy to actuate a by-pass valve to the water flow to the gas heater. 
     
     
         5 . The method of  claim 4 , further comprising opening the by-pass valve to increase the water flow. 
     
     
         6 . The method of  claim 2 , further comprising setting at least one temperature threshold according to a by-pass valve operating characteristic. 
     
     
         7 . The method of  claim 2 , wherein the step of determining a first rate of a first gas heating rate comprises at least one of a T-outlet temperature sensed value, a pre-heat time, a water flow rate, a flame on signal, a valve operating characteristic and a T-inlet temperature value. 
     
     
         8 . The method of  claim 2 , whereby a hot water delivery lag time is reduced by at least 50% compared to a conventional hot water heating method. 
     
     
         9 . The method of  claim 2 , whereby a hot water delivery lag time is reduced by a period that is from 15 seconds to 25 seconds. 
     
     
         10 . A method of operating a gas heater for water, the method comprising:
 receiving, at a controller, temperature data from one or more temperature sensors, wherein the temperature data comprises outlet temperature data indicating a temperature of water exiting a heat exchanger; and   based on the temperature data, outputting instructions for a valve configured to selectively permit water to flow through a by-pass water flow path to close, thereby preventing water from flowing through a by-pass water flow path;   determining that the outlet temperature data indicates a water temperature less than a first temperature threshold; and   in response to determining that the outlet temperature data indicates a water temperature greater than or equal to a second temperature threshold, outputting instructions for the valve to open, thereby permitting water to flow through the by-pass water flow path.   
     
     
         11 . The method of  claim 10 , further comprising:
 determining a water heating rate based at least in part on the outlet temperature data; and   outputting instructions for adjusting operation of a burner of the water heating system.   
     
     
         12 . The method of  claim 11 , wherein:
 the one or more temperature sensors comprises (i) an outlet temperature sensor configured to measure the temperature of water exiting the heat exchanger and output the outlet temperature data and (ii) an inlet temperature sensor configured to measure a temperature of water entering the heat exchanger and output inlet temperature data indicating the temperature of water entering the heat exchanger,   the temperature data further comprises the inlet temperature data, and   determining the water heating rate is further based at least in part on the inlet temperature data.   
     
     
         13 . The method of  claim 12 , wherein determining the water heating rate is further based at least in part on a desired preheat time, a water flow rate, a flame-on signal, or a valve operating characteristic. 
     
     
         14 . The method of  claim 10 , wherein a location at which the by-pass water flow path rejoins the primary water flow path is upstream from the heat exchanger. 
     
     
         15 . The method of  claim 10 , wherein the second temperature threshold is less than or equal to a set point temperature indicative of a target temperature of water exiting the heat exchanger.