Water heater apparatus with differential control

Abstract

An apparatus for a water heater is configured to control heating operation of a water heater to maintain a desired water temperature. The various embodiments comprise a sensor that provides an output indicative of the sensed temperature of water in a water heater, and a controller in communication with the sensor. The controller is operable to initiate a present call for heat where the sensed temperature is a predetermined amount below a set-point temperature. The controller is also configured to determine whether a prior call for heat occurred within a predetermined elapsed time period preceding the present call for heat, and to respond thereto by delaying the start of heating operation in the present call for heat until one of a predetermined time period or a predetermined sensed temperature change has occurred.

1 . An apparatus for controlling heating operation of a water heater to maintain a desired water temperature, comprising:
 a sensor that provides an output indicative of the sensed temperature of water in a water heater;   a controller in communication with the sensor, the controller being operable to initiate a present call for heat where the sensed temperature is a predetermined amount below a set-point temperature, wherein the controller is configured to determine whether a prior call for heat occurred within a predetermined elapsed time period preceding the present call for heat, and to respond thereto by delaying the start of heating operation in the present call for heat until one of a predetermined time period or a predetermined sensed temperature change has occurred.   
     
     
         2 . The apparatus of  claim 1  wherein the controller is configured to delay the start of heating operation until the sensed temperature decreases by a predetermined sensed temperature change that is dependent on the number of prior calls for heat within the predetermined elapsed time period. 
     
     
         3 . The apparatus of  claim 1  wherein the controller is configured to delay heating operation until a first predetermined sensed temperature change occurs where a single prior call for heat occurred within the predetermined elapsed time period. 
     
     
         4 . The apparatus of  claim 1  wherein the controller is configured to delay heating operation until a second predetermined sensed temperature change occurs where two prior calls for heat occurred within the predetermined elapsed time period. 
     
     
         5 . The apparatus of  claim 1  wherein the controller is configured to delay heating operation until a third predetermined sensed temperature change occurs where at least three prior calls for heat occurred within the predetermined elapsed time period. 
     
     
         6 . The apparatus of  claim 1  wherein the controller is configured to delay heating operation until a first predetermined time period has occurred where a single prior call for heat occurred within the predetermined elapsed time period. 
     
     
         7 . The apparatus of  claim 1  wherein the controller is configured to delay heating operation until a second predetermined time period has occurred where two prior calls for heat occurred within a predetermined elapsed time period. 
     
     
         8 . The apparatus of  claim 1  wherein the controller is configured to delay heating operation until a third predetermined time period has occurred where at least three prior calls for heat occurred within a predetermined elapsed time period. 
     
     
         9 . The apparatus of  claim 1  wherein the predetermined elapsed time period is a time period immediately preceding the present call for heat, of between about 30 minutes to about 120 minutes. 
     
     
         10 . An apparatus for controlling heating operation of a water heater to maintain a desired water temperature, comprising:
 a sensor that provides a value indicative of the sensed temperature of water in a water heater;   a controller that initiates a call for heat when a difference between a set-point temperature and the sensed temperature exceeds a temperature differential setting, the controller being configured to delay the start of heating operation for a given delay time period where the controller identifies a prior call for heat within a predetermined elapsed time period preceding the present call for heat.   
     
     
         11 . The apparatus of  claim 10  wherein the controller is configured to delay heating operation until a first delay time period has occurred where a single prior call for heat occurred within the predetermined elapsed time period. 
     
     
         12 . The apparatus of  claim 11  wherein the controller is further configured to delay heating operation until a second delay time period has occurred where two prior calls for heat occurred within a predetermined elapsed time period. 
     
     
         13 . The apparatus of  claim 12  wherein the controller is further configured to delay heating operation until a third delay time period has occurred where at least three prior calls for heat occurred within a predetermined elapsed time period. 
     
     
         14 . The apparatus of  claim 11  wherein the first delay time period is at least 10 seconds. 
     
     
         15 . The apparatus of  claim 13  wherein the first delay time period is at least 10 seconds, the second delay time period is at least 10 seconds greater than the first delay time period, and the third delay time period is at least 10 seconds greater than the second delay time period. 
     
     
         16 . An apparatus for controlling heating operation of a water heater to maintain a desired water temperature, comprising:
 a sensor that provides a value indicative of the sensed temperature of water in a water heater;   a controller that initiates a call for heat when a difference between a set-point temperature and the sensed temperature exceeds a temperature differential setting, the controller being configured to delay the start of heating operation until the sensed temperature decreases by a predetermined amount where the controller identifies a prior call for heat within a predetermined elapsed time period preceding the present call for heat.   
     
     
         17 . The apparatus of  claim 16  wherein the controller is configured to delay heating operation until the sensed temperature decreases by a first predetermined amount where only a single prior call for heat occurred within the predetermined elapsed time period. 
     
     
         18 . The apparatus of  claim 17  wherein the controller is configured to delay heating operation until the sensed temperature decreases by a second predetermined amount where two prior calls for heat occurred within the predetermined elapsed time period. 
     
     
         19 . The apparatus of  claim 18  wherein the controller is configured to delay heating operation until the sensed temperature decreases by a third predetermined amount where at least three prior calls for heat occurred within the predetermined elapsed time period. 
     
     
         20 . The apparatus of  claim 19  wherein the first predetermined amount is an offset temperature decrease of at least 5 degrees Fahrenheit, and the second predetermined amount is an offset temperature decrease that is at least degrees Fahrenheit lower than the first predetermined amount, and the third predetermined amount is an offset temperature decrease that is at least 5 degrees Fahrenheit lower than the second predetermined amount. 
     
     
         21 . An apparatus for controlling heating operation of a water heater to maintain a desired water temperature, comprising:
 a sensor that provides an output indicative of the sensed temperature of water in a water heater;   a controller in communication with the sensor, the controller being operable to initiate a present call for heat where the sensed temperature is a predetermined amount below a set-point temperature, wherein the controller is configured to determine whether more than 3 prior calls for heat occurred within a predetermined elapsed time period preceding the present call for heat, and to respond thereto by delaying the start of heating operation in the present call for heat until the first occurrence of either a predetermined time of at least 10 minutes or the sensed temperature decreases by at least 8 degrees Fahrenheit.