초록 ▼

A controller for a water heater having a plurality of individual electrical heating elements changes the number of energized elements to maintain a predetermined minimum temperature. The number of “on”elements is related to the difference between sensed water temperature and a preset water temperatu

A controller for a water heater having a plurality of individual electrical heating elements changes the number of energized elements to maintain a predetermined minimum temperature. The number of “on”elements is related to the difference between sensed water temperature and a preset water temperature divided by a dead band factor. The heating elements are turned “on”and “off”in a programmed sequence whenever a change is required to optimize the equalization of operating time of the elements. The controller includes a microprocessor which monitors turn “on”or “off”of each element to continuously develop the “on”operational period of each element in relationship to all of the other heating elements since system initialization. The operation period is made relative to the load with the shortest period by substracting the lowest “on”time from all other loads so as to reduce the required memory size. The microprocessor periodically updates the status by processing of the last read and stored signals to create appropriate control signals for turning elements on and off in accordance with the longest and shortest operation periods respectively and thereby equalize element loading.

대표청구항 ▼

A water heater apparatus comprising a water storage tank having a plurality of separate heating means, comprising a plurality of power supply connectors one for each of said heating means and operable to energize the corresponding heating means and establish “on”periods and “off”periods of energizat

A water heater apparatus comprising a water storage tank having a plurality of separate heating means, comprising a plurality of power supply connectors one for each of said heating means and operable to energize the corresponding heating means and establish “on”periods and “off”periods of energization, sensor means for sensing the temperature of the water in the storage tank and establishing an output signal proportional to the water temperature, temperature preset means for establishing a signal proportional to a predetermined desired water temperature, status means to record the number of heating means in “on”periods in operation and to record the accumulated “on”periods and thereby the accumulated operating time of energization over a plurality of periods of each of said heating means, controller logic means for comparing the output of the sensor means and the preset means and said heating means in the “on”period to establish the number of activated heating means, and said controller logic means connected to said status means and having means operable to turn the heating means on and off in accordance with the historical accumulated operating time inclusive of a plurality of past “on”and “off”periods of operation and thereby the relative accumulated operating time of energization of each of said heating means.