Electric water heater control

• US 6,208,806 B1
• Filed: 06/23/1999
• Issued: 03/27/2001
• Est. Priority Date: 06/24/1998
• Status: Expired due to Fees

• Current Assignee: Aquabeat Pty Limited
• Original Assignee: Aquabeat Pty Limited
• Inventors: Langford, Newton
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): CAMPBELL, THOR S
• Application Number:
  US09/338,930
• Time in Patent Office: 643 Days
• Field of Search: 392/464, 364/492, 364/493
• US Class Current: 392/464
• CPC Class Codes: F24H 9/2021 Storage heaters

Abstract

A domestic water heater 10 includes a water meter 14 to count the units of water used each day and has a timer 17 to time the heating cycle each day. A programmable means 18 stores the water usage and heating data for a sixty day period and using statistical techniques determines the time period required for heating the water in the tank 10. The means 18 also stores power load curve data from the power generator and matches the required heating time to an appropriate portion of a low in the power load curve. The tanks may be placed in any one of 9 groups and a tank in each group will by virtue of the program in means 18 center the mid point of the calculated heating period on the same time during the off peak period. Tanks fitted with such controllers can be allocated into one of two or more categories to enable a power utility to reallocate the water heater power load into low cost periods of the power load curve.

Claims

1. An electric water heater which includes:

a) a water tank;

b) an electric heating element disposed within said tank;

c) a cold water inlet into said tank;

d) a hot water outlet from said tank;

e) at least one thermostat in said tank or a water meter connected to said inlet or outlet to measure the amount of water used and/or a calendar/clock and timer connected to said element;

f) a memory store connected to at least one of said thermostat, water meter and calendar/clock and timer to record daily readings of

i) the average temperature of the tank or the amount of water used in the period from one heating period to the next, or

ii) the power used or the time required to heat the water in the tank to the desired temperature,

 

and store the readings for a predetermined number of days;

g) a programmable means programmed to analyze the readings in the memory store and calculate for each day the time duration required to bring the water to the desired temperature;

h) said memory store including power load curve data collected from the power generator appropriate to the day of week and season; and

i) said programmable means being programmed to match the required heating duration to a low cost portion of the load curve.

2. A water heater as claimed in claim 1 wherein:

a) the cold water inlet is in the base of the tank

b) the hot water outlet is in the top of the tank and

c) the tank is configured to allow temperature stratification of the stored water.

3. A water heater power controller which includes:

a) A connection to at least one thermostat located in the water storage tank and/or a connection to a water meter in the inlet or outlet of the water tank to measure the amount of water used

b) a calendar/clock and timer connectable to the heating element of the water tank

c) a memory store to record daily readings of

i) the temperature change of the tank or the amount of water used in the period from one heating period to the next and/or

ii) the power or the time duration required, to heat the water in the tank to the desired temperature

 

and store the readings for a predetermined number of days

d) a programmable means programmed to analyze the readings in the memory store and calculate for each day the time duration required to bring the water to the desired temperature

e) said memory store including power load curve data collected from the power generator appropriate to the day of week and season and

f) said programmable means being programmed to match the required heating duration to a low cost portion of said load curve.

4. A water heater power controller as claimed in claim 3 which calculates the duration of heating required and selects the start and finish times to fall within a period of low power cost.

5. A load leveling system for power utilities which includes:

a) a power utility

b) a plurality of electric water heaters adapted to draw power from said power utility

c) the water heaters are formed into at least two categories based on power rating or water heating times

d) each water heater is also allocated into one of a number of groups such that the heating of the tanks commences at different times for each group and the groups are sized and the start times are staggered so that the total power consumption by the water heaters occurs during periods of lowest cost to the utility

e) and at least one category of water heaters is composed of water heaters fitted with a water heater controller which is able to calculate the heating period required for the water heater and time the period of heating so that its mid point falls at approximately the mid point of the heating period for the group it has been allocated to.

6. A load levelling system as claimed in claim 5 in which said water heater controller includes:

a) a connection to at least one thermostat located in the water storage tank and/or a connection to a water meter in the inlet or outlet of the water tank to measure the amount of water used;

b) a calendar/clock and timer connectable to the heating element of the water tank;

c) a memory store to record daily readings of

i) optionally the temperature change of the tank or the amount of water used in the period from one heating period to the next;

ii) the power or the time duration required, to heat the water in the tank to the desired temperature;

 

and store the readings for a predetermined number of days;

d) a programmable means programmed to analyze the readings in the memory store and calculate for each day the time duration required to bring the water to the desired temperature;

e) said memory store including power load curve data collected from the power generator appropriate to the day of the week and season; and

f) said programmable means being programmed to match the required heating duration to a low cost portion of the load curve.