U.S. patent application number 13/469682 was filed with the patent office on 2013-11-14 for water heater having improved temperature control.
The applicant listed for this patent is James Randall Beckers. Invention is credited to James Randall Beckers.
Application Number | 20130299600 13/469682 |
Document ID | / |
Family ID | 49547891 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130299600 |
Kind Code |
A1 |
Beckers; James Randall |
November 14, 2013 |
WATER HEATER HAVING IMPROVED TEMPERATURE CONTROL
Abstract
A water heating system for a water heater includes a water tank
and a heating element heating the water in the tank. A temperature
controller has a temperature sensor and a temperature setting
device that controls water temperature responsive to a user set
temperature. A demand controller controls the temperature
controller to override the set temperature responsive to demand for
heated water. Demand is determined by water use measured by water
flow. During non-demand periods the heating element can be turned
off.
Inventors: |
Beckers; James Randall;
(Rockville, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Beckers; James Randall |
Rockville |
MD |
US |
|
|
Family ID: |
49547891 |
Appl. No.: |
13/469682 |
Filed: |
May 11, 2012 |
Current U.S.
Class: |
237/8A ;
219/490 |
Current CPC
Class: |
F24H 9/2021 20130101;
Y02B 30/00 20130101; F24H 1/185 20130101; Y02B 30/14 20130101; F24D
12/02 20130101 |
Class at
Publication: |
237/8.A ;
219/490 |
International
Class: |
F24H 9/20 20060101
F24H009/20 |
Claims
1. A water heating system, comprising: a water tank having a
volume; a heating element adapted to heat the water in the tank and
having a heating rate; a temperature controller having a
temperature sensor and a temperature setting device adapted to
control water temperature responsive to a user set temperature; and
a demand controller adapted to control the temperature controller
responsive to demand for heated water, the demand controller
comprising: a water flow sensor adapted to sense an amount of water
flow through the tank; an intake temperature sensor adapted to
measure the intake water temperature; a current temperature sensor
adapted to sense a current water temperature; a set temperature
memory adapted to store the user set temperature; a intake
temperature memory adapted to store the intake water temperature; a
demand table memory adapted to store the water flow information for
periods of time over the recurring period comprising periods during
a day and days of a week; a current temperature memory adapted to
store the current water temperature; a processor adapted to store
the user set temperature when set by the user, adapted to
periodically read and store the water intake temperature; adapted
to read water flow sensed by the water flow sensor to store and
update water demand information for the water flow over a recurring
period of time adapted to periodically read and store the current
water temperature, adapted to determine when the current time is
within the demand period and to allow the temperature controller to
control water temperature to the user set temperature during the
demand period, adapted to determine when the current time is within
a non-demand period to disable the temperature controller during
the non-demand, adapted to determine when water heating is to start
during the non-demand period to raise the current water temperature
to the user set temperature at the start of a next demand period
responsive to the current water temperature, the user set
temperature, the volume and the heating rate.
2. A water heating system, comprising: a water tank having a
volume; a heating element adapted to heat the water in the tank and
having a heating rate; a temperature controller having a
temperature sensor and a temperature setting device adapted to
control water temperature responsive to a user set temperature; and
a demand controller adapted to control the temperature controller
responsive to demand for heated water.
3. A system as recited in claim 2, wherein the demand is determined
by a user setting of on/off heating periods.
4. A system as recited in claim 2, wherein the demand is determined
by water flow.
5. A system as recited in claim 4, wherein demand periods of the
demand are periods of a day and days of a week.
6. A system as recited in claim 5, wherein the demand periods
comprise periods when flow is above a threshold.
7. A system as recited in claim 6, wherein periods of demand change
over time based on changes in water flow.
8. A system as recited in claim 2, wherein demand periods of the
demand are determined by water temperature.
9. As system as recited in claim 7, wherein the demand periods
comprise periods when water temperature is below a threshold.
10. As system as recited in claim 2, wherein the demand controller
starts temperature recovery to the set temperature in a non-demand
period before a demand period.
11. A water temperature control method for a water heater,
comprising: setting a set temperature for water temperature of
water in the water heater; determining demand periods and
non-demand periods for use of hot water; and overriding the set
temperature during non-demand periods.
Description
BACKGROUND
[0001] A water heater, such as a residential water heater, can have
a water tank and a controller or thermostat where the user sets the
relative operating temperature of the heater so that water of a
desired temperature is produced by the heater. The settings can be
vacation, warm (approx. 95 degrees F.), hot (approx. 105-110
degrees F.) and very hot (approx. 140 degrees F.). As the heater
operates when the temperature of the water gets above the setting
the heating controller turns off a heat source, such as an electric
element for an electric water heater and a gas burner for a gas
water heater. When the temperature falls below a lower offset
temperature, the controller turns on the heat source. This control
where the water temperature is kept at the desired temperature is
performed continuously throughout each day.
[0002] During a typical day of hot water use there are times when
there is little or no demand for hot water, such as when the
residents are asleep or, if they work outside the home, when they
are at work. What is needed is a hot water heater that will not
heat the water when there is no demand.
DRAWINGS
[0003] FIGS. 1, 2, 3 and 4 depict an embodiment that turns on/off a
heating controller.
[0004] FIGS. 1, 5, 6 and 7 depict an embodiment where a temperature
setting controls the heating.
[0005] FIGS. 1, 5, 8 and 9 depict an embodiment with temperature
control.
[0006] FIGS. 1, 5, 6 or 8 and 10 depict another embodiment having a
start of heating control.
[0007] FIGS. 5, 6 or 8, 11, 12 and 13 depict an embodiment using
water flow or hot water demand.
[0008] FIG. 14 shows a control process.
[0009] FIG. 15 shows a demand period.
[0010] FIG. 16 shows a two tank system.
[0011] FIG. 17 shows a temperature based learning process of anther
embodiment.
DETAILED DESCRIPTION
[0012] As depicted in FIG. 1, a water heater 110 can include a tank
112, a temperature sensor 114, a temperature controller 116 that
monitors the sensor for the current water temperature and sends a
control signals to a heating controller 118 that controls the
on/off of the heating element 120.
[0013] To allow control of the heating of the water relative to
demand, a temperature storage 210, such as a RAM or PROM, is
included, as depicted in FIG. 2. The temperature storage includes
an on/off indicator 212 or bit for each period during a day, week,
month, etc. during which temperature control is to be performed.
FIG. 2 shows settings for a Saturday of a week and for the period
from 9:30-10:45 in increments of 1/4 hour. Each "0" indicator 212
indicates that during that period the heating unit 120 or element
is to be turned off and each "1" indicates that during that period
the heating unit 120 can be turned on and operated at the residents
desired temperature setting with the offset using the typical
control discussed previously.
[0014] To facilitate the indicator based control, as depicted in
FIG. 3, an input unit 310, such as a display with a temperature set
button, a number pad, day selector, etc. can be provided. The input
unit 310 allows the user to set the time periods when the desired
temperature water is to be provided. For example, the user can
enter a start time of 8:15 and an end time of 9:30 as depicted in
FIG. 2. A processor 312, such as a microcontroller, sets the
indicator bits of the temperature storage to "1" for the periods
between and inclusive of the start and end time. During operation
the processor 312 monitors the current time by accessing a time
clock of the system, accesses the storage 314/210 to obtain the
indicator value and when the heating unit 120 is to be turned off,
activates a relay 316, typically an electronic relay, that is
closed when an open signal is not applied, to disconnect or
interrupt the control signal from the temperature controller to the
heat control by opening the relay. When the indicator is "1" the
relay remains closed to allow the control signal to be sent from
the temperature controller 318/116 to the heat controller
320/118.
[0015] An alternate operation approach as discussed in the
embodiments is to load the temperature controller with a desired
temperature as needed and allow it to control the heat controller
as depicted by the dashed lines in FIG. 3.
[0016] FIG. 4 depicts an approach 410 to the process performed by
the processor 312. When the input unit 310 is activated 412 by a
user, such as the resident, the processor 312 determines 414
whether the user has activated the setting function. If so, the
user is allowed to enter start times 416 and end times 418. When
the no more start settings need to be made 420, the processor 312
sets 422 the temperature storage with the appropriate values for
the indicator. When the operation is not in the setting mode, the
processor 312 obtains 424 the current time and accesses 426 the
temperature storage 314 of the corresponding time period. If the
indicator 428 is a "1" or "on", the processor 312 keeps the relay
316 closed 430. If the indicator is a "0" or "off", the processor
opens 432 the relay 316. The processor 312 then waits 434 for some
period of time before continuing, such as 1 minute.
[0017] The system discussed above could operate in alternate
embodiments such as rather than having a storage or memory that
stores on/off indicators for time periods, a memory/storage could
store on and off times and the system would determine if the
current time was equal to or between the on/off times in an on or
off period.
[0018] As depicted in FIG. 5, the temperature storage 510/314,
rather than including essentially on/off indicators, can include
set temperatures 512 for each of the time periods in which the
water temperature is to be controlled, such as day, week, month or
year. FIG. 5 shows a change in set temperature between the periods
of 7:45 and 8:00 and between the periods 9:00 and 9:15, between the
temperatures of 80 degrees F. and 140 degrees F., such as when a
family might use hot water for bathing and breakfast on a weekday
or weekend day. As can be seen, in this embodiment, the water
temperature can be set for a desired temperature by the user. In
this example of the storage 510, the time periods are 15 minutes
each in length but could be other lengths such as 10 minutes or
less and 30 minutes or more.
[0019] The system, in addition to the components as shown in FIG.
1, the temperature controller 610/318 (see FIG. 6) includes the
temperature storage 612 and a processor 614/312 that is coupled to
the temperature sensor 616/114.
[0020] As depicted in the process 710 of FIG. 7, when the input
unit is activated 712, the system determines whether the function
for setting the temperature for the time periods has been selected
714. If so, the user is allowed to enter 716 the start and stop
time for a setting and the temperature that is to be set during
that period. The set temperature for the time period is stored 718.
In the example of FIG. 5, the user would enter the start and stop
time periods of 8:00 and 8:45 and the temperature of 140. The
system stores the set temperature in the temperature storage for
each of the time periods in that range, that is, the time periods
of 8:00, 8:15, 8:30 and 8:45. If no more temperatures are to be set
720, the system begins to control the water temperature. The
current time is obtained 722 and the temperature storage for the
time is accessed 724 to obtain the set temperature for the current
time. The current temperature as determined by the sensor is
obtained and compared 726 to the set temperature. If the current
temperature is greater than or equal to the set temperature, the
heating controller is turned off 728. If the current temperature is
less than the set temperature, the heat controller is turned on
730. The system then waits 732 for a period of time before
continuing.
[0021] In another embodiment of the system 810, including FIGS. 1,
5, 8 and 9, the temperature controller 812/610 (see FIG. 8)
includes a set temperature storage 814 storing a set temperature
which is accessed by a controller 816 which controls the heat
controller 818/118 relative to the set temperature. A temperature
management unit includes a processor 822 and the temperature
storage 824 (see FIG. 5) that stores the varying temperature
settings. The temperature storage 824 of FIG. 8 is accessed by the
processor 822 and the processor 822 loads a temperature setting
from the temperature storage into the set temperature storage 814
of the temperature controller 812 where the controller 812 controls
the water temperature according to the set temperature in the set
temperature storage 814 responsive to the sensor 826/114.
[0022] As depicted by the process 910 in FIG. 9, during operation,
the processor 822 (see FIG. 8), obtains the current time 912 and
then accesses 914 the temperature storage for the time period of
the current time. The set temperature for that time period from the
temperature storage is obtained and loaded 916 into the set
temperature storage 814 of the temperature controller 816. The
temperature controller then controls the heating controller based
on the temperature loaded into the set temperature storage. The
system then waits 918 for a period of time before continuing.
[0023] The embodiment discussed above could also operate in
different ways. For example, rather than store a set temperature
for each different period, the system could store triplets of on
times, off times and temperature settings. The system would then
determine a set temperature or the on/off of a heating unit by
comparing and the using the triplets to control the heating of the
water, such as setting a corresponding set temperature into the set
temperature storage of the temperature storage when the current
time is equal or between the on/off times of that temperature
setting. The system could also include a pair of set time and
temperature setting and when the current time equals the set time,
the temperature setting could be loaded into the set temperature
storage of the temperature controller.
[0024] A further embodiment of a heating process 1010 including
FIGS. 1, 5, 6 or 8 and 10, determines when to start heating the
water to ensure that a desired set temperature, such as 140 degrees
is reached by a set time, such as 8:00, as depicted in FIG. 5.
[0025] For a natural gas water heater, natural gas contains about 1
therm (th) of heat per 100 cubic feet of gas which is 100 k BTU
(British Thermal Units). The BTU of gas required to raise the
temperature in a gas water heater from a current temperature to a
target temperature is about:
gas BTU=gallon cap.*8.3 lbs/gal*(target temp.-current
temp.)/100000
[0026] If we assume 40 gallon capacity water heater, a target temp
of 105 degrees Fahrenheit (.degree. F.), a current temperature of
55.degree. F., the BTUs required to raise the temperature from the
current temperature to the target temperature would be would be
about:
0.166=40*8.3*(105/55)/100000
[0027] The time required is:
time required (hrs.)=gas BTU*100000/heat rate (BTU/hr. of water
heater)
[0028] If we assume a heating rate of 40,000 Btu (40 k) per hour,
the time required to go from 55 degrees to 105 degrees would
be:
0.415=0.166*100000/40000
[0029] That is, it takes about 0.415 hours or approximately 25
minutes.
[0030] With a 30 gallon capacity gas water heater having a burner
producing 20 k BTU, the time require is 0.625 hours or
approximately 38 minutes.
[0031] In determining whether to start the burner of a natural gas
water heater a determination such as set forth below can be
made.
start (yes if negative)=time of demand-current time-time
required
[0032] That is if the time of the demand minus the current time
minus the time required is negative, the burner should be turned
on. For example, using the 30 gallon example and 105 to 55 degree
example noted above, if the demand time is 8:00, current time is
7:00 and the time required is 38 minutes (0.63 hrs), then
8-7-0.63=0.37 and the burner does not need to be started. However,
if the current time is 7:30, then 8.0-7.5-0.63=-0.17 and the burner
is to be turned on. That is, with the time being required as 38
minutes, at 7:22 (or 38 minutes before the demand time of 8:00 or
8-0.63=7.37 or 7:22) the burner needs to be turned on.
[0033] For an electric hot water heater:
BTU=watts*3.412
[0034] If we assume a water heater with an electric heating element
capable of producing 4500 watts, the time (a tank temperature time)
required for a 40 gallon electric water heater to raise the
temperature from 55 to 105 is 1.08 hours or approximately 65
minutes. For a 30 gallon electric heater with an element producing
3 k watts, the time required would be 1.21 hours or about 73
minutes.
[0035] In this embodiment, as depicted in FIG. 10, the system
obtains 1012 the current time and temperature and then accesses
1014 the temperature storage for the next temperature change and
the time at which that temperature change is to occur. For example,
in FIG. 5 when the current time is 7:30 the next temperature change
occurs at 8:00 and the temperature rises to 140 from 80 degrees
Fahrenheit.
[0036] The system then determines 1016 whether heating of the water
in the tank is to be started as discussed above.
[0037] If not, the system waits 1018 until proceeding. This wait
time needs to be some period, such as one minute, that will allow
variations in the start time to be detected as hot water demand
changes.
[0038] If heating of the water is to be started, the set
temperature of the change is loaded 1020 into the set temperature
storage or the heating element, thorough the heat control, is
turned on.
[0039] The above discussed embodiment can also operate in other
ways, for example, rather than storing temperatures for time
periods as depicted in FIG. 5, the system can store triplets or
pairs as previously discussed and the system determines from the
temperature settings and the times whether to start heating the
water as discussed above.
[0040] Another embodiment of a water heater 1110 is shown in FIGS.
5, 6 or 8, 11, 12 and 13. In this embodiment a water flow device
1112, such as a digital water flow meter, (see FIG. 11) is provided
on the water intake or the hot water out flow pipe 1111 as shown.
This meter 1112 records the water demand for periods of time over a
desired period, such as a day, week, month or year.
[0041] The actual demand is recorded in a demand storage 1210, such
as depicted in FIG. 12 which shows actual demand for a one and
one-quarter hour period over the last 7 days in increments or
periods 1212 of one-quarter hour. As can be seen the average demand
in the 8:00 (am) period is about 20 gallons while the average
demand in the 8:15 period is about 1 gallon. For each new day, the
actual demand is preferably recorded over the demand in the storage
so that a running moving average can be determined. For example,
when Sunday arrives the demand for that day at the 8:00 period
replaces the 21 gallon value in the storage 1210 and the system,
using sensor 1118, controls controller 1120.
[0042] During operation of this embodiment, the time (a demand
temperature time) required to raise the average demand water
entering the water heater from the intake temperature to the set
temperature is determined. For example, as depicted in FIG. 5 if
the set temperature is 140 degrees F. at 8:00 on Tuesday, as
depicted in FIG. 12, the average demand for that period is 20
gallons and the typical intake temperature for water coming from an
underground water pipe entering a residence is about 60 degree F.
As previously discussed the time required for a gas or electric
water heater to raise the temperature of 20.5 gallons of water from
60 degrees to 140 degrees F. can be determined. The current
temperature of the water in the tank can be used to determine the
amount of time required to raise the tank temperature to the
desired temperature. This time can then be used to determine
whether the heating unit needs to be turned on as previously
discussed
[0043] Note an intake water temperature sensor can be used to
measure the actual temperature of water flowing into the water
heater rather than assuming that the intake temperature is
approximately the temperature of water entering the residence from
and underground pipe and this case be used to determine the time to
start reheating.
[0044] This embodiment can also determine the amount of time
required to raise the entire tank of water from its current
temperature to the set temperature. This tank temperature time and
the demand temperature time can be combined to determine when to
turn on the heating element.
[0045] As shown in the process 1310 of FIG. 13, the system obtains
1312 the current temperature from the temperature sensor and
obtains the current time.
[0046] The temperature storage of FIG. 5 is accessed and the demand
storage of FIG. 12 is accessed 1314 to obtain any change in set
temperature and the future demand.
[0047] The demand temperature time and the tank temperature time
are calculated 1316 and combined and used to determine whether the
heating element is to be on.
[0048] If so, the set temperature is loaded 1318 into the
temperature storage of the temperature controller. The system then
waits 1320 for a period, such as one minute, before continuing.
[0049] For example, if we assume that we have a 40 gallon natural
gas water heater with a heat rate of 40k BTU per hour, a current
set temperature of 80 degrees, a future set temperature of 140
degrees F., a tank water temperature of 100, degrees F., an intake
temperature of 60 degrees F. and a future demand of 20 gallons, the
time before the set temperature and the demand which to start the
heating of the water is to ensure a tank of water at the desired
temperature about:
time=(((40*8.3*(140-100)/100000))+(20*8.3*(140-60)/100000)))*100000/4000-
0
[0050] The above discussed embodiment can also operate in other
ways, for example, rather than storing temperatures and demand for
time periods, the system can store triplets or pairs of set times
and temperatures and sets of times and demand values and the system
determines from the temperature settings and the times whether to
start heating the water as discussed above.
[0051] In another process 1410 embodiment, see FIG. 14, the stored
demand can be used to determine whether to start or continue
heating the water. In this embodiment the user has set a desired
temperature for hot water provided during periods of demand, such
as 140 degrees and a default temperature or a non-demand lower
temperature setting, such as 80 degrees F. is used during periods
of low or no demand.
[0052] In this approach 1410, as depicted in FIG. 14, the system
obtains 1412 the current time and temperature (and the demand and
no-demand temperatures) from the sensors and time clock.
[0053] The demand storage of FIG. 12 is accessed 1414 to obtain the
current and future demand.
[0054] With the current water temperature, the demand temperature
setting, and the demand from the demand storage, the system (see
FIG. 14) determines 1416 whether it is a time when the heating
element needs to be on using one of the approaches previously
discussed.
[0055] If the water needs to be heated, the demand temperature is
loaded 1418 into the set temperature storage or the heating element
is turned on.
[0056] If the water does not need to be heated, the non-demand or
off-peak temperature setting is loaded 1420. The system then waits
1422 for a period, such as one minute, before continuing.
[0057] In another 1510 embodiment (see FIG. 15) the current actual
demand can be used to determine whether to essentially override a
lower user setting to provide heated water when in a user lower
setting period. In a typical off-peak period when there is low or
no demand, demand for hot water can occur. For, example, a user
might need to wash their hands, wash a single pot, start washing a
load of cloths or start a dishwasher that has unexpectedly become
full. When the activity is washing hands, it is likely that no
water needs to be heated, because the demand is relatively low, say
less than one gallon. However, when the demand is greater it is
possible water may need to be heated to the users demand
temperature.
[0058] In this embodiment 1510, the system reads 1512 the flow
meter to determine whether there is any demand or flow (see FIG.
15). This can be determined in a number of different ways, such as
by comparing a previous reading with a current reading.
[0059] If there is a detected demand 1514, the system begins
monitoring 1516 the demand, which can be performed in a number of
different ways. One approach involves taking a demand reading after
a period of time, such a one minute. This reading is compared to a
prior reading and any difference added to any previously stored
demand reading.
[0060] To determine whether to start heating the water demand is
compared 1518 to a demand threshold, such as the one gallon
previously discussed.
[0061] If the demand is above the threshold, the system determines
1520 whether water heating needs to occur in one of the approaches
previously discussed.
[0062] If so, water heating is started 1522 or continued to raise
the temperature to the demand period temperature and demand
monitoring is continued.
[0063] If the demand is not above the threshold, the system checks
1524 to see if the demand has stopped, such as when a current flow
reading is the same as the previous flow reading.
[0064] The system then stores 1526 the accumulated demand and then,
if in an off-peak period, sets 1528 the temperature to the off peak
value.
[0065] The system then waits 1530 a period, such as one minute.
After the period, the system determines 1532 if the stored demand
needs to be reset 1534 to zero. For example, if there has been no
demand for some period of time, such as an hour, the accumulated
demand is reset to zero.
[0066] Another embodiment, as depicted in FIG. 16, can include two
tanks 1610 and 1612 in the water heater 1614 with corresponding
heat controllers 1616 and 1618 that are controlled by a temperature
controller 1620. In this embodiment, the lower tank 1610 is kept at
a lower temperature, such as 80 degrees F. and the upper tank is
kept at the set temperatures set by the user. The system operates
to control the temperature of the upper tank 1612 as in the
embodiments discussed previously. Another approach is to set the
lower tank temperature at some lower offset relative to the upper
tank, such as 30 degrees F. less than the setting of the upper tank
1612 and the two tank temperatures are controlled using one of the
control approaches as previously discussed. More than two tanks
could also be used.
[0067] Demand has been discussed as being determined by water flow
into or out of the water heater. However, the length of time that
the heating element is turned on can also be used to measure
demand. A water heater set at a desired temperature setting, such
as 105 degrees F., actually fluctuates between the temperature
setting where the heating element is turned off and a lower offset
temperature, such as 100 degrees F., where the heating element is
turned on.
[0068] A typical water heater is located in a residence in a site,
such as a basement or storage room, having a relatively constant
temperature, such as 70 degrees F. In such an environment, the rate
at which the temperature declines from the desired set temperature
to the offset temperature is governed by the heat loss from the
water into the 70 degree F. environment. The loss time required for
this decline is relatively stable. Likewise, the recovery time
required for the heating element to bring the temperature up from
the offset temperature to the desired temperature setting is also
relatively constant and repeats throughout a low demand period as
the water heater is "maintained" at the desired set
temperature.
[0069] Temperature can also be used to control when the water
heater is on or off for energy savings. In a temperature
embodiment, a learning period, such as one or two weeks, can be
used during which the system learns the water use habits by
comparing the temperature to a threshold. As a larger amount of
water is used (or demanded), such as when taking a bath the
temperature of the water in the tank drops more than when hot water
is used for a short or low demand period, such as when hand
washing. The typical temperature drop in a short time period or
some temperature below that by a few degrees can be used as the
threshold. When the temperature drops below that threshold and then
rises back above that threshold that period can be used to define a
period of heavy use during which the water heater needs to remain
on. At other times the temperature of the water can be allowed to
continue to fall until heat needs to be applied to bring the
temperature back up to the normal setting at the start of a heavy
use period. One approach or process 1710 to determining these
periods is depicted in FIG. 17. A temperature of the water measured
by a temperature sensor is read 1712 and compared 1714 to the
threshold. If the temperature is at or above the threshold, the
system loops back to take another reading. This loop back can be
controlled by a wait period 1716 that divides the learning period
up into a number of periods, such as 15 minute periods. If the
measured temperature is below the threshold, the system can store
1718, in a memory table (such as a PROM), the temperature and/or an
indicator that the threshold has been crossed and that the heater
is in a heavy use period. The system then determines 1720 whether
the end of the learning period has been reached. If not, the system
loops back for another temperature reading. If so, the learning
period ends 1722 and the system starts operation to heat water
during the use periods and not during non-use periods as previously
discussed.
[0070] This recovery time of the water heater for the recovery
demand can be measured outside of the residence and assumed as a
standard or measured in the residence. This recovery time can be
used to determine whether there is actual demand for heated water.
For example, if the time that the heating element is on is longer
than this recovery time, the demand is actual user demand and not
recovery demand. By measuring the time period that the heating
element is on that is longer than the recovery time along with the
actual time at which the heating period exceeds the recovery time,
the time of day (day, week, month and year) of a demand period and
the length of demand period can be determined. Such determined
demand periods can be used to fill a table such as in FIG. 12.
[0071] The description previously provided discusses a system that
uses the current heat controller of a water heater. This controller
could be eliminated and a processor with a temperature sensor could
be used to control the water heating by activating the heating
element or unit directly, allowing a user to set a desired
temperature that would be maintained with an offset during demand
periods and allowing the temperature in the tank to fall during
non-demand periods.
[0072] The system also works with smart grid, peak demand control
systems that are operated by utilities to turn off appliances
during peak electricity demand periods using a load control switch.
A load control switch is a remotely controlled that is placed on
home appliances which consume large amounts of electricity, such as
and electric water heaters. Load control switches typically include
a communication module and a relay switch. The load control switch
operates similarly to a pager to receive a control signal from the
power company to turn off or reduce power to the appliance during
times of peak electrical demand. The device also can have a timer
that will automatically reset the switch back on after a preset
time. The embodiments discussed herein can be used to override or
interrupt the control signal or produce a reset signal when demand
occurs and the heating element is off because in an low demand
period and/or in a peak demand period.
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