Method for operating a water heater appliance
A method for operating a water heater appliance includes obtaining a plurality of water temperature measurements over a period of time, determining at least one heated water draw event for the water heater appliance, and establishing a future operating schedule for the water heater appliance. The water heater appliance is operated according to the future operating schedule.
1. A method for operating a water heater appliance, comprising:
obtaining a plurality of water temperature measurements for water within the water heater appliance over a period of time;
determining at least one heated water draw event for the water heater appliance based at least in part upon the plurality of water temperature measurements;
establishing an operating schedule for the water heater appliance based at least in part upon the at least one heated water draw event; and
controlling a heating element of the water heater appliance according to the operating schedule,
wherein the at least one heated water draw event for the water heater appliance is determined with the following:
W
=
{
n
:
∑
j
=
1
K
h
j
(
n
)
≥
α
K
}
where
W
is
a
set
of
samples
n
,
h
j
(
n
)
=
{
1
∑
i
=
(
n
-
1
)
N
+
1
nN
H
j
(
i
)
≥
N
/
2
0
otherwise
,
h j (n) is a sampled heated water draw event value at sample n on day j,
N is a number of minutes between samples,
H j (i) is a heated water draw event value at time i on day j that is one during heated water draw events and zero otherwise,
K is a number of days, and
α is a confidence factor.
2. The method of claim 1 , wherein the operating schedule includes at least one higher set temperature operating period and at least one lower set temperature operating period, each higher set temperature operating period of the at least one higher set temperature operating period corresponding to a respective one of the at least one heated water draw event.
3. The method of claim 1 , wherein said step of determining comprises determining the at least one heated water draw event for the water heater appliance by comparing a slope over time between at least two water temperature measurements of the plurality of water temperature measurements to a predetermined slope.
4. The method of claim 3 , wherein each heated water draw event of the at least one heated water draw event corresponds to a portion of the period of time during which the magnitude of the slope between the at least two water temperature measurements is greater than the magnitude of the predetermined slope.
5. The method of claim 1 , wherein said step of establishing comprises establishing the operating schedule for the water heater appliance with the following:
S
(
n
)
=
{
T
high
if
n
∈
W
T
low
otherwise
where
S(n) is a set temperature of the water heater appliance at sample n,
T high is a higher set temperature for water heater appliance, and
T low is a lower set temperature for water heater appliance.
6. The method of claim 5 , wherein T high is greater than T low .
7. The method of claim 5 , wherein at least one of T high and T low are selectable by a user of the water heater appliance.
8. The method of claim 1 , further comprising calculating a transition rate of the water heater appliance between a lower set temperature, T low , and a higher set temperature, T high , the transition rate of water heater appliance corresponding to a rate at which the heating element heats the water within the water heater appliance from T low to T high .
9. The method of claim 8 , further comprising adjusting the operating schedule for the water heater appliance based at least in part upon the transition rate of the water heater appliance.
10. The method of claim 9 , wherein said step of adjusting comprises adjusting the operating schedule for the water heater appliance such that water within the water heater appliance is preheated to T high at each transition between T low and T high in the operating schedule for the water heater appliance.
11. The method of claim 8 , wherein the transition rate of the water heater appliance is calculated with the following:
d
=
∑
i
Δ
t
i
∑
i
Δ
T
i
where
d is the transition rate of the water heater appliance,
Δt i are time intervals when water within the water heater appliance is increasing in temperature, and
ΔT i are temperatures of water within the water heater appliance when water within the water heater appliance is increasing in temperature.
12. The method of claim 11 , wherein d is calculated daily.
13. A method for operating a water heater appliance, comprising:
obtaining a plurality of water temperature measurements, T k , for water within the water heater appliance at times k;
determining a high volume heated water event for the water heater appliance;
establishing an operating schedule for the water heater appliance, the operating schedule including a time period during which the water heater appliance operates at a higher set temperature, T high , and a time period during which the water heater appliance operates at a lower set temperature, T low , the time period during which the water heater appliance operates at T high corresponding to the high volume heated water event; and
heating water within the water heater appliance to either T high or T low according to the operating schedule,
wherein the high volume heated water event is determined with the following:
W
=
{
n
:
∑
j
=
1
K
h
j
(
n
)
≥
α
K
}
where
W
is
a
set
of
samples
n
,
h
j
(
n
)
=
{
1
if
∑
i
=
n
(
n
-
1
)
N
+
1
nN
H
j
(
i
)
≥
N
/
2
0
otherwise
,
h j (n) is a sampled heated water draw event value at sample n on day j,
N is a number of minutes between samples,
H j (i) is a heated water draw event value at time i on day j that is one during heated water draw events and zero otherwise,
K is a number of days, and
α is a confidence factor.
14. The appliance of claim 13 , further comprising calculating a transition rate of the water heater appliance between T low and T high , the transition rate of water heater appliance corresponding to a rate at which a heating element heats the water within the water heater appliance from T low to T high .
15. The appliance of claim 14 , further comprising adjusting the operating schedule for the water heater appliance based at least in part upon the transition rate of the water heater appliance.
16. The appliance of claim 15 wherein said step of adjusting comprises adjusting the operating schedule for the water heater appliance such that water within the water heater appliance is preheated to T high at the transition between the time period during which the water heater appliance operates at T low and the time period during which the water heater appliance operates at T high in the operating schedule for the water heater appliance.
17. The appliance of claim 13 , wherein said step of calculating comprises calculating the transition rate of the water heater appliance between T low and T high daily.