It appears that you have a base load in the 400-500watt level and during
your holiday period, nothing else is coming on- including the stove,
dryer and water heater etc as well as the A/C. Chances are that the
highest peaks occur when the air conditioner comes on but your graph
shows a lot of variation over a what appears to be a short period.
Yes, you have the possibility of hitting a peak when using a 1 minute
interval. On a 6 second interval, this chance is increased by a factor
but averaging over a minute should minimize the effect of this. Now it
comes down to your real purpose- detecting when the A/C turns on (within
a given +/- time count of 6 seconds, or whatever-- or detecting energy
usage over a given reasonable time. In fact, for the latter, what may be
more of concern is hourly averages as that will be more realistic in
considering daily energy usage. Short peaks do not affect the daily
energy usage simply because they are short. As an example, a meter often
used for measuring peak (KVA) demand which is of importance to utilities
in that it affects the ratings of equipment, are designed with a thermal
lag so that starting and other transients don't contribute to the peak
reading (some meters have a 30 minute rise time to full reading).
My observations really have nothing to do with J programming but more to
do with knowledge of power systems.
Don Kelly
On 8/26/2016 5:24 AM, Joe Bogner wrote:
Don, thank you for the ideas.
Looking closer, I see some spikes around when the A/C turns on. If I wanted
to have a 1 minute interval, I still probably need the multiple readings
per minute (let's say every 5 seconds) and either average them out or pick
some other point. Otherwise, I might sample the peak.
I agree with correlating with known sources on/off. For example, I turned
on the coffee pot this morning and saw that usage jumped almost 1000 watts.
I have a routine of turning on the coffee pot in the morning so that might
be easy to detect as well
https://dl.dropboxusercontent.com/u/20783971/energymon_intervals.pdf
The meter only measures watts.
Thanks again
On Fri, Aug 26, 2016 at 1:20 AM, dhkelly <[email protected]> wrote:
I would suggest that you could get away with samples taken at longer
intervals. You won't lose useful information as none of the major
appliances including the air conditioner should draw a startup peak power
for over 6 seconds and what you really need is the increase in load over a
longer time. In addition, the air conditioner is a motor load which has a
lower power factor than something dominated by a heater element.
A change between two readings at the interval you are using or an
interval of the order of 60 seconds (or longer) will essentially give the
same information -something changed in the interval- whatever it is.
Determining whatever is a bit more iffy. If you get large jumps at 2AM-
blame the air conditioner. If at 8AM it could be stove and/or water heater
(breakfast and shower) indicating that you got up then.
The trouble with a whole house monitor, is that a measure of changes in
power alone, may not really give you all the data to distinguish sources.
Another is that a high sampling rate may give variations that are really
not of interest. I think that a step would be to correlate the data with
your direct observations of what went on or off - when( i.e at the time you
turned on a major load such as a stove or dryer- both of which will cycle
their power levels "on/off" in the same way that an air-conditioner does.
(e.g. an oven will turn on until the desired temperature is reached, then
turn off , repeating this cycle to maintain a a given temperature (+/- a
bit) just as an air conditioner or dryer does).
Don Kelly
Does the meter also measure power factor or "vars"?
On 8/25/2016 8:05 PM, Joe Bogner wrote:
I posted an article that looks at some data I captured using a whole-home
energy monitor. I also posted the data. I put up a challenge for anyone
who wants to take a stab at it.
http://code.jsoftware.com/wiki/User:Joe_Bogner/EnergyUsageAnalysis
How often does the air conditioner or clothes dryer turn on?
How long does it normally run, when did it run the longest?
Is it possible to determine when I go to bed or wake up?
I'd be interested in any approaches to answering any of these questions or
other analysis on the data
For example, the air conditioner draws a significant amount of energy. I
just turned it on and my usage went from 1460-6000 watts.
Looking at the change in prior reading may be a good start
plot (}. reading - (_1 |.!.0 reading))
I have an electric dryer and electric oven.
I hope the data and article is interesting/useful
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