What the heck? the freezer in the house is getting hot! About a minute later, an email comes in that I actually check since I'm setting right there and it tells me that the house freezer is over 50 F.
Yes, my freezer sends me email. I set this up about 4 months ago when the door didn't get closed completely and was open for HOURS before I noticed it. It didn't cost me much to replace the stuff that had thawed out, I cooked it instead, but having it happen got me to thinking about alarming that kind of thing. I have a process called 'healthcheck.py' that I run as a daemon (all the time) that monitors the other processes and many of the devices that are reporting around the house. Things like the XBee coordinator process, the thermostats and the septic tank float are watched for problems and an email is sent every hour that they don't perform up to snuff. I just added code to this process to watch the temperature in the appliances to make sure they were OK.
I got up, walked over to the freezer, put the frozen french fries back on the shelf correctly, and closed the door. Problem solved and crises averted. All the scoffers out there that poo-poo'd me about putting a temperature sensor in the appliances ... No, none of the other folk that are automating and monitoring their houses had disparaging comments, it was neighbors and friends that just let the house react to things and then complain wondered why I bothered with that much work.
Really ?
What was really unexpected though was the aftermath of letting the freezer warm up like that. Take a look at this chart of the aftermath:
I suppressed the other appliances and expanded this to show a little normal operation on both sides. The big deal is how long it took for the freezer to return to normal. Because I left the door open for about two and a half hours the temperature went all the way from below zero up to 63 degrees. Then it took over 24 hours for the thing to get back to normal.
Wow, I gotta pay more attention to that door. What the heck was happening with the power usage during this time?
Here's the power chart for the same period, and I see that shortly after I closed the door the freezer went into a defrost cycle. That's a good thing because there had to be a bunch of ice all over the evaporator coil. The compressor was on trying cool a freezer with an open door and humidity from the house was freezing all over the coil lowering its efficiency. Then the ice maker took off to fill the empty ice bucket that I had emptied of sludge. The compressor ran for the entire 24 hour period getting the internal temperature back down where it should be, but the defrost cycles and ice maker ate some of the energy during this time.
So, the power bill will be a little higher this month, but notice that the freezer only uses around 150 watts. It won't cost me much at all. Once I started watching the appliances, it really impressed me how little power they use. A little Honda generator could power the appliances around my house for an extended power failure. That will almost certainly become a project in the future.
There's a couple of other things I want to point out to readers. First, the reason I left the door open was that I was playing with Grafana and got distracted. Second, the graph I was playing with actually told me something useful: the stupid freezer was getting hot. Third, I was immediately able to research the results of my screw up. What went on with the temperature recovery in the freezer and how that affected my power usage.
That is so stinkin' COOL. (pun intended)
So, I really recommend saving data for some period. I've never gone back more than a few months looking for some change or problem, but as shown here, a couple of weeks can really be valuable. I personally carry years of data, but that doesn't mean I have to; it also slows down my database queries. So, balance your own needs to what you want to do. Over time, you'll work it out.
Also, Grafana allowed me to look at different time frames and data really quickly. It took me just a few minutes to prowl through the data to understand what was going on. I could have done the exact same thing with other charting tools I've tried, but it would have taken me way longer. Man I'm glad they implemented MySQL in this tool.
I probably should go clean the freezer now, but at least it's working.
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