I have large freezer stocked with food. I'm going to be away for a few weeks and the house will be empty.

Here in Arizona we usually get power outages during storms in the summer.

So I'll have no way of knowing if any outage was ten seconds or ten hours.

I can tell if there was an outage because microwave clock will be messed up, but no idea how long, if food thawed and later refroze.

I guess I could put a block of ice and see if that melted, perhaps that's best way...

 

A plug in mechanical mains timer will tell you how long the power was off, as it will be behind time .

 

My bedroom alarm clock resets to 12.00 when the power returns, so I can calculate how long it was out for if it was less than 12 hours, but that is only good for one outage. You need a UPS on your freezer. They work well but the gel batteries in mine are only good for a year or two. You can get them with Li-Ion batteries now which should last a lot longer.
https://www.amazon.com/HOWEASY-Port...igerator+battery+backup&qid=1689877060&sr=8-5

 

A plug in mechanical mains timer will tell you how long the power was off, as it will be behind time .

The problem here is that you can't distinguish between multiple short power outages and a single long power outage. The effects on frozen food can be very different between the two.

 

I have large freezer stocked with food. I'm going to be away for a few weeks and the house will be empty.

Here in Arizona we usually get power outages during storms in the summer.

So I'll have no way of knowing if any outage was ten seconds or ten hours.

I can tell if there was an outage because microwave clock will be messed up, but no idea how long, if food thawed and later refroze.

I guess I could put a block of ice and see if that melted, perhaps that's best way...

Depending on the lengths you want to go to, it would be a relatively easy (you get to decide how "relative") to make a battery-powered data logger that logs power status when events happen.

If you have a device that is able to set its own time, such as using a cell network, an Internet time server, GPS, or WWV, then you could forego the need for battery power and just have the device log heartbeat timestamps at a sufficiently fast rate so that it would be easy to post-process the saved data later to map out when outages occurred and how long they lasted.

But then there's the problem of making decisions based on that data. If the power was out for two hours, is the food in the freezer safe to eat or not? What is the threshold? That not only depends on how long the power was out, but what the thermal mass in the freezer was (plus, of course, a lot of other things like the insulation of the freezer, but those are assumed to be fixed).

Putting a block of ice in the freezer gives you an indication that is much better correlated to the effect you are trying to measure -- namely, did things in the freezer thaw enough for you to be concerned?

One simple thing that people do is freeze a pop bottle half filled with water and put that in the freezer upside down. It doesn't make a mess if it melts, and gives you an indication of how bad the melt was. Plus, being sealed, you eliminate the sublimation factor.

A more sophisticated technique that a neighbor on the mountain used was to take a pop bottle and drill a hole in it just big enough to glue a funnel into. Then they filled the funnel with coarsely-crushed ice and put aluminum foil over the top (any kind of cover works, the idea is to reduce sublimation). The crushed ice would start to melt before any of the food started to thaw, how much water was in the bottle gave an indication of the overall magnitude of any problem that occurred, and whether the remaining ice in the funnel was still largely in chunks or had largely consolidated into a single chunk gave an indication of the severity of the longest outage.

On the defensive side, one thing you can do is to maximize the thermal mass in the freezer by putting filling as much of the volume with ice as you can -- gallon milk jugs filled about 80% with water work well for this, but soda bottles or anything else that is handy, including food containers, works as well. Then turn the temperature down as much as it tolerable. The increased energy consumption should be pretty minimal if there is no outage since the door won't be people opened and closed while you are gone. Another measure would be to put blocks of dry ice in the freezer. It should sublime slowly enough that it won't drop the temperature too much. You can even put it into styrofoam containers to better control this.

 

Get a temperature logger - there are many available.

 

Got to be a bit careful with a temperature logger, particularly with a frost-free freezer. They are frost free because they intentionally raise the air temperature enough to melt the frost, but not for long enough to thaw the contents. But, if this is known, taking that into account when interpreting the data should be pretty easy. It does still leave open a key underlying question, which is how long is too long when you see an elevated temperature. You might do something like embedding the temperature probe in a small package of something in order to get closer to an answer to that question.

 

A lot of home hardware that ties into the cloud will alert when the device becomes unavailable. Which would happen when the power goes out. Like smart outlets. Just have to set up and alert to notify you when the device becomes unavailable.

 

You have a nose for a reason. If the food smells "funny" don't eat it!

 

Apparently this was solved long ago. But first, this is a good example of a problem analysis trap (something very common in the world of software design by the way). It was a large error of judgment to think I could just reduce the problem to one of measuring outage duration. That wasn't the problem at all and as soon as we assume that we end up struggling with that new problem and begin to veer away from the true problem.

The problem is "did the food thaw" and that is readily solved with a shot glass of water, frozen and then with a coin placed on top of that frozen ice, the rest is a no brainer.

 

First thing that came to mind is a chart recorder that can record for a week at a time. Set it up to read out line voltage. Every time it varies you'll see it on the chart. You can determine if there were 100 outages each lasting for 1 hour or one outage that lasted for 100 hours. Or anywhere in between. And it doesn't have to be the numbers I mentioned. I just mentioned those numbers as examples. If you're gone for 14 days, on a 7 day chart recording you can still see outages. It's possible one may overlap another, but you'll still be able to get a good idea.

Chart recorders are not cheap. I don't imagine they're terribly expensive, but I get the goal of this thread - to know if your food has been compromised.

 

It occurs to me that a chart recorder would need an independent power source in order to record line outages. Hence, the recorder would likely need a substantial UPS. And since I've been scanning recorders from a few hundred to over a thousand bucks - it can be an expensive endeavor. Plus, you'll likely need a way to translate line voltage into a temperature reading or a pressure reading. For a temp reading, a low voltage such as a transformer to drop power way down, then using a voltage divider network you can get the output range somewhere that the recorder can THINK it's reading a temperature. Not so easy a task but doable.

A mechanical clock will let you know how many hours behind current time. If it's 12:00 noon and your mechanical clock is reading 3:00 then either the power has been out for a total of nine hours or 20 hours. If it's out for 24 hours and 5 minutes you may think it's only been out for five minutes. That's where a chart recorder would provide more valuable data.

I DO like MikeA suggestion. If power is out you can send someone in to hook up a generator and power the freezer for that period of time.

One last suggestion: A Generac generator. One that goes on when power fails for 30 seconds or longer. That way regardless of Arizona's power grid - you keep your frozen foods frozen. If you're going to spend any money - spend it on something more useful. Some of the recorders I saw could be in the $9,000.oo range. A generator would keep you cool in the summer and warm in the winter. Lights on when everyone else's lights go off. Freezers freezing grid or no grid. All you need is a consistent source of natural gas to power the generator.

Here's one for $3800 with transfer switch to automatically separate from the grid and power the home when power fails. It's 10,000 watts. That's 83 amps at 120VAC or just about 42 amps at 240VAC. Small, but big enough to keep certain things powered. And this one is wifi enabled. You'll know even when you're away - if power goes out. Unfortunately, as wattage goes up so does price.

 

Here - Rocky Mountain Power has text alerts that tell you how long the power is expected to be out in my area. Last time it was out it was down for three hours while they replaced a transformer. They said power would be back on by 5:00 PM, but had power back by 1:00 PM. They seem to like to give themselves some room for unexpected complications. And you don't have to buy anything.

OK, that's enough from me.

 

Something like an Arduino with an RTC and SD card module, set up to record temperature or whatever (line voltage?) at 5 minute intervals, powered from a wall wart. If the power fails, it stops recording.

Or, maybe just have it record something to the card to the effect of "x oclock and all's well" at some interval, and check when the last record was made. If the time difference is longer than the normal interval, save that to a separate file and write it to a character LCD.