Where are we with freeze alarms?

softdown

Not looking for a phone call. Just a noise and the ability to set the temperature for the alarm. Seems that calling you when the temp hits 45F might be standard procedure with freeze alarms. Perhaps I am using the wrong search words. 

Being a prepper I store food and drinks in several rooms. Nothing else matters if we don't have food. Glass bottles and aluminum cans can't handle a "hard freeze" of course. I'd guess that 24F may produce a hard enough freeze to fracture the glass and aluminum containers. That guess is as wild as it can be. Plastic is likely safe for quite awhile longer.

This area can easily see -30F. So a storage unit could witness a "hard freeze" with the right weather conditions. 

I only heat 800 sq. ft. Or 10% of the entire building. The temperature of the rest varies  depending on passive solar heating. 

Generally the cooler the food and beverage the better. Just need to avoid the hard freeze. 

BB.

I did some quick searches, and the only statement I could find was don't go below 40F.

The point at which items freeze is usually dependent on the amount of sugars and other ingredients in the specific item (for example, sea water freezes at ~-4C or 24.8F)... But It appears that the "raw" food only may go a couple degrees F below 32F before crystallization (freezing) begins.

Not exactly an answer to your canned good question, but I did run into this neat chart about the optimum storage conditions for a whole bunch of fruits and vegetables:

https://www.engineeringtoolbox.com/fruits-vegetables-storage-conditions-d_710.html

Proper storage conditions - temperature and humidity - are required to maximize storage life and maintain quality of harvested fruits and vegetables.

Fresh fruit need low temperature and high relative humidity to reduce the respiration and slow down the metabolic processes. The table below indicates optimal temperatures and moisture conditions for some common fruits and vegetables (here is an example of the first few entries).

Product	Optimal Storage Temperature		Chill Point		Freezing Point	Optimal Humidity	Top Ice Accepted 1)	Water Sprinkle Accepted 2)	Ethylene Production	Sensitive to Ethylene 3)	Approximate Storage Life	Comments
	(oF)	(oC)	(oF)	(oC)	(oF)	%
Apples	30-40	-1-4			29.3	90-95	No	No	High	Yes	1-12 months	Chill sensitive stored at 35-40 F (2-4 C)
Apricots	31-32	-1-0			30.1	90-95	No	No	High	Yes	1-3 weeks
Artichokes	32-35	0-2				90-95	Yes	Yes	No	No
Artichokes, Jerusalem	31-32	0-2			28.0	90-95	No	No	No	No	4-5 months

The major issue, of course, with canning/glass jars is the damage to the container once freezing begins (damage to container, failure of lid seal). And then the issue of changes to texture of what is frozen (some may be OK, others may turn to mush).

-Bill

Estragon

As Bill says, it depends on sugar content, etc, but freshwater ice is at minimum density near 0°C/32°F.  It's most dense at~4°C, drops slightly as it cools to just above freezing, then drops a lot as it freezes (density drop = ~8-9% increase in volume IIRC).  Once frozen, density increases (volume shrinks) a bit as temps get colder.

https://www.engineeringtoolbox.com/ice-thermal-properties-d_576.html

So it's not just temp, but also time that matters.  Eventually water will "hard freeze" in freezing temps, doing so more quickly in lower temps.

If I wanted to be sure to avoid freezing, I'd keep the prepper supplies buried below the frost line with a rigid insulation access hatch.  Ground temp around here is ~7°C year-round.  

softdown

Estragon said:

As Bill says, it depends on sugar content, etc, but freshwater ice is at minimum density near 0°C/32°F.  It's most dense at~4°C, drops slightly as it cools to just above freezing, then drops a lot as it freezes (density drop = ~8-9% increase in volume IIRC).  Once frozen, density increases (volume shrinks) a bit as temps get colder.

https://www.engineeringtoolbox.com/ice-thermal-properties-d_576.html

So it's not just temp, but also time that matters.  Eventually water will "hard freeze" in freezing temps, doing so more quickly in lower temps.

If I wanted to be sure to avoid freezing, I'd keep the prepper supplies buried below the frost line with a rigid insulation access hatch.  Ground temp around here is ~7°C year-round.  

That would work but digging through concrete floors would be tedious at best. I'm not sure if my supply rooms ever get below 40F. I want an alarm if they get to freezing. I get pretty energetic if an alarm sounds. Energy is nice when in their 60's. 

Estragon

How about a cheap thermostat, wired to trigger an alarm instead of (or as well as) starting a furnace/heater?

mike95490

I use a kerosene lantern in my greenhouse and plumbing sheds to keep frost out.  Might work for food storage too.

softdown

Estragon said:

How about a cheap thermostat, wired to trigger an alarm instead of (or as well as) starting a furnace/heater?

Pretty much describes what I am looking for. Have yet to find the ideal solution. As opposed to 'lost power' alarms? Those are easy to find. 

softdown

mike95490 said:

I use a kerosene lantern in my greenhouse and plumbing sheds to keep frost out.  Might work for food storage too.

The 1890s went that way>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

The plan is to either use small propane heaters or simply move the endangered liquids. I think it takes a really hard freeze to damage canned foods as a rule. 

mike95490

softdown said:

.........The plan is to either use small propane heaters.....

I'd found the propane heaters were too hot, and pilot only, not warm enough, got tired of lugging propane tanks up and down frosted hills.  Kero seems to be just right

softdown

This is what I came up with: https://www.ebay.com/itm/Wireless-Digital-2-Sensor-Refrigerator-Freezer-Thermometer-Alarm-Low-Temperature/352707984328?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Just started using it yesterday. Have not set the audible alarms so don't know the efficacy of those. So far, so good though they do not transmit through several walls involving steel and ~60 feet - no surprise there.

Estragon

Looks like it should do the trick. 

I used some similar ones, but had to stop as the rf signals were triggering some remote controlled lights on or off, apparently at  random.