Cold storage, explained with real data.
Articles about keeping walk-in coolers, freezers and reefers at the right temperature. Written from real sensor readings and real questions from the people who run them.
We publish the data behind every article, so you can check our claims yourself.
Last updated 18 October 2026 · Author: Vimal Bhaya
Start with a tutorial.
TemperatureWise vs Competitors.
Twelve honest comparisons. We post our price, name what each rival does well, and say when to buy theirs instead.
The alerting problem.
A mini-tutorial on why freezer alarms cry wolf, and how to make alerts that people still read at 3am. Five short pieces, in the order that fixes it.
The physical reality.
Most monitoring that fails does not fail in the software. It fails because a walk-in is a metal box, because a coin cell cannot push a radio in the cold, or because the sensor ended up on the wrong wall.
What if the monitoring fails?.
Nobody distrusts refrigeration. They distrust the thing that is supposed to be watching it. What a power cut does, what an internet outage does, and what you actually have to buy.
Which kind of monitoring to buy.
Before you compare brands, work out what kind of thing you are buying. A cheap sensor, a build of your own, the controller already on the wall, or a system. Three of the five parts end by recommending something other than us.
How walk-in coolers and freezers work, and how they fail.
How each box works, what normal looks like in real readings, and the symptoms of each common failure. A cooler pair and a freezer pair, each with what to check before you call.
Walk-in refrigeration parts, one at a time.
What each part does, how it fails, and which symptom that failure shows up as. It starts with the evaporator coil and the expansion valve. More parts will follow.
Reach-ins, prep tables, display cases and reefers, and how they fail.
How each one works, what normal looks like, and the symptoms of each common failure. Five pairs, from the undercounter on the cookline to the reefer in the yard, each with what to check before you call.
Or diagnose a fault in a few taps.
Or jump to one article.
Why temperature alarms cry wolf, and how to stop it.
Every alarm threshold an operator might pick, replayed against 5,179 real readings from a freezer that failed. There is no setting that gives you both a quiet week and useful warning.
Walk-in cooler alarm: what to set it to, and how long it should wait.
Every common setting and delay replayed against 46 days of a busy, healthy cooler. The delay decides how many alarms you get, more than the number does.
Threshold vs rate-of-change alerting.
The steepest hour in our whole record was a freezer working perfectly. The real emergency crept up at less than a degree an hour. Why the slope, not the reading, tells you which one you have.
Glycol buffers, and why air temperature lies.
Your groceries survive the drive home because food changes temperature slowly. Air does not. What a sealed bottle of antifreeze around the probe actually fixes, and when it is the wrong choice.
Alerting more than one person.
A 3am alert to one sleeping phone is the same as no alert. How escalation from email to SMS to a ringing phone works, why it is set per freezer, and what to ask any vendor before you sign.
What a good alert looks like at 3am.
Six things an alert has to say before it is worth waking somebody. Built from a real Sunday morning alert that bought two working days of runway over a holiday weekend.
Will wireless work through a walk-in freezer wall?
How well do your phone calls go in an elevator? A walk-in panel is the same steel box, and the link has to cross it in both directions.
LoRa, LoRaWAN, 433MHz, Wi-Fi and Zigbee compared.
The same comparison in numbers. Link budget for each, what LoRaWAN adds to LoRa, where Wi-Fi HaLow fits, and why 433MHz runs on a short leash in North America.
Metal walls, long spans and multi-room sites.
On a real 190 by 95 foot production floor the far freezer is 208 feet and ten walls from the network cabinet. Why adding access points does not fix that.
Battery or wired: what survives -20°F.
The coin cell in your remote is rated colder than your freezer and still dies in it, because a rated range is measured at a trickle and a radio transmit is not a trickle.
Where to place a sensor in a walk-in, and where not to.
A walk-in is not one temperature. Five places a sensor ends up, what each is really measuring, and the quiet failure where a weak radio pushes the sensor to where the signal is.
Probe types: thermistor, RTD, 4-20mA.
Two of those are sensors and one is a wire. What each actually is, when platinum and a calibration certificate are worth paying for, and why placement matters far more.
What happens when the power goes out.
The sensor in the freezer runs on its own battery and does not care. Three of the four links between it and your phone are on mains, and the two that break are the gateway and your router.
What happens when the internet goes out.
Does it alert? Yes, from our servers, within one missed reading. Does it backfill? No. Why a visible gap in a record is worth more than the tidy straight line some systems draw across it.
Polling interval: how fast is fast enough?
Four different numbers get called the refresh rate, and vendors quote whichever is smallest. What each interval costs you, measured on our own failures.
Sensor accuracy, drift and calibration.
A healthy freezer swings further in one afternoon than a modern sensor drifts in a decade. Where accuracy matters, where it does not, and when a calibration certificate is genuinely required.
How long installation actually takes.
Thirty to sixty minutes for two walk-ins, no electrician, nothing switched off and no holes. Most of that hour is spent deciding where the sensors go, not mounting them.
No hub, no subscription: what you buy.
You cannot remove infrastructure, only move it. A no-hub Wi-Fi sensor is using your router as the hub. Our whole price list is here, and so is the case where you should buy something cheaper.
Consumer sensors or commercial monitoring.
The cheap sensor is accurate enough and always was. Our own entry sensor is consumer hardware, so the yearly fee is not buying a better thermometer. Here is what each price point actually gets you.
Build your own or buy it, at 10, 50 and 160 coolers.
A Pi build is cheaper per cooler at every scale, and the gap widens. What changes is who owns it. Worked in hours instead of dollars, the break-even is ten hours per cooler a year.
Refrigeration controller or standalone monitoring.
Your controller already reads the box, so why add a sensor. Because its probe sits in the evaporator return air to run the coil, not where the food is. Both numbers are correct.
Cellular or Wi-Fi, and which link you are choosing.
Cellular is not a better sensor or a better radio. It changes the route out of the building and nothing about getting the reading out of the freezer. Where the radio lives decides the cost.
CoolBot or a real walk-in, and what an inspector checks.
A health inspector publicly argues a CoolBot is not a walk-in. He is half right. Certification is a shortcut rather than a law, which is why an uncertified room has more to prove.
How a walk-in cooler works, and why it should never ice.
A cooler clears its own frost every time it switches off, so ice on its coil is always a fault. The parts, the layouts, and the normal numbers from manufacturers' manuals.
Walk-in cooler troubleshooting, symptom by symptom.
A warm box, wet walls, ice on the coil, frozen lettuce or water on the floor. What each one usually is, what you can check yourself, and when to call a technician.
How a walk-in freezer works, and what normal looks like.
The parts in plain words, the three layouts that cover almost every walk-in, and three normal days of real readings. A healthy freezer warms on purpose a few times a day, then comes back down.
Walk-in freezer troubleshooting, symptom by symptom.
Ice on the coil, stuck at 20°F (-7°C), a frozen drain or a door frozen shut. What each one usually is, what you can check yourself, and when to call a technician.
The walk-in evaporator coil, and what its ice is telling you.
Light frost that clears at every defrost is normal. Ice that stays is a fault, and where it sits points to the cause: defrost, a heater, the drain or a starved coil.
Walk-in expansion valves: capillary tube, TXV and electronic.
The part that meters refrigerant into the cold coil comes in three kinds. How each one works, which one you probably have, and how a fault in each shows up in the box.
How a reach-in cooler works, and what normal looks like.
A whole fridge in one cabinet that clears its own frost each time it rests. The five layouts, the makers' normal numbers, and a real day from a busy restaurant's drinks fridge.
Reach-in cooler troubleshooting, symptom by symptom.
A warm cabinet, an undercounter cooked by the line, frozen lettuce or water on the floor. What each one usually is, what you can check yourself, and when to call.
How a reach-in freezer works, and why it heats its own coil.
The cooler's machine run colder, with heaters on the coil, the drain and the door. Why it defrosts a few times a day, and seven makers' schedules side by side.
Reach-in freezer troubleshooting, symptom by symptom.
An iced coil, a defrost gone wrong, a door frozen shut or ice in the bottom of the cabinet. What each one usually is, what you can check yourself, and when to call.
How a refrigerated prep table works, and what keeps the pans cold.
How the cold air moves round the pans on a forced-air rail, and how a cold-wall rail differs. Why food stays cold only below the fill line, and the room the table is tested in.
Prep table troubleshooting, symptom by symptom.
Symptoms split by forced-air and cold-wall rails. Warm food in the pans is usually the fill, the lid or the room, not the machine. Plus frost, frozen lettuce and a hot cookline.
How a refrigerated display case works, and what normal looks like.
An open case holds its cold behind a falling curtain of air, and the store's air is most of its load. The load line, night curtains, defrosts and the normal numbers.
Display case troubleshooting, symptom by symptom.
A broken air curtain, warm top shelves, warm readings at defrost, ice, water or fogged doors. What each usually is, and how to tell a normal defrost from a failing case.
How a reefer unit works, and what normal looks like.
Cold air goes out over the load and comes back underneath. The gaps the load must leave, continuous and start-stop modes, shore power, defrost and the rules.
Reefer troubleshooting, symptom by symptom.
A warm load, a defrost alarm, a unit that will not restart, or a trailer dead on shore power. The alarm codes behind each, and what to check first.
The Philadelphia freezer that failed in April 2025.
The incident the alarm article is built from. A failed defrost timer, $150,000 of frozen stock, and the full temperature record with the raw readings attached.
TemperatureWise vs ThermoWorks NODE.
NODE is the one operators name most. Here is what it gets right, where the two differ on alerting, range and detection, and when each is the better buy.
Read article CompareTemperatureWise vs Jolt for Restaurants.
Jolt is an ops suite. TemperatureWise is a temp system. Here is what each does, what each costs, and which problem you are solving.
Read article CompareTemperatureWise vs Sensaphone Compared.
Sensaphone has 40 years and a POTS line that works when all else fails. Here is where the two differ on detection, dashboards and cost.
Read article CompareTemperatureWise vs Monnit for Cold Rooms.
Monnit is a horizontal IoT platform with 30+ sensor types. TemperatureWise does one thing: catches cold-chain failures early. Here is the comparison.
Read article CompareTemperatureWise vs SmartSense by Digi.
SmartSense is the enterprise answer with pricing you cannot see. TemperatureWise posts the number. Here is where each belongs.
Read article CompareTemperatureWise vs Swift Sensors.
Swift Sensors has 30+ types and a split track record. Here is where the two differ on focus, pricing and how they catch faults.
Read article CompareTemperatureWise vs Therma, now GlacierGrid.
They post a monitoring price. The product they rebranded to sell is demand response. Here is why extra cold without mass in the walls is hard on food and on the machine.
Read article CompareTemperatureWise vs TempTrak.
TempTrak is Copeland's healthcare monitor: five minute updates, a local strobe, no public price. Here is how it compares when a kitchen got the quote.
Read article CompareTemperatureWise vs Checkit.
Checkit installs sensors, runs checklists, and signs you for 36 to 48 months. TemperatureWise posts the monitoring number. You can run both.
Read article CompareTemperatureWise vs CoolBot Pro.
CoolBot Pro already has Wi-Fi monitoring. It watches the one room it runs, and it cannot make a freezer. TemperatureWise watches every box.
Read article CompareTemperatureWise vs MarCELL Pro.
One box and no Wi-Fi: MarCELL Pro is cheaper. From the second box, one cellular modem at the site wins. We show both totals.
Read article CompareTemperatureWise vs Temp Stick.
Temp Stick is $149 with no subscription, on your Wi-Fi. TemperatureWise is what you buy when the router is the thing that dies.
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