What if the monitoring fails?
By Vimal Bhaya, Founder and Lead Systems Architect · Last reviewed 9 September 2026
Nobody in this market distrusts refrigeration. They distrust the thing that is supposed to be watching it. "What happens when the power goes out" and "does it alert me if it loses the internet" are the two questions that quietly kill deals, and almost nobody answers them with a number.
This is a six-part tutorial that answers them precisely, including the places where our own answer is the worse one. Every figure comes from a published standard, a vendor's own specification page, or our own case-study exports.
The 6 parts, in order
By the end you will know which four things have to be working for a reading to reach your phone and which three of them are on mains, why an alert about silence has to be raised from the cloud rather than on your site, what a gap in a record is worth against a straight line drawn through it, how far past a limit a box can get between two readings, how accurate a sensor actually needs to be and when a calibration certificate is genuinely required, how long an install really takes and where the time goes, and the six line items in every quote in this market.
-
1. 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. So the alert has to be raised from the other end, because a device that has lost power cannot tell you it has lost power.
Read part 1 -
2. What happens when the internet goes out
A different failure, and it deserves a different answer. Does it alert? Yes, within one missed reading, from our servers. Does it backfill? No, and your record has a gap. Here is why a visible gap is worth more than the tidy straight line some systems draw across it.
Read part 2 -
3. Polling interval: how fast is fast enough?
Four different numbers get called the refresh rate and vendors quote whichever is smallest. Here is what each interval actually costs you, measured on our own failures, plus the fact that changes everything: the fastest movements in a freezer are all healthy defrosts.
Read part 3 -
4. Sensor accuracy, drift and calibration
The Food Code asks for ±3°F (±1.5°C) on air. A healthy freezer swings up to 23.8°F (13.2°C) in one day. The box moves more in an afternoon than a modern sensor drifts in a decade, so here is where accuracy matters, and when a calibration certificate is genuinely required.
Read part 4 -
5. 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 rather than mounting them, and the cost nobody budgets for is the first week of tuning the alerts.
Read part 5 -
6. 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, and for a walk-in that usually turns into a hole in a panel and a technician's visit. Our whole price list is here, and so is the case where you should buy something cheaper.
Read part 6
How to use this
Read them in order if you are starting from scratch. That is the usual path. If you already know which piece you need, jump to it from the list above.
The figures in this series come from the FDA Food Code and the CDC's vaccine storage guidance, from published vendor specification pages and datasheets, and from our own Philadelphia freezer and Mississauga reefer case-study exports, recomputed for these pages. Every source is listed at the foot of each part.
This tutorial follows the alerting problem, which is about what to do with the readings, and the physical reality, which is about getting them out of a metal box. This one is about whether the whole arrangement can be trusted to still be running on a wet Sunday in February.