Refrigerator and Freezer Monitoring Tutorial

Staying on top of freezer and refrigerator temperatures can be difficult, especially if you have multiple locations with a variety of cold storage systems. Installing a freezer monitoring system can provide assurance that your food or vaccines or other valuable items are stored safely and within the set temperature range.

Let me walk you through the basics of how freezer temperature monitoring works. We'll cover how you can use sensors, automated alerts (ex. email/SMS), and battery backup to provide 100% peace of mind.

Your obvious first step: Temperature Sensors

Temperature sensors are the most important tool for freezer monitoring systems. With so many to choose from, though, how do you get started?

This TempDefender G2 is an IP-equipped host for small sensors, including a temperature and humidity sensor. Sensing temps is particularly important in outdoor cabinets, as they include no climate control. This type of monitoring is equally applicable to freezer/refrigeration applications, as long as you choose sensors with the right operating temperature and measurement range.

My background at DPS Telecom is, quite obviously, in the telecom space. I'm an expert in temperature monitoring, but refrigerator/freezer monitoring has a handful of differences that I had to learn and apply. Let's cover everything you need to think about when selecting a temperature sensor/probe for your freezer or refrigerator:

1. It's important to select temperature probes that can withstand freezer temperatures. Obviously, your probe needs to survive in the location where you install it. Choose wisely depending on whether you have typical refrigeration just above freezing or deep sub-zero temperatures in a freezer.
2. Choose sensors that provide accuracy within a few degrees, at minimum. Freezer monitoring doesn't usually require amazing accuracy for sensors, but you can't afford to be more than a few degrees off. Check manufacturer specifications for accuracy before buying, then verify the readings with calibrated handheld sensors after installation.
3. Pick sensors you can conveniently power. On your first project, you might not pay much attention to the power input voltage required for your sensors. For seasoned veterans, that's one of the first things they'll notice. The hassles of installing a voltage converter and running a lot of extra wiring are significant. Look for sensors that match your site voltage. Even better are sensors that are bus-powered by your head unit.

Other sensors can have value, too

In my years in the remote monitoring space, I've learned to help my clients err on the side of additional sensors. When installing any kind of remote monitoring, the most expensive part of the project design is the first sensor. That requires a head unit, thinking about power, etc. Every additional sensor is a relatively small incremental expense that really improves the "site picture" you get when you look at your alerts and status screens.

In the context of monitoring the cold chain or miscellaneous cold storage applications, two primary sensors come to mind:

• Humidity sensors provide more detail about the performance of your compressor, since dehumidification happens simultaneously with colder temperatures.
• Air flow is something we always recommend for HVAC monitoring, and the same logic applies to freezers and refrigerators. Your ability to maintain cold in your refrigerated area depends on your ability to cycle chilled air. Monitoring actual airflow can provide an earlier warning a of a system failure than just waiting for the temperature to rise significantly. Every second you save during the detection phase reduces your expensive spoilage losses.

Step Two: Remote Monitoring via a "Head Unit"

Once freezer temperatures and other values are monitored with sensors, you need some kind of "head unit" that collects that data and puts it onto your network (or notifies you through some other means). At DPS and in the general remote monitoring industry, we call these "RTUs" (Remote Telemetry/Terminal Units).

The freezer alarm with your head unit should be set to activate when temperatures, humidities, air flows, or other measured values fall outside acceptable ranges, ensuring any dangerous or unexpected changes are identified quickly. This can locally render as flashing lights or loud alert beeps.

Beyond those basics, your freezer monitoring system should be set up to provide some form remote temperature monitoring. This way, even if you are not at the site, you will be alerted by an instant alert when freezer temperatures fall out of your set "normal" range.

At DPS, several different types of automated alerts are typical for our clients:

• You can leave the analog gauge display of the RTU's web browser interface open so that you can see any alarm conditions.
• You can configure your RTU to send you/others an email whenever an alarm occurs.
• You can have your RTU send you SMS-via-email using your provider's email gateway (ex. ###-###-####@txt.att.net)
• You can have your RTU send SNMP trap messages to your central SNMP manager that you already use for other network/system monitoring.
• You can have your RTU report to the T/Mon alarm management platform to view alarms as a list, on a map, etc.

Freezer temperature monitoring with automated alerts should be part of any cold storage plan to ensure products stay well within the set range and save you from unnecessary losses.

Step Three: Battery Backup

For added peace of mind, consider a freezer monitoring system that has built-in battery backup. This ensures the freezer temperature monitoring system runs for an extended amount of time even when power is out or other disruptions occur.

This is especially important when you consider that commercial power failures are one of the biggest threats to any continuous cold chain. You need you monitoring system the most precisely when power is lost.

Depending on the scale of your facility, it might be enough to have a DC-powered RTU that runs on your protected DC battery plant. If you don't have this option, even a simple AC UPS used to power desktop PCs during a power failure will have enough power to run a tiny monitoring device for hours and hours.

You can also consider built-in battery backups to make your monitoring device truly independent of outside power. At DPS, we've done this on occasion as a semi-custom device type when our clients have needed it.

How to get help with your project

Temperature monitoring in your freezer or refrigerator might not be the most complicated remote monitoring project I've ever had to work on, but it's also not terribly simple. There are problems that you can step right into if you've never done anything like this before on your own.

I'll give you guidance as you get started so that your project moves forward correctly.

For assistance choosing, buying, and installing the best possible freezer monitoring system, call me at 1-800-693-0351 or email me at sales@dpstele.com

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 17 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and opt...