How to Eliminate False Temperature Alarms in Freezer Monitoring

Basic Temperature Alarm Logic

False alarms on freezers are annoying, but worse than that they lead to alarms being ignored all together. This makes you vulnerable to equipment failure and loss of inventory. The steps below will walk you through how to eliminate false alarms while improving your freezer monitoring system.

Nearly every freezer has a defrost cycle, and every freezer needs to be accessed and stocked. Between defrosting and restocking, poorly implemented alarms will trigger regularly - even when there are no problems whatsoever.

There are two basic ways to prevent these false alarms: the first is to setup smart time delay logic, and the second is installing the temperature sensor in a thermal mass.

Time Delay

Most ControlByWeb devices have a user programmable time delay. Instead of sending an alarm immediately, the device starts a timer. If the temperature hasn't recovered by the end of the time delay, the alarm will be sent. This means you won't be bombarded with temperature change notifications and will only be alerted when a serious problem occurs.

Thermal Mass

A thermal mass is usually a bottle that holds the temperature sensor, surrounded by either glycol or glass beads. It has a major disadvantage: it's the slowest way to get an alarm. Its job is to change temperature slowly the way that food or liquids would. Therefore, it's great for simulating food temperature for the purposes of record keeping.

The Best Method for Alarms

The Time Delay method is recommended for alarms. It lets you fine tune your settings to eliminate false alarms while giving you the earliest valid notification of a problem. This method is the best of both worlds and will give you more time to react to an issue before it becomes a disaster.

Setting up a time delay (Smart Alarms) on a ControlByWeb 400 Series/FridgeAlert device

On the 400 Series Products:

1. First, create a timer. Timers can be found in the I/O Setup tab under “Timers”.
   
   

   Figure 1 - Click to expand

2. Then, create two conditional tasks: one task that starts the timer when the temperature rises above your threshold, and a second task that sends an alarm if the temperature is still above the threshold when the timer expires.
   
   The timer will need to run slightly longer than a typical defrost cycle, restocking event, or any other planned change in temperature. Most customers find that 30-40 minutes (1800-2400 seconds) is sufficient.
   
   

   Figure 2 - Click to expand

   

   Figure 3 - Click to expand

   
   *The displayed values are often used in many different applications, but your fridge/freezer a different time delay or temperature settings.

On the FridgeAlert:

1. Set an Alert Maximum Temperature and Alert Minimum Temperature. Then set the Alert Delay to be around the time of a defrost cycle or restocking event in seconds.
   
   

   Figure 4 - Click to expand

These Smart Alarm settings ensure that the alarm will only trigger when a serious problem has occurred. If you continue to experience false alarms, log the temperature of your fridge/freezer for a few days and determine the normal operation times/temperatures and set alarm conditions accordingly.

We'd love to discuss your temperature monitoring system needs. Contact us to discuss your application.