MT11 Freezer Monitoring

MT11 Freezer Monitoring

Here are some pictures of an MT11 installation with a glycol temperature probe in a walk-in freezer at a local restaurant. The freezer is in the back of the building and their are two concrete walls between the sensor and an MR36 AP and an MV32 camera. The distance is about 30 feet. The wall closest to the AP and camera also has sheet metal on one side of it. There is a hallway through both walls, but it is still a challenging BT wireless connection. I moved the MT11 further away from the probe and in line with the hallway to get the best BT wireless connection that I could and even though the signal strength is not great, it is working reliably. The hardest part of the install was drilling through the freezer wall. I only had a 1/2" drill bit on hand and it was barely long enough to go all the way through the freezer wall. The installation video on the Meraki web site says that you need a 15 millimeter hole to route the sensor cable through, which works out to roughly a 5/8" drill bit. Despite that, the plug end of the sensor fit through the 1/2" hole. Total installation time, including the pre-configuration of the MT11 and software updates was about 45 minutes and about 20 minutes of that time was spent drilling through the wall with a marginally sharp drill bit. 


Glycol ProbeGlycol Probe

The temperature probe plugs the hole very well and you can clearly see the probe immersed in the glycol.




The MT11 is positioned to take advantage of the straight hall way path to the AP and the camera. I did fill in the hole in the freezer wall with some silicone sealant too. The adhesive cable clamps would not stick to the metal walls of the freezer but they would stick to the fiberglass on the support beam. I used the provided magnet to attach the MT11 to the metal wall.


Dashboard viewDashboard view


The freezer goes through a semi-defrost cycle every six hours. The temperature never gets above 22F and generally stays around 12F. The temperature graph on the dashboard view clearly shows this. The RSSI is not great, but the connection is stable with no problems. Another quality Cisco Meraki product!

Kind of a big deal

@jbright : great !

Kind of a big deal

Thanks for sharing. I remember fitting out an insulated container as a server room years ago and drilling into the stainless steel walls was not fun, even good quality drill bits would only last half a dozen holes before becoming blunt.

A model citizen

About 10 days after the probe was installed the freezer failed. The MT11 gave the customer enough warning so that he was able to move the food out of the unit before the temperature got too high, thus saving about $1000 worth of product, and easily paying for the cost of the sensor. The picture below shows the temperature graph capturing the failure of the freezer and its return to service a few days later.


cooling failurecooling failure 


Building a reputation

great idea and project