TV2 showing one lab fridge temperature

Three easy steps: Getting temperature sensors into a refrigerator

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Three easy steps for getting a temperature sensor into a refrigerator.

All refrigerators have a temperature probe which is connected to the compressor to regulate the internal temperature of the refrigerator.  However, the need exists foImage result for refrigerator with Temperature sensor inside glycol bottler a second temperature sensor to trigger an alarm or keep a record of the internal temperature.  These temperature sensors can be either wired or wireless.  But whether they communicate with another piece of equipment via a wired or wireless connection the need to be positioned inside the refrigerator.  These sensors almost always have a wire which goes to a display or a transmitter.

So, how do you get the sensor inside the cold cavity with the wire leading to the display or a transmitter and not have the wire create an air gap as it is threaded between the gasket and the door frame.  The challenge is to get the probe inside the refrigerator and still maintain a good seal, so the refrigerator stays cold.

If you have large walk-in refrigerators you can drill a hole through the side or top of the unit, insert the wire and then fill the hole with some sort of thermal sealant. You can do the same thing with smaller refrigerators.  There is no reason you can not drill a hole in the refrigerator wall.  The only danger is that you could puncture a coil.  But the coils should all be located on the back of the unit.  Your drill bit will go through the outer metal shell, an inch or so of insulation and the inner plastic shell.  There are no cooling coils in the walls of a normal stand up refrigerator.  But, do check first to verify that the cooling coils are on the back of the unit.

Some smaller refrigerators, particularly scientific refrigerators, have a port through which the wire can be threaded.  If a port exists it will be filled with some sort of filler; molding clay, Styrofoam, plastic, etc…  Generally, the port will be on the back of the refrigerator but look at the back and the sides for a hole filled with some easily removed filler.  Once you have identified the port:

 

  1.  Remove the filler from the port;
  2. Thread the wire through the port, positioning the sensor near the center of the fridge;
  3. Reinsert the filler, pressing it around the wire.

If your refrigerator does not have a port through which the sensor can be threaded:

  1. Open the refrigerator door and thread the sensor wire between the gasket and the door frame near the upper hinge. Draping the wire over the top of the door hinge will help keep the sensor wire from moving around;
  2. Position the sensor near the center of the fridge. Numerous studies have shown that the temperature near the walls or front or back of a refrigerator is much warmer than the air in the center of the refrigerator;
  3. Tape the wire against the door frame so that it stays in place. Duct tape is best because it will adhere to the wire and door even given the cold temperatures of the refrigerator.

A small gap may be left between the door and the door frame, but it should be small enough that only a tiny bit of air can escape from the fridge into the outside air and the internal temperature should not be affected.  If you are worried about the resulting gap you could drill a hole in the gasket.  Refrigerator gaskets generally have an expandable bellows below an internal magnet which ‘snap onto’ the metal door frame to provide a seal against outside air.  Drill a hole in the bellows, underneath the magnet, and thread the sensor through the hole.  Then squirt some silicon in the hole so that it fills the hole in the gasket.  You can get a tube of silicon from any hardware store.