Milk cooling chest

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Revision as of 14:26, 19 October 2015 by Ahoussney (Talk | contribs) (procedure)

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Milk cooler hack

Raw milk needs to be cooled quickly - ideally brought below 40F as quickly as possible (2 hours is a reasonable maximum target) - simply putting milk jars in a refrigerator will not cool it fast enough to maximize safety and longevity of the milk. On top of that, consumer grade refrigerators will often struggle to handle the load of several gallons of warm milk. It can take hours to cool milk this way and the strain that all this puts on the compressor of the fridge will shorten it's life. Plunging milk jars into an ice water bath is best - but that requires making a lot of ice and the extra step of removing the jars and putting them in the fridge after cooling.

A larger-scale solution is to purchase and install a bulk-tank to cool the milk. A simpler cheaper method that works for up to about 4 -6 cows is a chest freezer modification: the milk cooler hack.

Materials Needed:

  1. chest freezer that can hold water.
  2. silicone caulk
  3. STC-1000 temperature controller or similar cheap knockoff (such as inkbird ITC-1000) with probe.
  4. wire to power the unit. (Since unit draws less than 3 watts of power - this wire can be very small. I used 20 gauge but you can check gauge tables and use something even smaller if you have it on hand)
  1. 14 gauge wire or better for switching leg for chest freezer. A piece of an old power chord or a plug wire from a defunct appliance works great.
  1. Wire nuts and/or electrical tape
  1. optional: mounting hardware


  1. clean and seal all seams under the waterline with silicone
  2. decide where you want to mount the controller on the outside of the chest freezer. Consider the following:
    • accessibility and visibility for checking temperature and changing settings
    • routing wires back to compressor: power, switching and probe wires inside the unit.
    • a location where the unit will not get brushed or knocked off by passers-by
  3. Locate the cooling lines on the inside of the freezer nearest the area where the controls will be mounted - Most chest freezers have radiator coils (the ones that get hot) running horizontally around the inside of the outer wall of the freezer and cooling cools (the ones that get cold) running horizontally against the inside of the inner wall of the chest. To locate the cooling lines - sometimes it helps to plug in the freezer and splash the sides with water. To locate the heating lines place your hand on the outer wall and feel for hot spots. Watch as the water freezes around the cooling lines. If you can't locate the lines you will have to be very careful drilling holes since puncturing a line will release the coolant and destroy the chest freezer.
  4. avoiding the areas where the lines run mark a spot to drill a hole through both sides (inner and outer) of the chest freezer wall.
  5. pick the smallest drill bit that will work to make a hole that the temperature probe will fit through.
  6. Carefully drill through both sides. If you don't know exactly where the lines run, drill VERY carefully just through the wall material and insert a wire to probe around and see if you can locate the lines. Drilling near the top edge is believed to be safer since coils seem to be rarely located there.
  7. Feed the smaller end of the temperature probe through the hole - don't put it in backwards! The exposed wires need to be outside and the sensor bulb needs to be inside and submerged below the water line.
  8. connect the temperature probe to the sensor

Programming the cooler