Just put the finishing touches on my freezer conversion smoker - PID & Cold Smoker

Discussion in 'Electric Smokers' started by scottphillips1, Nov 12, 2012.

  1. Hi,

    My last smoker was a 1950's era refrigerator turned electric smoker with a burner and burner controller from an old stove.  Needless to say, temperature control was a real pain.

    This summer our big old Whirlpool deep freeze died.  I just finished converting it into a PID controlled smoker with an integral cold smoker as well as a door mounted fan to assist with initial pellicle formation, so I don't have to leave meat sitting out on the kitchen counter.

    The electronics are mounted in a box, fan and low voltage power supply were purchased second-hand from a great electronics surplus store in Boise, Idaho, called Reuseum.  The Mypin PID, 25amp relay, thermocouple, and heatsink and door latches came from Amazon.  The remaining parts came from my own workshop or Home Depot.  Blake Trailer, here in Star, Idaho, cut the sheet metal for the inside of the door for me.

    Overall, it works great, but I need to learn a little bit more about the PID and how to refine its programming.  It holds temperature plus or minus 4 degrees, which is better than I used to have, but I think it can do better.  The hottest I've run the smoker to date is 230 degrees.

    The cold smoker is a venturi type unit powered by a hacked up soldering iron and an aquarium pump.  The "smoke chamber" is a stainless steel water bottle and it slides into a soup can.  The venturi was made out of 1/2" pipe fittings.  When running, the cold smoker increases the inside temperature of the smoker about 5 degrees above the ambient temperature.  It's also set up to run from the control panel on a one hour time or indefinitely in manual mode.

    I used quite a bit of galvenized metal in this conversion.  I know that some are of the opinion that this is bad, but I figure if the temperture of my smoker ever gets high enough to vaporize the zinc coating on the metal, I'm going to have a much bigger problem on my hands anyway.  With only five smoking sessions on this new unit, the inside is pretty well seasoned with a hard baked on coating of smoke.

    So far I've smoked a batch of salmon, a few pounds of cheese, jerky, ribs, and a Canadian bacon.  Today I'm going to smoke another batch of salmon.


    Scott Phillips

    Star, ID

    I left the original magnetic seal on, but the door warped a bit when I replaced the inner plastic liner with sheet metal, so I had to add toggle clamps to shut the door tightly.  The clamps are mounted to aluminum plates to prevent the self tapping screws from pulling free from the freezer's thin sheet metal box. Near the top left of the photo you can see the screened smoke vent; I may put a pipe on this in the future.  A small meat thermometer is set through the door so I can double check the temperature the PID displays.

    Here's the control panel and the cold smoker generator.  The smoker's wiring runs inside the outer freezer shell.  Notice the aluminum plate near the cold smoker - this is an access point I used to snake wires through the freezer.  Near the bottom left side of this photo you can see the wiring that feeds through the door of the smoker to drive the low voltage fan.

    The control panel features a PID for setting the temperature, a switch to turn the PID/burners on and off, a switch for the door mounted fan, and a timer/two way switch for controlling the cold smoker (either timed operation of continous operation).

    Here's the cold smoker I built from an old electrical enclosure, a soup can, metal water bottle, aquarium pump, soldering iron and a few pipe fittings.  It produces a ton of smoke, will burn for at least four hours (and maybe longer) on a partial bottle of chips, and only raised the temperature of the smoker by 5 degrees, no matter how long it runs.  The metal bottle is removable from the soup can.

    This shelves in this conversion are original to the freezer, but I cut out the cooling lines and removed all of the plastic hardware.  They are supported on 1/2" conduit.  The conduit slides into 1/2" holes drilled into each side of the cabinet.  Two self tapping screws hold each shelf to the conduit.  You can see the end of the thermocouple mounted into the square metal plate near the middle of the right side of the smoker.  The vent is located near the upper left inside corner of the smoker.

    My two burners came from a thrift-store George Forman grill.  Each one is rated at 750 watts.  I also salvage the high temp wire from the grill, so I don't have to worry about my wiring melting.  The burners are mounted in upside down cake pans.  I had to cut rectangular holes in the pans with tin snips for the burners to fit.  The pans are screwed to the floor of the smoker with self tapping screws.  Let's hope my wife doesn't try to bake a cake anytime soon!

    A large aluminum computer fan is tucked behind this adjustable vent plate.  I made the vent out of aluminum.  I may rebuild this vent to allow for more air to be sucked through by the fan.  When cold smoking, I leave this vent closed.  The aquarium pump that powers the venturi provides sufficient airflow to move old smoke out of the freezer.  For hot smoking, I've been running this vent wide open.

  2. mneeley490

    mneeley490 Master of the Pit OTBS Member

    Interesting and resourceful design. Thanks for sharing!
  3. driedstick

    driedstick Smoking Guru OTBS Member SMF Premier Member

    Very nice Scott
  4. deltadude

    deltadude Master of the Pit OTBS Member

    Scotphillips, very ambitious conversion!  Hats off looks awesome, sounds like it works as you planned, and even better your eating some fine smoked foods..  Great Job!
  5. Thanks, Deltadude.  It is working perfectly!  The challenge now will be to refine my technique to take advantage of precise temperature control, which is something I've never had before.  My second batch of salmon was perfect - moist, flaky but firm, and incredible flavor! I've got 8 pounds of ground beef jerky that will get smoked tonight.


    Scott Phillips

    Star, ID
  6. fagesbp

    fagesbp Smoking Fanatic

    I love this design. How high have you gone on temperature? I want to build something similar but I need to be able to get up to 175 or so for smoking sausage.
  7. bluebombersfan

    bluebombersfan Master of the Pit OTBS Member

    Looking good!  I always love watching home builds!!
  8. The highest temperature I've taken it to so far is 230 degrees when I cooked some ribs last weekend. This wasn't the maximum temperature it would reach...I had set the PID for 225 F and the smoker overshot the temperature by 5 degrees, then dropped back to 225 F.  It was a cold day outside, too - below 32 F.  With the George Forman burners, I suspect it would reach 350 pretty easily.

    I still need to fasten some rods on the inside top of this smoker to make it easier to hang sausages.

    I've been using it nearly every day and am very pleased with its performance.  Regarding holding temperature, I figured out the issue I thought I had wasn't really an issue at all.  It had more to do with the inside steel lining of the smoker warming at a slower rate than the air in the smoker.  Specifically, it was overshooting the programmed temperature when I'd first fire it up...all the metal in the lining was acting like a big heat sink around my thermocouple.  When I let it warm up to temperature before putting food in, it holds temperature within .3 to .5 degrees.


    Scott Phillips

    Star, ID

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