The start of a fridge conversion

Discussion in 'Fridge/Freezer Builds' started by builder59, Feb 19, 2009.

  1. builder59

    builder59 Smoke Blower

    Hello all,
    My name is Ron and I am going to convert a commercial refrigerator into an electric smoker. During the build I will have photo's and as much documentation that I can provide. I have no prior experience with this but I have years of smoking under my belt. I will be asking alot of questions from successful conversion owners. It is my intent to try and really document this for anyone's future use. Wish me luck I'm gonna need it.

    Here is the first couple of pics to where I'm at now.

    This is the exterior before I started anything.

    This is the interior before I started anything.

    I believe I'm going to two of these for my heating element
    Heater,Strip,120 V
    Stainless Steel Finned Strip Heater, Voltage Rating 120 Volts, Power Rating 1250 Watts, Overall Length 15 1/4 Inches, Mounting Dimension 14 1/4 Inches
    >More Details...


    I would like to ask the ones who have done this, will these work and can I hook them up to one pid. Also I want to be able to program the pid for different times and temps in one cook cycle. If they make one could you tell me which one to buy.

    I am also going to purchase the Bradley smoke generator for my smoke source.

    That's it for today.

  2. smoking gun

    smoking gun Smoking Fanatic OTBS Member

    I have a bunch of 10 KW duct heaters. They are 240 volt though They'll heat on 120 but of course only at 5 KW.
  3. Ron

    Looks like a great project!

    Here is a link to the Auber PID that you would need to have the capability to "ramp" (program) the temps up such as in doing sausage.

    The next thing you have to consider is the 1250 watt, 120 volt elements will each draw approximately 10.42 amps. Now, most residential circuits are 15 amps and sometimes as high as 20 amps, so, with the 2 heaters alone you would be at nearly 21 amps. If you were to try to wire it all up to one circuit you would continously blow the breaker. You will have to supply power from two seperate circuits. In addition you will have to take into consideration anything else that is on either of these circuits. Because you are supplying power to each element seperately, each element will need to have it's own Solid State Relay (SSR). This is really not a big deal as the SSR's are in-expensive and the PID is capable of controlling mulitple SSR's. Here is a link to the SSR's that you will need. You'll need two of them.

    I'm not sure if you need a heat-sink on the SSR's but they too are in-expensive and to rule on the side of safety I would use them. Here is a link to the heat-sinks. you'll need one for each SSR.

    I'm not sure what type of thermocoupler you are going to use but this is the one that I use and have had no problems with.

    The Bradley Smoke generator uses very little power and could run off one of the circuits with one of the finned strip heaters.

    Some of the finned strip heaters require air flow so that the element itself doesn't overheat. You may want to check with Grainger to see if this is the case or if it can be ran "free air" so to speak.

    One other thing to look at is the type of insulation that is in the commercial fridge. You just want to make sure it will take the heat and not give off toxic fumes. If it's a problem you can re-insulate it with Roxul Mineral Wool insulation which is rated at around 2000 degrees.

    Hope that helps you out Ron. I look forward to seeing your progress.

  4. Smoking Gun

    I can't remember where I read it but I thought if you ran a 240v element at 120v you would be running at roughly 1/4 the watts. In this case that would work out to about 2500 watts at 120 volts which again would draw about 21 amps.

    I'm certainly not an electrician, this is just what I recall. I'll have to see if I can dig up where I got that from.

  5. builder59

    builder59 Smoke Blower

    I spoke to the tech at Auberins and he talked me into the programmable smoke controller for $149.00 and thought that one 1500 watt 120 volt would do the job. He was stating that by the time I bought the separate components I would be almost there and still have to manufacture the box. He also sold me a loop circuit controller for $30.00 for the fan. I hope I did not pay too much. If I paid say 50.00 more I guess it would be worth the time.

    Do you think 1500 watts will be sufficient?
  6. cowgirl

    cowgirl Smoking Guru OTBS Member

    Welcome to the forum Ron, glad to have you aboard!
    You might want to stop by roll call and introduce yourself when you get a chance. Looking forward to seeing how your project goes!
  7. Ron

    You can reach Suyi Liu who is the guy to talk to at Auber Instruments at [email protected] He is really good at answering questions via email.

    If I understood your post correctly, you are going to use two finned strip heaters that are 1250 watts each. Thats a total of 2500 watts and that's why I suggested putting your own PID controller together yourself. The pre-built unit in your post is a good unit but I don't think it will handle the 2500 watts your going to throw at it. I wonder if he misunderstood you and thought you are going to run just 1250 watts?

    I would shoot him an email to clarify.

  8. builder59

    builder59 Smoke Blower

    He talked me out of going with two 1250's saying that it may be difficult to get the heat down with two. Something about how current flows to them and they having a threshold and a minimum starting point. He thought one 1500 watt would do the trick. What are your thoughts?
    Thanks for your help.
  9. Ron

    So are you going to go with one 1500 watt finned strip heater? Or another type of element?

    I know the one I built started life as a proofer which has a fair bit more area inside it than a fridge. I'm running two 1100 watt finned strip heaters. Mine heats fine but I'm certainly glad I didn't go with less heat though.

    Yours, being the inside of the fridge may be ok with the 1500 watts but I'm really not sure. What are the inside dimensions of your commercial fridge? I'm just curious in comparison to mine.

    It would be nice if you had access to a 1500 watt element that you could just set in it and let it run full throttle to see what kinda temps you and how much time. This would be great if you could do it without having to buy one first.

  10. builder59

    builder59 Smoke Blower

    It would be nice to be able to try one out but don't have one. I may be able to return it but I kinda doubt it. My dimensions are 27" wide 24" deep and 60" tall. So I'm at around 22 sq. ft. It has 1 1/2" thick foam in the walls that is pretty dense.

    I have steel insides and I went today and picked up 026 gauge 304 stainless steel sheets for the inside. I bent them up this evening and will install them over the steel insides and make an airtight seal from the existing interior as I will fire caulk all interior seams. I made a bottom, top sides and back, when you look inside now all you will see in pure stainless.

    By doing this I don't think I will have to worry about any issues with the foam insulation. Anyone with other info on this I am all ears as I don't want to get sick. It just seams to me that I have basically isolated this thing from the original carcass. I will post pics tomorrow of the install of the stainless.

    I made the cover for the interior of the front door the same dimensions as the original plastic so I could re use the rubber seal. I only plan to heat this to 250 degrees and only a few times as I don't really need that kind of heat unless I'm cooking chickens. Will I have any issues with that. If so I have already thought about fireplace roping. The fridge seals awesome with the factory seal I really want to keep it if possible. One last thing it really only shows about 1/4" to the interior of the smoker so I hope it will not melt.

  11. Ron

    I think the factory fridge seal is worth a shot. I've seen some posts where people say they are fine so it won't hurt to try using it. Simple enough to change to woodstove/fireplace rope afterwords anyway.

    I'm still not sure about the 1500 watt element. The interior dimensions are pretty similar to mine so I'm not sure what to tell you. Hopefully someone else will comment on this because I have seen other posts on builds that use hot plates which are usually no more than 1500 watts. However, having said that they are usually using a pan & wood chips on it for smoke. I'm assuming the smoldering wood chips would also produce some heat.

  12. morkdach

    morkdach Master of the Pit OTBS Member

    1500 watt is way plenty i run 750 to 900 watt in most of my stuff i have a 1500 watt in christene and have to control it letting it run full time it pushes 450*
  13. mulepackin

    mulepackin Master of the Pit OTBS Member SMF Premier Member


    I pm'd you about the element, etc. I used in mine. It is 1500 watts, and has worked just fine at attaining and holding smoking temps in weather down to around 0 deg. It did have a little trouble this Dec. when it was hitting -20 with 40 mph winds, and I was doing 12 turkeys. I plan on adding some fire brick, and a diffuser plate to help with heat retention and recovery. The factory seal has held up very well. If it doesn't I would consider the seal that Allied Kenco uses before wood stove seal. Other members have had better success with it.
  14. builder59

    builder59 Smoke Blower

    Morkdach and Mulepackin. Thank you for your input also to Walleye1, you have been alot of help. Here is the latest for the work today.

    This is the start of the gut.

    Tearout of the cooling coil.

    Cleaned up and the door completed.

    The bottom and what I will use for the drain.

    All sheet metal is 304 stainless in 026 guage. I bent it up at Dave Lamb Heating & Cooling. I use him for my builds so he was nice enough to let me use his slitter, brake and shear. It was a breeze with his equipment. Only took about an hour and a half to bend every piece if steel for the project.

    I have three sheets that are 36" by 8' and I paid $86.00 a sheet from Oakland Metal Sales in Auburn Hills Mi.

    So far to this point I have six man hours into the project with my brother Bob helping with the sheet metal, he's the man when it come to using a brake.

    I'll be also installing an interior top and the sides and back as well as capping the foam at the door area.

    I'll post more in a few days when the parts start showing up.

    I'll temporarily mount the heating element and test temp before any final install.

    So far I have about $270.00 into not counting the electronics. I think my build will cost about $630.00. A little more than I wanted to spend but I figured if I was going to do I might as well do it right. At least in my mind it is right. I sure hope the heck it works!! LOL!!

    Thanks for keeping interest.

  15. mulepackin

    mulepackin Master of the Pit OTBS Member SMF Premier Member

    It's sure looking good so far. I was going to ask you if you were a tinner, while viewing the pics, but you answered that question for us. Again, great looking build. Keep us posted.
  16. Lookin' good Ron!

    I look forward to seeing your progress.

  17. morkdach

    morkdach Master of the Pit OTBS Member

    looks good so far i like your sheet metal work. stainless is nice but you really could use mild steel no rust once you get a good seasoning on it.[​IMG]
  18. builder59

    builder59 Smoke Blower

    Wish I would have know that about three days ago. LOL thanks anyways. I have a cookshack 50 that about every two years I power wash her out and give her a good cleaning then re season her.. I can taste the difference so overall I'm glad I went with the stainless.

    Today I did an experiment,

    Barn was 40 degrees before I started the wood furnace. I took a 8x8x16 cinder block from outside which was 19 degrees. Put a 500 watt charcoal starter on top of the block and shut the door. In one hour I had a temp of 160 degrees and the barn was 62. I opened the door and checked the foam since I don't have that wrapped just yet and felt how warm the walls were. I shut the door after about 30 seconds and the temp was 135. After a half hour temp was 120 degrees. After one hour I had 108 degrees. I don't think it will be too bad with the 1500 watt element I went with. My thermometer was one of those electronic deals with the oven and food temp, I just stuck it in the hole in the middle and let it dangle about an inch inside the cabinet. I hope to be able to achieve 250 degrees and not have it run full time. Again this temp will more than likely be used only once or twice a year.

    At 160 degrees the foam that was not covered that you can see in the above photo's was not affected at all.

  19. morkdach

    morkdach Master of the Pit OTBS Member

    Ron when i run a 750 to 900 watt i use a charcoal pan with about 6 coals and small handfull of chips. the coal will light it self and this help maintain a constant with a water pan. i just use a small pererated pan 10 to 12" like a pie pan
  20. davenh

    davenh Smoking Fanatic OTBS Member

    When I did my freezer build I opted to remove the foam and line with regular R13 fiberglass insulation. Everything I could find Kinda said best case the foam might be good to 250. MES limits the temps in their units to 275, I think due to the foam insulation they use. If your not planning to go too hot you maybe ok.

    Here is a link to common insulation ratings.

    The blown in fridge foam is most likely Polystyrene or Polyurethane.

    Your build is going to be a good one [​IMG]

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