Converting Electric Kitchen Ovens to Smokers
I have been asked a number of time about my electric smokers made by converting cast off electric residential kitchen ovens. I used converted electric ovens as my primary smokers well before I discovered the Kamado world. Done properly and safely following accepted electrical practices, they are great for a wide range of uses!
I build my own by converting electric kitchen ovens to smokers and running them on 120 volts instead of 220 volts. I have done several mainly using single ovens. The one shown below that I have been using for several years is a double oven from a friend’s kitchen renovation. The upper oven is the main smoker and smoking dehydrator for use with smoke and the lower oven is reserved for a subsequent conversion to a (no-smoke/clean environment) dehydrator. Simple to do these conversions if you have the right knowledge base and skills. Works great once you fine tune the mechanics and get the hang of its characteristics. Best thing is cast off ovens are often free and they are very well insulated! With the right external PID type temperature controller and weather enclosure plus the smoke maze they are very inexpensive to do. Just a bit of basic (re)wiring and mechanical skills needed.
The application of the external temperature controller and the home electric kitchen oven conversion makes this a very powerful and well controlled dehydrator, cold smoker chamber, sausage & jerky smoker and even a general smoker in a fully insulated system. What more could one what in a “smoker”?
Here are some views my current conversion that gets a lot of use in sausage making. This promptly got named the "Johnny Smoker" for the obvious similarity in silhouette and shape.
1-The Johnny Smoker
2-Weatherproof Enclosure T1-11 Siding & Cement Board Doors
3-Double Oven - Smoker & Dehydrator
4-Interior View & Smoke Maze
5-My Homebrewed PID Based Temperature Controller
6-Air Intakes & External Smoke Generator Ports (I can use a homemade round tube based chip wood smoke generator)
7-Rear Exhaust Stack (PVC pipe works fine here as a chimney stack off the iron pipe exhaust at oven temps up to about 350-375 degrees)
The Basics Concepts (see cautionary note & disclaimer at end of the article)
An oven with a working set of heating elements (actually just the bottom element) is utilized. A convection oven with working convection portion also is excellent. That, plus electrical and circuit wiring knowledge and skills, a bit of mechanical skill and a touch of framing type carpentry for an enclosure are required.
Most electric residential kitchen ovens operate on 220 volts. A heating element designed for 220 Volts will work on 110 volts but it produces only 1/4 the heating ability. So a 2400 watt normal element on 220 offers 600 watts on 110. Plenty for smoking below 300 degrees - although at the higher end the oven preheat takes a while.
There are two ways to do the oven conversion with regard to temperature control.
Internal Temperature Control Reuse: For normal smoking temperatures, the oven control system can be reused. Most ovens have a lower end of 170 to 200 degrees. Older mechanical type thermostat ovens are sometime easiest. What is required is to use the internal controls is to rewire the heating elements and wiring paths to work on 110 volts instead of the 220 volts, appropriately adjusting internal wiring in the oven as needed (a wiring diagram often printed or rolled up inside the control housing box is handy to have) to eliminate using "one side" of the normal 220 volt wiring. This wiring conversion to reuse the oven control may be simple or complex depending on the oven. It some cases on the newer ovens maybe even not possible to reuse the internal controls.
External Temperature Controller: Alternatively and often simpler with more versatility is to use an external temperature controller. They advantage here is simplified wiring in the oven itself (i.e. essentially none) and the ability to dial in temperatures way below a normal oven dial. As low as the ambient temperature in fact or even as a cold smoker with no heat. Sausage smoking general starts at 130 degrees F and goes up to 170 degrees – a normal oven control cannot do this. Dehydrator temperature is generally 145 degrees F. For dehydrating one can keep the oven door cracked open initially for more moisture removal.
As noted before, the application of the external temperature controller and the home electric kitchen oven conversion makes this a very powerful and well controlled dehydrator, cold smoker chamber, sausage & jerky smoker and even a general smoker.
The temperature control is accomplished with either a suitable external self-contained "off the shelf" unit or a home rolled one using an inexpensive PID based controller.
One such system is a home brewed PID controller with temperature sensor able to cover your desired cooking range (say up to 300 degrees), a power relay and some simple wiring and an enclosure. Auber Instruments products is one source. Like the SYL-2362 controller, the R30A mini power relay, and one of the companion temperature sensors types good to at least 300 degrees F or more.
In the case of the external controller, the oven controls are not used at all and the oven heating element is suitably connected directly to the temperature controller unit. Use the lower element. Two wires from the heating element terminals (which are disconnected from their original internal wiring) to the controller and it is wired. No electricity is then connected to any other internal oven wiring. In fact it could even be removed. The controller should be rated for at least 10 amps (i. e. 1200 watts) for one element – 20 amp is even better if you contemplate using the upper and lower elements together. Be aware using both elements at the same time can approach the limits of a 15 or 20 amp circuit. You only really need the lower.
Locate the temperature sensor in the mid oven near the top. You can even run the cabling though the door gasket or drill a small dedicated access hole in the oven body.
Mechanical Conversion (Intake and Exhaust Ports)
The mechanical conversion consists of drilling ports for air intake and exhaust flow. Use a cross flow for obvious reasons of smoke distribution.
Put the air intake on the lower left front side wall of the oven wall (clearing the rack guides) or in the lower left front bottom -- or both. This should be one or two ports (1 3/8 inch diameter) suitable for a piece of nominal "1 in" black iron pipe. Use a length of black iron pipe nipple held in the hole by using the star shaped metal threaded electrical conduit ring nuts - one on each side. To do this, the external shell hole is drilled large enough to pass the nuts rings so the nuts fasten to the inner oven wall on each side. Yes, the electrical conduit ring nuts fit the same size plumbing pipe as they do electrical conduit.
The exhaust, is located on the right upper rear panel of the oven or on the right top at the rear. One or two of the same 1 in pipe holes and a suitable length of pipe nipple. A "large size" stepped drill bit that goes to 1 3/8 inches hole fits the 1 in pipe. Harbor Freight has these. They are perfect for drilling the interior porcelain coated steel oven wall and the metal external shell. Ovens are double walled separated by insulation. Two intakes and exhaust ports are probably ideal as they can promote a good airflow that can be adjusted by a simple piece of aluminum foil.
Cabinet (Weather Enclosure)
Some sort of weather enclosure is useful. Kitchen ovens are not waterproof. For a long time one of my single oven conversions was just mounted on rollers and rolled out the shop for use. Inconvenient if it was raining (think water and electricity) when I wanted to use it. My current one can be used rain or shine in the cabinet which can be closed while in use. Simple carpentry skills need here.
Finally – smoke generation. There are a number of ways to do this but they must not rely on heat in the smoker to generate the smoke. Internally, and most often I use an A-MAZE-N Products smoking maze with sawdust. I underline sawdust. Pellets will not work as I have consistently had them go out in the low temperatures in the smoker. No offense to their pellet smoke generator – works fine in hot grills. Buy the maze that does both for versatility. I place the maze in the lower left of the oven on a shelf in the lowest position over or next to the intake vents. Why? Well the fresh air flowing through the oven by convection help the sawdust burn and the cross flow smoke filled the oven on its way to the exhaust. Bingo!
Alternatively, it is possible to size one of the intake port holes to take one of the external tube style smoke generators that take wood chips. I do this with a homemade generator of this type when I want to use chips.
There you have it … not a fully step by step tutorial as this write-up is a concept guide to illustrate what might be done. It could stimulate thinking among some of the Kamado Forum Gurus who are considering the next experiment for the cooking patio… especially for dehydrating, cold smoking and low temperature sausage style smoking and such. Please observe all cautions and best practices and note the disclaimer below.
To paraphrase the TV commercials…So… if you have the skills and knowledge, can and want to - please act now to save a cast off electric kitchen oven from the dump and prevent a tragic waste of a potential high performance smoking machine.
Disclaimer & Cautionary Statement:
The information provided above involves electrical skills related to lethal household electrical voltages and currents as well as high temperature heating elements. The information above is provided only as an illustration of concepts and ideas. It is not, nor is it intended to be, a detailed procedural guide. Improper or incorrect application or use of the above concepts can result in injury, death, or fire. The contributor takes no responsibility for this information as to accuracy or fitness for use for any particular purpose.