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Converting Electric Kitchen Ovens to Smokers

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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. :mrgreen: :mrgreen:

1-The Johnny Smoker

1-The%20Johnny%20Smoker.jpg

2-Weatherproof Enclosure T1-11 Siding & Cement Board Doors

2-Weatherproof%20Enclosure%20-T34%20Sidi

3-Double Oven - Smoker & Dehydrator

3-Double%20Oven%20-Smoker%20amp%20Dehydr

4-Interior View & Smoke Maze

4-Interior%20View%20amp%20Smoke%20Maze.j

5-My Homebrewed PID Based Temperature Controller

5-PID%20Temperature%20Controller.jpg

6-Air Intakes & External Smoke Generator Ports (I can use a homemade round tube based chip wood smoke generator)

6-Air%20Intakes%20amp%20External%20Smoke

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)

http://7-Rear Exhaust Stack.jpg

 

 

 

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.

Temperature Control

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.

Smoke Generation

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.

Conclusion

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.

 

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5 minutes ago, ckreef said:

Great post. Interesting concept. Love your disclaimer. Before that you could hear the lawyers run to get in line. 

Thanks.  Yeah, its a darn shame common sense apparently died in the general populace a long time ago - perpetuated by the twisting of the true definition of what tort law is really supposed to mean.  

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Awesome! My grandpa and dad both ran appliance shops when I was a kid, I remember we had an old gas oven that was gutted and turned into a charcoal smoker for fish. Lots of salmon and smelt were smoked in that thing! Thanks for the detailed write up and ideas. 

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Thanks for the write up.

That looks like a fun and affordable project.

Sad that so much of our freedom is taken away by insurance companies. If I has a dollar for the times I have heard because of insurance--and of course the lawyers they insure against.

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Hello I am very interested in rewiring an old oven to 120V like you have done to use in curing powdercoat as installing 220 volt outlets in the garage would be expensive and We really wouldn't need it to be that much hotter than 200 degrees. Perhaps 300 for cerrakote but I'm sure we could work with 200 and just cure for a longer time.  I have had the darnedest time researching how to do so though. Half of the internet seems to believe it will burn down your house. The other half seems to think you could just wire the oven straight to 110 and it wouldn't give any problems except the lowered heat output. Could you give any more detail on the rewiring process using the old controls?

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On 3/12/2019 at 3:09 PM, geekdude said:

Hello I am very interested in rewiring an old oven to 120V like you have done to use in curing powdercoat as installing 220 volt outlets in the garage would be expensive and We really wouldn't need it to be that much hotter than 200 degrees. Perhaps 300 for cerrakote but I'm sure we could work with 200 and just cure for a longer time.  I have had the darnedest time researching how to do so though. Half of the internet seems to believe it will burn down your house. The other half seems to think you could just wire the oven straight to 110 and it wouldn't give any problems except the lowered heat output. Could you give any more detail on the rewiring process using the old controls?

 

You would really need to have a wiring diagram to do it correctly and safely.  And some basic electrical and wiring skills.  If one of the ovens with electronics it gets even more tricky and might not even be doable using the internal controls.  Old style mechanical thermostat is potentially easier.   And it is not just a plug and play thing.  You cannot just take the wiring coming out the back of oven meant for 230 volts and wire 115 volts right to it.  It must be analyzed and  will need some rewiring of the internals. 

 

To get to 300  - 375 or so degrees and be able to preheat in reasonable time , hold temps and recover after opening door etc, requires one to use both top and bottom elements at same time when on 1115 volts - and in that case a good 20 amp circuit is needed depending on the original bake & broil element's combined wattages when adjusting for 1/2 voltage level.  Going from 230 to 115 volts drops heating power of the element by 1/4. But with both top and bottom elements running you can still hit between 15 -18 amps current.

 

Simplest way is to not use any of the oven controls and internal factory arranged wiring and just utilize an external PID controller and just control the element(s) directly through a relay.  There are a number of them out there but one needs to ensure the temperature sensor on the PID is rated to take the heat  - just cause the controller will do higher temps (say above 212 degrees) the sensors on the cheapest ones probably don't go beyond that before the insulation melts on the sensor wires.

 

I use an Auber Instruments Universal 1/16 DIN PID Temperature Controller  Item #: SYL-2362 and one of their Mini Power Relay SPDT 120V 30A Item #: R30A.  The sensor to use is one of the PT100 RTD style with suitable temp range on the wire insulation or a Type K thermocouple with temperature suitable insulation on the wire. The controller can be set up for either. Put it all in a suitable “project” box, wire it up with electric cord and on/off switch with the PID controller switching the relay connected to a duplex socket.  Then wire stout electric cords directly from each of the oven element(s) to plug into the controller.   Put sensor in the oven in suitable place.  Set up the parameters on controller and you are off and running.  By doing it this way you can pick which element you want to plug in and if you want one or both.  Usually the broil element is higher wattage.   So now the oven is just an insulated box with heating the heating element controlled externally.

 

As  noted in a manner akin to using  the external controller,  one can rewire an oven with a mechanical thermo in a similar way.  Just wire the elements themselves to the thermostat (following correct practices of the themostat and such) and then to the AC line feed through a switch.  Again suitable electrical knowledge is needed to trace out the wires and perform a safe modification/rewiring.

 

If you don't think you can do it safely with you knowledge and skills .... well then don't.   I end with the  same:

 

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.

 

As  noted,  one can wire the oven with a mechanical thermo in a similar manner.  Just wire elements to the thermostat and to the AC line feed through a switch. 

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Thanks. We picked up an old electric stove with non digital components yesterday. I am going to have my dad do the rewiring. He has a much more advanced understanding of electricity than I do and is confident that he understands how to do this safely.

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