Control Box Questions
Oven Structure
Oven Wiring and Heating

Control Box Questions

1. What do I need other than your control box to build an oven if I have built my own enclosure? 

Heaters, heater wire and supply wire . The control box is pre-wired and includes a temp probe. 

2.  Does the timer shut everything off or just the heaters? 

Just the heaters. The digital controller stays on. The timer only shuts down the heaters. You do have a a bypass switch if you want the heaters on all the time.

3. Does the box have progressive control? 

No. All heaters are on or off, they do not come on in stages.

4. Do I need to program the controller? 

No it is programmed and ready to use. Some customers use the auto tune feature as described in the control manual but it is not needed. 

5. Can I use a 220v fan with the control box?

 No it is wired for a 120v fan. 

6. Do you offer boxes for 3 phase? 


7. I have 208v will the box work? 

Yes it will work, but you will have less heater output than you would on 240v 

Oven structure

1. What thickness metal should I use for the inside and outside 

      Most use 24g-22g inside and 24-26g outside , you can use thicker metals but they will take longer to heat up , less metal to heat up makes for faster ramp up times 

2. How thick should I make my walls? 

Generally 1” per 100 degrees heat rise. Most ovens are 4” thick 

3.  What type of insulation do I need? 

Mineral wool insulation or the white fiberglass insulation is recommended

 Oven wiring and heating 

1.  How many heaters do I need? 

3x3x4 oven   2 - 3kw heaters

4x4x6 oven   4 - 3kw heaters

6x6x6 oven   6 - 3kw heaters 

These are just guidelines. A 6x6x6 oven is about the biggest you can go with electric, after that you will need to look into gas fired ovens. 

2. How many amps will my oven draw? 

A 3kw heater will draw 13 amps on 240v.  If you're running 2 heaters, 26 amps draw will also depend on how many volts you have. Using an ohms law calculator will give you the correct amp draw. 

3.  What size wire should I use to supply my control panel? 

This wire should be sized depending on how many heaters you are running . You will need to figure out how many amps you're going to draw to size this properly, consulting a qualified electrician is best for this 

4. Do I need high temp wire to all of my elements? 

Yes, it is highly recommended 

5. How much wire do I need for my oven? 

Figure out where the control box is going to be mounted and where the heater hooks up. Measure the distance and times by 2. The high temp wire we sell is single stranded so you need to run 2 pieces to each heater from the control box. 

6. How many heaters can I put on each contactor? 

Each contactor can handle 40 amps, but its recommended that only 2 heaters be hooked up to each contactor 

7. Do I need a fan? 

Fans do help circulate the heat inside the oven, there are numerous pictures on the internet on fan construction and installations. 

8. I want to install a light what do I need? 

A porcelain light base works well with a screw in appliance bulb.



1. My heaters do not heat 

You will need to get a digital volt meter to test what’s not working. 

Start with checking for incoming voltage, you should have 120v on line 1 and 2, measure from line 1 to neutral, it should read 120v. Then line 2 to neutral it should have 120v.  Then line 1 and 2 should have a combined 240v.   If you have proper voltage on the distribution block where the power supply hooks to then move to the contactor.  If you do not have proper voltage trace wires back to the service panel. 

 If you have proper voltage at the distribution block, turn the oven on and wait for the “click”  when it clicks, see if you have 240v on the bottom of the contactor where the heater wires hook to. If you do not have voltage coming out of the contactor you need a new contactor.  It is not uncommon for a contactor to go bad. 

If the contactor does not “click” on you might need a new digital controller. The easiest way to see if you need a new digital controller is to supply power to the contactors with a jumper wire. On the contactors there are 2 male terminals on the sides, these are for the coils. One side of the coil goes to netural the other side goes to line 1 or 2. Put a jumper from 1 or 2 to that side, if the contactor clicks on and the heaters start heating then the digital controller needs replaced.  Also if the contactor does not click it may suggest the coil in the contactor has went bad so you will need a new contactor. 95% of the time it’s the digital controller that goes bad

 A heater may also go bad you will need to check continuity to see if it shorted out. A heater is either good or bad  they do not go bad over time.

 2.  My oven has heated up great when I built it but over time it got slower what is it?

 Check electrical connections, over time electrical connections can become weak using a digital volt meter will not help. You must check connections to insure your wires are secured properly. 

Other Questions

If you have any other questions - please fill out the contact form and we will be in contact with you as soon as possible.  

*Control boxes are built and assembled by Ted from Ted's Fabrication.   If you prefer to contact by phone - our shop line is 717-647-7818 please note that due to working on orders - return calls may take some time.  Emailing direct or filling out the contact form is the quickest way to receive a reply.