This thread is intended to document an electrical control panel build for use with a powder coat oven.

Legal Disclaimer:

Warning – All wiring projects involving AC voltage are inherently dangerous and can cause serious injury or death if done improperly. You assume all responsibility for the electrical work that you perform and the dangers involved therein. If you are at all unsure about completing any aspect of this or any other wiring project, consult a qualified electrical contractor to perform the service(s) for you.

Always follow electrical code requirements specific for your location. Before undertaking any electrical project contact your local electrical authority and your insurance company to ensure that you comply with all policies, regulations and authorities concerning this work.

I’m using a PID, Timer, SSR, alarms, switches, etc. Some of the steps are obvious, but this step by step procedure may provide some guidance for anyone considering their own oven control build.

Before purchasing components determine what capabilities you desire in the operation of your oven.

Do you need ramp/soak capabilities from the PID controller which would allow you to control the rate of temperature rise in the oven ?
Do you desire a built-in timer function that will turn off the oven elements after the cure cycle is complete?
Do you want internal lights and or a recirculating fan, high temperature or timer expiration alarms?
Do you prefer an SSR or Contactor relay to control the oven elements?
Have you determined the wattage necessary for the planned oven size?

These are all questions you need to answer before purchasing components and starting construction of the control unit.

Purchasing considerations: When purchasing, the first consideration is to make sure all components are compatible.

PIDs – Most of the lower priced PIDs such as the TET-612, JLD-612, TC-408, Auber SYL-2362 are capable of driving either an SSR or contactor and have 2 sets of output relay contacts for alarms. However, if any of these models are used to drive a contactor(versus an SSR), then one set of output contacts is consumed for use by the contactor.

Ramp/Soak controllers such as the Auber SYL-2342(contactor model) and SYL-2352(SSR model), only have one set of output contacts for alarms.

Higher end controllers such as the Watlow Model 93’s are configurable in many designations, so before purchasing one of these models be certain that it is configured to suit your requirements. One nice advantage of using a Watlow is that they are made in the USA and can be repaired if they malfunction, unlike the Asian offerings.

Most PIDs, regardless of the model, can support (2) SSRs or (4) contactors if multiple relays are necessary for your configuration.

SSR’s and contactors – The decision of which type relay to use is a personal choice imo. Some sort of relay is necessary as the PID controller internal circuitry is not capable of directly switching the amperage loads of a typical oven heating element(s).

SSRs by design are capable of switching multiple times per second and have a switching life usually in the millions of cycles. They have no moving parts and accomplish the switching by use of semiconductors. The switching process generates heat so a good heat sink is necessary. They can fail either open or closed so if overheating is a concern then use of a high temperature alarm could be considered.

SSR’s typically switch only one leg of a 240 volt power requirement for elements so be certain to disable the electrical mains power supply prior to working on the elements.

SSRs can be found in either AC or DC input voltage models, with the DC version being the most common.

Computer fan/heatsink combinations work well for cooling but these fans will require a 12VDC power source(discussed more in the build section).

Contactors are electro-mechanical relays that open and close contacts using an electromagnet coil. Their switching produces an audible click/clack sound and their life expectancy is normally in the hundred thousand cycles.

Contactor models can be found with input coil voltage requirements in many variations of AC or DC voltages so be certain to get one that matches your intended power supply. A 120VAC coil contactor is probably the most commonly used type in Powder Coating ovens.

Contactors also come in various pole or contact sets. For a 240 volt oven a 2 pole is most commonly used. If you have a higher amperage load requirement the element loads can be broken up and switched over a 4 pole contactor of a lesser amperage rating than what would be required if using a 2 pole model.

When using a contactor, the PID parameter controlling cycle time must be reduced to slow the on/off cycling process or the contactors life expectancy will be reduced.

Timer, toggles, alarms, etc. – In the build section I will discuss a number of components I have found to work well. This is not an all inclusive list and there are many choices of components. At the very end of the build I will list some sources I’ve found for various components.