Written by Rickdatech
There are two goals we consider when making control panels for our Appleseed processors. Safety and Automation. We will cover Safety first, then Automation, then show some examples of control panels that offer both Safety and Automation.
The scariest thing that can happen when operating an Appleseed is for it to catch fire inside the tank. This happens when the heating element is activated while uncovered. The heating element depends on having a fluid covering it to carry away the heat. If it is not covered then it will over heat and burn out in a condition called "dry firing". When an element dry fires, it will often melt a portion of the element making it useless. It also gets hot enough to ignite the methanol in the tank. This will send smoke and flames out the vent and can spray you down with biodiesel.
Before we cover control panels, lets look at some processor design elements that mitigate problems we have when this happens.
- If we forget to turn off the heat and pump the biodiesel to our wash tank it will dryfire when the element becomes uncovered. The pressure inside the hose or pipe you're using to transfer the biodiesel will be equal to the sum of the pressure in the tank plus the pressure developed by the pump. This can turn a lazy stream into a fire hose.
- If you're holding the hose it will jump out of your hands and spray you and your work area down with biodiesel. It's better to hard plumb the connection. I like to pump my unwashed biodiesel into the wash tank through a hard connection through the standpipe. A steel connection is best, but I will often use hose or tubing with camlocks to hold it all together.
- The biodiesel will come out of the standpipe going straight up and will escape the wash tank if it is uncovered. I do two things to prevent problems here. First I mount a TEE on the end of the standpipe to deflect the flow from the pump to the sides of the wash tank rather than straight up. Second I place a lid on the wash tank. The lid includes a vent connecting to the processor so the air from the wash tank is used to fill the processor when the biodiesel is transferred.
If our vent is not plumbed to the outside of our workspace, the smoke and flames can come out of the vent into our workspace. Steel vent piping would be preferred; however PVC pipe and PVC hose have both shown to hold up when properly installed. Properly installed includes hose clamps and good clean glue joints.
If you accidentally apply power to your processor while it is empty and you have a valve on your vent, the pressure can build up enough to pop a hose off a hose barb. Make sure you leave the vent valve open when the processor is not in use. To prevent the hoses from popping off the hose barb, the best choice is to use all steel plumbing and eliminate hoses. All hoses need to be double clamped to prevent them from poping off. If you do include a valve on your vent, then also include a pressure relief valve, set for 30psi or less on the tank, to provide an alternate path for the pressure to escape. The good news is that the pressure does not build up enough to actually rupture PVC hoses.
There are three actions that can cause an element to dry fire:
- Forget to turn off the power to the heating element before draining.
- Accidentally turn on the heating element when the processor is not in use
- Turning on the heating element too early when filling the tank.
Timer and Switch
We don't have to make it foolproof so that it's impossible to dryfire. That would be nice, but all we really have to do is to increase the odds against it happening enough that it won't likely happen. If we modify the equipment address the most common cause, forgetting to turn the heat off, then we can address the other causes with education and processes.
One of the simplest controls used on the Appleseed to multiply the odds is the spring wound timer. Use the timer to control the heating element and if you forget to turn it off before adding the methoxide, it will time out before you drain the processor. Spring wound timers are not foolproof. They do fail and fail in the on position. Using a toggle switch to control the pump will help prevent confusion about which switch to use to turn on the heat. That reduces the odds of accidentally turning on the heat when the processor is not in use. Also it's a really good idea to unplug the processor between batches. We wire the incoming power to a commercial (high amperage) light switch. The output of the light switch powers both the pump and the spring wound timer. The spring wound timer powers the heating element. Before you can get heat, you have to both toggle the light switch and crank the timer.
Turning on the heating element too early is mostly a matter of education. Those that have reported doing it, also claimed ignorance about the consequences. Knowing that applying power to an uncovered heating element will cause a dry fire and tank fire is usually enough to prevent it from happening. I have a minimum fill level marked on my processor and I don't apply power unless it contains the minimum required oil.
It is arguably one of the simplest control panels you can add to an Appleseed. It is not the safest nor does it supply any real automation. Our next control panel does provide a little automation and a slight improvement on safety. It is a little more complicated, but most homebrewers will be able to build it.
Panel with Thermostat Feedback
This panel brings the oil up to temperature and turns itself off. It is designed for 120V power with a maximum heating element loading of 1500W. Plug the heating element of your appleseed into the lower receptacle. The upper receptacle can be used either for an indication lamp or to power your pump. It will be powered only when the element is heating. A shop lamp will give a strong indication that the heat is on. However if you plug your pump into the upper receptacle, it will circulate the oil until it reaches temperature then shut itself off to provide some automation. The green button starts the heating cycle. The red button stops heating. It also shuts itself down if there is a power interruption. Since it has integrated feedback from the thermostat, it is imperative that the water heater be wired exactly as shown in the diagram. We retain the power pigtail on the Appleseed so that you can unplug it from the control panel when it is not in use. Unplugging the Appleseed prevents the power from being applied accidentally when not in use.
This is the classic heavy equipment on/off button and relay combination with the added twist of feeding the coil voltage through the thermostat. The On switch is a momentary contact switch that when pushed bypasses the relay contacts. This power feeds through the lower half of the receptacle (the receptacle is one capable of wiring the upper and lower outlets with different power sources.) to the water heater pigtail and to the lower thermostat. If the oil is below the set point temperature the power will be applied across the thermostat and on to the element to provide heat to the oil. A voltage line (blue line in drawing) is run back to the control box from the switched side of the lower thermostat through a normally closed momentary contact button acting as the Off button. This voltage line energizes the relay and keeps the relay energized even when the normally on momentary contact pushbutton used as the on button has released. When the oil reaches temperature the thermostat will switch the power off to the element and remove voltage from the coil causing the coil to disengage. Pressing the stop button also has the same effect. The coil voltage can be tapped to provide power to the upper outlet while the coil is energized. A shop lamp can be plugged into this outlet to provide a strong visual indication of "Heat ON".
Please read up on GFCI protection and overload protection for your pump as they are both needed and covered in detail elsewhere on this site. This control panel does not prevent you from turning on the heat before the element is covered. Always ensure you have at least six to nine inches of oil covering the top of your element before turning on the heat or you risk burning out your element and starting a fire inside your tank.
Bill of Materials
|1||Plastic Junction Box from Lowes|
|1||15A wall outlet (commercial duty)|
|1||On button, NO momentary contact, green|
|1||Off button, NC momentary contact, red|
|1||30A relay SPST|
|1||Pigtail from 12/3 15A extension cord|
|.||Assorted crimp on wire terminations|
|1||Spool of 12ga multistrand wire|
|1||Steel outlet cover plate|
|1||Wire Clamp for mounting wires to panel|