Not too shabby for a first cut.
- First, I would advise against running high current for a switch. The biggest reason is high current switches are $$$. Use some low current switches, like those from automationdirect.com to drive a coil on a contactor. Auber has some in expensive 40 amp ones. Use the contacts on the contactor to carry the load. You will need one for Hand and one for Auto on each one. As well as two for the large element selector.
- For the auto control some say a DSSR is required to switch both legs. In this situation I agree. Run both legs through a DSSR for the 240v element auto control.
- Likewise, run both of the Hand power legs through both contacts of the Hand contactor.
- For small loads, like the pumps you can use small mechanical relays.
- E-STOP is recommended.
To save a little cash and room you can ommit the element selector contactors by gating control power through the switch.
Here is a general explanation of switches with contact blocks.
There are 2 Main categories of switches, Push Buttons and Selectors.
Are exactly what the name implies, you push the button to actuate it.
Push Buttons are divided into 2 main modes of actuation.
- Push the button down the button turns on, remove your finger and the button returns to off.
Push On/Push Off
- Push the button down and it turns on, push it again it turns off.
Selector switches are multi position switches, typically 2 or 3 positions. There are two different main modes of actuation for selectors as well.
- Return to means the switch will return to a standard position when released. Two position switches either Return To Right (RTR) or Return To Left (RTL). Three position switches are usually Return To Center (RTC)
- A selector switch with a maintain function will stay in the position they were last placed.
A panel switch itself does not control electricity, it is a mechanical device. When a push button is in the 'on' position a piece of plastic protrudes from the bottom, when the switch is in the off position it retracts. Two position selector have one mechanical actuator as well. When the switch is in one position the actuator sticks out and retracts in the other position. Three position selectors have two actuators, one for the left hand position, the other for the right hand switch position. When a three position switch is in the center, bother actuators are retracted.
The actuators on a switch interact with contact blocks that are attached to the back of the switch with screws. Each contact block has 2 wire terminals, one on each side of the contact. There are 2 types of contacts blocks
Normally Open (NO)
- When the actuator is retracted the contact in the block is open, not allowing electricity to flow. When the switch actuator is extended it causes the contact block to close allowing electricity to pass.
Normally Closed (NC)
- These work directly opposite of a NO contact. When the actuator is retracted, the contact is closed allowing current to pass. When the actuator extends it causes the contact to open, prohibiting the flow of current.
Contact blocks are stackable! you can screw another contact block on top of another of any variety. The contact blocks have their own spring loaded actuator to pass on the position of the switch actuator below it. This allows for control of multiple circuits using the same switch.
How do you tell if a three position switch is in the center position? Easy! Put two NC contact blocks on both sides of the switch and wire them in series (In one, connect the other side to the other block, and out the second block). When the switch is in the center position both actuators are retracted closing both NC contacts allowing current to pass.
So, starting with the element selector switch. Use a 2 position maintained selector. Install two NO blocks and two NC blocks. Connect 1 NO and 1 NC to your 110v for relay control and connect 1 NO and 1 NC to the PID output. You can run one wire for each and use a jumper to connect the 110 and PID out to the second blocks.
For element 1 you will install 2 NO blocks, one on each side of a three position maintained selector. On the Hand (Manual On) block connect one side to the NC contact on the selector switch with 110 on it. then run the other side to the coil of your Hand contactor. Next run a wire from the other NC contact on the element selector switch connected to the PID output to the Auto NO contact of the element 1 switch. Then run the other side to the control signal to the DSSR.
For element 2 you will install 2 NO blocks, one on each side of a three position maintained selector. On the Hand (Manual On) block connect one side to the NO contact on the element selector switch with 110 on it. then run the other side to the coil of your Hand contactor. Next run a wire from the other NO contact on the element selector switch connected to the PID output to the Auto NO contact of the element 1 switch. Then run the other side to the control signal to the DSSR.
When implementing an E-Stop button, you put it in front of ALL of the other control buttons and switches. So if the E-stop is pressed, there is no power provided to any of the switches, which means they cannot turn on their corresponding relays, SSRs, and contactors. The end result is everything turns off! E-stops fall into the push button category btw, but they are usually a push on/pull off OR push on/twist off.
Wow.. wasn't expecting this to turn into a dissertation