Control Panel with On/Off/Auto Switches

[Jinkies]

I'm designing up a control panel for an electric BIAB setup. I'm looking for it to have two modes, three with off. On, which is basically just on and then auto where the relay is connected to a automated controller of some sort, craftbeerpi, brewblox, PID controller, etc. I haven't come across many designs for the On and Auto functions. The only way I can come up with is two contactor relays per switch. One per mode. I attached a picture of the design to this post using a 120V setup to a pump. Am I overcomplicating this or is this the best way? I could go with a one pole contactor but for some reason it felt like a better practice to cut both lines. Thanks in advance!

 

[Bobby_M]

Is the On/Off/Auto function for the pump or the element heat? Regardless, there's no need to switch the neutral.

 

[ITV]

With the assumption that you are using this to control a pump, as I would not recommend an On mode to control a heating element, I would make the following changes:

Wire the automation controller relay in series with the Auto mode to switch contactor coil.

Wire the On mode so that it will energize the contactor coil bypassing the Auto mode described above. This will eliminate the second contactor.

No need to switch the neutral on a 120VAC circuit.

If the intent of the automation controller to rapidly switch on/off the contactor coil, then you need to reconsider using a contactor for this application.

I'm not sure on how this design fits an electric BIAB application, it is more suited for a HERMS application. Maybe you can eloborate on the intent of this circuit.

 

[Jinkies]

Is the On/Off/Auto function for the pump or the element heat? Regardless, there's no need to switch the neutral.

Thanks. I was thinking that but I guess just trying to be extra safe. The On Off Auto would be for the pump and the element. Obviously at 240, I'd need to run both hot wires through a contactor.

 

[Jinkies]

With the assumption that you are using this to control a pump, as I would not recommend an On mode to control a heating element, I would make the following changes:

Wire the automation controller relay in series with the Auto mode to switch contactor coil.

Wire the On mode so that it will energize the contactor coil bypassing the Auto mode described above. This will eliminate the second contactor.

No need to switch the neutral on a 120VAC circuit.

If the intent of the automation controller to rapidly switch on/off the contactor coil, then you need to reconsider using a contactor for this application.

I'm not sure on how this design fits an electric BIAB application, it is more suited for a HERMS application. Maybe you can eloborate on the intent of this circuit.

I'll post the full design here shortly. This was the basic design for a pump. However I would extrapolate this to the element (with the full knowledge that it requires a 2 pole contactor). I'm using the contactors primarily for safety. I've also read SSR are notarious for leakage and I will need a contactor to fully stop power.
As to the pump, I was avoiding wiring the contactor through the relay due to duty cycle concerns but for a pump that probably is not an issue. I think I had it drawn up the way you said to begin with. Changed it to the way I have it shown and couldn't get my brain back to the original. But you are right there really isn't a reason to use two contactors with the switch there.
This is to allow for pump automation, although currently my valves are all manual so it's a bit of an unnecessary add-on. As to the heating element, I was thinking of putting the Auberin SSVR to control the ON portion of the heating element.

 

[Bobby_M]

Many people here support the idea that anything worth building is worth overbuilding. I've fallen into that trap before and highly recommend being more pragmatic. I know the fear of building something simple and all the regret you'll have not building in a cool feature.

Go ahead and put a 3 position selector in for the pump, but start with idea that it's just going to be an on/off switch for the pump. No need for contactors or relays.

The load side for the element should have a 2-pole relay to kill the hots. The coil can be enabled by a push button or 2 position selector that says "element enable".

If you use the Auber DSPR-320 controller, you will not need an on/off/auto mode for the element. The controller itself already has a razor-sharp PWM mode to control the boil with a fair bit of automation built in. I can also trigger pumps via the built in events relays (which could be used for the pump "auto" position if you wish).

If you don't want the controller itself or the pump switches to operate when you are not brewing, a simple main/key switch can be used to disrupt the power to those. This does not need to control a larger contactor or anything because it's all very low current. I know that some people stack an extra "main" contactor in, but I don't understand or agree with its use.

Here's what I ended up with, except I used the DSPR320 instead.

 

[Jinkies]

Many people here support the idea that anything worth building is worth overbuilding. I've fallen into that trap before and highly recommend being more pragmatic. I know the fear of building something simple and all the regret you'll have not building in a cool feature.

....

Thanks! Yeah It's easy to overdo it for sure.

 

[Scout]

I don't see why not use a three position switch with two normally open contacts both wired to the same contactor.