School me on BCS electrical architecture

[auburntsts]

So the control box architecture that I’ve seen (PID or BCS with analog switches) for heating elements shows both a contactor and an SSR to control power to the elements. If I understand it correctly, the SSR is used in conjunction with the PID/BCS interface and the contactor is for the analog switch(es) on the panel face – do I have that right? If so, in a BCS-only panel with no analog switches for element control, could you ditch the contactor and power the elements directly off the SSR?

 

[mredge73]

You only need 1 SSR per element.
Additional contactors are unnecessary, they are often used to for manual on/off or e-stops.
You do still need some form of circuit protection, fuse or breaker.

I built mine into a breaker box, this way the breakers double as cutoff switches.

 

[Silentdrinker]

The SSR allows the low voltage of the BCS to turn on/off higher voltage. The contractor uses 110v to turn on/off 220v. Since the BCS is only 5v, and SSRs are used for low voltage input, the SSR is needed. Since the elements are 220v and the manual switch uses higher voltage, instead of a lower 5v, a contractor is used because it’s designed for higher voltage input.

Both do exactly the same thing, it’s just a difference of the input voltage. This is also why the 110v devices, like pumps, don’t use a contractor. The switch is routing the 110v needed. But they still use an SSR to allow the BCS to control its power.

I’ll add that the contractor isn’t for the purpose of the Estop. Even if you don’t want to have manual control, absolutely install an Estop button for emergency situations. It can also be useful during the brew process.

I’ve had to use my Estop for emergency issues but I’ll also use it to cut power if I need do do something. It’s an easy way to keep all processes running but cutting all the power. Once I finish what I need to do, deactivate the Estop and it continues as if nothing happened.

Of course it’s all doable on the screen, but when your hose pops off while the pump is running and starts spraying everywhere, you’ll want to act fast and not try to access the UI buttons.