Failsafe for automated HLT filler

[Sadu]

Hey everyone. I'm in the early stages of making an automated brewery and are currently working on the HLT (modified Grainfather sparge water heater).

I have this pretty much working. But I'd like an independent failsafe in place in case my software crashes or whatever. I really don't need that incoming solenoid valve locked open and flooding my garage.

So what's a good stand-alone failsafe to use for this?

I was thinking either a switch or sensor mounted at the top of the HLT connected to a relay that would cut power to the solenoid (which is NC).

A float switch seems like a logical option here (I've ordered one from China and are waiting). But open to other ideas. Appreciate any advice on what everyone else uses for as a failsafe.

 

[day_trippr]

How about running the same circuit that opens the feedwater solenoid through your proposed float switch?
That would fail-safe your controller...

Cheers!

 

[Sadu]

How about running the same circuit that opens the feedwater solenoid through your proposed float switch?
That would fail-safe your controller...

Cheers!

Yeah I wasn't sure how much current the solenoid draws and whether the float switch would handle it.
But if the draw is low enough then this would be super simple, a good thing in this context. Cheers.

 

[origin]

Another option would be to wire the float switch to a relay, and then take a contact from the relay and run the solenoid power through it. You could also take a contact from that relay and wire it to your controller for float switch status.

I would also think about putting a max timer for the water fill. So if it's no full after X minutes, then shut off the supply and trigger an alarm. That way if you do have a failure and overflow, it doesn't flood your area.

 

[Bobby_M]

Install a float valve at the very top. While the solenoid valve is the SOP, a float valve will stop the fill in a failure.

 

[Vale71]

Install a float valve at the very top. While the solenoid valve is the SOP, a float valve will stop the fill in a failure.

Second that. If the solenoid is NC a power failure or catastrophic failure of the electronics will mean that water flow is immediately shut off. The only other failure mode is the inflow valve getting stuck open (mechanical failure) and a float switch will not protect you from that, at best it could turn on an "overfill" buzzer to warn you. A float valve is a mechanical failsafe and will protect you from mechanical failure as well.