Mash-Tun PID Controller Diagram- Is it right?

[KyleWolf]

Hi everyone.

I am designing a fairly simple HERMS set-up. Right now I am planning on starting off at 1 pump and eventually upgrade to a 2-pump system. I am designing my PID-Controller and wanted to make sure I have the diagram correct. The idea is simple. a 3-way switch for "Auto, Off, and Manual" for the pump that recirculates the mash through the HLT. Manual is just "On" for all other functions for the pump not pertaining to the mash (sparge, chilling, etc) and Auto will have the pump turn on and off according to the PID and RTD sensor that goes to the mash-tun.

The idea for the design is so I could add parts of the system "al a carte" as the equipment is purchased (second PID, gas valve, and pump for HLT, PID for boil kettle, etc).

Really I just want to make sure the design I have will do what I want it to do. Which again is basically...
1) Auto-turn on of off the pump according to the temp measured by the PID/RTD sensor (Auto)
2) Turn off the pump (off)
3) Have the pump run continuously (Manual)

Thoughts/Suggestions/Etc are always welcome! Thanks a lot.

 

[Leadpencil]

I am building my panel the same way. I dont think that you can go directly from the PID to an outlet.
I dont have a schematic for how I wired but what I did was use two SSR's. I have the signal from the PID going on one leg of the three way switch then to the SSR for running in Auto. For Hand I ran a second 24 volt line to the switch and then to a second SSR.

 

[KyleWolf]

Do you have a jumper that connects the two SSR outputs to the line running to the outlet?

 

[Leadpencil]

yes i do. one power source on the 120 volt side.

 

[KyleWolf]

Gotcha. After looking at the design, do you think this could possibly work? If not then I will just go with the 2 SSRs like you have.

The idea here is that when the "auto" switch is flipped, power will run to the PID, The PID can then dictate the power that runs to the SSR.
Similarly, for the "manual" switch, power runs directly to the SSR and circumvents the PID. The SSR then determines if power is running to it from either source and then kicks the power on or off to the outlet. Does this sound closer?

 

[Leadpencil]

The power to operate the SSR is 12 volts dc. you will need a separate dc power supply to feed your Hand Off Auto switch. Typically these switches have two different power sources coming in.

 

[Bobby_M]

Fewer people are switching the pump for HERMS due to the fact that the sensor may sit in a pocket of hotter mash and never kick on even if the majority of the mash is colder than desired. Better consistency can be had by constant recirculation and using PID to regulate HLT temps.

That said, the way you can easily do what you want here is to have the ON position directly feed 120v hot to the pump outlet while "auto" feeds it to the SSR. Pumps only pull 1-2 amps so the modules on selector switches can easily handle it directly.

 

[KyleWolf]

Thanks everyone. Bobby, that is actually what I was just putting together when I realized that I had unread messages on this thread. I will reform the image and re-post later. As for the method for monitoring the temp, I appreciate the idea and it was something I had considered. The position of the sensor I was planning would have been on the outside of the mash-tun where the hoses connect to the tun, that way the temp is being measured from the flowing wort out. I also would have kept the HLT only a few degrees warmer than the mash.

Using the PID to directly control the water temps via a gas valve was my original idea, though originally the plan was for a direct fire recirculating mash Just like this set-up, but felt it would be easier and cheaper to do a HERMS (easier to built a little bit at a time), but maybe I was wrong about that...