2 PIDs, 1 element, switch control

I am wondering if it is possible (and how) to wire a system in which you can switch between two different PIDs to control a single element (my planned system is a two vessel no sparge HERMS, one PID to Kettle w/ element, the other to the MLT). The goal would be a selector switch to choose whether the MLT PID or the Kettle PID was controlling the element in the Kettle.

I am planning to use 1 SSR and 1 DPDT Relay to a 240V/5500W element.

I would like to use one 3 position switch at the DPDT relay (since there would be a switch there anyway), but am not sure if this is possible or how to wire it (without another SSR & relay).

Otherwise, would something like this work?


Thanks for any help.

I think you have it right.
How are you going to handle two sensors? If that's the plan.

I'm confused on why you would want two PIDs for one element. Couldn't you just change the PID settings depending on if you are boiling or mashing?

I was hoping to have the ability (as long as I had two PIDs anyway) to select which PID was controlling the element in the Kettle/HLT, since each would be measuring temp at a different point (one in the kettle, one in the MLT).

I thought the flexibility to control temp during a HERMS recirculation based on either probe might prove useful as I dialed in my process/system (particularly if it was simple to wire the option).

In summary: The PID wired to the MLT or the PID wired to the Kettle could control the the kettle element (particuarly during HERMS recirculation).

...for all I know using the MLT PID and tempt probe would just lead to a bunch of overshooting.

Just use the one PID, and switch it to manual output (around 60% for my system) to achieve a good rolling boil

I apppreciate the thought, but I'll have 2 PIDs regardless even if one is only reading temp. from the MLT. AND since I'll have two, and two possible temp probe readings to use as control points for a PID, I was wondering if switching between them was possible.

Regardless the kettle PID will run in manual during the boil. This switch would (might) only be use during mash/HERMS.