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HERMS / RIMS controllers

Has anyone used the Johnson Controlls A419 ( … oller.html) controller to controll a March pump ( … -plug.html) thus controlling the temp of their MLT on a semi automated HERMS or RIMS system?

I get the terms mixed up…

If you are going to run the wort through a coil in a hot bath, that should work with out a problem.

If you are running the wort over a heating element, then I believe you want to turn the element on/off. Other wise the wort will be scorched when the pump is not circulating it.

Another option is the “less expensive” controller I’ve linked to in the past on ebay.


A standard on/off temp controller works fine for the ‘hot bath’ type. You can either have it control the pump and manually adjust the hot bath, or have it control the element and leave the pump running, provided the element does not draw more than the temp controller relay. Positioning the temp sensor properly for pump control can be tricky as there is often a big thermal gradient from where the hot water enters and where the cold wort sits, at least in my rectangular cooler. Controlling the temp of the bath is preferred since it’s less manual adjustment.
You don’t need a PID for this type because you are not boiling (which requires PWM to be useful), and the element is not in direct contact with the wort. But a PID is nice because it will greatly reduce overshoot.

For the RIMS, you probably need a PID to limit the power output of the element in addition to controlling the set point. It may be able to do it with a standard controller if your element is low enough output, but you’d have no way of adjusting this and just have to cross your fingers.

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