HLT Element Controlled by MLT Probe?

[jimg@gsp]

In BCS-460 4.1, are there any drawbacks to setting up an output control to regulate a HLT heating element controlled by a MLT temperature probe?

Generic example:
HERMS
Output 0 set to HLT element
Temp Probe 2 set to MLT

Mode Heat/Cool Temperature Probe Setpoint
Output 0 PID Heat Temp Probe 2 154

Thanks.

[oakbarn]

I have found that the closer the Probe is to the Element the better the control. I tried to control the HLT Element with my "MLT Tee In" Probe that was on the inlet side of my MLT and After the HERMS. I never got it to control well. I now control with a Probe in the HLT. I do have to get that about 2 to 4 degrees F above my desired "MLT Tee IN" Temp, but the BCS PID controls it within 0.1 degrees.

[JonW]

I agree with Oakbarn's approach of directly controlling the HLT temp set to within 2-4 degrees of the mash temp.

The problem with doing it the way you are describing is that you don't have any direct feedback as to what is actually happening with the HLT temp. Let's say your MLT loses prime and is not recirculating as expected. Your HLT temp would then keep climbing unbounded since the MLT would never increase in temp or get to 154 as your setpoint. You could mitigate this by also having a temp probe in the HLT and set an exit condition when it hits an upper limit of say 158-160.

[jimg@gsp]

Great point. I will take your advise and stay with the HLT probe.

Thank you both. Much appreciated.