Mash Pid and temp probe question

GlennMcD · Joined: 07 Oct 2013 Posts: 51 Location: Louisiana

This may have been asked before, but why would the mash pid not control the firing of the hlt element? I ask due to the temp difference I get between hlt and mt, can’t seen to hit the temps consistently. I am about 10 degrees difference between the two.

**kal** · Posted: Sat Nov 30, 2019 6:25 pm Post subject:

Hi!

The mash PID temperature probe is too decoupled from the HLT heat source. There needs to be tighter coupling for it to work together otherwise you could have runaway conditions. It's a question that does get asked a lot and there have been other threads about it I'm sure. Here's one:
http://www.theelectricbrewery.com/forum/viewtopic.php?t=31578

Having a HLT to MLT temperature lag is a very common issue. Using parts that are different from the ones I recommend in our build instructions can cause this. 10 degrees is very high however. Most that have a lag mention 2-3 degrees.

To minimize the difference, make sure to:

- Calibrate both the MLT and HLT temp probes per the instructions here: http://www.theelectricbrewery.com/control-panel-setup
Unless both are calibrated with a known accurate thermometer at the mash temp, you don’t know if what you are seeing is accurate.
- Make sure to set up the PIDs per the instructions here: http://www.theelectricbrewery.com/control-panel-setup
- Use the thicker walled hoses I recommend here: http://www.theelectricbrewery.com/hoses
Thicker hoses will lose less heat. Try to minimize distances as well.
- Set your mill gap crush per the recommendations here (0.045 to 0.050"): http://www.theelectricbrewery.com/grain-mill
You want to mill looser for good flow, not tighter.
- Use the pumps I recommend here to ensure adequate flow: http://www.theelectricbrewery.com/pumps
- Run both pumps at 100% open when mashing. To get good flow without any channeling use the kettles I recommend here: http://www.theelectricbrewery.com/kettles-overview

For example, users have reported on our forum and by email how they were seeing a temperature differential between the MLT and HLT and were able to make it go away by swapped out their hoses and pumps for what's recommended in the build instructions. A quote from one of them:

"I had originally tested the HERMS with the thinner 1/2 ID silicon and had my pumps setup with the inline heads (long story). I was landing about 1-2 degrees cooler in the mash kettle. I swapped out the pump heads for the front inlet and swapped out the silicon with what you recommend and I now hit the same temp!" - Todd W.

Other things that are sometimes done differently that can cause a differential:

- Make sure the heating elements are wired correctly and being fed 240V and not 120V. Running heating elements at 120V will result in 1/4 the power you expect. You can check this by looking at the amp meter. A 4500W element will draw 18.8 amps while a 5500W element will draw 22.9 amps.
- Brewing in a very cold location may cause the MLT temp to drop slightly by the time it reaches the MLT temp probe.

This question gets asked a lot on the forum too. These threads may provide further hints:

http://www.theelectricbrewery.com/forum/viewtopic.php?t=25474
http://www.theelectricbrewery.com/forum/viewtopic.php?t=26408
http://www.theelectricbrewery.com/forum/viewtopic.php?t=28283
http://www.theelectricbrewery.com/forum/viewtopic.php?t=25474
http://www.theelectricbrewery.com/forum/viewtopic.php?t=30387
http://www.theelectricbrewery.com/forum/viewtopic.php?t=26722
http://www.theelectricbrewery.com/forum/viewtopic.php?t=30603

Good luck!

Kal