Placement of PID Thermocouple?

[JonClayton]

Finally added the PID control to my stand yesterday but I still need to drill/mount the thermo probe in the mashtun. My mashtun is a converted keg with a false bottom. During the mash I recirculate from under the false bottom back to the top of the grain bed through locline.

The consensus among my brewing friends is that I need to place the probe under the false bottom to get the most accurate readings for my PID. What do you think?

 

[Welderbydaybrewerbynight]

I'm also at this stage in my stand good question

 

[bucfanmike]

im designing mine and i think im going to place a 'T' inline with the ballvalve and put the thermocouple there. It will always be in the wort flow. Now i havent yet done this so its just in my head, but I have seen others done this way. There is no way I could get mine mounted to be below the false bottom otherwise.

 

[JonClayton]

That's not a bad idea.. thinking out loud here - my type K thermocouple is threaded but I have not measured it. It is real small though, maybe 1/4" maybe even a bit less. Most T's that I have seen are 1/2" NPT, do you think they make some sort of reducer to screw the thermo into and then into the 1/2" T?

 

[bucfanmike]

quick search shows this, im sure they can be found much cheaper than grainger

http://www.grainger.com/Grainger/PA...=CSE:GoogleBase-_-Plumbing-_-Fittings-_-1DGE5

edit: our vendors rock
http://www.bargainfittings.com/index.php?route=product/product&product_id=71

17 for grainger, 3 for bargainfittings

 

[JonClayton]

That looks like it would work just fine. Hmm, you have me thinking... my ball valves still pull from under the false bottom through the pickup tube, but there is no reason I can't put a T inline on the ball valve that has the quick connect for recirculating the mash. I think that will work great!

I also have to figure out how to program this PID. We somehow got it set for a 1000 degree offset last night on our first attempt. So it was 50 degrees outside and the exposed probe was reading -950 degrees :~)

I am nervously excited about this. Very excited to have the PID installed, nervous that I am adding one more thing that could go wrong on a brew day.

 

[mabrungard]

If you are direct firing on the bottom of the keg mash tun, then mounting the probe under the false bottom is the right place. You want the probe as close as possible downstream of the heat source in the wort loop. If this is a RIMS, then the probe should be mounted at the outlet of the RIMS tube.

 

[JonClayton]

Good point as well mabrungard. I am direct firing the mashtun and using the PID to control the mashtun burner.

 

[KaSaBiS]

If you are direct firing on the bottom of the keg mash tun, then mounting the probe under the false bottom is the right place. You want the probe as close as possible downstream of the heat source in the wort loop. If this is a RIMS, then the probe should be mounted at the outlet of the RIMS tube.

Sorry for stirring up an old thread, but as I am designing a herms system, wouldnt you want the probe on the inlet of the heat exchanger (output of the MT)? if the TC probe is after the rims tube or hex it will not give you the full mash temp.

 

[acidrain]

I'm just finishing mine now (RIMS), and have really studied the options...
I've concluded that for the control and heat exchanger part of the system, the TC (or better yet, a three-wire thermister) needs to be just downstream of the element.
For monitoring the actual mash temp, you'll need a second probe somewhere in the mid-mass of the grains.