E-Herms Stirrer Necessary if Temp Measured at Wort Output?

Hey all,

So I've been searching the forums trying to figure out how I'm going to put together my e-HLT/HERMS. I have many questions regarding wiring and PID controllers in general, but I know that although I've spent hours on here, there are still posts out there that will answer my questions. What I haven't been able to find is the answer to this question:

If the temperature probe on the PID controller is measuring the wort output temperature, why is a stirrer necessary? Yes, the water will be different temperatures throughout the HLT, but all of the combinations will sum to one temperature output. Along these same lines of thought, do you all think a rib-cage style coil would work better in order to have the coils throughout more of the water?

Thanks for any reply.

PS If someone knows a link off-hand describing the basics of PID controllers, SSR, etc., I would be much obliged. Thanks again.

You will get varying opinions on this. I do not stir or recirculate the water in my HLT. My thermocouple is on the output side of the heat exchange coil. I also have two 4500 watt elements in my HLT. I am sure that I have stratification in my HLT but it does not seem to be a big deal. That said, heat exchange will be more efficient if you stir or recirculate the water in your HLT. If I only had one 4500 watt element in my HLT, I would stir or recirculate.

I have one 5500 watt in my tank with the sensor on the output . The only time I need to stir is bringing it up to temp. Once there and the temps are stabilized you don't need to stir. Everthing should work together to keep your temp spot on . I once recirculated the hot liquor with a pump but it made no difference in keeping mash temp.

It might be a good idea to try an aquarium bubbler to inject air for stirring the HLT. I read a writeup on that recently here. From a bulk heat exchange standpoint it may not make much difference. But agitating the HLT water while recirculating will give you better heat exchange via turbulence. = Better results.

Thanks for the replies. After thinking last night, I believe my plan is to now have my stand be an inverted T, essentially, with the HLT and BK on the outsides. This seems to be the best option to have the PID temp probe on the output of the HERMS, as it allows me to recirculate the HLT for temp monitoring with a pump and gravity feed from the MLT back into the HLT. Goal was to keep it a one pump, one controller system. (BK will still be propane)

I was planning on keeping it 120vac with either a 1500w or 2000w element. Think this will create any more or less stratification than the 4500 or 5500w elements? Any thoughts on if having a ribcage HERMS will help the PID from overshooting as it will be in contact with more the Hot liquor?

Thanks again for the replies.