Heated Mash Tun?

[baltobrewer]

As for the temp probe, measure the wort leaving the MLT or the grain bed itself.

Hmm, I'd say measuring at the outlet of the HERMS coil will give you the most accurate read. I measure mine at the outlet. Then again, I'm not step mashing so temp ramps are not especially critical...

[Monster Mash]

You want to measure the output of the mash tun. The liquid leaving the mash will give you the temp of the grain bed, the temp coming out of the HERMS is always higher until the grain bed catches up.

[derfburg]

Thanks for all the help, Looks like I am just going to man up and go Direct fire RIMS using this TOP. Just have to add a burner and a Keg to Mash in. I plan on putting the probe in a Tee right before the return on the pump, about 3' from the MLT outlet. That way I can also use it to monitor the recirc when chilling.

Hows that sound, please advise.

[teal]

You want to measure the output of the mash tun. The liquid leaving the mash will give you the temp of the grain bed, the temp coming out of the HERMS is always higher until the grain bed catches up.

(I don't have either system but I like to think I will eventually and this is based upon my thinking and research)

My question then is "is it okay to have to have your output higher than the grain bed? That's the same as overshooting temps, right?"

If you want your mash temp to be 154° lets say, if you put your temp reading at the exchanger output, you can't overshoot this temp. It's reading the fluid mash temp at the hottest it can be. The controller and exchanger will never overshoot your target temp as you recirculate the mash. (be that a RIMS tube or HERMS coil)

If you're reading the fluid temp as you draw it out of the mash but before it's cycled through the exchanger - that temp reading is about 2-3 minutes behind that the temp of the fluid is before it goes through the heat exchanger. It will be cooler than what you're placing back on top of the grain bed. Your controller is going to keep adding heat until what's being pulled out, 2 to 3 minutes after ging through the grain bed. Seems to me you could way overshoot your temps - accidentally due to that lag time. Temp in will be, by necessity, hotter than target temp to get output temps to hit 154°.

So target temp 154° - thermocouple at the output of your heat exchanger (be that RIMS element or HERMS coil) there's no way you'll ever overshoot - the couple/controller will keep applying heat no greater than to keep the temp 154° during the mash. Constantly.

Target temp 154° - thermocouple at the MLT output - reading the temp of the mash after filtering through the grainbed, controller will keep adding heat to the mash in circulation until what you draw out matches target temp. But that's mash that's spent 2 to 3 minutes filtering through the bed - cooling off, so the mash going in on top of the bed might be 160° or more degrees.

Aren't you essentially scorching the fluid/grains until the bottom fluid has cooled to your target temp?

[Ozwald]

When using a HERMS system, you don't continually raise your HLT/exchanger temp. It gets set at 1 temp & you leave it alone. Let's say you're ramping from a protein rest up to saccrification. Each exchanger is different, mine happens to have a 10 degree offset, meaning if my HLT is set at 164, the wort leaving the exchanger won't get above 154. So to ramp up from 120 to 154, I set the HLT at 164 & leave it alone. At first the numbers are going to climb pretty quickly since there's a large difference between the returning wort & the main mash bed. By the time I get to 150, it's crawling & it takes a little bit of time to increase each degree. But I'm still only returning 154 wort. So if I'm measuring the output of my MLT, when it hits 154, I know that everything above it is also 154. No overshooting, no scorching. The problem with putting the thermometer between the exchanger & MLT is that it doesn't matter what the actual mash temp is, it's always going to read within a few degrees of your adjusted offset - mash is 120, return is 154 - mash is 150, return is 154. After you learn your system & the offset, you can determine what that temp is by looking at the HLT temp & subtracting your offset. You could use the return temp for a controller, but you're just asking for more potential problems. Wire the controller directly to the HLT.

To answer your first question, no, it's not the same as overshooting temps. Even if the returning wort is at 180, you have to consider the thermal mass of the mash itself. 180 wort hitting a 154 mash is going to drop temp instantly. Not directly to 154, but it'll be a lot closer to 154 than to 180. Hell you can batch sparge with boiling water & not overshoot temps in many cases. Same with infusion mashing where your additions are typically done at boiling to reduce volume.

[Ozwald]

Also note that you can change your offset by how you brew. If someone else brewed on my system, they could potentially get a slightly different offset than I do. Things such as how fast you recirc really affect it. As long as you dial in your process, the offset is easily & reliably duplicated. I've pushed mine a few times & was able to get as low as a 7 degree offset. I don't use that since that recirc speed doesn't allow me to set the grain bed tight enough for my taste.

[teal]

Ok - thanks. Makes sense.

[Ozwald]

No worries. I really love brewing on my HERMS system. It was kind of like going all grain - a little overwhelming until I got everything put together. The learning curve is similar as well.

I would recommend getting a couple digital thermometers with probes you can move around. Check different points of your mash, watch your return temps, etc. It'll help you learn your system's in & outs.