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Old 02-25-2012, 03:18 PM   #11
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Originally Posted by lschiavo View Post
...the difference from top to bottom of the mash can be substantial.
If you're using a controller based system this is exactly why you want to measure the output of your HEX rather than the output of mash tun. If you're controlling off your mash tun out and you missed your strike water temp, it will have a tendency to overheat the HEX.

For example, let's say your target mash temp is 152F and you didn't hit your strike water temps and ended up at 142F. Your system is going to keep heating the mash until your temp at the bottom of your mash reaches 152. That means the liquid being returned to the top of your mash is greater than 152...lets say 162 for arguments sake. The 162 liquid continues to heat your mash past 152 until it reaches equilibrium. Long story short, if you try to control it this way you're introducing lag time into your system and you'll overshoot your mash temps.

On the other hand, if you measure at the HEX out, you'll never overshoot your mash temps because the liquid exiting the HEX will never exceed your set mash temp. My system generally heats at least one degree per minute. So in the same scenario above, if I was shooting for 152 but strike temp was 142, I'd get up to 152 in no more than 10 minutes. At that point the heating element shuts off and only intermittently turns on in order to maintain temps. So you get much tighter temp control measuring it this way. If you're measuring the temp at the mash tun out just for informational purposes rather than actually to control temps, there's no harm in it but I don't think it's necessary.
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Old 02-25-2012, 08:27 PM   #12
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Originally Posted by bruin_ale
Exactly why I measure both (I have a 12" probe stuck into the center of the mash), but I like the idea of measuring the MLT out - maybe I'll change things up in the future to that.
I like it. Here's how I set mine up:

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Old 02-25-2012, 08:40 PM   #13
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Quote:
Originally Posted by microbusbrewery

If you're using a controller based system this is exactly why you want to measure the output of your HEX rather than the output of mash tun. If you're controlling off your mash tun out and you missed your strike water temp, it will have a tendency to overheat the HEX.

For example, let's say your target mash temp is 152F and you didn't hit your strike water temps and ended up at 142F. Your system is going to keep heating the mash until your temp at the bottom of your mash reaches 152. That means the liquid being returned to the top of your mash is greater than 152...lets say 162 for arguments sake. The 162 liquid continues to heat your mash past 152 until it reaches equilibrium. Long story short, if you try to control it this way you're introducing lag time into your system and you'll overshoot your mash temps.

On the other hand, if you measure at the HEX out, you'll never overshoot your mash temps because the liquid exiting the HEX will never exceed your set mash temp. My system generally heats at least one degree per minute. So in the same scenario above, if I was shooting for 152 but strike temp was 142, I'd get up to 152 in no more than 10 minutes. At that point the heating element shuts off and only intermittently turns on in order to maintain temps. So you get much tighter temp control measuring it this way. If you're measuring the temp at the mash tun out just for informational purposes rather than actually to control temps, there's no harm in it but I don't think it's necessary.
I see your point with the way you are controlling your system. My HEX water (HLT) is set to my mash temp so there is no way for me to overheat. When I ramp, I just bump up the HLT temp and continue to circulate until my MLT out is where I want it. Same as yours but different
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Old 02-25-2012, 09:55 PM   #14
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I use two cheap e-bay aquarium temp controllers in my HERMS, one for the HLT burner, and a second that controls the pump. I have thermowells at the MLT in, MLT out, center of the HLT, center of the MLT, and even one in a separate pot. I usually measure the temp for the burner controller at the center of the HLT (I also have a stir motor to keep the water circulating). I measure the pump controller at the MLT in (HEX out). It mostly serves as a back-up device to shut the pump off if something goes wrong and the temps spike or drop unexpectedly. I usually stick a couple thermometers in the thermowells that aren't in use just to be able to verify that things are doing what they're supposed to be doing.

My HEX coil is mounted to a stock pot lid, so I can use it as an IC, or configure things any number of ways, including using the other pot to make the HEX separate from the HLT for faster step mashes. I rarely if ever configure it that way though, and usually have it mounted in the HLT.

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Old 02-25-2012, 11:21 PM   #15
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Quote:
Originally Posted by lschiavo

If you only measure temp at the HEX out, how do you know the actual mash temp? When I ramp with my system, my HEX out is exactly my set temp (60 ft 3/8 copper coil).

The wort exiting the mash is the temp I'm interested in and the difference from top to bottom of the mash can be substantial.
Others have chimed in already but since it is the hottest point and since I am continually recirculating, the HEX out is where I hit and maintain my target temperature.

I do monitor my Mash temp and the two always equalize but you need to measure HEX out to control mash temp, if you do it the other way round you lose the exact control over temp HERMS provides.

The wort exiting the MLT will be the coolest point, soon to be heating in the HEX, I don't see the point in measuring this for control.
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Old 02-26-2012, 12:05 AM   #16
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Quote:
Originally Posted by lschiavo View Post
I see your point with the way you are controlling your system. My HEX water (HLT) is set to my mash temp so there is no way for me to overheat. When I ramp, I just bump up the HLT temp and continue to circulate until my MLT out is where I want it. Same as yours but different
Ahhh, that makes sense. Just out of curiosity, are you using electric or gas to heat your HLT/HEX? And how long does it take you to get from mash up to mash out temps (168-ish)? My eHERMS does a little over a degree per minute but I would thing a gas fired HERMS would be able to ramp up quicker (I guess subject to burner size).
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Old 02-26-2012, 01:18 AM   #17
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Quote:
Originally Posted by microbusbrewery

Ahhh, that makes sense. Just out of curiosity, are you using electric or gas to heat your HLT/HEX? And how long does it take you to get from mash up to mash out temps (168-ish)? My eHERMS does a little over a degree per minute but I would thing a gas fired HERMS would be able to ramp up quicker (I guess subject to burner size).
My system is all electric. HLT is a sankey with a 4500W element. I am around a degree per minute on 10 gallon batches. Usually about 15 minutes will get me to mash out. I have everything but the time to add a second element in the HLT. Ramps should be much quicker then.
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Old 02-26-2012, 01:25 AM   #18
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Quote:
Originally Posted by coogee

Others have chimed in already but since it is the hottest point and since I am continually recirculating, the HEX out is where I hit and maintain my target temperature.

I do monitor my Mash temp and the two always equalize but you need to measure HEX out to control mash temp, if you do it the other way round you lose the exact control over temp HERMS provides.

The wort exiting the MLT will be the coolest point, soon to be heating in the HEX, I don't see the point in measuring this for control.
I realize there are different control systems out there hence the need for monitoring temps at different locations in the system.

My HEX coil is always at mash temp so monitoring that is pointless with my system. I monitor MLT out so I know when the entire mash is at the target temp.
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Old 02-26-2012, 01:28 AM   #19
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Here she is...

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Old 11-24-2012, 06:12 PM   #20
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Hey guys, I'm building a HERMS system and I have a question:

If you are using a cooler for a mash tun, why continue to circulate after you have hit your mash temp and things have had a chance to equalize? Doesn't that happen pretty quickly? Why continue to run the pump and HEX?

My current system will maintain a temp with about a degree loss in the MLT cooler over an hour... getting it to the exact temp I want has been the problem thus far and that's why I'm building the HERMS system.

Also, what flow rate do you go for? As much volume as possible without getting a stuck mash/sparge?

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