Recirculation question

[Tidwellc]

Sorry if this is the wrong place to ask this question, didn't know where else to ask.

Currently in the process of designing an electric HERMS setup, and am trying to cost-engineer it as much as possible for the first iteration, and then add fancier pieces down the road. I was planning at first on doing a two-vessel system with just a MLT and HLT. I'll just use gravity to lauter into the kettle and then boil on a burner.

Anyways, my question is, does the water in the HLT need to be recirculated as well during the mash? I was hoping to get away with just one pump at first but then I realized it would be difficult to regulate the HLT temp evenly without it being circulated. Also, would the PV for my PID controller be the HLT water temp? Or the actual mash temp?

 

[augiedoggy]

Sorry if this is the wrong place to ask this question, didn't know where else to ask.

Currently in the process of designing an electric HERMS setup, and am trying to cost-engineer it as much as possible for the first iteration, and then add fancier pieces down the road. I was planning at first on doing a two-vessel system with just a MLT and HLT. I'll just use gravity to lauter into the kettle and then boil on a burner.

Anyways, my question is, does the water in the HLT need to be recirculated as well during the mash? I was hoping to get away with just one pump at first but then I realized it would be difficult to regulate the HLT temp evenly without it being circulated. Also, would the PV for my PID controller be the HLT water temp? Or the actual mash temp?

Have you seen these $20 pumps? http://www.ebay.com/itm/171032628600?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT They are food grade and good at boiling temps... Ive been using mine for over a couple years and they work well...The pid in your setup would regulate the HLT temp which controls the mash temp.

BTW you will want a second pump to keep the water moving evenly in your HLT otherwise the herms wont work well...I learned that the hard way when I used herms before upgrading to rims.

 

[kal]

Anyways, my question is, does the water in the HLT need to be recirculated as well during the mash?

Yes, to avoid stratification and also give you an accurate HLT temp reading.

Also, would the PV for my PID controller be the HLT water temp? Or the actual mash temp?

I recommend measuring the HLT water temp in circulation. The mash temp will follow. More info my temp probe and HLT build articles.

Good luck!

Kal

 

[jrcrilly]

It is the recirculating mash temp that you want to control. I'll use a sensor in the HLT with a PID to control HLT temp when preheating it and a different sensor in the HERMS return line with a PID to control the HLT burner during recirculation. If you want to use RIMS, that is easier. You'll just need a sensor in the MLT with a PID to control the MLT burner (heater) during recirculation. I'll have that option as well. It will offer faster response than the HERMS due to the smaller volume in the mash tun so would be good for mashout or step mashing.

 

[augiedoggy]

It is the recirculating mash temp that you want to control. I'll use a sensor in the HLT with a PID to control HLT temp when preheating it and a different sensor in the HERMS return line with a PID to control the HLT burner during recirculation. If you want to use RIMS, that is easier. You'll just need a sensor in the MLT with a PID to control the MLT burner (heater) during recirculation. I'll have that option as well. It will offer faster response than the HERMS due to the smaller volume in the mash tun so would be good for mashout or step mashing.

Why would a rims System require a MLT burner? Are you sure your not confused? That makes not sense the way I'm understanding your statement, one would make the other redundant.
As mentioned many times in many threads when this comes up and above the best way to Control temps accurately with a herms is to control the hlt water temp since it is effectively the heating source for the herms coil/heat exchanger... I experimented with probe placement and found this to be true too.

 

[kal]

... and a different sensor in the HERMS return line with a PID to control the HLT burner during recirculation.

I disagree. Reasons listed further below.

As mentioned many times in many threads when this comes up and above the best way to Control temps accurately with a herms is to control the hlt water temp since it is effectively the heating source for the herms coil/heat exchanger... I experimented with probe placement and found this to be true too.

+1.

I've experimented by using other places like the HERMS coil output temp and it's not the best way as it's too decoupled.

For example, if you control the HLT heat by the HERMS output temp, if you turn off the mash recirculation pump for a few minutes (such as to dough in) the temp probe cools off fast and your HLT temp jumps through the roof because the system thinks the mash is cooling off when in reality it isn't.

The result is after you finish doughing in your HLT temp's 20+ degrees too hot (or even hotter) and you end up overshooting your mash temp when you turn the mash recirc pump back on.

If you keep the probe to control the HLT temp in the HLT, it'll never overshoot as you don't turn off that pump.

If you remember, you an turn off everything when you mash in, but then your HLT temp will drop a bit.

Kal

 

[jrcrilly]

Why would a rims System require a MLT burner? Are you sure your not confused? That makes not sense the way I'm understanding your statement, one would make the other redundant.

Some RIMS systems use an external heat chamber and recirculate the mash through that. In those systems, an MLT burner would be redundant. Some RIMS systems use an MLT burner; on those, an external heat chamber would be redundant. Mine is the latter.

 

[jrcrilly]

For example, if you control the HLT heat by the HERMS output temp, if you turn off the mash recirculation pump for a few minutes (such as to dough in) the temp probe cools off fast and your HLT temp jumps through the roof because the system thinks the mash is cooling off when in reality it isn't.

Yes, that could happen if you let it. If you have PIDS watching both the recirc temp and the HLT temp, you can just switch to the HLT-controlled PID when not recirculating. That also permits preheating the HLT to strike temp under PID control when there is nothing to recirculate.

 

[augiedoggy]

Some RIMS systems use an external heat chamber and recirculate the mash through that. In those systems, an MLT burner would be redundant. Some RIMS systems use an MLT burner; on those, an external heat chamber would be redundant. Mine is the latter.

Ok I get what your doing ... You dont use a rims tube but its still a RIMS system because you recirculate while direct heating your mash... I would think you would need a lot of flow to keep temps even that way?

 

[augiedoggy]

Yes, that could happen if you let it. If you have PIDS watching both the recirc temp and the HLT temp, you can just switch to the HLT-controlled PID when not recirculating. That also permits preheating the HLT to strike temp under PID control when there is nothing to recirculate.

Why not just always use the HLT pid as usually done? Since it works perfect and there is no downside or switching of controllers needed? I am failing to see any advantage your proposed setup?

 

[jrcrilly]

In my initial tests I monitored the HEX output temperature because that was the variable I wanted to control. I ran it with that temp controlling the HLT burner to see if there was overshoot and there wasn't. Then I ran a test brew with the setup and all was well. I already had a second PID watching the HLT temp for preheat so the only thing needed to provide both alternatives was a double throw switch ("HERMS/off/HLT") rather than a single throw ("off/auto"). I don't know that one is superior to the other but from tests so far I see no downside to running it in my preferred mode.

 

[FuzzeWuzze]

I disagree. Reasons listed further below.



+1.

I've experimented by using other places like the HERMS coil output temp and it's not the best way as it's too decoupled.

For example, if you control the HLT heat by the HERMS output temp, if you turn off the mash recirculation pump for a few minutes (such as to dough in) the temp probe cools off fast and your HLT temp jumps through the roof because the system thinks the mash is cooling off when in reality it isn't.

The result is after you finish doughing in your HLT temp's 20+ degrees too hot (or even hotter) and you end up overshooting your mash temp when you turn the mash recirc pump back on.

If you keep the probe to control the HLT temp in the HLT, it'll never overshoot as you don't turn off that pump.

If you remember, you an turn off everything when you mash in, but then your HLT temp will drop a bit.

Kal

What are your thoughts about just measuring the MLT temp via the HERMS coil exit? I agree controlling anything from the HERMS coil is not the way to go. I know that you measure your mash temperature at the output of your MLT, why not at the Input(HERMS exit)?

Granted they should both be identical really my thinking was that i'd want my water to be 154F going in, not measuring the 153F or whatever it is by the time it gets out the MLT which would mean my HLT would compensate another +1F and i'd be dumping 155F mash back in...

I have no idea of real numbers that just an exaggeration, for all i know the difference between the input and output is probably less than .5F with how fast i am recircing everything.

 

[Yooper]

What are your thoughts about just measuring the MLT temp via the HERMS coil exit? I agree controlling anything from the HERMS coil is not the way to go. I know that you measure your mash temperature at the output of your MLT, why not at the Input(HERMS exit)?

Granted they should both be identical really my thinking was that i'd want my water to be 154F going in, not measuring the 153F or whatever it is by the time it gets out the MLT which would mean my HLT would compensate another +1F and i'd be dumping 155F mash back in...

I have no idea of real numbers that just an exaggeration, for all i know the difference between the input and output is probably less than .5F with how fast i am recircing everything.

In my system, there is a 3° differential between the temperature of the water in the HLT, and my mash temperature. I run a three vessel keg Herms set up. So, for a desired sustain mash temp of 152° I just set my PID for 155°. I suspect that it is very common.

 

[augiedoggy]

In my system, there is a 3° differential between the temperature of the water in the HLT, and my mash temperature. I run a three vessel keg Herms set up. So, for a desired sustain mash temp of 152° I just set my PID for 155°. I suspect that it is very common.

yes depending on the temp in my room and grainbill size. I have a 1-4 degree drop variance between my rims exit temp and my MT exit temp due to the hose travel from the rims and the MT itself losing a degree or so. I thought this was smaller but recently discovered my pid was reading off a couple degrees. I just normally set my rims for a degree higher than target mash temps.

 

[eric19312]

Ok I get what your doing ... You dont use a rims tube but its still a RIMS system because you recirculate while direct heating your mash... I would think you would need a lot of flow to keep temps even that way?

I recirculate while direct firing mash. Measure temp on pump return. Have an inexpensive probe thermometer with up down set point alarms that makes a noise that tells me to manually turn the burner on and off. Have a Norcal false bottom in my kettle and run a decent flow rate perhaps 2 gpm always on. I run the burner as low as it will go and end up turning the burner on and off less than 10 times during course of a 60 minute mash. This is uninsulated 15gallon bayou classic kettle with the lid on. I could probably do better if I insulated it but might be difficult to protect the insulation from the other burners on the stand so I don't bother.

 

[FuzzeWuzze]

In my system, there is a 3° differential between the temperature of the water in the HLT, and my mash temperature. I run a three vessel keg Herms set up. So, for a desired sustain mash temp of 152° I just set my PID for 155°. I suspect that it is very common.

Yes yes, i understand that and i do that.

But Are you measuring the temperature at your HERMS exit(dumping into the MLT), or at the MLT Exit ball valve? I know Kal always measures at the output, but as i said in my mind at the output you would always be getting the mash at its "coldest" therefore the mash being recirc'd in the top might be a bit warmer(after the HLT compensates) than what your actually measuring? That was my question for Kal, why he chooses to measure at the output(other than it being how industry does it which is what i think his explanation was on his site) if there is any real tangible difference or not.

Hopefully that makes sense...as an extreme non real world example lets say your wort drops 5F from the time it enters your mash tun until the time it exits. So at your output you see 154F, your HLT though will be at 159F pumping 159F wort back in the top through the mash which is obviously not what you wanted...obviously i dont think in the real world you lose much of any temp going through a mash but ive never tested.

 

[Yooper]

Yes yes, i understand that and i do that.

But Are you measuring the temperature at your HERMS exit(dumping into the MLT), or at the MLT Exit ball valve? I know Kal always measures at the output, but as i said in my mind at the output you would always be getting the mash at its "coldest" therefore the mash being recirc'd in the top might be a bit warmer(after the HLT compensates) than what your actually measuring? That was my question for Kal, why he chooses to measure at the output(other than it being how industry does it which is what i think his explanation was on his site) if there is any real tangible difference or not.

Hopefully that makes sense...as an extreme non real world example lets say your wort drops 5F from the time it enters your mash tun until the time it exits. So at your output you see 154F, your HLT though will be at 159F pumping 159F wort back in the top through the mash which is obviously not what you wanted...obviously i dont think in the real world you lose much of any temp going through a mash but ive never tested.

Oh, I don't measure the output OR the input- I measure the mash temp sort of in the middle. The output doesn't really matter, although it would be close to the mash temp, since it's recirculating. The input doesn't matter either to me- it's the mash temp I want to maintain. I used to check it, but haven't for years. I think it was like 2 degrees cooler than the water in the HLT, but it could have been 1 degree. I just can't remember.