3-Way mixing valve on HLT

[dludwig]

So I am building my herms system and instead of going with 2 soleinoid valves I am going with 0-10VDC 3-way mixing valve. Should I be controlling the leaving wort temp or the mash temp? I have the ability to monitor both But what would be the best one to control the valve with?

 

[Walker]

I think you are going to need to describe the system you are building before anyone can answer.

The HLT on my HERMS system has only one valve on it, and that's the one that lets the hot water flow out, so I am not sure what you are planning to do with a controlled solenoid on the HLT.

 

[dludwig]

I will get some plumbing diagrams drawn up and posted, if I explain the control sequence in detail would anyone mind taking a look and giving me there opinion?

 

[Bjornbrewer]

I take it you're using the mixing valve as a kind of bypass around your heat exchange coil? Not sure why you're doing that, but I would monitor (not control) the temp of the wort leaving the system going back to the MLT. monitoring the mash temp may make the system too slow and overshoot. Unless you have your PID set correctly.

 

[dludwig]

I take it you're using the mixing valve as a kind of bypass around your heat exchange coil? Not sure why you're doing that, but I would monitor (not control) the temp of the wort leaving the system going back to the MLT. monitoring the mash temp may make the system too slow and overshoot. Unless you have your PID set correctly.

I am using the mixing valve to control the mash temp. Evrything I have looked at uses one NO solenoid and one NC solenoid valve to control the temp. The mixing valve should give me more control as it is a modulating valve. If I only need 20% of my circulated wort passing thru the heat exchanger then I can do that. PID control seems to work better with a analog control sequence. I have plenty of automation experience but not any to do with brewing beer. I will be using a Reliable Controls MACH-Stat for my controller. This is a six in eight out controller. I will have four PID loops to do whatever I want with. The controller also has a LCD display and five programmable buttons so I can tune my PID loops without connecting a laptop. Any ideas/opinions would be appreciated!

 

[Bjornbrewer]

if you're controlling the temp of the water the HEX coil is in, why do you need to also control the amount of wort to pass through it? That part I'm not getting, but anywho...my vote is to still monitor the temperature of the wort going back to the MLT.

Trial and error I guess. good luck!

 

[kladue]

Use the mixed wort temperature after the mixing valve for control and monitor mash temp to stop wort heating about 2 degrees short of mash target temperature. I control steam injection for wort heating in a similar manner and it works well for step mashing but has the advantage of raising wort to desired temperature without overheating. One concern will be wort in HEX coil will be much hotter than desired as you reach end of heating time and incoming wort is almost at setpoint.

 

[kwantam]

The big downside I see to this---unless I'm misunderstanding this, which happens a lot ---is that by virtue of the fact that you're mixing heated and unheated wort, you are guaranteeing that the wort in your exchanger is hotter than your target temp when you are slewing the temp around. For example, if your target temperature is 6 degrees hotter than the bulk temp in the MLT, and your control system has decided to set the valve at 50%, that implies that the temperature coming out of the heat exchanger is 12 degrees hotter than the MLT, or 6 degrees over target. So while your MLT temp never overshoots, you're still potentially overheating the wort as it goes through the exchanger.

Am I missing something here?

 

[dludwig]

The big downside I see to this---unless I'm misunderstanding this, which happens a lot ---is that by virtue of the fact that you're mixing heated and unheated wort, you are guaranteeing that the wort in your exchanger is hotter than your target temp when you are slewing the temp around. For example, if your target temperature is 6 degrees hotter than the bulk temp in the MLT, and your control system has decided to set the valve at 50%, that implies that the temperature coming out of the heat exchanger is 12 degrees hotter than the MLT, or 6 degrees over target. So while your MLT temp never overshoots, you're still potentially overheating the wort as it goes through the exchanger.

Ok Never thought of that problem. Is that why most people use the two solenoids and on/off control? When using on/off control would I just cycle the valves to maintain my desired output temp?

 

[kladue]

The ideal setup for HERMS would be either a plate or tube CFC where wort flow is constant and hot water is circulated from HLT through heat exchanger water circuit to control leaving wort temperature. With a few more valves one could use the same heat exchanger in mashing and later wort chilling without switching plumbing or hoses. With 2 pumps you could have a system to move HLT water to mash for strike, refill with sparge water and heat to 175, circulate water to heat wort for step mash, pump HLT water to mash for sparge, refill HLT with ice and water and circulate to chill wort after boil. With one proportional or floating control valve in the water circuit of the heat exchanger, wort temperature control should be fairly easy to do. For the Brewtroller folks the floating control type valve would just need 2 digital points, for the PID folks an analog input valve and analog output PID controller model would work. Using the heat exchanger during boil would take care of sanitizing by passing boiling liquid through it, and post boil cleanup would take care of things left behind.
Here is a quick and dirty diagram http://picasaweb.google.com/kevin.ladue/HXBrewSystem#5510550717803399378

 

[dludwig]

kladue,

Thanks a bunch man. I like your diagram as I have not seen one of this design. The only issue is now I am going to have to buy two pumps. On the brite side the HLT should be much easier to build being I will not Have to mount a heat exchanger inside of it. Also seems I will have better control of the wort temperature and avoid overheating. What did you draw your diagram with?

 

[dludwig]

One more thing, As I will not be using the second pump for post boil fluids I shouldnt need a march pump for that process. I can easily get my hands on a radiant floor pump or something similiar to pump Heated or Chilled water through heat axchanger and use the march pump for any wort transfer. Anyone have any coments/concerns on this idea?

 

[kladue]

The drawing was in cad, if you want I can add the temperature sensors and control logic for temperature control. With a plate type exchanger you should be able to do large temperature steps by maintaining HLT at 175 with a on/off controller as temperature control is not critical, use one PID control for wort temperature control valve, and another on/off for mash temperature control to water pump and PID. As to pumps, the water side could be one of the bronze circulator pumps as it never touches the corrosive wort, the wort pump could be one of the little giant MD3-HC series with higher head pressure output than the march 809 models. It is easier to valve down flow than to lament not enough flow with undersized pump.
As to the control sequence:
Fill HLT with strike water and heat to strike temp
Pump to MLT through heat exchanger bypass
Dough in and start recirculation pump
Refill HLT with sparge water and heat to 175
Use mash temperature controller to power water pump and temperature control PID for step or temp maintenance
Pump sparge water to MLT while moving wort to BK
Refill HLT with cold water and add ice at end of boil time
Recirculate boiling wort through heat exchanger and back to BK to sanitize
Place hose to fermenter in top of BK then pump boiling wort back into BK to sanitize valve and hose
Start water pump and open temperature control valve to chill wort
Open valve to fermenter when wort temperature is reached
Clean up

 

[dludwig]

Kladue,

The drawing you have is fine although it would be nice to see one with a sequence. If you dont have it done dont worry about it though. Would you be concerned with potentially clogging the Plate Frame Heat Exchanger when circulating mash? Plate Frame Exchangers have very small passageways, most are so small you cant even gravity feed through them. I have built myself a CFC with plans of moving to PF in the future. Just out of curiosity what do you do for a living?

 

[dludwig]

I forgot something again, Why not add one more valve to the system so you could drain to fermenter directly from the heat exchanger?

 

[kladue]

For the fermenter fill from leaving side of the heat exchanger you could move V-7 to after the heat exchanger. The reason for it before the heat exchanger was to allow the cold break and trub to drop in the BK before transfering to fermenter.
I do industrial process control systems in a wide variety of plants, water/waste water treatment, power generation, pulp/paper, gas transmission, refineries, high tech. The work encompasses purchase, calibration, installation, and start up of control systems for various customers. The upside is it pays well, the down side is some of the work places are not the safest (Nomex coveralls, radio, and escape respirator mask required PPE) and I am on the road all the time managing projects now. I have plenty of time on my hands evenings and weekends so I spend it developing control software for my automated brewing system and designing additional sub systems while I am in Chandler Arizona again.