Pot for HERMs

[evanvine]

Just pump at what your mash tun will flow at without cavitating.
Mine has a column vent which prohibits it.



This was my HERMS Mk 1, but it shows the vacuum release pipe on the Mash tun.

 

[AndyW]

Is there any issue with too much pot insulation in only being able to increase temperature by applying heat. Any overshoot in temperature is then locked in. Is there usually enough heat loss in the piping to be able to get a good enough two way response or do you have to approach the set point with care?
I like Vossys solution to the possible volume "problem" very neat.

 

[Vossy1]

Is there any issue with too much pot insulation in only being able to increase temperature by applying heat

It would be best to always undershoot but if push comes to shove you can always put cold water in the HE. I always liked the idea of being able to drain down the HE when not in use, but that would also serve the purpose of being able to replenish the HE with cold water should the need arise, during a brew.

Is there usually enough heat loss in the piping to be able to get a good enough two way response or do you have to approach the set point with care?

The PID should take care of approaching the set point for you as it will overshoot and undershoot the set point until it holds steady. It's always best to put the PID into 'learning' mode during any brew due to environmental factors/temp flucs.

 

[AndyW]

I was also thinking about being able to add cold water. Having insulation and a variable cold water flow, if needed, is a more controllable situation than no insulation.
This then got me thinking whether I could use the as yet un-designed herms heat exchanger as part of the wort cooling setup. The problems of clogging and some described cleaning practise has put me off plan A which was the plate chiller. It might not be practical, I need to do some sums.

 

[MacKiwi]

My hope is that there will always be a bit of thermal loss (from pipes, for example), so the HERMs will always be adding a bit to stay where it needs to be. If it overshoots, then it should come down to the target temperature in time due to the losses.

You can always manipulate the P/I/D parameters to ensure it does not over-shoot, although it will take longer to converge on the target temperature in this case.

 

[Vossy1]

My hope is that there will always be a bit of thermal loss (from pipes, for example), so the HERMs will always be adding a bit to stay where it needs to be. If it overshoots, then it should come down to the target temperature in time due to the losses.

If you do it that way the PID will need to be put into learning mode at each use as the environmental temps will change from it's previously learned programme. PIDS 'learn' in learning mode via response to the system, if the system changes it needs to re learn those responses. Naturally if the variables are minimal, ie, your gear is in a heated garage, you may get 'away' with it. A sign that your PID isn't coping with it's previously learned parameters is a small but steady fall in temp. I always put my PID into 'learn' mode, the way I see it it can't do any harm.

 

[MacKiwi]

Noted, thanks Vossy. I'm planning on building my own PID with a microprocessor and a digital temperature probe, so I should be able code up any learning algorithms that are required...

... I say with the confidence of never having done this before

 

[pittsy]

wow , take a simple idea and complicate the crap out of it , i just watch what's going on while i mostly sit doing nothing (probably posting on here on my laptop etc) and all i have is a gas burner , thermo ss mash tun , pump , herms pot (just a ss standard pot with copper coil in it) and 3 thermometers (which i've now upgraded to fixed ones) and i do 6 step temps with decoction . If you want to do the 90 min mash at 66c why the hell go to all the trouble of all that lot :nah: money up the wall . Honestly is really is easy to control , easier than adding water for step mashes .

 

[Vossy1]

Pittsy, you're opinions are noted but the reason behind the HERMS section is so that folk can talk about HERMS whilst folk who don't care for it don't even have to look in this section, let alone post negatively in it :lol:
It may seem complicated to those who don't use it, but so did your first AG before you'd tried...didn't it...HERMS systems are no different, once you're used to them they're a doddle

 

[pittsy]

it wasn't negative , i was saying how it is easier if kept simple but if complicated equipment is used for a simple task it may be far more trouble to make/build than is required . To an onlooker reading some of the above posts may well have given up on the idea of using herms thinking it was a mad field of science and high engineering . :thumb:

 

[BarnsleyBrewer]

Noticed the undercounter fridge in the kitchen Jim..... 2 cornies in??

 

[Vossy1]

Perhaps you didn't mean to be negative p, but I can't see any way of viewing 'throwing your money up the wall as being positive'.

i was saying how it is easier if kept simple but if complicated equipment is used for a simple task it may be far more trouble to make/build than is required

I wonder what brewers of the 19th centruy would say about your set up :lol: ...let alone mine

To an onlooker reading some of the above posts may well have given up on the idea of using herms thinking it was a mad field of science and high engineering

:lol: might not be a bad thing

 

[evanvine]

Noticed the undercounter fridge in the kitchen Jim..... 2 cornies in??

Nice idea BB, shame it's a tumble drier!

 

[Fil]

?? pid learning mode?? i may have the wrong end of the stick BUT...

Is learning mode analogous to the autotune function on my sestos unit?? if so i dont think you want to run your units in learning mode on a brew run. if not ignore the rest of this....

being far from expert on the subject only reading up on it after taking a punt on ebay and reading a post in here by Taz n his shutle pc case pid , and not being any where near as an accomplished brewer as many in here, my understanding is that when tuned to a job a pid will heat up Never overshooting running on a principle of using just a proportion of the power needed when getting close to target like 'the math frog' jumping half the distance to his hole each hop and never getting there :)

While when in autotune mode the system is testing different power inputs to the system to test the responce so overshoots of target are frequent and the process may be protracted due to extra tests occouring..

So afaik its best to autotune the system with it running with similar volumes, starting temps etc to a realbrewday so it can learn the most efficient way to heat up and maintain the specific target given the volumes and conditions expected on brewday.

if you want to be a purist, if step mashing each step should be autotuned in advance and the 3 control vars P I and D noted down for each step, however as your heat source power and volumes will be the same you may discover a virtually consistant P I and D value for each step?? however only autotuning each step will answer that.

afaik 2,5 and 1 are standard default settings, as i just use my pid for a single hlt task at the mo i didnt bother noting down the tuned vars. now im interested in what they are.. :).

 

[evanvine]

"Learning mode" is just Vossy speak for "Auto tune".

 

[Vossy1]

"Learning mode" is just Vossy speak for "Auto tune".

T'is true Jim :lol:

So afaik its best to autotune the system with it running with similar volumes, starting temps etc to a realbrewday so it can learn the most efficient way to heat up and maintain the specific target given the volumes and conditions expected on brewday.

True, which is why I said if your gear is in a heated garage you won't have any problems. If however you brew in a garage like mine, even though the brews may be identical, in summer it's +30 deg c, in winter -5+, so depending on how your gear is insulated it can make a difference to the learnt parameters, well it does with mine, hence re tuning each brew...it's not hard, just the press of a button

 

[Fil]

ahhhh penny drops.. :)

 

[barneey]

A big thank-you to Awolphotography, who saved me the trouble of making one of these myself. Here's some piccies of my newly acquired HERMs (ironically, delivered by a courier company called MyHermes)...

Thought that looked familiar, wonder who built that :whistle:

To answer another question the element was a standard burco style one of ebay from memory a 2.4 or 2.7 :grin: if your building one you need to off centre the hole slightly otherwise the element wont fit

 

[MacKiwi]

You should scratch your signiture on these Barneey, so even after they've been bought and sold, we know who the artist is They might be collector's items in a few years...

So I've been tweaking things a bit. Firstly, it needed wiring, so I used a hole-saw to make a wee hole in the bottom to fit a cable gland...



Then I soldering onto the element tabs. A quick check with a multimeter showed that the pot was NOT earthed to the element, due to the element having rubber gaskets on both sides, so to avoid any potential :electric: I added an earth wire from the elements earth to the pot body...



I will eventually cover the holes in the bottom with something...

The pot came with 10mm -> 1/2" BSP compression fittings, but it turns out the coil is 3/8" pipe (9.525mm). Fortunatley 3/8th -> 1/2" compression fittings do exist, so with those added, I could fit the elbows/tee-piece and add the temperature probe. It is one of these...

http://dx.com/p/water-proof-ds18b20-tem ... 0cm-142889

and is 6mm in diameter. So a 6mm -> 3/8th compression fitting, and a 3/8th to 1/2" reducing bush, and I had it connected to the tee.



I don't have the PID control loop implemented yet, but a quick trial shows that the heat exchange works. If I plug it in and pump water from the mash-tun through it, it raised the temperature at around 1.5 degrees per minute. So I can now do step mashes at least!

 

[djcorbetto]

What are you thinking of covering the holes with? I want to some work on my thermo pots but I want to be sure that I can cover it and it look nice at the same time.