Thermometer placement

Simple pot still distillation and construction with or without a thumper.

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demon00
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Thermometer placement

Post by demon00 »

I have a 6 gallon stock pot still with a 3/4 in, column elbow and about a foot out to a 36in water jacket condenser.. my question is , I used a thermometer just off the side of the top and my temps were off about 15-20° , would it work ok to drill a hole in my elbow and put my thermometer in there ? It's a digital probe type, and just seal around it with flour paste when I operate ?? Thanks
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zed255
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Re: Thermometer placement

Post by zed255 »

I think most here will advise you the best place for a thermometer on a still, especially a pot still, is the package in which it came.

There are many answers to this question already posted, and depending on what information you are trying to get from the operation of the still and who is answering you may get very different opinions. I do not have vast experience but it sounds to me like you tried to mount it externally. That will always read low, even if you insulate around your measurement point and probe. For an accurate reading the probe must be in the vapour path or liquid you want to monitor.

Two places that offer anything at all are, in my humble opinion:

1) At the top of your column positioned to measure the vapour temperature about to enter your condenser. This will give you an approximate indication of the output ABV.

2) In the boiler positioned to measure the liquid temperature. This will give you an approximate idea of the remaining ABV of your wash.

In general a thermometer is like jewelry for a still. It looks fancy and might make you feel good, but is not required to go dancing. Your senses and good cuts afterward will do more for making quality booze than a thermometer.

All that said, on my reflux rig I do like to use a thermometer to watch not the specific temperature but rather watching for change. This helps determine when to lower my collection rate and ultimately the end of my run when refluxing a neutral. When the vapour temp creeps up and the takeoff rate is too slow then tails are arriving (in fact they are already there but this observation means continuing is no longer reasonable).
Last edited by zed255 on Sun Feb 11, 2018 8:28 am, edited 1 time in total.
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fizzix
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Re: Thermometer placement

Post by fizzix »

+1, what zed said so perfectly.
I long got rid of my lab thermometer on the head during pot still mode. It was only waiting to get snapped in half and told me absolutely nothing I could use.
In reflux mode, it gave me about a minute heads up that the spout was ready to produce. Through change only, no specific temperature.
And later it would rise further to indicate tails, which I pretty much had already realized by sense of taste/smell.
It sho' nuff looked fancy though.
Appalachian spirits
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Re: Thermometer placement

Post by Appalachian spirits »

I use thermometers throughout the system. Not so much because they're needed but i have a 30 gallon pot and i got a great deal on em. And they look cool lol. The only advantage is that at a glance i can see what the temp is throughout the system so if im getting too hot i immediately know. To be honest i use the one on my condenser the most as i can adjust the chill water to maintain exactly 60 degrees F at the collection point. With time spent running You can tell what your rig is doing by "watching the spout" and you will know if you need to adjust temp by the distillate flow. The more you run it, the more you know it.
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Saltbush Bill
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Re: Thermometer placement

Post by Saltbush Bill »

I agree totaly with Z and Fizz. Thermometers on pot stills are unnecessary. They also cause more confusion and drama for the average newbie than anything else I can think of.
Newbies with thermometers are to busy looking at the thermometer and trying unsuccessfully to chase temps all over the place to learn how the still works and to learn what to do with their senses.
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Yummyrum
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Re: Thermometer placement

Post by Yummyrum »

demon00 wrote:I used a thermometer just off the side of the top and my temps were off about 15-20° ,
How do you know its off by 15-20 degrees ? what are you comparing it against ?
demon00 wrote:would it work ok to drill a hole in my elbow and put my thermometer in there ? It's a digital probe type,
Yes , here's one I prepared earlier ......LOL this was my first pot still head I built and I stuck a thermometer in it . I actually soldered a small piece of pipe to the hole and wrapped the thermometer shaft in teflon tape to seal it but also ensure that the thermo shaft was only in contact with the Vapour and not touching the sides of the still.
Pot still 001 resize.jpg
I made my second Pot still riser , I didn't bother about adding a thermo port because I never watched the bloody thing at all after the first run .....like the others have said , told me nothing my hands and tongue couldn't .
LOL , I can see the old shitter in the back ground of that pic .
Pot still 002 resized.jpg
Third pot still ....Naah no thermo
Nearly.jpg
Fourth Pot still build ......You'd think after going to this much bother a few more minuates to stick in a thermo port would be a doddle .........but Naah no Thermo....don't use
PICT0246.JPG
Having said that just recently We were discussing the difference in temp between one in the boiling liquid and one in the head space and one at the top of the riser . There are some interesting results I got from some tests . Look at the un- packed graphs ...they are relevant to your pot still . You will see that there are slight differences but only a degree viewtopic.php?f=16&t=71451
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Saltbush Bill
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Re: Thermometer placement

Post by Saltbush Bill »

Yummyrum wrote: demon00 wrote:
I used a thermometer just off the side of the top and my temps were off about 15-20°
How do you know its off by 15-20 degrees ? what are you comparing it against ?
I see this comment often Yummy and agree.........."my temps are out" .....compered to what ?
What temp do you want it to read ? What do you think it should read ? Why do you think it should read that ? Those and many more questions spring to mind.....It would just be so much easier if newbies didn't use them, and weren't given advice that it was a good idea to do so.
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jonnys_spirit
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Re: Thermometer placement

Post by jonnys_spirit »

I have two thermo ports on my pot still. I never used them for many runs but last couple I have started watching them. I do like using the one at the top of the riser in the vapor path to see how close to 212 I get in a stripping run before
Calling it quits.

It sorta gives me an idea where I’m at in the run and how much further I’ve got to go.

Cheers!
-jb
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i prefer my mash shaken, not stirred
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googe
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Re: Thermometer placement

Post by googe »

Smell, taste and feel is all you need.
Here's to alcohol, the cause of, and solution to, all life's problems.
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Desvio
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Re: Thermometer placement

Post by Desvio »

The best placement for a thermometer is in the trash, time and your senses (like Googe mentions) is all you need. I often gage it by touch, or maybe I'm just caressing my still... Either way, I'm usually pretty accurate without a thermometer.
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thecroweater
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Re: Thermometer placement

Post by thecroweater »

I have learnt not to change a mind made up so if you are determined to have a thermometer there are some ways better than others. Threaded bimetal types are fairly easy to install and anywhere in the vapour path will do as they are only good for a very rough guild in a pot in any case. If using a removable pin type then make a sealed thermowell at the top and do this out of 1/4 inch or smaller copper for maximum conductivity. This will give you info like when to turn on water and start to pay close attention but no information that you can really run the still by :thumbup:
I see you joined in 08 so likely folks are not telling you much you don't know in that regard but as stated many new chums get fubared chasing temps hence the direction of the above comments. Personally I kinda like thermos on pots as it saves me touching the Lynne arm to indicate when to get the cooling going but if you have a flake then it is truely obsolete.
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