steam (water) coming over at 92C?

[katzgejm]

so i charged my still with nothing but tap water, both to give it a good clean and also to check my thermometre's accuracy. it's located at the top of the column, so i was expecting steam to come over at very near to 100C, but it started coming hard in the 80s and plateaued at 92C. what's going on here? i doubt it's off 8 degrees!

[shadylane]

The thermometer might not be 8 degrees off but it's placement in the column might be.
This is one of the problems with trying to use a thermometer to measure vapor temperature.
Test the thermo by dipping it in boiling water if you want to measure it's accuracy.

[ranger_ric]

Well water boils at 212° sea level /100°
Elevation could have some to do with it. Some thermometer error could add in...

However I am quite certain that the boiling point did not change for your still...(unless you are putting a vacuum on it)

Send pics of your still and thermometer placement. other than that what difference does it make what your thermometer reads. It is either vapor or it is not..

[carbohydratesn]

Air pressure will change the boiling point of water, your still isn't perfectly insulated, and your thermometer, like most, is off by a few degrees. Don't worry about it.

You're going to have to learn how your still behaves, and this is part of it. Don't expect your thermometer to be perfectly accurate, it won't be. Just treat it as an extra piece of information you can use - it isn't something to be relied on.

[3d0g]

Boil a pot of water. When do you start to see steam?

[Spooled]

As these guys have taught me, who cares what it reads. Pay attention to what happens at certain readings. The thermo is basically just to let you know your in the ball park to have something happen. For example when my thermo hits between 60 and 70 degrees Celsius I finallt turn on the cooling water. Then I still wait till my still decides it's time to knock down some distillate. Basically it saves water. lol

[moosemilk]

Boil a pot of water. When do you start to see steam?

+1

You see it long before it boils. Better place for therm on pot still is in the potato (kidding, kinda). Put it so the therm is in the actual liquid, if you must.

[chris_zx2]

As these guys have taught me, who cares what it reads. Pay attention to what happens at certain readings. The thermo is basically just to let you know your in the ball park to have something happen. For example when my thermo hits between 60 and 70 degrees Celsius I finallt turn on the cooling water. Then I still wait till my still decides it's time to knock down some distillate. Basically it saves water. lol

This is exactly what I do, in terms of temperature I forget everything I've learned about temperatures and use the thermometer as an indicator of what's next and how soon. Write down your findings under different conditions and you can predict pretty accurately when your flow will start and when to cut off.
On a pot still its not advisable to use it for cuts tho.
And I also have my thermowell installed at the top of the column and have repeatable results.

[katzgejm]

Boil a pot of water. When do you start to see steam?

true of course, but you'd think when the water is at a full boil, the vapor temp would be 100C.

i'm at great lakes altitude, so that shouldn't account for much more than 1 degree.
the thermometer is at the top of the column. it gets its reading from exactly where the vapor moves into the condensing tube.

i'm not too bent out of shape about it, just very surprised to see an 8 degree variance. really goes to show you just how unreliable the reading would be to make cuts, as you're all saying!

[Drunk-N-Smurf]

You also have to remember that waters boiling point is based on pure water. Most water is not pure. so the boiling point can vary by a few degrees dependant on the makeup of your water.