Temperature vs power control...does it really matter?

[Distillusioned]

Negative-two-ly, yeah that title is very click-baity...sorry.

Negative-one-ly, I have looked at the hotplate mods that would allow power control.

Zerothly, this is what got me thinking: https://homedistiller.org/forum/viewtop ... =1&t=12049

Firstly, I recognize this is a potentially hot topic.

Secondly, I will absolutely not argue that temperature control is a good thing (i.e. not a George/PID disciple).

My hotplate, however, does cycle based on temperature.

During a stripping run, I crank it to maximum and it does what it does. No worries.

When I do a spirit run, I crank it to max until it feels like the condenser is about to produce (literally by feeling the lyne arm temp). Then I turn it down and make minor upwards adjustments as the output tapers off during the run.

So, my question is, "if I'm willing to babysit the control knob during the run (and honestly, I get bored without something to do), does it really matter than my heat source is temperature controlled?"

I'm happy with what I produce, so in that sense, it does not matter. I'm just shooting the shit...and probably rehashing old topics.

[CopperFiend]

The method of delivery of heat to the boiler is irrelevant, be it based on the voltage delivered to elements (SCRs) or a hot plate that is at a certain temperature. The reason using temperature to control a distillation is pointless is if you try to achieve a certain boiler temperature. This doesnt seem to be what you are doing as you are altering the hot plate temperature, which is not the same.

In short, you aren't controlling temperature, you're controlling the heat input to the boiler only, which is what we all do.

[howie]

i was happy with what i produced, trying to jiggle a thermostat element, until i got a proper power controller.
then i had to chuck all my early work back into the boiler.
i think to achieve, and maintain, some sort of EQ in the column, you must have a good constant rolling boil.
if you watch a boiling liquid, it literally takes a couple of seconds to change the vapour output when the power is altered.
you do not want to to happen in a column you have just spent the last hour getting to EQ.
and this is what i think happens when you use a cycling power source, like a thermostatically controlled hotplate.
that is my theory anyway.

[Saltbush Bill]

i was happy with what i produced, trying to jiggle a thermostat element, until i got a proper power controller.
then i had to chuck all my early work back into the boiler.

We live and learn, you don't know what you don't know, till you do know.......then all becomes apparent.

[Yummyrum]

Distillusioned

I have yo admit to doing just like you did for a few runs when I was starting off . I did it because my still started to puke , switched it off , then back on , off , on

Had no idea what I was doing other than it seemed less heat into the boiler made it run better . …. I was , like you , using power control .

Its rough and ready and although it gets the job done .
But ….

When the boiler is getting 100% power and the boiler is vigorously boiling , the vapour is a mix of everything smearing out of the boil .

When the boiler is getting no power , then the vapour production slows to a stop…. You get nothing .

Somewhere in between , is a happy place where the vapour coming off the boil is the higher boiling point products . Push it a bit harder and you will excite and push out the slightly lower boiling point products at the same time .

So what we want is to put just enough power in that we get enough excitement of the highest boiling point product but not so lower power that it takes all week to do run .

Getting back to switching on and off .
The faster you can switch on /off/on/off , the less extremes . The boil hovers closer around the desired middle boil rate .

[LWTCS]

Its all about stabilizing your gradient.
You'll just never make anyone's best spirit by fiddling with the knob for the duration of a run.

[Demy]

You simply need to improve your adjustment system .. what you have on your plate I suppose both type bimetal thermostat, what it makes it is lit off or maximum heat varying only time between cycles so you will always have thermal changes ... what you need to do is build (or buy ) a separate controller, up to the maximum the thermostat of your plate and adjust from the "good" thermostat .. The controller will allow you a constantly delivered heat, similar to the gas knob of your kitchen .. Find many discussions about the type of Controller and do-it-yourself projects, if you have difficulty ask and someone will help you.

[Distillusioned]

You simply need to improve your adjustment system

I've looked into doing a power control modification to my hotplate, but I'm having a hard time convincing myself that it's worth the effort. I've had plenty of experience with electronics, process control, and so on, so it's not like it's scary or whatever...but I'm lazy. lol

My point was that it seems to run fine even though the hotplate cycles based on temperature. I turn it down during a spirit run, so it's cycling on/off at a lower temperature. Then, as the stream slows, I nudge the knob up a bit. I go from start to finish with a pretty consistent rate of output. I imagine, given the volume of liquid in the pot, it can't really gain/lose all that much heat, given how short the on/off cycle times are.

I've read so much about how stock hotplates' controls are no good for our purposes, but I'm just not seeing it in practice. At least, that's been my experience with it. I dunno.

Edit: it is a pretty nice hotplate, so maybe that makes some difference.

[shadylane]

Its all about stabilizing your gradient.
You'll just never make anyone's best spirit by fiddling with the knob for the duration of a run.

That's a fact.
Set the power for what the content of the boiler needs.
And leave it alone or only make small changes during the run.
The boiler temp will slowly rise as the run progresses.

[NZChris]

My point was that it seems to run fine even though the hotplate cycles based on temperature. I turn it down during a spirit run, so it's cycling on/off at a lower temperature.

I doubt that. Most of those hot plates do not have a thermostat except for an over-temperature bi-metal switch built into the plate that prevents it from overheating and can be a bloody nuisance if you want to run a still on one. When it activates, it cuts the Watts in half.

What most of them have is a simmerstat, which controls the percentage of time the power is on for. To add to the confusion, some sellers are calling these controllers thermostats, even though they cannot control temperature.

[Distillusioned]

My point was that it seems to run fine even though the hotplate cycles based on temperature. I turn it down during a spirit run, so it's cycling on/off at a lower temperature.

I doubt that. Most of those hot plates do not have a thermostat except for an over-temperature bi-metal switch built into the plate that prevents it from overheating and can be a bloody nuisance if you want to run a still on one. When it activates, it cuts the Watts in half.

What most of them have is a simmerstat, which controls the percentage of time the power is on for. To add to the confusion, some sellers are calling these controllers thermostats, even though they cannot control temperature.

I'll admit, I have never opened it up to verify for myself. I have just accepted what the manufacture said it was.

From the manual: "...the thermostat adjusts itself to maintain the temperature..."

[Saltbush Bill]

The whole point is that you are not trying to " maintain " a temperature. The make up of the wash does that automatically. You are only trying to control how vigorous the boil is.

[jonnys_spirit]

It’s an easy mod to replace the built in controls on a 1500W cadco hotplate with an scr. Then you don’t need to fiddle with anything and you get the benefit of a constant power source. I added a diffusion plate to mine as well as an scr.

Cheers!
-j

[NZChris]

It should read, "...the simmerstat can be adjusted by the user to maintain the desired simmer..."

Put a thermometer in a pot of water on your hot plate, bring it to the boil, then try to use the 'thermostat' to adjust the temperature of the water while maintaining the boil.

[Sulaiman]

I would either

add a 'dimmer' (SCR/TRIAC/phase angle modulator) controller, either internally or extermally
Or
Put an oil bath on the hotplate, which will stabilise the temperature when using a simmerstat.
https://en.wikipedia.org/wiki/Bain-marie

[LWTCS]

From the manual: "...the thermostat adjusts itself to maintain the temperature

Yes that is precisely the problem with respect to distillation.

Again, as long as you are drawing off distillate for a kettle charge that has alcohol contained within, you will never (ever) be able to control the kettle temperature.
It is impossible.

[Demy]

It is possible to use the original thermostat somehow (a way that I don't like it) maybe in pot-still mode but thinks how difficult it would be in a reflux column when you try to stabilize it ..... I often use those plates (mine I am cheap) and I can confirm that an external controller will improve your distillation a lot, I consider it one of the things really to do, I have built my with a SCR module with a ridiculous shopping. I have distilled with and without the controller so I could see the difference.

[Distillusioned]

I understand how the liquid's temperature is determined by its makeup. I understand that it's futile to chase after a temperature. Taking that NZChris is correct regarding simmerstat vs. thermostat, my thread title is perhaps now inaccurate. I posit the altered question becomes, "hotplate's internal control vs. external power control...does it really matter?"

I've been using this hotplate for the better part of a year, and it drives the still pretty good as far as I can tell. Without making the modification and seeing for myself, I reckon I'll never know if it makes "enough" of a difference to justify the effort (minimal as it may be).

Previously, I was using my stove in the house. It is an old model that does indeed provide constant power. But, it was with a small, makeshift pot. I can't fit my new one under the range hood. With the substantial size difference, different condenser styles, etc., it would be an apples-to-oranges comparison. And, in fact, the big one produces better output than the little one did, even though I'm using an inferior heat source.

[Distillusioned]

It is possible to use the original thermostat somehow (a way that I don't like it) maybe in pot-still mode but thinks how difficult it would be in a reflux column when you try to stabilize it ..... I often use those plates (mine I am cheap) and I can confirm that an external controller will improve your distillation a lot, I consider it one of the things really to do, I have built my with a SCR module with a ridiculous shopping. I have distilled with and without the controller so I could see the difference.

I don't have a reflux, just a simple pot still. When you say you saw a difference, was that reflux, pot, or both?

[Demy]

I used in Pot-Still mode

[Distillusioned]

It should read, "...the simmerstat can be adjusted by the user to maintain the desired simmer..."

Put a thermometer in a pot of water on your hot plate, bring it to the boil, then try to use the 'thermostat' to adjust the temperature of the water while maintaining the boil.

Not doubting simmerstat vs thermostat, but I think I'd need to bring the water to some non-boiling temperature to get some more meaningful data. That would give me an idea of how much swing I get in temperatures while it cycles on and off. Not sure if that would be useful data or not....

If I understand what a simmerstat is, it really is just a power controller with a really, really extended duty cycle.

[OtisT]

Distillusuoned

Answering your subject line. Yes, it does matter on a spirit run.

A simple solution for you would be to use a heat sync. No electrical skills required. By placing a relatively large mass between your hotplate and boiler, you lessen the highs and lows of your power input and if sized proper, you can get a very steady boil going in your still and see a consistent output rate from your spout.

When I used a 1500w hot plate, I found that about 3 pounds of aluminum was the minimum size and my sweet spot. Any less and I could still see the power swings (by measuring output rate.). The 3 pound sync was a 10” x 10” x 1/4” sheet of aluminum.

I should add that you need good surface to surface to surface contact. Very flat surfaces and no debris on any surface. Keep them flat and clean. I once had just a small bit of plant material on the plate once. A piece of leaf I think. That caused hot spots in the boiler pan and some minor scorching. You will have the same concern with a hotplate/boiler connection, and the plate just adds one more surface to surface connection to maintain.

Otis

[jonnys_spirit]

I’m pretty sure a simmerstat is full power on/off for a certain amount of time.

On my cadco there is a lamp in series with the element circuit that indicates when the element is receiving current. With the simmerstat installed the lamp is either full on/off. With an SCR the brightness of the lamp is proportional to the current/power.

If you use a diffusion plate it acts as a heat sink and will smooth out the cycling of the hard on/off activity with a simmerstat.

I use the diffusion plate in conjunction with an SCR to spread out the heat distribution on the bottom of the boiler - not so much for cycling since the SCR doesn’t cycle.

[OtisT]

It should read, "...the simmerstat can be adjusted by the user to maintain the desired simmer..."

Put a thermometer in a pot of water on your hot plate, bring it to the boil, then try to use the 'thermostat' to adjust the temperature of the water while maintaining the boil.

Not doubting simmerstat vs thermostat, but I think I'd need to bring the water to some non-boiling temperature to get some more meaningful data. That would give me an idea of how much swing I get in temperatures while it cycles on and off. Not sure if that would be useful data or not....

If I understand what a simmerstat is, it really is just a power controller with a really, really extended duty cycle.

Measuring the output rate of your pot still will give you the most meaningful data set. A consistent output rate is what you are trying to achieve. Otis

[Setsumi]

as SBB and LWTSC said, you want to have a constand boil. you want to control how vigorous you boil. on of cycles that is too large will not give a constant boil, it will surge. try what Demy said, it is easy enough.

[Distillusioned]

Measuring the output rate of your pot still will give you the most meaningful data set. A consistent output rate is what you are trying to achieve. Otis

Well, I sometimes collect into smallish beakers, and my output rate is pretty consistent. Not saying I'm sitting there with a timer, but it's subjectively pretty consistent. That, of course, doesn't account for any variations that may be present within each collected volume.

[Distillusioned]

If you use a diffusion plate it acts as a heat sink

The hotplate has a cast-iron surface, so I reckon I'm witnessing a bit of that effect.

[S-Cackalacky]

If you use a diffusion plate it acts as a heat sink

The hotplate has a cast-iron surface, so I reckon I'm witnessing a bit of that effect.

A metal plate (heat sink) will help to somewhat mitigate the problem. A better solution might be to modify the internal wiring to eliminate (bypass) the thermostat control, so that the power is always full on and buy/build a power controller to give a steady and controllable amount of power to the hotplate. I think I remember some older threads that give some instruction in how to do this.

Hotplates are inefficient. The preferred solution would be an internal heating element and power controller.

[Distillusioned]

If you use a diffusion plate it acts as a heat sink

The hotplate has a cast-iron surface, so I reckon I'm witnessing a bit of that effect.

A metal plate (heat sink) will help to somewhat mitigate the problem. A better solution might be to modify the internal wiring to eliminate (bypass) the thermostat control, so that the power is always full on and buy/build a power controller to give a steady and controllable amount of power to the hotplate. I think I remember some older threads that give some instruction in how to do this.

Hotplates are inefficient. The preferred solution would be an internal heating element and power controller.

I might give that a shot. I can probably borrow a controller from work for a weekend to see if it makes enough difference to me to bother.

I've been thinking of adding a tri-clamp fitting for an internal element. It would be a good excuse to buy a new TIG welder, too! I welded for many, many years, but I've been in software development for the last decade-and-a-half, so all I have left is a flux-core machine. That's some nasty, dirty welding. My last full-time welding job was 100% TIG welding, and you really get spoiled with how much more pleasant it is.

[NZChris]

It should read, "...the simmerstat can be adjusted by the user to maintain the desired simmer..."

Put a thermometer in a pot of water on your hot plate, bring it to the boil, then try to use the 'thermostat' to adjust the temperature of the water while maintaining the boil.

Not doubting simmerstat vs thermostat, but I think I'd need to bring the water to some non-boiling temperature to get some more meaningful data. That would give me an idea of how much swing I get in temperatures while it cycles on and off. Not sure if that would be useful data or not....

If I understand what a simmerstat is, it really is just a power controller with a really, really extended duty cycle.

I have no idea what meaningful data you would get, not for distilling anyway. You can't distil anything if your charge isn't boiling.

Yes, a simmerstat is a power controller. If it's dial goes from 0-12, like those on my stove, at 6 it will give you 50% power by annoyingly switching off and on. When you're cooking your dinner, you hardly notice the effect. For distilling, it needs to be fully on and controlled by an external controller like the SCR you've been recommended. Even that might not work if you trip the plate's internal over-temperature switch, (that cannot be removed without destroying the plate).