I have a recovery still that works great but I’d like add a temperature controlled shut-down switch to the power (120v AC).

I monitor the vapor temperature in the condenser column with a remote barbeque thermometer. When it rises a few degrees over the vapor temp of the alcohol it sets off the receiver in the house and I know it’s done. I then jump up and go turn off the power to the boiler (SS beer keg).

I’d like to put together an inexpensive temperature controlled switch that will cut the power to the boiler either by sensing the temp of the boiler contents (it is usually done when the boiler surface temp reaches about 205 degrees) or by tapping into the barbeque thermometer and turning off the power when the thermometer triggers the “done” alarm.

Anyone done this and can tell me the parts and pieces they used?

I’ve looked at PID thermostatic controls but I don’t know enough about them to choose the right one or what other specific parts are needed (thermocouple, etc.).

Thanks,
-Jay

What, nobody has done this type of thing? This site is filled with dozens of people far smarter and more creative than me. Please share!

Do a search. I looked for "PID control" and it returned dozens of recent posts including some on methanol recovery.

There are several different ways to achieve this. If you want cheap you could use the high limit control off of a hot water heater. Its the part of the T-stat with the red button. I am not sure at what temp they are set to trip but it is likely marked right on it, it has to be reset manually...
A PID or another type of thermostat can also be used in conjunction with a contactor or SSR.
When you figure out how you want to do it post back if you are unsure how to connect it up and I can help you out.
Here is a hen scratched drawing I did for Drewry that should give you some ideas about control...
Jon

For really cheap take a look at the thermal switches on RS components.If you go for this I would use 2 in series for redundancy and pick the ones with the manual reset(red)button.(this will shut your system down until you reset)These are rated for 240v but its a bimettallic switch and will work quite happily on 120v-its the tempreture that is driving it(there may be equivalents on the USA site for 120v).Wire your live power through this(or these )in one side out the other then on to your heater/system.Here's a link below and I've attached a pic of the 90 deg c opening switch-similar to your requirement
http://uk.rs-online.com/web/se...r=AND(avl%3auk%2csea

thermo_switch.jpg (10 KB, 28 downloads) thermal switch pic

I use soemthing like what you're looking for. A thermostat senses the oil temperature and shuts off a latched relay that controls the heat permanently when it reaches an adjustable setpoint.

I've used a variety of thermostats, including ones from scrapped airconditioners, scrapped frying pans, scrapped industrial controls, and new ones from McMaster-Carr.

The relays I prefer are industrial 2-pole double-through "ice-cube-relays" (ICR's). A household light switch is used to "latch" the relay, or to over-ride the temperature control, depending on how it's wired.

The same circuit can be used with a float switch to control a pump.

I'll post a diagram shortly.

Cheers,
JohnO

See my entry at Graydon's Biodieselpictures for some latching relay control information. If you need more details, let me know.

Cheers,
JohnO

Ah! Great info. All good. I will get through the links soon.

I did do some calling and talked to an outfit that sells PID controllers pretty reasonably. He said they are coming out with one that will be an off-at-setpoint and require manual reset. With a latching relay and the proper thermocouple to sense temperature this seems like a pretty straight forward device to set up.

Thanks,
-Jay

Weird - over the weekend I added a photo of the cuicuit diagram. Now it's gone. I'll try again this evening. Sorry.

You can get PID's cheap on eBay. Most PID's including the one I linked to have an alarm function that can be set to do what ever you need...
Jon

built mine 6 months ago..

yep auto shut down..

uses 2 Watlow 935 PID controllers. 1 DUAL SSR.

PID 1 - controls the pot temp
PID 2 - controls the vapor temp at the temp of the reflux column.
auto shut down..
note both PID have 2 outputs..
i use the 2nd output on PID 1 to latch an alarm condition with the POT temp hits 205F..this latches a relay( a smaller SSR, in reality) that kills power to the heating element.

If you'd like I think I can create a diagram, but I most warn you first its complex.

-dkenny

dkenny

I'd like to see the controller diagram for the one that shuts down the heating element.

I don't control the heating element on mine. It plugs right into the wall and runs full bore until all the alcohol is boiled off. The temp of the glycerin slowly rises until at about 205 to 210 degrees the alcohol is gone and the vapor temp starts to rise. That sets off my BBQ alarm and I go unplug it.

Auber instruments has a little, single display model that is close to being perfect for this except that once the temp of the boiler (or vapor temp) drops to the minimum it turns on again unless you use a latching relay. However the tech I talked to there said they are coming out with one very soon that will have the latching process built in so it will shut off power to the SSR and not come on again until manually reset. So all you will need is the controller, a thermocouple, and an SSR for power to the element.

-Jay

JGK,
that would be the key.. the 2nd output on the watlow 935 can be a latching alarm..I have mine setup to alarm in the off condition..meaning the SSR is on until the alarm occurs. then latches off until a manual reset.

I start working on a diagram.

-dkenny

Here's a simplified diagram.
the pump control( manual switches are not included)

2009_reactor_control_setup.jpg (49 KB, 62 downloads) dkenny controller

Nice diagram.

So you can control the heater using either the vapor temp monitor or the glycerin temp monitor, correct?

Probably a bit fancier than what I'm looking to do but it has more flexibility.

Thanks,
-Jay

Jay,

yes it controls both the vapor temp and the pot temp. it is a little bit fancy, but it works well.

it add other element to control the heat I just need to series the SSR control wires

-dkenny

I use a love tempture controller Ts2 the hole set up coast me $65.00. most controller are only up to 5 amp then you need a ssr to run them this one is 15 amp and work great for me. http://www.dwyer-inst.com/Prod...9&sPageName=Ordering

I like the PID set-up very much, but there is a cheap method.
I assume your BBQ alarm has a certain voltage.
Get a relay for that voltage and wire it parallel to the alarm.
Hook up an SSR to the normally closed contacts.
As soon as the BBQ alarm goes of, the relay cuts in as well, thereby cutting the current to the SSR and your heating is switched off.
A "normally open" contact on the SSR should make sure that it STAYS off.

what happens on the BBQ alarm when the temperature falls below the alarm point? the relay open there by allowing the SSR to turn back on? heating again?
if so this might work for normal operation but not a shut-off condition..the condition that shuts down heating until the user resets the PID.

-dkenny