Sciencemadness Discussion Board

Temperature Control for an electric Oil Bath

javagamer - 2-3-2010 at 17:38

Hi,
I'm looking at purchasing an electric oil bath because it appears it would be more versatile than a heating mantle and much more convenient that heating an oil/water bath with a hotplate or flame. Specifically, I'm looking at getting item # CG-1100-03 from ChemGlass (http://www.chemglass.com/product_view.asp?pnr=CG-1100) because I found what seems like a reasonable a price for one.

The problem is it uses 1500W and so it's hard to find a temperature controller for it. I was already planning on ordering a variac, but not one nearly large enough to use for this. It seems all variacs in the 15-20A range are rather expensive so I'm wondering if it wouldn't just be worth it to actually buy a temperature controller if they're only a little more.

Or, if it would be possible to reasonably control the temperature by plugging it in when I need it hotter, and unplugging it when I don't?

Also, if I get a variac that goes up to only say, 500W, could I still use the oil bath below it's maximum temperature?

Basically, I just want your advice on how I can most economically control this oil bath, or if I should just look elsewhere.

Skyjumper - 2-3-2010 at 17:47

http://www.chemglass.com/product_view.asp?pnr=CG-15001? Thats fairly (very) expensive...

aonomus - 2-3-2010 at 17:50

You could always ebay a solid state relay, PID oven controller, and K type thermocouple. I think that combination might work once set up.

entropy51 - 2-3-2010 at 18:01

That is one beautiful oil bath, but you might want to Google "Fondue Pot" first. Depending on the size you want, these can do the job and can be controlled with a variac. Fondue pots are equipped with a simple temperature controller, but they don't give really good control.

I've been using Pyrex dishes with a coil of nichrome wire powered by a variac for ages and they are pretty cheap. Another alternative is an aluminum pot with an immersion heater in the oil.

That's a lot of money for an oil bath IMO.

[Edited on 3-3-2010 by entropy51]

javagamer - 2-3-2010 at 18:03

Most sensors that I found either didn't go up to 250C, didn't go up to 1500W, or were just really expensive (for me). I'd say I'm looking to spend $300 at most on a temperature sensor considering I found the oil bath for less than that. Would something like http://www.drillspot.com/products/493511/tempco_tkz10202_ana... work?

If I can't find something I can afford I might just go with a mantle, while I'd be stuck to one flask size for that flask they seem more convenient since I don't have to deal with any medium and they use less power.

Magpie - 2-3-2010 at 18:53

Quote: Originally posted by javagamer  

Or, if it would be possible to reasonably control the temperature by plugging it in when I need it hotter, and unplugging it when I don't?


You don't want to have to do that.

Using a smaller variac is likely possible. But if you didn't manage the system just right you could burn out the variac. I would advise against this.

There are times when you need an oil bath and times when a mantle is just fine. A mantle is much easier to set up/take down and responds faster to changes in heat setting. You often don't know just how much heat you will need over the course of an experiment and this can change during the experiment. A flame responds even faster. I wouldn't want to be hemed in to a one-size-fits-all piece of equipment.

My oil bath set up is a magnetic-stirrer hotplate, steel cooking bowl, type K thermocouble, PID controller, and DOT 5 silicone brake fluid. Punch in the bath temperature I want and I'm all set. The mag drive stirs the heating oil and the reactants in the flask, using two stir bars, of course. I'm happy with these arrangements and don't see what I would change even if the changes were free.

javagamer - 2-3-2010 at 19:02

So, a steel bowl and hotplate together can get hot enough? How long does that take to get to say 100C? I figured an electric oil bath would be much more convenient and responsive, but maybe not for the price.

Also, how do set up your your PID controller with the oil bath? Is the hotplate just turned on full and plugged into it? I haven't worked with one before, but it sounds worthwhile.

watson.fawkes - 2-3-2010 at 19:14

Quote: Originally posted by aonomus  
You could always ebay a solid state relay, PID oven controller, and K type thermocouple. I think that combination might work once set up.
It does work; mine's housed in an old PC power supply box. The only thing that's problematic at all is finding cheap thermocouple jacks. You can always hard-wire the thermocouple, too, but that's less convenient.

javagamer - 2-3-2010 at 19:24

Thermocouple jacks? Is that for attaching the thermocouple to the bath b/c the oil bath I'm looking at getting already has a clamp for a thermocouple.
Also, didn't see you mentioned a relay too, that sounds pretty nice. I'll look into how much that would run me.

Update: So, would something like http://cgi.ebay.com/Thermocouple-type-J-Watlow-3-16-sheath-N... + http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=35026... + http://www.virtualvillage.com/40a-ssr-solid-state-relay-for-... work? I haven't decided on these yet, but I want to be sure that I have the concept down. It looks like the PID controller can connect to the relay and the thermocouple. To attach the relay would I cut open a small extension cord and just have one of the wires run through the relay?

[Edited on 3-3-2010 by javagamer]

watson.fawkes - 2-3-2010 at 20:23

Quote: Originally posted by javagamer  
Thermocouple jacks? [...]It looks like the PID controller can connect to the relay and the thermocouple. To attach the relay would I cut open a small extension cord and just have one of the wires run through the relay?
A thermocouple jack accepts a thermocouple plug, which many thermocouples come equipped with. It means you can unplug it when you store it or move it around or use a different thermocouple; it's much more convenient.

Your shopping looks OK, with some concern about what kind of sheath is on the thermocouple.

The manual for the PID controller will having wiring instructions, but you've got it basically right. Remember to switch the hot lead, not the neutral.

Magpie - 3-3-2010 at 08:44

Your PID controller link shows that it comes with a type K thermocouple.

I've seen those solid state relays on eBay for about $10.

When my camera battery gets charged I'll post a picture of my homemade controller.

Magpie - 3-3-2010 at 10:28

Here's a picture of the controller I use for oil bath temperature. From right to left: PID controller, solid state relay mounted on a heat sink, outlet box for 120VAC. In the foreground is the detachable TC and several feet of TC wire. Wire with a wire size adequate for the highest anticipated amps in the given wire. If you have any questions, please ask.





PID controller.jpg - 57kB

Rosco Bodine - 3-3-2010 at 14:00

http://www.sonicelectronix.com/item_21714_Presto+Professiona...

This will handle up to a 5,000 ml flask

Another useful one is this

http://www.sonicelectronix.com/item_21712_Presto+11-inch+Ele...

[Edited on 3-3-2010 by Rosco Bodine]

javagamer - 3-3-2010 at 14:50

Quote: Originally posted by Rosco Bodine  
http://www.sonicelectronix.com/item_21714_Presto+Professiona...

This will handle up to a 5,000 ml flask

Another useful one is this

http://www.sonicelectronix.com/item_21712_Presto+11-inch+Ele...

[Edited on 3-3-2010 by Rosco Bodine]

Is the temperature on that first one in Fahrenheit? If so that looks like just what I wanted! Something much more convenient than a hotplate for most of the stuff I do and if need be I can still use my hotplate for really high temperatures. Is the temperature control on it somewhat reliable, or would I still want a setup like Magpie's? Even if I do, this definitely seems worth it.

entropy51 - 3-3-2010 at 15:10

I was trying to point you in that direction

I think a fondue pot is better than a skillet because it is deeper than a skillet, is less likely to spill hot oil (ouch) and will hold a bigger flask than a skillet. The temperature control on the one I have is not bad, but the control is better if you plug it into a variac.

[Edited on 3-3-2010 by entropy51]

javagamer - 3-3-2010 at 15:20

Quote: Originally posted by entropy51  
I was trying to point you in that direction

I think a fondue pot is better than a skillet because it is deeper than a skillet, is less likely to spill hot oil (ouch) and will hold a bigger flask than a skillet. The temperature control on the one I have is not bad, but the control is better if you plug it into a variac.

[Edited on 3-3-2010 by entropy51]

I was actually talking about the multi-cooker he suggested. I don't think I'll be working with flasks larger than 5L any time soon, so it should fit fine.

Rosco Bodine - 3-3-2010 at 15:28

Yeah 400 F is about maximum....maybe 450 F.

Those little thermostatic probe controllers appear to hold the temperature pretty closely, and some of them have little neon cycle lamp. They are definitely close enough for routine work. If you need very exacting control you can just use a setting higher than the temp you need to maintain and plug the appliance into a switched outlet controlled by a probe and PID controller. Some of the high end crock pots or turkey roasters may have a digital controller and probe already.


[Edited on 3-3-2010 by Rosco Bodine]

javagamer - 4-3-2010 at 14:41

Ordered, will update on how well it works once it arrives. Thanks everyone.

Bikemaster - 9-3-2010 at 11:53

Fondue pot work really good. Even the temperature control work really good. Two days ago I try this setup to hold oil at 148 C and the temperature vary only from 150 C to 145 C durin over 3 hour .
The only think that I will change is the oil that I use, because vegetable oil smell like hell at these temperature. I think it will a judicious purchase to buy 8 dot oil... my pocket will don't like...

[Edited on 9-3-2010 by Bikemaster]

starman - 9-3-2010 at 17:03

Bikemaster raises a good point about the fluid.Just what is the preferred OTC, cost concious best choice.I hear brake fluid is favoured by some.I've used linseed oil up to about 180C without excessive fume or odour.

entropy51 - 9-3-2010 at 18:35

According to this MSDS linseed oil has a flashpoint of 222 C and an autoignition temperature of 343 C, suggesting it might be a good choice. A long time ago I spent the $$$ to buy some good silicone oil, and it has laster forever and a day.

aonomus - 9-3-2010 at 20:42

Doesn't linseed oil polymerize on air exposure? Thats why its used as the oil in oil based paints right?

Bikemaster - 10-3-2010 at 07:57

For the moment I use canola oil and it smell a lot when heated, I think I will try the linseed oil next time. Canola oil have a boiling point of 240 C compare to the boiling point of 340 for the linseed oil, so it should smell less.

watson.fawkes - 10-3-2010 at 18:38

Quote: Originally posted by aonomus  
Doesn't linseed oil polymerize on air exposure? Thats why its used as the oil in oil based paints right?
Linseed oil is the original oil, yes, but no longer the only one; there are a number of other oily resins also used now. More to the point than paint, linseed oil is also a traditional medium for varnishes, which is what you'll have to deal with if used as a heating medium, that is, the bathtub rings made of varnish. These are cleanable, with effort and solvents, but may or may not be worth the trouble, depending on your particular money vs. time vs. risk aversion trade-off.

javagamer - 10-3-2010 at 18:42

I've heard good things about mineral oil, any reason not to go with it? I have plenty lying around and so long as I don't have to change it out every time it should be economical enough.

Bikemaster - 11-3-2010 at 07:15

Mineral oil is really good for for a bath fluid, but not really at high temperature http://www.hartscientific.com/products/bathfluid.htm
It only rate acceptable up to 175 C, but if you don't need these temperature, it seem to be a good issue.

javagamer - 11-3-2010 at 12:07

Oh, what's the problem with mineral oil beyond 175? It doesn't start to boil until over 300 iirc. Either ways, I know my hardware store has linseed oil, so if I need any I can just get it.

Lambda - 11-3-2010 at 15:13

Hi @javagamer,

If You decide to build your own Thermostat, then switching with a Zero Crossing Solid State Relay will give considerable less Switching Distortion. On eBay, they are real Cheap, going for about $5-10

Also, I strongly recommend You to put one or more Thermal Fuse(s) in Series with the Heater Element in the advent of Circuit Failure to prevent overheating and Ignition of Your Oil Bath. They are real Cheap too, so You really should NOT omit this extra safety feature into Your Oil Bath Thermostat Design. Boiling, and Burning Oil is just too Dangerous !

Kitchen Oil Fire ! :o



You can Buy Thermal Fuses in any Shop that deals in Espresso Coffee Machines (>100 °C for High Pressure Boiling Water and Steam) and Oil Frying Pans (like those used for French Fries / Chips).

Thermal Fuses:
http://www.ivaldi.fr/pages_anglaises/regul-ftus.html
http://www.cantherm.com/products/thermal_fuses/index.html

For a little Info on Solid State Relays, and Zero Crossing TRIAC Driver Chips, You may find a few useful Tips here:

Schematic for Electrolysis Device:
https://www.sciencemadness.org/whisper/viewthread.php?tid=13...

And for Schematics on Thermostat Devises, You may find a few useful Links here:

Thermostat Schematics:
http://images.google.nl/images?um=1&hl=nl&client=fir...

David Bowie & Pat Metheny - This is Not America (1998):
http://www.youtube.com/watch?v=0YUe786PYUk

Lambda

Lambda - 11-3-2010 at 20:32

Quote: Originally posted by javagamer  
... Either ways, I know my hardware store has linseed oil, so if I need any I can just get it.


Linseed Oil can Polymerize and the reaction is Exothermic, and Rags Soaked in it can Ignite spontaneously. Due to its polymer-like properties Linseed Oil is used on its own or blended with other oils, resins and solvents as an impregnator and varnish in wood finishing, as a pigment binder in oil paints, as a plasticizer and hardener in putty and in the manufacture of linoleum.

A Devastating Shop Linseed Oil Fire (I guess that this Unfortunate Guy should NOT have left Linseed Oil Impregnated Rags lying around after all):





@javagamer, I am just trying to Boost Your Confidence !! :D, and I would think twice about using Linseed Oil !!!

Why not use Solid Paraffin (Candle Wax, can also be Stearic Acid, seldom Beeswax nowadays) which can have Boiling Points in excess of 450°C, or Vaseline (also called Petroleum Jelly, Boils at about 350°C) instead ? :cool:

n-Paraffins:
http://chemicalland21.com/petrochemical/n-PARAFFINS.htm

Vaseline (Petroleum Jelly) MSDS:
http://www.bmed.mcgill.ca/REKLAB/manual/MSDS/Materials%20Lis...

Hot Chocolate - So You Win Again:
http://www.youtube.com/watch?v=WJvdy00LcPI

Lambda

not_important - 11-3-2010 at 20:57

Quote: Originally posted by javagamer  
Oh, what's the problem with mineral oil beyond 175?


Flash, autoignition, and smoke points. Flash point is the temperature it is 'easy' to ignite the hot material and generally is around the temperature that fumes start to be annoying while the smoke point certainly is where fuming/smoke is a problem.

Partially hydrogenated peanut oil is used for frying in some areas because its smoke point is reasonably high (~220-230 C), it's untreated level of poly-unsaturates is fairly low so it doesn't need too much hydrogenation, and the crop is grown locally so it's not too expensive. Cottenseed oil is another.


starman - 12-3-2010 at 05:00

I note the vaseline MSDS states to "keep away from heat and other sources of ignition".
Candle wax should be OTC and relatively cheap.BTW I didn"t recommend linseed oil for use,merely stated that I have used it with no problems,then invited further discussion.The cheap(non medical) mineral oil (parrafin oil in Australia) always had excessive fume problems even at relatively low tempreatures.
If I could find a non chem-house supplier of high grade silicon oil I'd do as Entropy 51 and make the investment.

javagamer - 12-3-2010 at 17:25

Haven't tested it with anything but water yet, but so far it seems like a very good investment. Thanks for all your help everyone.

SWilkin676 - 7-4-2010 at 12:26

Check out the fry daddy - actually made for hot oil
http://www.walmart.com/ip/PRESTO-FRY-DADDY/9219298

My partner uses Grapeseed oil regularly with no fires - temperatures in the mid 200 C range. You can get it a lot cheaper on ebay than trying to buy it local.

I thought I had a cool idea to replace sand in a sand bath with silicon carbide until my sweetie pointed out that might be a bit rough on the glassware....

Suzee

peach - 1-5-2010 at 03:37

Quote: Originally posted by SWilkin676  
Check out the fry daddy - actually made for hot oil
http://www.walmart.com/ip/PRESTO-FRY-DADDY/9219298

My partner uses Grapeseed oil regularly with no fires - temperatures in the mid 200 C range. You can get it a lot cheaper on ebay than trying to buy it local.

I thought I had a cool idea to replace sand in a sand bath with silicon carbide until my sweetie pointed out that might be a bit rough on the glassware....

Suzee


Dammit! :D I was just about to post that.

A deep fat fryer.

You can get them at any well stocked outlet of cheap electrical products.

Sure, the dial might not be calibrated properly, but that's what a thermometer is for. I wouldn't trust the dial temperatures on anything and, besides, the actual plate temperature isn't the issue, it's the solution temperature. Even people like IKA put external temperature probes on the plates that cost upwards of a 1k a piece.

densest - 1-5-2010 at 08:45

Would DOT-5 silicone-based brake fluid be useful? DOT-5.1 glycol based fluid? Both should be useful at 200C. The glycols absorb water and their boiling points go down. It's not clear how to remove absorbed water. Maybe anhydrous MgSO4 or something like it would work.