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javagamer
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Temperature Control for an electric Oil Bath
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.
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Skyjumper
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http://www.chemglass.com/product_view.asp?pnr=CG-15001? Thats fairly (very) expensive...
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aonomus
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You could always ebay a solid state relay, PID oven controller, and K type thermocouple. I think that combination might work once set up.
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entropy51
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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]
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javagamer
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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.
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Magpie
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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?
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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.
The single most important condition for a successful synthesis is good mixing - Nicodem
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javagamer
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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.
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watson.fawkes
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| 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.
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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.
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javagamer
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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]
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watson.fawkes
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| 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.
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Magpie
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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.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
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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.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Rosco Bodine
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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]
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javagamer
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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.
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entropy51
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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]
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javagamer
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| 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.
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Rosco Bodine
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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]
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javagamer
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Ordered, will update on how well it works once it arrives. Thanks everyone.
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Bikemaster
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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]
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starman
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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.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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entropy51
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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.
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aonomus
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Doesn't linseed oil polymerize on air exposure? Thats why its used as the oil in oil based paints right?
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Bikemaster
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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.
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watson.fawkes
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| 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.
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javagamer
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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.
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