Author Topic: Stable heat source  (Read 1061 times)

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  • Guest
Stable heat source
« on: March 25, 2004, 10:54:00 AM »
As im moving closer to my LWR i was trying to find a stable heatsource. So an oilbath was considered, but I also needed a stable temp for the 36hr reflux.

I was adviced to buy a "crockpot",  witch i did.
Only thing is, when i tested it yesterday the lowest setting ran up to 140C. :(


I used tfse and saw somebody used a coffemachine, as it held their coffe temp stable @ 95C.
Mine is stady @ 80C.

Now im out of money an patience, so i wondered if i should reflux 80C. Would that even work?

And if not will 140C kill the product?

What would be the best choice of two evils?

Swim just wants SOME product for his first LWR.
Then he'll improve tech-unique and equipment...

Please advise...


  • Guest
« Reply #1 on: March 25, 2004, 01:01:00 PM »
Just take the crock pot back, and tell the store clerk it gets WAY too hot to make speed in.
On a second thought, don't do that at all.

Anyway, I think 80°c is too cold and 140°c is too hot. (Well, the internal flask temp would be around 120°c - 130°c.)

You could either increase the oil/flask temp variation (somehow...) OR look at a different heat source.
Sorry I cant really help much.


  • Guest
internal temp
« Reply #2 on: March 25, 2004, 01:25:00 PM »
The internal flask temp reaches the sam temp as the oilbath after some time...

so 140C is too hot to make any usable product at all?


  • Guest
deep fat fryer
« Reply #3 on: March 25, 2004, 06:55:00 PM »
Spend twenty five bucks for a variable temperature deep fat fryer. Modify the lid to let the flask extend out of the fryer. A hacksaw does nicely. The temperature range fluctuation is pretty small on these, and the range of temperatures they provide is within the range you need. Additionally these are cool to the touch, and have thermal limit protection against overheating.


  • Guest
Heh, thats what i did.
« Reply #4 on: March 26, 2004, 11:17:00 AM »
Heh, thats what i did.
BUt the lowest setting (didnt state what temp it was, just "low" ) was 140C...

I recon i can modify the resistor, but im not sure how to do this...

Any brigth bees with ideas?


  • Guest
You could
« Reply #5 on: March 26, 2004, 01:04:00 PM »
Depends on the resistor, sometime's a little bending of the temp sensor or even a dimmer switch in series may help a little.


  • Guest
« Reply #6 on: March 28, 2004, 03:18:00 AM »
BUt the lowest setting (didnt state what temp it was, just "low" ) was 140C...

I recon i can modify the resistor, but im not sure how to do this...

Any brigth bees with ideas?

A crockpot shouldn't get THAT hot; it is designed to slow cook foods just below the boiling point of water.  However, that is during normal operation with 4ltrs of soup that absorbes and loses heat.

That said, if u tested a little water/oil in the crockpot it would obviously heat up quicker and get hotter than a larger volume.  It may be worth experimenting with a larger volume of water/oil and change the position and submersion level of the flask.  This should allow lower and more stable temps to be maintained.

Also consider the temperature differences between oil and flask contents.  Swix has seen differences of up to 30`C.

Lastly, if the resistors/switch etc can't be modded, it may be worth looking into power points with programmable ON/OFF timing.


You may experiment and find that 30min on/off cycles keeps the oil at optimum temp.

If not, then accept that it really is a CROCK-pot (haha, mee foe funny)...and move onto something else


  • Guest
second hand electric frypan
« Reply #7 on: March 28, 2004, 05:19:00 AM »
all the honey i was present during the preparation that was made with a crappy old second hand aluminium frypan. they have nice temperature controls starting at about 70 or so (well, not marked with a temp but they go down that low)

not that i've seen much honey made ;)

anyway, 140 degree liquid temperature means 120 degree flask temperature roughly. You could somewhat reduce how much heat it makes by blowing a fan over it to cool it a bit.

I think that the best solution of all would be a thermostatic switch, one that has been calibrated so it's within 2 degrees of what it says on the dial.

just take it back to the shop and say that it seems to be too hot on the lowest setting and it makes a mess of whatever it was you were trying to gently cook on it ;)

oh, yea say 'i couldn't turn it low enough to stop bla bla bla from boiling over, it's no good for what i need it for' and flutter your eyelashes winningly....  ;)


  • Guest
re: heat source
« Reply #8 on: March 28, 2004, 07:11:00 AM »
you know, there are alot of student grade heating mantles on the market now, with a built in variac, for under 100 dollars. that is new. think what kind of deal you could get on used stuff.


  • Guest
« Reply #9 on: March 28, 2004, 03:51:00 PM »
LIght bulb, LIght bulb, LIght bulb, Yeah! (chant along, its fun)

the temps are in the range, and its easily adjustable by proximity. and very close to totally free.
experiment with flask holding sytems/clamp/stages/gantry details. temps do vary over life of bulb, but just check them as you go. seems to get real hot at end of life.
cant beat it for clandestine usage--though a fry baby is way better if you find one a the thrift store or have the retail new $. Candy therms are about 2$ to verify temps.

  but are you sure you ave a crock pot and not a Duthch oven(basically a hgh sided fry pan)?  Or--have you confused yer centigrades and farenheits? if not than you have purchased a dangerous product and should seek refund. Really--just march the fuck back in and DEMAND refund or creds. You the consumer are right. Real Crock pots dont even GO that high!


  • Guest
« Reply #10 on: April 13, 2004, 02:13:00 PM »
Well, i thought i bought a crockpot. The only way i could figure out what a crockpot was (i dont speak english all to well), was to search google for images. But i probably bought a deep fat frier instead....  ::)

Dosent seem pay to be stupid does it  :o


  • Guest
F or C
« Reply #11 on: April 15, 2004, 06:39:00 PM »
Make sure you are reading the metric 140c not 140f.Max on mine is 160c,.


  • Guest
" simple adjustable stable heat source"
« Reply #12 on: April 15, 2004, 07:54:00 PM »
Put a dimmer on an immersion heater in the oil. Accurate to a couple degrees with a decent dimmer.


  • Guest
useful for discrete setting hotplates too...
« Reply #13 on: April 16, 2004, 02:53:00 AM »
useful for discrete setting hotplates too probably... (swim is the proud owner of just such a solid element hotplate, sparkless but no temperature control). These things are at the hardware store used on light switches - i'd completely forgotten about how those things work and that they are inline mains power resistors that can be found at any hardware store. bloody good idea. I might be wrong though, if they aren't rated for the kinds of wattage a heating unit draws (500+) then that would be unsafe, a higher wattage resistor would be needed, otherwise the resistor could burn out, causing burnt plastic, or at worst, starting a solvent fire. So make sure that any variable resistor attached to the cooker is rated to equal or higher wattage than the heating device.


  • Guest
It won't be a variable resistor
« Reply #14 on: April 19, 2004, 09:25:00 AM »
How big do you think a variable resistor would have to be to dissipate all that heat? He's going to:

A: Fix/modify the thermostat
B: Get a variac
C: Use a lamp dimmer or other chopping device
D: Buy a new crock pot

If he can't find a crock pot for under 10 bucks at a thrift store, he isn't trying. I can bet every option is going to be more expensive and/or dangerous than D. How much do you think a variable resistor that can dissipate 500 to 1000 watts of power would cost?


  • Guest
celsius or farenheit?
« Reply #15 on: April 20, 2004, 12:02:00 AM »
i'm with popi....that sounds like farenheit....most cookers of any sort that i've come across have a minimum temp. below 100 do realise i'm accusing you of an act of get that....


  • Guest
« Reply #16 on: April 20, 2004, 04:13:00 PM »
Well im no so stupid that i confuse fareheit with celcius since celcius is the  default temperature unit here.
And so was deep friers starting @ 140C...

Still i managed to find one aftere visiting 7 stores... :P

So now i have what i need, thanks for the responses though!