Green Coffee Buying Club
Coffee Discussion boards => Hardware & Equipment => Topic started by: CAGurl on March 31, 2010, 07:56:02 PM
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The Sunpentown Turbo Oven (SO-2000) has a heat dial with increments from 300 to 500.
Do you think that it puts out any more heat when set at 500 than when set at 300?
I've been assuming that it just puts out the same amount of heat and turns itself off when it hits the set point, but it would lend even more control to the roasting process if it actually worked differently at different settings.
Anyone know?
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The element is "on" or "off", nothing in between, and is under control of a cheap and sloppy thermostat. If you set it to 390f it might go to 410 before shutting off and not come back on until the temperature drops to 350f which maintains the average temperature to the set 390f. That's why most folk disable the thermostat and run it wide open or under control of a variac, for coffee bean roasting purpose that is. With a variac you are controlling the actual heat output and can dial in a particular rate of degree rise per minute.
Dan Brewer
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Thanks, Dan.
Can you recommend a particular variac, or are they a generic sort of a beast?
Susan
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Well, on the other hand.
I roasted three separate batches this afternoon, and I think that going in and simply disconnecting the heat control may be my next project.
I primed the roaster with both the UFO and the TO heaters set to high, and until the thermoprobe read 400.
Then I turned off the bottom heater and set the TO heater to 354. The thermoprobe indicated a temp drop down to 235 and then started back up; the heater light never went off while the roast coasted up to FC in 7 minutes and ended about 3-4 minutes later, when the thermoprobe read about 419.
But, if I just set the dial to 500 and let her rip but lift the handle periodically, it would accomplish the same thing as disconnecting the thermostat, wouldn't it????
Hmmm....
Maybe I'll try that tomorrow.
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I put mine one all the way and lift the handle to control the roast... I actually have the heater run through a PID controlled relay bu for the most part I am using the PID for the temp and raising/lowering the handle to control the speed of the heat rise... then again I seperated the heat rom the fan so my fan is on all the time and my heat is only thing the PID and handle effect..
(hope that is not too cornfusing :icon_scratch:
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I put mine one all the way and lift the handle to control the roast... I actually have the heater run through a PID controlled relay bu for the most part I am using the PID for the temp and raising/lowering the handle to control the speed of the heat rise... then again I seperated the heat rom the fan so my fan is on all the time and my heat is only thing the PID and handle effect..
(hope that is not too cornfusing :icon_scratch:
Actually that was enlightening, because I hadn't actually considered the issue of the fan at all.
Thanks.
Does anyone have a diagram of the interior wiring of one of these Turbo Ovens?
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Thanks, Dan.
Can you recommend a particular variac, or are they a generic sort of a beast?
Susan
Sorry, i can't. I've had a huge one for years that is used on vintage stereo equipment. One of our to/ufos has the thermostat strapped out and is run with no variac. The GF likes to use it and manages a decent profile by raising the to at the first sign of FC for about 30 seconds.
Dan Brewer
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I guess in an ideal world, leaving the fan powered constantly and running the heating element through a variac would be groovy.
If you know your thermostat tho', and what sort of inertia/momentum you have with your batch sizes, a stock oven works pretty good.
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Well, looks like I'm going to play with the "stock oven" for a while and see if I can master my roasts with it.
Partly because I couldn't get all the screws off to get the oven apart :-)))))
Partly because I don't even have a variac.....:-(((((
Partly because it seems like it must be manageable with a bit more work than I have put into this so far"-))):-(((
AND, partly, because ..... eventually there will be a Milowidget....:-)))))
Susan
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Susan,
Have you now abandoned the "Gompas" handle?
:)
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Susan,
Have you now abandoned the "Gompas" handle?
:)
Oh yeah, probably back in December...
Susan
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Susan,
Have you now abandoned the "Gompas" handle?
:)
Oh yeah, probably back in December...
Susan
I see. You gonna keep this one for a while?
???
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Has anyone here gone into this particular TO and messed with its wiring?
I emailed Sunpentown but they "don't have" a wiring diagram (right.....:-(((()
but I'm wondering if my approach of going in through the bottom (fan) is the right way to tackle opening her up.
Susan
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Has anyone here gone into this particular TO and messed with its wiring?
I emailed Sunpentown but they "don't have" a wiring diagram (right.....:-(((()
but I'm wondering if my approach of going in through the bottom (fan) is the right way to tackle opening her up.
Susan
I doubt that the Sunpentown is much different from the Galloping Gourmet/Decosonic/Whatever. There really aren't that many wires in there. If you open it up, you'll see what I mean. The power cord branches off, and from there you just follow to the T-stat, or the timer, or the lights, and you'll figure out what you need to figure out.
You've made it thus far in life; I have every confidence that you can conquer this one too.
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I'm wondering if my approach of going in through the bottom (fan) is the right way to tackle opening her up.
Susan
That's the correct way but what mods have you decided to do?
Dan Brewer
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I'm wondering if my approach of going in through the bottom (fan) is the right way to tackle opening her up.
Susan
That's the correct way but what mods have you decided to do?
Dan Brewer
Oh, that.....hmmmm....
I'm not altogether sure yet, but I want to see if I can get into that cavity to look around before I start sourcing parts.
My primary ideas (none is original) are to disconnect the thermostat, make the fan run independently of the heater, and wire in an infinite switch to control the heat ramp up.
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I'm wondering if my approach of going in through the bottom (fan) is the right way to tackle opening her up.
Susan
That's the correct way but what mods have you decided to do?
Dan Brewer
Oh, that.....hmmmm....
I'm not altogether sure yet, but I want to see if I can get into that cavity to look around before I start sourcing parts.
My primary ideas (none is original) are to disconnect the thermostat, make the fan run independently of the heater, and wire in an infinite switch to control the heat ramp up.
Wondering what you mean by that.
Like I hinted at earlier, the split-wire/variac setup would be neat. But if you're going to be close to the roaster and can bear the thought of adjusting the temp dial from time to time, none of that is necessary and the stock thermostat will serve you just fine.
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the first thing I would test is if the fan turns off when you lift the handle or if only the heat turns off when you lift the handle.. if only the heat you don't need to split the heat and fan unless you are going to PID or milowidget it.. and for the short times I turn mine off with the handle the fan could turn off and it would probably not make a difference... I just turn the heat knob all the way up and watch the temps on a separate thermometer...
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An "infinite switch" is what is behind the knob on an electric switch and controls the power to the coil and so controls the heat.
The fan is currently controlled by the handle along with the heat. AND, since eventually I'm sure I would want to Milowidget the thing, now is as good a time as any to split those two.
And, although I do intend to practice more with this oven without modification, what I notice so far is that the minute the heat gets turned "off", the temperature drops. It doesn't hold steady for any time at all, and that doesn't seem like a good thing for the roast process.
Susan
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An "infinite switch" is what is behind the knob on an electric switch and controls the power to the coil and so controls the heat.
The fan is currently controlled by the handle along with the heat. AND, since eventually I'm sure I would want to Milowidget the thing, now is as good a time as any to split those two.
And, although I do intend to practice more with this oven without modification, what I notice so far is that the minute the heat gets turned "off", the temperature drops. It doesn't hold steady for any time at all, and that doesn't seem like a good thing for the roast process.
Susan
Hmm.. if yours drops temp as soon as you lift the handle than your fan is probably turning off... mine actually climbs temp a little when I lift the handle.. (probably the fan speeds up because the heater is not drawing so much power) if you decide to crack it open it will be pretty clear what wires go to the fan.. I put those wires on a new power chord and closed it up...
I pre-heat to 400 then dump in my beans... maybe burp the top if the temp is getting to 300 before 3 minutes then at 350 deg I will lift the handle for 20 to 30 sec. / then 20 to 30 sec. on... etc to slow down for caramel zone slowing down for 1st crack is trickier.. depends on the bean and were I want the roast to go.. but the on/off is more like 15 on and 10 off not 20 or 30 sec.. you have to watch the rate of temp climb.. and turn the heat back on before it stops climbing or your temp may drop before it climbs again.. (on a really good day it can become almost trance like, but that is not always a good thing)
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And, although I do intend to practice more with this oven without modification, what I notice so far is that the minute the heat gets turned "off", the temperature drops. It doesn't hold steady for any time at all, and that doesn't seem like a good thing for the roast process.
Susan
That does not concur with my experience whatsoever. You may be using very small batches, but even at that, there should be some 'momentum' in the bean mass. With 8oz. (or my usual 14oz.), if I run it up to say 350 and turn the heat off, it will continue to climb to about 365, all on its own. That's why, if I want to hold it in the mid 350's for caramelization, I shut it down in the low 340's. Maybe you are leaking lots of air, letting too much heat out.
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My experience is the same as Peter's. I wonder perhaps if your temperature probe isn't down in the bean mass enough?
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My experience is the same as Peter's. I wonder perhaps if your temperature probe isn't down in the bean mass enough?
I was going to ask Susan that, but forgot. Please tell us how you are monitoring your temps.
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Given your questions and answers, I will try a few more roasts later today and see if I can answer your (and my) questions better.
I don't think I'm losing heat because I have the foil wrapped around the roaster between the UFO and the aluminum spacer.
Here are pictures of my three roasts from day before yesterday and also of the probe set-up. I see that the probe might be problematic, but I doubt if I can get it any more "in the bean mass" without increasing the bean mass to a higher quantity of beans that I want/need.....Maybe what I need is something to corral the beans into a narrower radius....
Susan
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Susan ... you should check out how Peter has changed the wires turning the beans. Quite a clever idea. Follow the SC/TO thread.
:)
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For the record, with the supentown analog TO the fan and heat turn off when the handle is lifted but the fan stays on when you turn off the heat via the thermostat. I thought about doing some mods with the heat and fan using my variac but I find that I can set the thermostat so that often as first crack is in full swing the heat turns off for a short while. My thermocoupler will note little to no decrease in temp if first crack is cracking away. In fact at this point temps are more often increasing as the exothermic reaction is taking place. This gives the beans a little time to even out at this stage before moving forward. I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass. As a reference I start hearing FC around 270-280*f.
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For the record, with the supentown analog TO the fan and heat turn off when the handle is lifted but the fan stays on when you turn off the heat via the thermostat. I thought about doing some mods with the heat and fan using my variac but I find that I can set the thermostat so that often as first crack is in full swing the heat turns off for a short while. My thermocoupler will note little to no decrease in temp if first crack is cracking away. In fact at this point temps are more often increasing as the exothermic reaction is taking place. This gives the beans a little time to even out at this stage before moving forward. I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass. As a reference I start hearing FC around 270-280*f.
WOW?!?! my probe is basically the same as peter's and I am at 385F to 405F for 1st crack... but I suppose the numbers are not as important as the roast curve you use the numbers to duplicate...
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I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass. As a reference I start hearing FC around 270-280*f.
Mine also. Using a 20ga K-type thermocouple & Fluke.
Dan Brewer
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For the record, with the supentown analog TO the fan and heat turn off when the handle is lifted but the fan stays on when you turn off the heat via the thermostat. I thought about doing some mods with the heat and fan using my variac but I find that I can set the thermostat so that often as first crack is in full swing the heat turns off for a short while. My thermocoupler will note little to no decrease in temp if first crack is cracking away. In fact at this point temps are more often increasing as the exothermic reaction is taking place. This gives the beans a little time to even out at this stage before moving forward. I should mention that my TC probe comes up through the SC pan and sits just off the pan under the bean mass. As a reference I start hearing FC around 270-280*f.
WOW?!?! my probe is basically the same as peter's and I am at 385F to 405F for 1st crack... but I suppose the numbers are not as important as the roast curve you use the numbers to duplicate...
I'm soooooo glad you said that, because my temp reading is usually around 410 when I am hearing FC. But, my probe (as you can see in the picture previously in this thread) is all the way to the center of the UFO and probably just at the top of the bean mass. Probe placement obviously matters, but that's a huge difference.....
Susan