Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Turbo Oven Roasters
Who is here? 1 guest(s)
Page 1 of 2: 12
 Print Thread
Made another turbo roaster......
Mbb
Top  #21 Print Post
Posted on 05/26/2020 9:20 PM

Quote

mtbizzle wrote:

Quote

Mbb wrote:

Its tstat works to keep it limited. Set on max 400, it held 410 when i tested....

Hmmmm....do the turbo really put out 1300w then? Id have to say....maybe no.
...

Seriously, this works well


Sorry to jump back... three months, and elbow in w/ my own question. Mbb what you said in your original post caught my eye, not sure I am understanding you right, but maybe it'll help me a bit...

I found a nice deal on a used Flavorwave AX-797DH. It's a 1300w TO, has heat settings up to 500F and three fan settings.

I had read from some veteran turbo oven folks, most TOs are 1200-1400w, just get highest wattage you can. And have found one or two people using this one. Was a good price so I picked it up.

Did a quick test, with a thermocouple in the original glass oven, no beans or anything inside. Set to 500f and just measured temps.

Well, to my dismay... it began cycling off/on starting at 360f on my tcouple. Never really got hotter than 390-394f on my tcouple... so much for 500f..????

But Mbb... you seemed to say something about 400-410f on yours?

Hoping somehow what I saw w/ my test is normal, but it seems to me this TO won't roast coffee. Shock


Turbo ovens generally have a curve
They heat up, as they heat the temp they cycle at increases...eventually its close to the setting, that may take 5-10 min. This built in "curve" helps them work. So yes, initially they start cycling at a lower much lower temperature than You're expecting. The bimetallic thermostat switch does not work correctly until it reaches operating temperature its designed for.

If you only got 400, you may be trying to heat too large a dpace with too much surface area losing heat, or you got bad oven. Or you simply didn't wait long enough for the temperature to line out.

Ive never set one that hot without closely monitoring air temp. I dont like to see ET over 460F or so. At 500.....it ruins coffee if it reaches that....can make it very bitter. Undrinkably bitter. Better to use lower temp setting as a safegard and smaller charge of coffee imo. At least for learning.

The bad....everytime that tstat cycles, your bean surface temp cycles too....even with a diode kerping power at 50%.

Imo... You're better off bypassing all that and just running the heating element on a $20 router speed control, at a non cycling power you have cobtrol over. Once you learn to control it, it'll make better coffee. The downside, you have to learn how to control it through trial and error. letting the built-in thermostat control the curve is not a bad way to get your feet on the ground with it though
Edited by Mbb on 05/26/2020 9:34 PM
 
mtbizzle
Top  #22 Print Post
Posted on 05/26/2020 9:32 PM

Quote

Mbb wrote:
So yes, initially they start cycling at a lower much lower temperature than You're expecting.



OK, that's good to hear.

Quote


Ive never set one that hot without closely monitoring air temp. I dont like to see ET over 460F or so. At 500.....it ruins coffee if it reaches that....can make it very bitter... Better to use lower temp setting and smaller charge of coffee imo.


Makes sense. I was just testing to see if this thing would get hot enough to use... No sense in trying to turn this TO into a roaster, if it won't get hot enough. So I essentially set it on max to see where it would go.

Quote

If you only got 400, you may be trying to heat too large a space with too much surface area losing heat, or you got bad oven.

Yeah, on my tcouple, it was not reaching 400f. This was in the glass oven that the TO comes with, it was empty. Do you think the fact that it was empty would be enough to explain that temperature shortfall? I let her work for something like 15 min, was not getting tcouple readings above 395f. Kinda a bummer as I assumed that meant it was a dud.
Roast: Kaldi wide, SR800 + projects
Grind: Lab sweet, Bentwood, giota w/ MP burrs, Commandante
Pull: Decent, La Pavoni, Elektra Microcasa a Leva, Faemina anno 60, Kim Express
 
Mbb
Top  #23 Print Post
Posted on 05/26/2020 9:38 PM

Quote

mtbizzle wrote:

Quote

Mbb wrote:
So yes, initially they start cycling at a lower much lower temperature than You're expecting.



OK, that's good to hear.

Quote


Ive never set one that hot without closely monitoring air temp. I dont like to see ET over 460F or so. At 500.....it ruins coffee if it reaches that....can make it very bitter... Better to use lower temp setting and smaller charge of coffee imo.


Makes sense. I was just testing to see if this thing would get hot enough to use... No sense in trying to turn this TO into a roaster, if it won't get hot enough. So I essentially set it on max to see where it would go.

Quote

If you only got 400, you may be trying to heat too large a space with too much surface area losing heat, or you got bad oven.

Yeah, on my tcouple, it was not reaching 400f. This was in the glass oven that the TO comes with, it was empty. Do you think the fact that it was empty would be enough to explain that temperature shortfall? I let her work for something like 15 min, was not getting tcouple readings above 395f. Kinda a bummer as I assumed that meant it was a dud.


I never tried the glass so I can't say.
But on a tiny stir crazy base with about 3 in of room between the heating element shield and the bottom and also insulated......... Never had a problem getting the temperature up with mine.

Another possibility...the tstat is just fubar. A resistance heating element is pretty simple .... Usually works, or it doesn't. Just apply voltage A poor wiring connection could introduce enough resistance to limit heat too.

On the roaster im playing with here....the turbo starts at 90%, but im down to 45% power by 1C......and thats bringing 16oz to 1C in 8 min. The base is running only constant low 15% power. ET might get to 430 ish
Edited by Mbb on 05/26/2020 9:53 PM
 
Mbb
Top  #24 Print Post
Posted on 05/26/2020 10:00 PM
Here's an image of what the cycling ET curve built into the turbo roaster looks like as it heats up....and this one had a diode in parallel with the thermostat so that it only dropped to 50% power instead of zero when the thermostat switched off. Without the diode there's much more dramatic temperature swings. Theres dramatic smoothing on the BT curve because it cycles when the ET cycles

You can see it began cycling at 360, for a set point that was 430 ish probably

images2.imgbox.com/a9/f4/UKv9K4ZK_o.jpg
Edited by Mbb on 05/26/2020 10:07 PM
 
Gullygossner
Top  #25 Print Post
Posted on 06/25/2020 1:32 PM

Quote

Mbb wrote:

Finding the forced airflow..... improved taste by eliminating smoke inside.

Also helps control flick...better than heat control
Cooling....is better than not heating

Not there yet, but getting better at it.
Goes kind of slow when you got to drink a pound of coffee every time you roast

autocharge didn't pick up on this roast for some reason and I forgot to click it until didn't see ror curve

I'm not using the adjustable vent opening so I'll probably just make a discharge tube there that directs the chaff into a catch container

images2.imgbox.com/a1/b8/lkep6Ad9_o.jpg


You mention not using the adjustable vent opening, are you just using the external blower to force any smoke/heat out of the setup around fc?
 
Mbb
Top  #26 Print Post
Posted on 06/28/2020 8:30 AM

Quote

Gullygossner wrote:

Quote

Mbb wrote:

Finding the forced airflow..... improved taste by eliminating smoke inside.

Also helps control flick...better than heat control
Cooling....is better than not heating

Not there yet, but getting better at it.
Goes kind of slow when you got to drink a pound of coffee every time you roast

autocharge didn't pick up on this roast for some reason and I forgot to click it until didn't see ror curve

I'm not using the adjustable vent opening so I'll probably just make a discharge tube there that directs the chaff into a catch container

images2.imgbox.com/a1/b8/lkep6Ad9_o.jpg


You mention not using the adjustable vent opening, are you just using the external blower to force any smoke/heat out of the setup around fc?



I use air on low 5% the whole time most of the time....it reduces variation in BT. It does remove heat though. About 1 min into 1C I kick it to 20%.
Edited by Mbb on 06/28/2020 8:39 AM
 
renatoa
Top  #27 Print Post
Posted on 06/28/2020 9:03 AM
5/20% of what ? What is the power/flow of the blower ?

I am using a 20W 140 m^3/hour (82 cfm) 4" hidroponic blower at 100% all the time, the influence on air temperature is about 4 C degrees cooling, but I have enough margin to afford this.
The airflow is just right for smoke and 80% of chaff, but not enough for cooling or total chaff removal, the turbo vortex is more powerful than the outside suction, there is still remaining chaff under the perforated bottom of the SS roasting insert.
The opening in oven wall is a for 28 mm diameter pipe, close to yours.
The difference is that my blower sucks air from cyclone, and cyclone from TO, your seems to push air into TO, but no clear where the chaff is going...
Edited by renatoa on 06/28/2020 9:11 AM
 
Page 1 of 2: 12
Jump to Forum: