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Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Fluidbed Roaster

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Rolling your own heat element (and Max on a dedicated 120V 20A circuit)?
Cheekius Geekus	#1 Posted on 08/18/2016 10:38 AM
Newbie Posts: 10 Joined: March 30, 2015	Greetings all, I started a thread on my plans/design goals for a 1kg Fluid Bed roaster http://forum.home...ad_id=5063 (and have gotten some great info/feedback there). One of the things that came up was how much green you could roast on how much wattage of heat gun elements (and how big of a circuit you would need). I was exercising my Google-Fu and tripped across this: Winding a Kanthal A1 Element http://dcknives.b...or-an.html I find it pretty fascinating because he really walks you through the calculations. His "Design notes" (at the end) result is: 3 heating elements, wired in parallel that gives him 2215 Watts that he can run on a single dedicated 120V 20 amp circuit. His target temp is 1100F. He's making an oven, not a roaster, but still... Quote In some designs it makes sense to have several elements in parallel. One helpful formula is the parallel resistor formula. Rtotal = 1/(1/R1)+(1/R2)+(1/R3)... For my 120 Volt oven, I made three elements. I measured each one with the ohmmeter and recorded the values. R1 = 19.6 R2 = 19.4 R3 = 19.5 Plugging in the numbers I got: 1/(1/19.6)+(1/19.4)+(1/19.5) = 6.499 Ohms 120 Volts / 6.499 Ohms = 18.46 Amperes 120 Volts * 18.46 Amperes = 2215 Watts This works well for me on a dedicated 120V 20A circuit. I'm guessing that for our (FB Roaster) purposes one would need to wrap them around a metal core like this: https://www.hejet...ment-kits/ If one ran their blower off of a different 120V circuit, would this not be a practical way of generating the maximum amount of heat + lift and yet avoiding going into 210V territory? Side note: I see that they make inexpensive Heating Coil Winding tools like: https://www.amazo...01CFGQOMY/ Thoughts anyone?


seedlings	#2 Posted on 08/18/2016 12:12 PM
1 1/2 Pounder Posts: 4226 Joined: June 27, 2007	Kanthanal and NiChrome are conductive, so be sure to wind them on insulator material standoffs (mica, ceramic, etc), and not in contact with metal. I tried this twice. My suggestion is to get coiled wire, not straight, probably around 19-gauge. I tried straight wire without success. It really is much simpler and repeatable to buy one pre-made (because any element will eventually fail). Heat hun: https://www.maste...s/has-043k Dryer: http://www.partse...urceCode=6 CHAD Roaster: CoffeeAir II 2# DIY air roaster Grinder: Vintage Grindmaster 500 Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover


KramE	#3 Posted on 09/10/2016 1:10 PM
1/4 Pounder Posts: 53 Joined: March 29, 2015	Have you made any progress in this regard? I'm interested to see what you decide.


oldgearhead	#4 Posted on 09/12/2016 8:50 AM
1 1/2 Pounder Posts: 1128 Joined: February 10, 2011	Electric heat depends on CFM. My heat element is rated at 1000 degrees F, but that is at 23 CFM. It takes 60 CFM for me to lift 500 grams for green beans so the temperature drops as the CMF is increased. However, the beans get lighter as they are roasting so I'm down to about 40 CFM at first crack and 520 DF. My heat gun element has lived for 5+ years doing at least 2-3 roasts of 1000 grams per week.,.My advice get commercial heat gun elements..You will need 200 volts. No oil on my beans...

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