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10/19/2021 6:22 AM
Welcome tarunk!

10/17/2021 12:40 PM
Ploni and nader fouad, Welcome!

10/15/2021 2:19 AM
merlot85, maycondelpiero and hoeltz, Welcome !

10/14/2021 10:06 AM
Thanks for the addition to the group. Seriously considering building a drum roaster along the lines of oldgrumpus's. Love the design and craftsmanship.

10/14/2021 4:00 AM
Morning, ar3mia ! and... coffee drink

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Selecting a heat source
Dan
Let's kick the tires on this new forum. With homeroaster's penchant for computerized control and profiling, how fast a heating system responds is very important when selecting a heat source. Did you know? When natural gas was first introduced in the US it was immediately adopted by commercial coffee roasters. Why? Because it was easier to control than the previous heat source, coke. Can you imagine trying to reduce the heat in a huge coke fire?

Here are the results of a test I did a few years ago. I selected four, commonly used heat sources for home roasters, electric (3 types) and gas. To perform the test I turned the heater on full blast, plotted the time it took for it to reach 400? when measured with a thermocouple located 4" above the heater, and then turned the heater off and plotted its cool-down. As you can see, gas is very fast with nichrome just a few seconds behind it.

claycritters.com/coffee/images/heater%20response%20time.jpg

Tubular = nichrome sheathed in steel tube, i.e. electric resistance range and hot water heater elements
Quartz = 500W halogen light
Nichrome = bare, coiled nichrome (I used my sample roaster setup)
Gas = 10,000 BTU natural gas stovetop burner

I hope this helps, Dan
1 pound electric sample roaster, 3 pound direct-flame roaster, both handmade; modified Mazzer Mini grinder, LaSpaziale Vivaldi II automatic espresso machine. When the electricity goes out I make vacpot coffee from beans ground on my Zassenhaus hand grinder, and heat the water with a teakettle on the gas range.
boar_d_laze
Just a few observations by way of keeping the convesation going:

So much depends on the individual roaster, it's almost impossible to make a meaningful generalization about heat sources. For instance given an equal amount of therms, a slow rotating, heavy, solid, cast-iron drum will respond slower to a heat source -- regardless of its nature -- than a light, perforated, stainless drum; and so will ET.

No matter what type of heat source you're using, as long as it's sufficiently powerful to raise BT by 15F/min it's more than sufficiently powerful. There are a lot of roasters which can do that. Anyway, good roasters tend to prefer a controlled rate of rise rather than a record-beating sprint. As a general rule (with lots of exceptions): Fast roasts are bad roasts.

A roaster which can't do 10F/min after drying, is adequate but limiting. (A) Trust me; (B) Don't ask.

Shedding heat depends more on other factors -- type of roaster, fan, damper control, type of drum in a drum roaster, etc., than it does on the nature of the heat source. Don't underestimate the importance of slowing, stopping, or even reversing ET increase at certain stages of roast development. Slowing the roast down is, perhaps, the most important tool of profiling.

With a few exceptions: If you want an agile, commercially made, commercial type, drum roaster, with a 2kg or greater capacity, you're looking at gas; but if you want a good, commercially made, home-roaster with a capacity of about 250g or less, you're looking at electricity; and there are several good roasters of each type in the 500g - 1kg class. By and large, the distinctions are economic (including product liability considerations), rather than roast quality.

[I'm not an expert by any means, just a guy who's recently bought two different roasters in the 500g - 1kg sample/small-commercial range, one electric and one gas, and did a lot of research on this topic.]

BDL
USRC 1lb Roaster, Chemex+Kone, Espro, Various FPs, Royal Siphon Vacuum, Yama Ice Drip Tower, Bunnzilla, La Cimbali M21 Casa, Ceado E92.
CookFoodGood
coffeeroastersclub

Quote

Dan wrote:

Let's kick the tires on this new forum. With homeroaster's penchant for computerized control and profiling, how fast a heating system responds is very important when selecting a heat source. Did you know? When natural gas was first introduced in the US it was immediately adopted by commercial coffee roasters. Why? Because it was easier to control than the previous heat source, coke. Can you imagine trying to reduce the heat in a huge coke fire?

Here are the results of a test I did a few years ago. I selected four, commonly used heat sources for home roasters, electric (3 types) and gas. To perform the test I turned the heater on full blast, plotted the time it took for it to reach 400? when measured with a thermocouple located 4" above the heater, and then turned the heater off and plotted its cool-down. As you can see, gas is very fast with nichrome just a few seconds behind it.

claycritters.com/coffee/images/heater%20response%20time.jpg

Tubular = nichrome sheathed in steel tube, i.e. electric resistance range and hot water heater elements
Quartz = 500W halogen light
Nichrome = bare, coiled nichrome (I used my sample roaster setup)
Gas = 10,000 BTU natural gas stovetop burner

I hope this helps, Dan


Dan, what was the wattage regarding the Nichrome wire? And if you were to choose between nichrome and gas, what would you choose and why?

Just picking your brain. Thanks.

coffee drink

Len
"If this is coffee, please bring me some tea but if this is tea, please bring me some coffee." ~Abraham Lincoln
Dan
Good points, BDL. As you've surmised, I was only looking at the heaters themselves, not the roasting system. I will say this, PIDs are more accurate with fast-acting systems, which means that they'll have a more difficult time of controlling a tubular heater when the profile calls for a reduction of heat because of their long cooling lag time, even with a decent ventilation fan. For me, my test shows that you can use any heat source you want, but if you want great control for you profile, forget tubular electric heaters, and oh, coke, too!
1 pound electric sample roaster, 3 pound direct-flame roaster, both handmade; modified Mazzer Mini grinder, LaSpaziale Vivaldi II automatic espresso machine. When the electricity goes out I make vacpot coffee from beans ground on my Zassenhaus hand grinder, and heat the water with a teakettle on the gas range.
boar_d_laze
Several smilies lend themselves to "coke" jokes. For instance:

Grin

cool

party

smoking and, worst of all

rockon

But, I'll refrain.

BDL
USRC 1lb Roaster, Chemex+Kone, Espro, Various FPs, Royal Siphon Vacuum, Yama Ice Drip Tower, Bunnzilla, La Cimbali M21 Casa, Ceado E92.
CookFoodGood
JackH
I don't think we should discount tubular heaters for small to medium roasters.

Tubular heater works very well for me and other turbo roasters. Much safer and If you don't have computers/pid's, you can learn the lags and how to deal with them with manual control.

I would think the gas fired solid drum designs would have lags too.
Edited by JackH on 08/19/2013 1:57 PM
---Jack

KKTO Roaster.
tamarian
Hard to tell from the graph x-axis resolution, but it looks like Nichrome takes twice as long as gas in terms of response time, but both are quire responsive compared to the other choices.

My PID experience with Nichrome is not that responsive (30-45 seconds delay), while Ian's PID with Nichrome is quire responsive (goes in straight lines). My (heavily and unnecessary insulated) heating and roast chamber are all heavy steel pipes, his is stainless steel and glass.

Another item of interest in selecting heating element is degradation over time. After 150+ roasts with 4kW Nichrome coil, it started to have a hard time with 1Kg batches, which were quite easy when new. I now do 1lb until gas conversion is complete.

Can someone confirm if they experienced this degradation with Nichrome?
Wa'il. 1 Kg PID'ed gas-fired fluid bed roaster, GS/3MPS, K10F
oldgearhead

Quote

tamarian wrote:

>snip<

>snip<
Another item of interest in selecting heating element is degradation over time. After 150+ roasts with 4kW Nichrome coil, it started to have a hard time with 1Kg batches, which were quite easy when new. I now do 1lb until gas conversion is complete.

Can someone confirm if they experienced this degradation with Nichrome?

I have around 175 roasts from my 120V, heat-reclaiming,one-pound, fluid-bed roaster. So your question prompted me to repeat a test from two years ago:
Beans = None
Blower @ 20 VDC
RC inlet restriction= 0.30 sq inch
RC outlet restriction= 0.40 sq inch
Heating element = 1550 watt HAS-043
Controller setting = 70% (1050 watts)
RC inlet temperature after T+ 6 minutes =
500?F (today, ambient = 87?F)
511?F (July 2011, ambient = 82?F)

Note: I do not roast beans with the 0.40 sq. inch outlet restriction,
because the bean movement control is much better at 2x the inlet restriction (0.637 sq. inch).

Not sure how valid this is because the t'couple hasn't been touched for two years either...
Edited by oldgearhead on 08/19/2013 1:25 PM
No oil on my beans...
oldgearhead
..also large gas trains require burner drilling every 2-3 years as the holes do close up during use..
No oil on my beans...
Dan
Tamarian, yes, relatively speaking nichrome is slower than gas, but practically speaking, they are both fast, or at least fast enough for our purposes, especially when you consider that neither the gas of electric heater will be turned completely. OGH says tubular can be used taking the lag time into account. That means that anything faster ought to be fantastic, right?

To asnwer your question, according to my nichrome supplier, nichrome oxidizes. It oxidizes when heated very hot. And then when it cools it flakes off the oxidation. Given enough such cycles, the wire gets smaller, resistance goes up, until finally if fuses out. The trick to nichrome longevity is two-fold. First, make sure it doesn't glow any brighter than orange (not yellow or white), secondly, makes sure the PID is cycling fast so it never really cools off below a dull red until you are finished with the roast.

Hope this helps, Dan
1 pound electric sample roaster, 3 pound direct-flame roaster, both handmade; modified Mazzer Mini grinder, LaSpaziale Vivaldi II automatic espresso machine. When the electricity goes out I make vacpot coffee from beans ground on my Zassenhaus hand grinder, and heat the water with a teakettle on the gas range.
greencardigan
The nichrome oxidizing and flaking issue is interesting. I'm glad I'm using the TC4 with phase angle control so my nichrome temps should be very steady. I've done about 50 roasts in my dual nichrome heatgun element roaster without any issues.

I still see the practicality of using gas versus nichrome being related to roaster size. Nichrome may be more practical for smaller fluid bed roasters but definitely gas for larger roasters.
oldgearhead
Okay we seem to have conflicting ideas about the aging nichrome wire heating elements. One is that it looses its heating ability as it gets older and the other says it sheds some mass, gets thinner, hotter, and then fails.

I have a master Appliance HAS-043 element with 175+, 445 gram roasts.
I use manual (%Output) not PID. My controller has a long (10 second) duty cycle so at the sub-500?F temperatures, I'm sure considerable 'cooling' of the element does occur.

I ran one test yesterday to see if the temperature had fallen off any, and that test was negative. So today I followed up with the watt-meter.

Primary Voltage = 120.2 VAC
Voltage Drop (element on) = 2.3 VAC
Current = 13.3 Amp
Watts = 1534

Summary:
1) After 175+ roasts and many more temperature test cycles the Master Appliance nichrome wire heating element in my roaster seem unaffected.
2) I think the shedding-mass theory is probably correct, but for home-roasting, don't worry about it...
No oil on my beans...
JackH
OGH,

I have one question about using nichrome wire or even whatever is used in poppers, heat guns etc.. Do you think there should be a "cooling shutdown", reducing the heat gradually with the fan on full to keep the element from failing?

I see this on my hot air SMD rework station. when turned off, it steps down the power in stages and keeps the fan on fully and then shuts off.

Jack
---Jack

KKTO Roaster.
oldgearhead
Jack,
with my set-up there is no analog control the heater is either on or off (bang/bang). The duty cycle is 10 seconds so at 70% it's on for 7 seconds and off for 3 seconds. However, there is always a cool down with air before shutoff.

Did something change when I wasn't looking on how we post photos on the forum? I don't see the old address bar..
No oil on my beans...
JackH

Quote

oldgearhead wrote:


Did something change when I wasn't looking on how we post photos on the forum? I don't see the old address bar..


I just fixed it. This forum category is new and one of the settings was not set for attachments. Should be OK now.

Jack
---Jack

KKTO Roaster.
oldgearhead

Quote

oldgearhead wrote:

>snip<
... However, there is always a cool down with air before shutoff.

>snip<

..and the logic won't allow the heater on without air on..

Thanks for fixing the photo post.
:
oldgearhead attached the following image:
861-1633_large_15.jpg

No oil on my beans...
Dan
These are nice heaters. I have one installed on a parts washer/dryer I build for work. It is used daily and is still heating after two years. On my machine, I installed a pressure switch so that the PLC doesn't turn on the heater until the blower produces pressure to indicate it is actually running.
1 pound electric sample roaster, 3 pound direct-flame roaster, both handmade; modified Mazzer Mini grinder, LaSpaziale Vivaldi II automatic espresso machine. When the electricity goes out I make vacpot coffee from beans ground on my Zassenhaus hand grinder, and heat the water with a teakettle on the gas range.
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