Still trying to figure out airflow in the Hottop

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espressojr
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#1: Post by espressojr »

A recent discussion that included the use of the fan in the Hottop pushed me to post this question as it is something I have been wrestling with for the last month since I got my Hottop.

Ethiopia DP Gr. 1 Yirga Cheffe Aricha-Current crop at Sweet Maria's

I just moved from an SCTO roaster to a Hottop B with a TC4C setup. I was happy with my previous setup and got good results but wanted to try something different.... Boy did I get what I asked for ;-)

I've only got about 14 roasts under my belt with the hottop and I'm slowly learning how to control my roaster (steady as she goes captain!) but one concept that still evades me is the use of airflow (via the fan). I've read as many posts as I could and it seems there is no clear consensus on the use of airflow. I know that there are a lot of people working with different roasters so I would ask that you please keep this discussion limited to the hottop.

Based on what I have read, this is my general approach to using airflow:
-During the last minute or so of drying (around 270F), I turn on the fan to 25% to remove humidity.
-I keep the fan at 25% through development until right before FC (around 360F) when I turn it up to 80% to remove smoke. I'm still not sure how the fans works in relationship to temp as I usually turn down the heat at this point to 50%.
That's it...

Right now I am not 100% satisfied with my results. There seems to be some lack of clarity that I had with the SCTO. I wouldn't call it baked or smokey - it's hard to put my finger on it. The roasts have improved as have my profiles (they are smoother without so many small ups and downs). I would be delighted if anyone would be willing to try some of my coffee and let me know where they think the problem lies.

In general, I am trying to emulate what others have done in the "roast and learn" posts, with (depending on the bean) a 5-6 min drying phase, 3-4 mins to FC, and then 2-3 mins development. I still haven't mastered the slow rise after FC as mine continues to rise quicker than I would like which means I am playing with the temp/fan more than I should to slow things down more.

I keep my charge weight consistent at 230g and charge temp at about 350BT (as registered on my machine- for some reason the BT is always 50-60 lower than ET while it is warming up, is probe placement that different?) which gets me to 300F BT in about 5 ½ mins. If I want a slower drying phase, I drop at 320 and if I want a faster one, I drop at 380. I am feeling pretty good about the drying phase 

I'll try to post one of my recent profile charts when i get home.
thanks in advance
jim

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cimarronEric
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#2: Post by cimarronEric »

espressojr wrote: I'm still not sure how the fans works in relationship to temp
Fan is drawing cool air into the drum, countering the effect of the heat element. Higher fan=lower ET. If you're having trouble with stretching development, try more fan.
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espressojr (original poster)
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#3: Post by espressojr (original poster) »

thanks eric... on my first few roasts I was playing with the fan and really didn't notice that much change in the BT or BT RoR. Doh! I should have been paying attention to how it affects the ET (which in turn will affect the BT). one of those lightbulb moments. :!:

fu11c17y
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#4: Post by fu11c17y »

hello fellow hottop user.... 8)
espressojr wrote:as registered on my machine- for some reason the BT is always 50-60 lower than ET while it is warming up, is probe placement that different?
That's cool you observe that as well. I was asking myself too, and have gotten so used to it that I've kinda forgotten about it. One would think the two probes should read the same before the charge... right?? :?
espressojr wrote:playing with the fan and really didn't notice that much change in the BT or BT RoR
That's what I notice as well. I also remember that I noticed a slight ET rise when I turned up the fan, but my memory has fainted and I did not take precise notes on that effect. I think it may have to do with how the airflow is drawn through the few small orifices in the hottop drum chamber to the back of the roaster where the fan is. If the airflow goes through near where the heating element is, and if the ET probe is closed to where the air goes through to the back, then I suspect that could cause what we are observing. But I suppose the airflow is hot enough yet not too hot, that it does not change the BT in any meaningful way. On airflow dynamics, one can only conjecture, since airflow is not easy to measure... :?:

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JohnB.
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#5: Post by JohnB. »

First thing you should do is replace the rear filter element with a stainless computer fan filter so you have some actual airflow. My Hottop is far from stock so what I do isn't going to help you much but I can easily stretch the 1C to finish out 3-5 minutes if I chose. Read through some of the Hottop Mods threads & get some ideas on how to improve your HT but start with the airflow.
LMWDP 267

espressojr (original poster)
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#6: Post by espressojr (original poster) »

sorry- out of town for a couple of days...

I have replaced the rear filter with a scotch-brite type of pad that I clean after every few roasts so I think I have maximized the airflow possibility.

My main question boils down to the role of air flow in roasting on the Hottop. Is it solely to help regulate temperature?

or

Does the use of the fan influence the flavor profile by removing moisture during drying or smoke removal during development?

any insights would be appreciated....
jim

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Randy G.
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#7: Post by Randy G. »

One of the things I heard early on in these discussions was that since beans are giving off gases and moisture, the presence of them around the beans, within reason, has little effect. My personal use has been to run the fan just enough to keep the smoke from emanating from the various orifices other than the rear fan and to use it when I screw up and get a too fast ROR, particularly near the end of the roast.

If you have ant telemetry (or even just the HT display), run an empty roast (no beans) with the heating element at around 30% and use the fan to stabilize the temperature. With the TC4C+HTC setup it gives you good control over the fan. Now try the same thing at around 70% heat and see what control you have over heat with the fan.

It will give you a good feel for the machine. Sure, it behaves very differently with the beans in there, but I think in the long run you are worrying about more than you have to.

TIP: I had my B-2K apart for some photos I needed and so am doing a few minor repairs. I took a number of the grimy parts and put them in a five gallon bucket of cold water with two scoops of Oxy-Clean. Some had baked-on crud (like the inside of the outer shell and the axle shaft of the drum) that had baked on crud I have not been able to get off for quite some time. How long? This machine started out as a B then was a B-K and later updated to a B-2K. It has been disassembled probably a dozen times over the years. I had to do two soaks to renew the oxyclean in the bucket. The drum looks new now and the total soak time was only about three hours.
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johnny4lsu
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#8: Post by johnny4lsu »

If you have ant telemetry (or even just the HT display), run an empty roast (no beans) with the heating element at around 30% and use the fan to stabilize the temperature. With the TC4C+HTC setup it gives you good control over the fan. Now try the same thing at around 70% heat and see what control you have over heat with the fan.
This is really good advice...I'm gonna try this out

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JohnB.
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#9: Post by JohnB. »

How you use the fan has a lot to do with how you have your Hottop set up. I run a higher output heating element, have the front filter blocked off, stainless mesh rear filter as well as a few other mods. My older HT-B started out as a P & has been upgraded to B-2 specs except for the more recent style temp sensor.

I use the fan to pull moisture out towards the end of the drying phase, maintain an even heat flow through the drum during the ramp to 1C, Boost the heat flow when needed & to reduce the heat in the drum during the stretch after 1C starts. At one speed or another the fan is on from late in the drying phase to the end of the roast so it is also helping to pull any smoke out of the roasting chamber.

I'll second Randy's OxyClean recommendation. I keep a tub of the Oxi Free around to clean my cloth syphon filters & started using it a couple years ago to clean the HT filter screen, chute cover & other parts. Works as well as a hot Cafiza solution.
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espressojr (original poster)
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#10: Post by espressojr (original poster) »

thanks Randy and John. Great insights that I will put into practice... just helps with the learning curve.
jim

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