Hot Huky ... sometimes

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Rickpatbrown

#1: Post by Rickpatbrown »

I've recently encountered a problem were my Huky gets really excited some roasting sessions. It's happened two or three times now, with normal, calm behavior in between.

Basically the problem is that the Huky gets super hot. The roasts really fly. The gas gauge says the normal things (4.5, 3.0, 2.0, 1.0, 0.5, 0.1 ... etc), but obviously the drum is way hotter. My ROR spikes super high and the roast finishes in like 6 or 7 minutes instead of 8 or 9. It will behave this way the entire 6 roast session.

Then, next month, it's back to normal. 40F/minute ROR peak ... 9 minute roasts.

Here's an example


The background roast is the same green. I've roasted it a million times since December. The charge is the same. Gas is mostly the same I've recently lowered my pre first crack gas increase to 6" on the Magnehelic vs 7". BTW, I use a Magnehelic to measure fan pressure ... so I am pretty consistent. I obvioulsy adjusted my approach when I realize it's acting crazy. You can see how much I attenuate the gas, but still roast super fast.

Another weird point is the MET probe (Manifold Exhaust Temp). This actually shows lower readings for the hot/fast roast.

I'm always roasting the Gesha at the end, so the roaster is warmed up for both.

Yesterday, I roasted the Gesha again and had a very normal session, so the "cool" setting work just fine.

The end, you see a jump in gas setting to 4.0. This is were I switch the Huky infrared stove from 2 flame setting to 1. This directs the flame to just the center of the burner, but causes a big jump in gas pressure (0.1 Kpa all of a sudden going through a small area makes a higher pressure).

Anyone have any ideas what could cause this? And how do I fix it.

I'm using a variac to control fan. I have an adjustable regulator at the propane tank, but I never adjust it. Plus, the stock Huky gauge says that pressure is the same (at least right after charge. Later, I use lower setting than background to try to salvage my beans)
-The bean mass is definitely the same. I have to shake the mason jar to get the roasted beans to just fit. I'd notice if it was off by even 10 grams.
-Is the stove acting up?
-I roast in garage, so ambient temps are wildly different. But last two sessions have been summer time weather.
-Is there a blockage?

Marcelnl
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#2: Post by Marcelnl »

weird....I have replaced the stock burner a while ago, the ceramic was worn with pieces rattling around inside and it would not keep flame very well.
new bowl from Mr Li arrived in two weeks and all was good again.
I did not see what you describe though, so your problem may also be a blockage on the air side (chaff?)
LMWDP #483

Rickpatbrown (original poster)

#3: Post by Rickpatbrown (original poster) » replying to Marcelnl »

It's possible that a blockage at the exhaust manifold "elbow" (right before the Magnehlic air hose tap) could cause the Magnehlic reading to be correct, but airflow in the roaster to be super low.

But it's hard to imagine that causes accelerated roasting. I'd think it would be the opposite.

Another question might be, what settings allow people to get to dry end in 3:30 minutes. Normally, I set my roaster to high gas and only get dry at 4:30 minutes.

Marcelnl
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#4: Post by Marcelnl »

I do not soak, and power up to max, which is 4.5-4.7KPa, and that gets me to dry end around 3.40-3.50 if I want to but that is with a perforated drum....I'm sure that does not translate to a fixed drum.
LMWDP #483

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chuckcoffee

#5: Post by chuckcoffee »

Rickpatbrown
I use a Magnehelic to measure fan pressure ... so I am pretty consistent.
Can you post a picture of your setup. Where are you measuring the fan air pressure?

I roast outside and blockages in the winter months happen due to condensation which can wet the chaff. I have the t setup. The 2nd gate valve (#2) is prone to blockages along with the initial exhaust(#1)as it bends. I monitor air pressure with the Phidget 1136. If i see pressure drop (about a 15% drop) I will take apart these 2 locations and clean out with a wood skewer. So I remove the t fitting and the long pipe that is down stream. I have found over time that if I rotate the 2nd gate valve during the roast maillard zone it reduces the tendency of blockages.

When I have a blockage temps become erratic and can become very hot. So I would recommend checking during the roast if it is occurring. I use oven hot mitts and a small flashlight.


Rickpatbrown (original poster)

#6: Post by Rickpatbrown (original poster) »

chuckcoffee wrote:Rickpatbrown



Can you post a picture of your setup. Where are you measuring the fan air pressure?
... blockages in the winter months happen due to condensation which can wet the chaff. I have the t setup. The 2nd gate valve (#2) is prone to blockages along with the initial exhaust(#1)as it bends...

When I have a blockage temps become erratic and can become very hot.
I tapped a barb fitting into the initial exhaust bend (#1 in your picture). Yhe small diameter black silicon hose connect this fitting to the Magnehlic. If a blockage occured anywhere except the 1" in front of this, I would see it in the Magnehelic. The Mag. had proven to be exceptionally accurate.


Close-ups of Hukies are always tough because they are so shiny, lol.

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chuckcoffee

#7: Post by chuckcoffee »

Nice, I like that setup with the Magnehelic

Really only way to tell is to check the potential blockage points with a flashlight on future roasts. Any feature on the inside of the tube can be a starting point for blockages. I sometimes get minor ones where my 1/8" copper tube comes through for the phidget.

Just asking but do you remove chaff after each roast?

Btw getting a cyclone setup if you are doing multiple roasts in a session is a great improvement and one less thing to worry about.

Could you send some details on the Magnehelic model and where to purchase. What was involved in setting this up?

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Chert

#8: Post by Chert »

I don't know how the variac exactly works, but if your input voltage on a given day were a bit higher for some reason, maybe that could increase your fan at the same variac setting to explain more convection compared to lower voltage input. Just a thought on your dilemma.
LMWDP #198

Marcelnl
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#9: Post by Marcelnl »

provided the variac is doing 110- 110 duty the line voltage variations are small...10% more input voltage is going to be proportionally less if the fan is set to a lower voltage.
All a Variac does is lowering an input voltage over an adjustable range.
LMWDP #483

Rickpatbrown (original poster)

#10: Post by Rickpatbrown (original poster) »

Chert wrote:I don't know how the variac exactly works, but if your input voltage on a given day were a bit higher for some reason, maybe that could increase your fan at the same variac setting to explain more convection compared to lower voltage input. Just a thought on your dilemma.
Yes. The variac actually needs to be set to very different settings, depending in how much chaff is collected in the Huky cake sieve pan. The chaff makes it harder to pull air through, so I need to turn it up each successive roast. That's where the Magnehlic comes in handy. I can just turn the fan up (higher voltage), until the pressure is exactly right. The Magnehelic us very sensitive. I dump the chaff every 3 batches, or after a particularly chaffy natural.