PBC calibration tests

[Polarbear777]

Calibration tests with no food to characterize settings.
All using a level basket of KBB, and subset of that ignited by PBC chimney and lid clamped on immediately.

I’m sure things will change with food load, but gives an idea how settings may affect things. Ambient temp was 30-40F.
Altitude is sea level.
Temperature at cook is either above 200 or above 300 (when it’s high enough to start cooking)

Updating the Plot, Added a test with B&B Char Logs that gets a 24hr+ cooktime.

[RobertC]

What's "Temp Cook" and how do you calculate %Diff?

[Edited to add:] Also, do you weigh the briquettes before and the ash after?

[RobertC]

Each KBB is 25g, so there are 18/pound. You could count them at the beginning to make sure you have the same amount.

The reason I was asking if you weighed the ash was because it's obvious you're not getting complete combustion so it would be interesting to see how much was burning at different apertures.

[Polarbear777]

Percent diff is just the cook time increase over the other cases. Red cases in the table represent 300F+ cases compared with each other.

[Butchman]

I’d choose the green line! That’s my setting btw.

[BourBonQ]

What's your altitude? Thanks for posting.

[BourBonQ]

Scratch that. I see your note about sea level.

[cgrover60]

Looks like your 1/8 vent results are right on par for sea level. What device were you using for the "PBC Pit Fan" results?

[Polarbear777]

Was using a pit bull fan but I dialed the max speed back a bit at hour 5 and hour 8 (225 Case) to minimize the fluctuations.

Somewhere arround 1/8 to 1/4 in stock configuration will work for low and slow and 1/2 for 300+ cooks like chicken. Stock configuration 8 hours isn’t bad (almost 5 at 300+) but I wanted to see if I could let it go overnight without worrying. The fan accomplished that and guards against ambient temp/wind fluctuations.

In in all cases there was some unburned charcoal. The less air, the less complete the combustion. The fan almost but not quite uses it all. In my other setups I have the fan directed up through the coal box, but here it’s just blowing around the coals.

Also so be sure to turn off the "lid detect" feature on your fan controller. If the temp is high, the fan stops, the temp drops so fast that it triggers the lid detect, which by default keeps the fan off for several minutes, which is enough time to kill the fire in some cases. It’s deceptive because you go out to check and the fan is back on, but no fire.

[Larry Grover]

Good stuff, unraveling the mystery of this machine! In the future I'd be curious to see multiple probe data (how even the temps are on each side of the barrel.) I took such a hit buying the PK I was going to sell my PB but I might just have to hang onto it awhile longer.

[Polarbear777]

I had multiple probes running so I have the data. If I can find the time to look at it...

[Polarbear777]

Without looking at it closely, in the 225 fan controlled case it looks like the differences are less than 50 and closer to 30.

I had the two pit probes mounted near the edge of the barrel one just below the grate level and the other a bit lower and about 90 degrees away. The three food probes are just draped over the rods.

[RobertC]

30 degrees variation on a target temp of 225 seems like a lot.

[Polarbear777]

There’s a large variance but the average is pretty good.

[Larry Grover]

Five probes...your my hero man! Interesting data, now that the calibration testing is done where are you going from here?

[Polarbear777]

...now that the calibration testing is done where are you going from here?

Have to have a rain cover (water heater pan with bricks and a pan bolted on the inside fits over the lid handle). And an onboard thermo at grate level, and a sliding door that can seal shut instead of just the stock circular hole so i can have full control with the fan. And two mounted probes and a sealing probe port for the rest so I don’t mess them up sliding rods or food around

[RobertC]

That's a big rain cover.

[Larry Grover]

Far out man! So where are you going from here? Gonna turn it into a space ship?

[Polarbear777]

I hate dealing with fabric covers and they trap moisture. My custom hacked metal covers didn’t budge in 50 mph winds.

[FireMan]

So, what did lt taste like? Just wonderin.

[Polarbear777]

Very good. Beef ribs were good too, but they somehow escaped pictures.

[phoccer]

Great info! Thanks for posting! I've found similar results with my Pitmaster IQ 110 hooked up in that it really helps keep the PBC in a tighter range.

[Polarbear777]

I was wondering if the early control problems you were having were related to the "open lid detection" "feature" I described.

[phoccer]

Very well could be. My last two runs have been without the fan. Next one will be with the fan with that feature disabled. Very cool to see it can go 225 all night long. I have a bag of B&B Briquettes to try and those things burn FOREVER.

[jfmorris]

Looking at those graphs, I am actually impressed by how stable it is for 8 to 9 hours without any fan or control. That may influence my to get a PBC by summer, and push off any pellet cooker purchase until another year. I want something that uses less charcoal and wood than my offset, but with more capacity than my kettle/SNS.

[Polarbear777]

Of course with food as a heat sink it won’t run quite the same.

The fan buys you extra time and guards against ambient temperature fluctuations (wind) and means you don’t have to crack the lid or damp down.

But I am impressed with how well it runs in stock configuration in benign weather.

[N227GB]

Have to have a rain cover (water heater pan with bricks and a pan bolted on the inside fits over the lid handle).

That's a good idea! The other evening we had a brief rainfall for around 15 minutes, with zero precip in the forecast. The ambient temp in my PBJ dropped over 15 degrees. The only part that got wet was the lid. Come summertime we'll have daily localized downbursts in the late afternoons, so fabricating a rain cover is on my to do list.

[ItsTom]

Just ordered my PBC Jr. yesterday to supplement my Kamado Joe classic. I was wondering if anyone has thought of or (better yet) tested wrapping the drum with insulation, like some folks do with a water heater. I'm a bit nervous about how changes in ambient temps or wind will affect my cook times. Never was much of an issue with the kamado.

Thanks,
Tom

[Polarbear777]

Was also thinking if you had another drum that was bigger and put the PBC inside, you would have air insulation. You’d have to use a pipe for the input hole and maybe make holes for longer rods so you can access everything while cooking. (And I’d have to make portals for my controller and hard mounted thermometers.)

[phoccer]

I haven't done a ton of cooks on my PBC, a dozen, but I haven't seen changes in ambient temps or wind having a huge influence on my cooks. As Polarbear777 mentions, you can definitely create a narrower range of operating temps by connecting a controller.

[Polarbear777]

Right, and I don’t know if insulation would buy you a ton of extra time vs the controller. Yo also don’t want the fire too low or your smoke quality suffers. I’d do an A/B insulation and non-insulation run, but now that I’m done with my mods, I’m just going to make food for a while :-)