New Offset Burning Through Wood

[beardedgeego]

Back story. Years ago I wanted to smoke a butt. I did it with charcoal on a grill. I did 2 in about 2 years. Wife said I worked too hard and it was too good to only cook once a year. So she bought me an electric smoker. That’s been 5 years ago when I joined this forum. I read more than I post.
3 times in the last 5 years I went to smoke something and my electric smoker was broke down for whatever reason.
Last time was Thanksgiving this year when I put the turkey on.
SO. I studied on this forum, the googler, Tik tok, etc.

Buddy is a welder/fabricator with a pretty big business. Gave me a piece of 30” pipe and let me use his shop to build this behemoth. I also sell steel for a living so I had excellent access to the stuff to finish this thing with the current price of steel.

I used Feldons stuff for firebox/ exhaust size.
It’s 30” OD, 8’ long smoke box. Same diameter, 2’ 8” firebox. 6” OD tube @ 48” on the exhaust. No exhaust dampener. Only intake dampener, which appears to need to be full open for proper temps.

4 thermometers. One closest to firebox is of course too hot. Other 3 are manageable.
My issue is that I’ve tried to keep as close to 225° as possible for 5.5 hours now. I’ve burned 15 sticks of wood. Sticks are about 5” x 5” x 20”.

Would dampening the exhaust help hold temp better? Does this sound like a normal amount of wood?

 

[JckDanls 07]

I'm thinking another intake vent ABOVE the firebox door... This vent helps pull the heat from the fire into the cook chamber...

They say Feldons calculator is known to have some issues... Daveomak has a calculator that is proven to create an excellent smoker ( I used it to build mine in signature below)... Look at mine and in the fourth picture you will see the vent I'm talking about ...

Others will be along to help...

 

[JckDanls 07]

Here's his thread.. read through it and run your numbers to compare with Feldon

Standard Reverse Flow Smoker Calculator... by DaveOmak and others... Ready to use.. rev5.. 6/19/15.

Here's to "Alien BBQ" and the folks that first put the calculator together and "1728 Software Systems" for this great "Circle Calculator" and all the folks at "SmokingMeatForums", with a special shout out to Ribwizzard, that contributed their ideas and feedback while this thing was coming...

www.smokingmeatforums.com

 

[beardedgeego]

Mines not a reverse flow, but everything is pretty close. Within about 10%

Im just astounded at the amount of wood Im burning through! Didn’t expect it to use this much. I don’t really know what I expected, but it’s def using wood!

 

[SmokinEdge]

That’s a large pit by any standard. The fuel burned to maintain 225* doesn’t sound outrageous either, but as Keith posted above, you need an upper air inlet on the firebox. This inlet will not feed the fire, but will move the hot air at the top of the firebox on through the cook chamber. This is more efficient and could cut down on wood consumption if you learn to control the air inlet to the fire. Damping the exhaust is never recommended by me. open exhaust and manage the fire. That’s a big firebox, you need to more efficiently move the heat out of the FB into the CC.

 

[Mr. Zorg]

Just FWIW I have a butterfly shaped air intake register on my small diameter (16") patio offset smoker. I actually block off part of the upper part of this butterfly because the incoming air through there isn't being used for combustion. It just sucks up fire heat to bring it up to ambient temperature which is lower efficiency.

On my 24" diameter trailer mounted combination horizontal and vertical offset smoker, I have only the lower half of a butterfly intake. I had my fire grate fabricated so it sits just above this opening - 100% of my incoming air comes below the fire grate and it runs fine. Of course that combination design effectively has a much higher top of stack than a typical horizontal offset.

I use a combination diffuser and radiant shield plate in both these smokers. Are you using any such plate, or tuning plates in your smoker? That's a pretty long run from your firebox side to your exhaust side. I guess I oughta ask if you've mapped your food grate temperatures across from the firebox side to the exhaust side as well.

 

[beardedgeego]

I’ve been thinking about a shield plate/tuning plates. Of course this is the first night with it

I’ve got 4 thermometers right at the cook grate

my intake vent is a 12” circle. Half below my fuel grate the other half above it

With the intake 100% open and 3-4 pcs of wood + existing coals, I’ve got these temps from the firebox side to the exhaust:
350
255
225
250

so aside from that first one being so high, which would be alleviated by tuning plates, it’s not bad. I’m about to swap a couple thermometers to make sure the 2nd from the end isn’t bad. I don’t know why it’s reading lower

 

[beardedgeego]

Note. Next to last thermometer is no good.

 

[Mr. Zorg]

Even with the diffuser plates I use, which 100% block the firebox radiant window, it's still a bit hotter at the firebox end due to the hot diffuser plate.

To me, too much of your hot gasses from the firebox are hugging the upper portion of the cook chamber, and tuning plates or a diffuser plate will really help with fuel efficiency. If you ave a non-contact IR thermometer you could check the outer wall temperature along the top of your cook chamber.

Even with tuning plates or a diffuser plate, I can change the temperature profile by lowering the trailer tongue, front of my pit, to get a hotter firebox side temperature to crisp or sear some things if I want. Then bring it back to a slope that's just enough to not have grease run into the firebox to even out the cook chamber temperatures more.

You may want to mount some way for set screws etc. to lock your diffuser plate or tuning plates in place once you get them where you're happy with them.

JM2C

 

[beardedgeego]

Update. Analog thermometers that I installed with the build were pure trash. I’ve smoked a couple times and it holds temp quite well.

Been using Weber Bluetooth thermometers. MUCH better.

Today I cut into the top of the firebox and built a griddle then seasoned it! Can’t wait to get some eggs in the mornings when it fire it up!

 

[jcam222]

I’ll leave the science to those who know smoker builds. That said less than 3 sticks an hour doesn’t seem unusual to me. You built a whopper and it’s going to eat some wood. After buying my Lang 84D it didn’t take me long to learn I was going to need a steady supply of wood. Out of curiosity did you build one that big to cook a lot at a time or mostly because you had the large 30” pipe? If the latter and with your access to steel you may want to build a smaller more fuel efficient unit.

 

[Sven Svensson]

That’s very impressive. Nice work.

 

[civilsmoker]

That’s a huge smoker and your build looks really nice. Having a griddle on top of the FB is cool. I have a flat top barrel stove for our canvas tent that we cook everything on.

Just a couple thoughts, it appears to me that you need to increase the intake air as others have said.....adding one in the upper FB should help! I would double the intake area for flexibility for cooking at a wider range of temps.

Next a log each 20 min for a smoker that big isn’t that far out of the expected. You can try to adding 2 to 3 chimney worth of coals to increase the coal base heat to help reduce the log fire but that’s more of a balance you need to find through experimenting.

Tuning plates will help even things out a bit but having a differential temp like that is a very good thing for large cooks. Ie having the FB side 325 - 350 and the other 225 - 250 is sweet! Ie you put slow cooks on the cool side mid temp cooks in the middle and then birds and roasting items on the hot side. I mean how cool is it to do crisply skin chicken at the same time you are doing low and slow.....that is awesome! This is a strength to an offset that a reverse flow doesn’t have.

Final thought is the only analog dial temp gauge I trust is tel tru. I have tried many others and it’s just a crap shot. But tel tru earn their price. Mine are spot on with my digitals

 

[beardedgeego]

Just realized griddle pic didn't post

 

[civilsmoker]

Nice!

FYI - If you take the cut out and make it so you can place it over the griddle (create an air gap space) when you smoke, it will help insulate and improve the burn rate.