Propane Setup for large upright smoker?

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Fischerman

Newbie
Original poster
Jan 16, 2023
10
18
Currently building a 70 cubic ft upright reverse flow smokehouse. Will mainly be used for sausage but hope to also be able to go higher temps for brisket/pork butt, etc and lower temps for cold smoking cheese/salami.

Found lots of useful info here on a setup using PID controller, safety valve/thermocouple, solenoid for high flow and a separate line around the solenoid to keep constant low flame in the burner.

The setups I have seen on this site keep the low flow going over the entire burner at all times with the PID opening the solenoid and adding flow when the temp needs to rise. I'm worried that this constant flame would keep the temp in the cooking chamber higher than 140* and for sure too high for cold smoking cheese/salami etc.

Would it make sense to install a pilot light with thermocouple so that only the pilot burns when the solenoid is closed. Once the solenoid opens the main burner lights from the pilot. Any downsides to this type of setup?
 
Here is a rough schematic of my build. I apologize for my lack of artistic ability lol

In theory this should allow for automatic control of cooking temp/time, smoke generator on/off and auto shutdown when meat reaches desired temp.

I relied heavily on previous users posts about this type of setup. Thank you!!! One concern was inaccurate tuning of the PID due to the longer preheat time from cold. I added a mechanically controlled bypass to the electric solenoid for the main burner gas line. This should allow for full temp on the main burner to preheat, close the bypass and let the PID run the smoking/cooking cycle after preheating.

Smoker is being constructed with 1” tube steel frame, stainless steel sheet with 1” mineral wool insulation.

Let me know if you see an issues with this setup. Will post updates as the build progresses. E8B1892A-150E-482F-9343-249CB1592717.jpeg
 
Smoker is almost finished. We are running into an issue with the propane burner…..

Pretty sure it’s an air flow issue…the burner will run forever when on the bench vice. When we put it into the firebox we get to about 80deg and the burner + pilot extinguishes, takes about 12min. As we keep relighting the burner, time till extinguish gets less and less. At 150deg it only burns for 30sec before extinguishing, you can hear it. Almost like a vacuum shuts it off.

We used a vacuum to simulate an exhaust fan and we can keep it running longer but still extinguishes intermittently.

Took 31min to drop from 157deg to 154deg so at least it’s insulated well but the burner issue kills the build.

Any suggestions?!?
 
Yep, on my suggestion.
You need forced induction airflow to do the up and down then up again path of the heat and smoke. It is not a natural draft.
The airflow must continue with or without the burner to prevent the hang smoke which gives a stale taste.
 
What kind of ventilation do you have in the burner area?
 
Yep, on my suggestion.
You need forced induction airflow to do the up and down then up again path of the heat and smoke. It is not a natural draft.
The airflow must continue with or without the burner to prevent the hang smoke which gives a stale taste.
So that means an intake fan and exhaust fan?
What kind of ventilation do you have in the burner area?
36sqin air intake to burner - 26sqin heat into cooking chamber and 30sqin exhaust
 
I have built many pipe burners....IMO you need an open area(s) under the burner to allow fresh air to flow upwards. If you dont have sufficient air supply around the burner the oxygen will will deplete when it get hot and the burner will go out. I suggest drilling some holes under the burner area before installing a fan for air supply. What is the size of the orifice at the gas mixer. It should be small in diameter about 1/16".
 
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Maybe I’m not understanding the build sketch, but it looks to me like you are flowing hot air to the top from the sides then trying to force the hot air back down all the way to the bottom? If so I see no way this will work. Hot air rises. To create draft or draw the intake must be low and exhaust high. The burner goes out because of lack of air flow, this looks to be caused by the lack of draft. Maybe a better explanation and detail of air intake and exhaust would be helpful. Remember that you can only intake as much air as you can effectively exhaust and vise verse.
 
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We increased the intake air vents by 100% and removed 80% of the angle iron channel the burner was resting in, to get some airflow around the burner. Seems to have fixed the problem!

The burner does go out while warming up at around 80-100degs without an exhaust fan drawing the air through the reverse flow design. Once the flow starts running out the exhaust the burner stays lit without the exhaust fan.

Will be adding 2 interior circulation fans from Auber. Hopefully those will promote the unnatural reverse flow, make sure we don’t have stale smoke and even out temps throughout the smoker.

Will have a range exhaust hood built into our meat shop roof so we can smoke inside. If the exhaust hood and circulating fans aren’t enough we will add a small exhaust fan into the exhaust chamber.

Waiting for our custom door gasket to arrive and adding the final touches in the mean time. Will post pictures and details once finished.

Here is the graph from first test run using the Auber controller and gas solenoid to automatically maintain temps. Temp stayed within a 2-3* range and was getting better as the auto tuning controller adjusted.
 

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Currently building a 70 cubic ft upright reverse flow smokehouse. Will mainly be used for sausage but hope to also be able to go higher temps for brisket/pork butt, etc and lower temps for cold smoking cheese/salami.

Found lots of useful info here on a setup using PID controller, safety valve/thermocouple, solenoid for high flow and a separate line around the solenoid to keep constant low flame in the burner.

The setups I have seen on this site keep the low flow going over the entire burner at all times with the PID opening the solenoid and adding flow when the temp needs to rise. I'm worried that this constant flame would keep the temp in the cooking chamber higher than 140* and for sure too high for cold smoking cheese/salami etc.

Would it make sense to install a pilot light with thermocouple so that only the pilot burns when the solenoid is closed. Once the solenoid opens the main burner lights from the pilot. Any downsides to this type of setup?

I am in the process of making a PID controlled smoker burner system and have decided that I will use a simple ON - OFF spark ignition system. I just need some more info on the proper solenoid valve to use for propane. If this doesn't work maybe I will have to consider a pilot type system.

JC :emoji_cat:
 
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