Minimum vent opening setting?


 
J

JakeBrown

TVWBB Member
Is there a minimum vent opening setting/configuration?

Situation:
My pit temperature is 5 degrees above target.
The WebUI has me believe the fan and the vent are fully closed (shown by 0% in the UI).
This will choke my fire.

foSBMLJ.png


Did I understand the UI correctly?

Settings/Configuration:
Fan output=
min 10%
max 100%
startup max 30%

Is there another setting to change to make sure the vent doesn't fully close?

Thanks,
Jake
 
The vent should fully close IHMO, that is how the damper tamps down the fire and lowers the pit temp.

If you want your servo damper to remain open while the HM is at 0% then you can adjust the lower SPD number so at 0% the damper is not closed.

Personally with the stock blower (which starts easily and will run at a very low speed) I wouldnt run the min fan speed up at 10%, I would back that down to 0%. If you run Min=10% the blower will accumulate up the time spent under 10% and release that in burst at 10% speed, so you will get the puff puff puff scenario if your HM needs to run under 10% to maintain your setpoint.

I also notice your Max is set higher than your Startup Max? This is kinda odd, typically the startup max is set higher (100%?) to stoke the fire when you first light the pit and the MAX is set lower to provide a lower flow during the cook, so a rush of air from the fan doesnt make the pit temp drop radically.
 
Last edited:
Thanks for the comment regarding the fan stratup. I changed it to 100%.

I really don't want to mess with the Servo Pulse Duration. These numbers indicate the fully closed and open positions, and shouldn't change. I can use the fully closed position to kill the fire.

What I wish for is a configuration so I don't kill the fire when lowering the temperature. I wish to set a minimum vent opening.

Better yet, I wish for some sort of ramp-down logic. Someone posted a script a while back that I need to try and figure out.

Jake
 
Ramp and hold functions are added to the latest snapshot release, though I don't understand how it would apply here...

When the sero closes the vent there is plenty of oxygen in the pit to keep the fire alive, as the oxygen gets depleted the fire shrinks in size which is what brings the temp down. If the fire is near the appropriate size the servo will open back up before the fire goes out, however, if the fire is way too big and causes a lot of overshoot the fire may be snuffed out before the pit drops to the setpoint and opens the damper. The setup is typically able to scale up/down the size of the fire a fair amount without putting out the fire in my experience.
 
I get a lot of smoke during the beginning of the cook (the entire neighborhood is getting smoked too). This is when I have to be careful not to snuff out the fire.

If I'm the only one having the problem, then I'll try something different. I plan on trying to add wood to the coals later, when the fire is hotter and going strong.
 
If you are using dry wood from when you start the fire that might be your problem. Dry wood chunks can start on fire easily and heat up the pit rapidly while the lump coal is barely getting going, then the HM chokes out the fire on the wood chunks leaving you without much burning. Either try soaking the wood chunks a bit first so they smoke rather than burn or get the fire going with lump coal first and then toss in your wood chunks.
 
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