Help figuring out what's wrong - won't burn all the fuel


 
I don't like the all or nothing fan. Does this mean I need to close off the exhaust vent a little more?
From the start of this test, I've had the BGE exhaust vent on the 5" pipe - with just the daisy wheel vents fully open.
 
at 7:30pm I flipped the larger vent on the BGE vent 1/2 way open. So, about 1/2 of the 5" pipe is wide open.
 
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RalphTrimble said:
Looks like the blower is getting the job done, do you have the blower max set to 50%?
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no. 100%.
startup max is 50%

monday%20test.PNG
 
it looks like it's struggling to get to 325-330F. An improvement, but not by much....but that's with the BGE vent at 50%.
At 8pm, I'll take it off completely and let the vent be a wide open 5" circle. I'm guessing that'll let too much heat out though. We'll see.
 
It seems odd to me to run the startup max at 50% and the max at 100%? I can see the logic in bringing them down but usually the startup max is the higher of the two...
I'm not sure I understand the "all or nothing fan" question.... I gather you mean how the fan seems to be running full boar and then cuts to zero when the pit temp is achieved? There are a few factors here. First of all, you are ramping up the target temp, so the HM is ramping up the fire with full output. I think if you held a steady set point it would eventually settle on a medium flow... The rate of attack and decay, so to speak, is set by the PID parameters, so PID tuning can help moderate that on/off situation.
You're gonna have to play with it a bit to see how much flow the pit needs, and make adjustments to the blower settings and the top vent until you're supplying the right flow of air, then PID tune to make it stable.
 
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Have you been running all your testing with startupmax 50% and max at 50%? That'd be a pretty good give away why you never achieved initial ignition in your previous attempts.

Also, I had totally misunderstood some of what you've said before. I had not idea that the BGE vent could swing fully out like the photo shows. I thought it was more like an Akorn which is essentially just a daisy wheel.

cfb30b3c9d99b59ddcad66870c0930b0.jpg
 
Another note..... Since you have your Startup Max set to 50%, every time you change your setpoint to a higher temp the blower actually SLOWS DOWN to half speed, because the HM jumps back to Startup mode when you change the set point.... I would change both max and startup max to 100% if you are having a hard time achieving your target temps.
 
RalphTrimble said:
BTW, are you using lump coal or briquettes?
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Briquettes. I used one filled Kingsford chimney starter full.
I just removed the BGE vent and am running wide open now on the exhaust vent. I also changed the startup to 100% - matching the max fan speed at 100%.
 
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I guess I don't understand how the startup mode works.
I initially set it to 50% because I would always get huge overshoots when first adding the coals to the smoker. I thought by dropping the max startup to 50%, it would minimize the initial overshoot. I forgot I had it set there....

Both fan speeds at 100% now. BGE vent is removed and the exhaust is wide open at 8pm
 
Good move, the startup max setting was making your blower slow down when it should be speeding up... Seems UNDERSHOOT has been your problem... lol
I would also suggest you try lump coal, it will burn hotter and longer in my experience... and you might need a bigger load of coals in there to hit higher temps...
 
RKHanso said:
I guess I don't understand how the startup mode works.
I initially set it to 50% because I would always get huge overshoots when first adding the coals to the smoker. I thought by dropping the max startup to 50%, it would minimize the initial overshoot. I forgot I had it set there....

Both fan speeds at 100% now. BGE vent is removed and the exhaust is wide open at 8pm
Click to expand...

Now that you've solved the underlying problem (and once you figure out if the blower works on your pit), let me know how the MicroDamper works out for you. I'd be curious to know if it'll work for a 64 gallon pit. I generally don't tell anyone to use it on anything above a 55gal UDS. So this will certainly be helpful to others
 
Startup Max is pretty simple. When you enter a new setpoint the HM enters startup mode and will spin the fan using the Startup Max setting until the target temperature is achieved, from then on it will use the Max setting. So if you change the setpoint it will go back to Startup Max until that setpoint is achieved. You are correct that on some pits having too high of a startup max may lead to overshoot, but those pits generally need to run the Max setting lower as well. Your pit seems to need a lot of stoking and overshoot hasn't been an issue, so I would run run them both at 100% unless you actually run into overshoot issues.
 
It appears that the standard HM blower will only get my smoker up to about 330 with the 5" exhaust wide open (see 7:50-8:10pm).
I'll put the BGE vent back on with the daisy wheel wide open and see if that will hold some heat in and temps go up, or if it will put the fire out.
 
RalphTrimble said:
I would suggest you put a big load of lump coal in the smoker and fire it up and do the same tests...
Click to expand...

OK. will do that tomorrow.

Meanwhile, I'll drop the set temp to 250F and see how long it will hold the temp and if all the fuel will burn. (that was my problem before, not enough air to burn all the fuel, as well as not being able to hold a temp higher than 300F).

At 9pm, I put the BGE vent on and really choked it down to barely open. The temp spiked up, but then dropped down. We'll see where it settles.
 
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could some of my problem be that I have a 1" intake pipe and a 5" exhaust pipe? Is this too big of a difference?
 
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