Question - oscillating above set point


 
G

Greg Fountaine

TVWBB Member
My settings are as follows, 4, .02, 5
I would expect the temp to oscillate around the set point, not above it?
18447478_10203292777636005_7990676097269425673_n.jpg
 
WSM 22" tonight. I would think if it is leaking air that the fan would simply not blow as much. But the fan is engaging before it drops below the set point.
 
Your graph shows your fan not blowing much.... and I agree, it looks like your pit is getting enough (slightly too much) air without the the HM running, so you either have air leaks or you need a damper of some sort.
As for the fan kicking on above the setpoint, that has to do with the PID settings and how fast the temp is falling toward the setpoint. If the temp falls slowly to the setpoint the HM will react gently, if it falls rapidly toward the setpoint the HM will react abruptly (again, depending on the PID settings)
What kind of pit probe do you have? If it has low mass it may react very quickly which makes the HM a little hyperactive.
 
Yes, reduce the top vent, that'll slow the flow and make the HM run more to keep up. I like to shoot for having the HM output at about 30% when the pit is at the target.
 
Greg Fountaine said:
My settings are as follows, 4, .02, 5
I would expect the temp to oscillate around the set point, not above it?
18447478_10203292777636005_7990676097269425673_n.jpg
Click to expand...
Mine looks like that when I don't have the lid down tight. I think it is down, but then a little wiggle and it snuggles down just a little more. Seems to happen more when I run the probe cables out under the lid.
You shouldn't need to gasket the sections (middle to bottom, top to mid,) but a gasket for the door, or a better door (or both!) really helps to keep the swings down.
With out leaks, you should be able to run with the top vent wide open, which is the preferred way to go.
 
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