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DigiQ DX questions

DeckhandDeckhand Posts: 318
edited November -1 in EggHead Forum
I have a DigiQ DX with a 10cfm fan on my Large. My 2nd cook with the Guru. Set the pit temp for 230.. Daisy Wheel open a sliver and damper open 1/4. Brought the egg up to temp (230) and held it. After an hour, I wanted to raise the temp so I pushed the setting to 250 with no other changes. The Guru huffed and puffed it's way to 270... puffin less often after it passed 230 but it was still puffing every few second when it hit 270 and the "hi" warning came on. It is dropping back but I wondered If I can expect this kind of overshoot whenever I raise the pit temp. Does the "alarm deviation setpoint" have any bearing on temp control...other than to sound the alarm?

Any info would be appreciated.

Comments

  • JeffersonianJeffersonian Posts: 4,244
    The alarm band doesn't have any influence on fan response, it's just for display purposes. I wouldn't expect an overshoot like this very often...mostly, my DX takes a little while to hit setpoint and it rarely overshoots as much as 10*.
  • Grandpas GrubGrandpas Grub Posts: 14,226
     
    The only time I have significant overshoot on the q2 is when I have the blower slider too open. You mentioned you had the slider opened 1/4 so I wouldn't expect too much of an overshoot.

    Not sure of the programming in the chip, nevertheless, I have noticed when I increase temperature if the q2 sets the blower duty cycle to 80% or more there is a slight overshot but then it settles back close to target. When forcing a lot of air or constant air flow into the lump to increase pit temperature, one can't expect a sudden stop of temperature increase when target is reached - hence a possible overshoot.

    If the increase required a blower 30 or 40 percent duty cycle then I would think the overshoot would be less significant. Some of this would depend on the programming of the q2 firmware.

    After a few years of using the q2 I don't get too concerned about +/- 10 or so degrees of target.

    Your post got me to thinking, and I looked at a couple of my Stoker logs. From what I can see on those logs there isn't much of an overshoot at all. I need to run a test with some significant temperature changes on the Stoker and look closer at the potential overshooting. The Stoker blower differs with the q2 in that the Stoker has a door that closes when the blower is not cycling. However, the Stoker blower's CFM can not be throttled down.

    GG
  • DeckhandDeckhand Posts: 318
    After the pit temp stabilized at 250° I raised it to 300° to see how it would react. Blower came on... few puffs at first, then more frequently until the egg reached 300°... It went to 308° but settled back to 300° within a very few minutes. Guess the ceramic hadn't had time to reach the higher temp. Thanks for the info... good to know that a slight overshoot is normal. Meanwhile, back at the chicken....
  • Do you have the open lid detect feature on? That will help reduce overshoot.
    The Naked Whiz
  • DeckhandDeckhand Posts: 318
    Yup, the "Open Lid Detect" was "ON." I did notice that if you leave it open for more than half a minute or so the blower will puff a few times then go into "fire up the forge" mode. Only a problem when relocating probes or basting several items. Gotta be quick... :ohmy:
    Would it mess up the Guru's "learning" to unplug the blower if I need to have the lid open for more than a minute? Worried that it might "think" the blower is having no effect and tell it to blow more which would create an overshoot when the blower was plugged back in. Could pull the power cord but that would erase whatever the Guru had "learned" during the cook.
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