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Temp/Time Charts: P0 - P7 for my Pit-Boss 820D

Discussion in 'Pellet Smokers' started by banjo, Jun 8, 2018.

  1. banjo

    banjo Fire Starter

    Note: Charts with corrected time scale have been uploaded; they are two comments down from this entry.
    Note: no meat on racks during these tests.
    Note: Charts at bottom of this post.
    Note: If anyone is interested in the raw data, let me know and I'll upload to my blog site. It's about 11 Meg.
    Note: During the test of P7, the fire went out.
    Note: I will be posting the temperature control setpoint to temperature/time charts sometime soon for settings 200 dF - 300 dF.


    A month or so back, a friend and I each purchased this model smoker. We were both disappointed in the temperature controller that came with the unit.

    I wanted to get a feel for what was going on, so I wanted to instrument the smoker with four (4) thermocouples, and two (2) relays.

    The thermocouples (type K, using Max31855 thermocouple amplifiers) would monitor temperatures at the following locations:
    • Combustion Chamber
    • Location in center of grill where meat usually is place first; as more meat is added, it typically is added left and right of the center.
    • The current location where the Pit-Boss 820D has their RTD temperature sensor (left front of smoke chamber)
    • Outside air temperature
    The two (2) 120vac relays were used to monitor (one each):
    • Auger motor
    • Fan motor
    Using a Raspberry Pi 3 (RPi), I wrote a C++ program to monitor these different devices (six total), at a 1-second interval, and to store that on the RPi. I streamed this across the network so that I could monitor all six values while performing the tests. The total tests took around six (6) hours, so a lot of data at 1 second for 6 devices.

    The test consisted of multiple segments, with each segment being associated with a single P setting (P0 - P7) or setpoint temperature (200, 225, 250, 300, 350) setting.Each segment had a time interval of at least 15 minutes, and some went to 40 minutes (I was sometime occupied and didn't get to switch the setting at the same times).

    I used Pit-Boss Pro Blend pellets for the test.

    I ran into a problem during the test of setting P7. While doing the setpoint temperature test for P7, the fire went out. Monitoring the augur state (on/off) and combustion chamber temperatures (which was falling), it was apparent that the fire had gone out, but more pellets were being feed to the combustion chamber. I let it go on for a while to see if it would re-light itself, but it did not. I set the smoker control unit to 'Off', then unplugged it to stop the feed, then removed the diffuser (the newer type, that is a curved plate the full length of the smoke chamber), and noted the combustion chamber was full of pellets, and they had just started falling into the floor area of the smoker. I dug all of the built-up pellets out, and restarted the smoker at P7. This ran away for a while with a high temperature. This will show up on the details for test P7.

    The test data is too unwieldy for a single post, as is the inclusion of the full data. Therefore, I have produced a chart picture of type png, which is readily viewable on most browsers.

    Below are the charts of the P settings for P0 - P7. The P setting does not use any temperature setpoints; it just sets the ratio of Auger on/off (fan is always on with this controller). With higher P values, the on duration remains the same, but the off duration becomes longer, so higher P values will result in lower low-end temperatures and bigger temperature swings. The P0 setting has the highest ratio of on-to-off values, and so has the lowest temperature swings, while the P7 setting has the longest time off, and so has the highest temperature swings.
     
    Last edited: Jun 8, 2018
  2. mike243

    mike243 Smoking Fanatic SMF Premier Member

    Thanks for the info,I have done a little testing but 6 was as high as I went,looked to be around 165 degree,80 or so out side,I suspect out side temps may affect the fire and cause flame outs with different pellets,dont think you can point at any 1 reason without a bunch of burning going on lol
     
  3. banjo

    banjo Fire Starter

    Here are the charts with the proper time scale in seconds.

    These are the thumbnails. Click on them to view the entire image.
     

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    • P7.png
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