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Why the SPP Method Is Different

Traditional grain conditioning reacts to the condition of the grain itself, which means problems are often caught after they start. The Sentry Pac Pro takes a different approach — it manages the condition of the air going into the bin, which prevents problems before they happen. Four qualities define the method:

  • Proactive — manages incoming air conditions rather than reacting to grain conditions

  • Adaptive — parameters expand and contract based on a rolling 21-day average, so fans only run at the most optimal times

  • Gradual — because the system works off a 21-day average, there are no large fronts of air pushed through the grain mass, avoiding the uneven-temperature problems that can cause

  • Frequent — frequent fan operation moderates uneven heating from the sun and helps prevent insect activity from starting

The method relies on three data points: Equilibrium Moisture Content (EMC), external temperature, and external relative humidity. Using the 21-day average of these, the SPP determines the best runtimes and parameters to keep your grain's temperature and moisture uniform and close to the outside average — which is what prevents moisture migration, bug activity, and hot spots.



Understanding Airflow & CFM

"Airflow" is your budgeted fan runtime (in hours) per day, based on your bin's CFM per bushel. Each night at midnight, that budgeted runtime is added to a running backlog, which narrows or widens the adaptive parameter bands. The system then combines those bands with current weather to decide when the fans actually run — so your fans may run anywhere from 0 to 24 hours a day, even though the airflow setting itself doesn't change.

Budgeting 4–6 hours per day is a good baseline starting point for most bins and typically produces the most uniform moisture content. Higher settings can actually reduce uniformity, since they widen the adaptive bands and lead to less consistent temperature control.

Recommended airflow settings by CFM per bushel:

CFM per Bushel (Fraction)

CFM per Bushel (Decimal)

Recommended Airflow (Hours)

1/20

0.050

8

1/15

0.066

6

1/12

0.083

4

1/10

0.100

4

1/9

0.111

3

1/8

0.125

3

1/7

0.142

2

1/6

0.167

2

1/5

0.200

2

1/4

0.250

1

1/3

0.333

1

1/2

0.500

1

2/3

0.666

0.5

3/4

0.750

0.5

1

1.000

0.5

1 1/4

1.250

0.25

1 1/2

1.500

0.25

2

2.000

0.25



Equilibrium Moisture Content (EMC) Explained

EMC is the moisture point at which a seed neither gives off nor absorbs moisture from the surrounding air — the seed and the air are in balance. Air at a given temperature and relative humidity will produce a certain Target Moisture Content in the grain over time.

Note: Runtime normally accumulates evenly enough that the average EMC while running stays close to the Target Moisture Content. But if most runtime accumulates while EMC sits toward one end of the range — common in predominantly wet or dry climates — the resulting moisture content can drift from target. Storage Modes 2 and 3 exist specifically to correct for that.


Target Moisture Content & Backlog

Target Moisture Content (TMC) is the moisture level you want the grain stored at — since the SPP Method is outcome-based, this target value is what drives the weather conditions that trigger the fans.

Backlog is the accumulation of budgeted runtime hours. Each night at midnight, the Airflow hours get added to the backlog, widening the adaptive bands; the actual fan runtime for the day gets subtracted, narrowing them back down.



The 5 Storage Modes

  1. Storage 1 — recommended for the USA corn belt. Fans run when backlog is greater than zero, temperature is within the adaptive band, and EMC is within the adaptive band.

  2. Storage 2 — recommended for dry climates or grain drier than TMC. Same as Storage 1, except the EMC band doesn't expand on the dry side.

  3. Storage 3 — recommended for wet climates. Same as Storage 1, except the EMC band doesn't expand on the wet side.

  4. Rewetting — fans run when EMC is greater than the moisture setting and temperature is within the constant band.

  5. Drying — fans run when EMC is less than the moisture setting and temperature is within the constant band.


Fall Cooldown

Fall Cooldown is an automatic feature that anticipates seasonal temperature drops and starts cooling the grain earlier than it otherwise would. It applies an offset based on the difference between the 42-day and 21-day average temperatures, and only activates when the 21-day average is lower than the 42-day average — reducing the risk of condensation during a sudden, sustained cold snap.

Note: For this to work accurately, the Sentry Pac Pro needs to be powered on continuously for at least 42 days. We recommend leaving the unit powered on even when bins are empty.


Supported Grain Types

The Sentry Pac Pro supports 21 grain types: Barley, Canola, Corn (Yellow), Edible Beans (Red), Flax, Fresh Red Lentils, Lentils, Oats, Peanuts (Kernel), Peanuts (Whole), Pinto Beans, Popcorn, Rice (Brown), Rice (Rough), Sorghum Milo, Soybeans, Sunflowers, Wheat (Durum), Wheat (Hard Red), Wheat (Soft), and Finola Hemp.

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