target temp & moisture

OPERATOR'S MANUAL FOR SENTRY PAC

Target temperature

The target temperature is the desired temperature for the grain.

It is the center point for either an adaptive or constant temperature band.

The target equals the 21 day average temperature unless:

  1. A target limit is in effect.

  2. Fall cooldown is in effect.

 The target temperature equals the limit instead of the 21 day average temperature whenever the average exceeds the limit.

An offset is calculated by the PAC when in fall cooldown. This is subtracted from average temperature to produce a lower target temperature.

fall cool down

Fall cooldown is an automatic feature. The objective is to anticipate winter’s approach and cool the grain sooner. An offset is calculated by subtracting the difference between the 42 day and the 21 day average temperatures. This is in effect only if the 21 day average is less than the 42 day average.

This can help to minimize condensation problems if a sudden cold from moves in and stays. The PAC can do this accurately only if it has been on for 42 days. This is one reason to leave power on even if the bins are empty.

This feature can be turned off by accessing “FALL COOLDOWN” under OPTIONS.

target moisture content (TMC)

The target moisture content is the desired goal. The setting made with the MOISTURE key is the TMC in the 3 storage modes and the 2 special modes.

TMC is the center of the adaptive EMC band in storage mode one.

TMC is the center of the constant EMC band used in special modes 1 & 2.

In storage mode 2, the EMC band is fixed at 0.2% on the dry side of TMC and the wet side adapts just like in strorage mode 1.

In storage mode 3, the EMC band is fixed at 0.2% on the wet side of TMC and the dry side adapts just like in storage mode 1.

Factors that affect TMC

Inaccurate temperature or humidity readings:

  1. Remote sensor box is affected by the sun or something else

  2. The temperature or humidity sensor has drifted or failed

Uneven runtime in band

Normally runtime accumulates so the average EMC while running is very close to the TMC. However, if most of the runtime is accumulated when EMC is toward one end of the range – especially with a larger amount of backlog – the resulting MC may be different than the TMC. Storage mode 2 & 3 are designed to correct for this if it is known ahead of time that a climate is predominately wet or dry.

Static Pressure

Fans build up static pressure to move air through grain. The higher the static pressure, the more heat build up there is in the air which reduces relative humidity. The following chart gives an estimate of this effect:

Static Pressure            Temperature Rise

0.5”………………………………………..0.37°

1” …………………………………………0.75°

2” …………………………………………1.50°

3” ……………………………………..…..2.25°

4” ………………………………………....3.00°

5” ……………………………………..…..3.75°

6” ……………………………………...… 4.50°
7” …………………………………………5.25°

8” …………………………………………6.00°

9” …………………………………………6.75°

10” ……………………………………..…7.50°

15” ………………………………………..11.25°

20” ………………………………………..15.00°

 

 

Equilibrium Deviations

Geography, season, variety, maturity, protein content, and other factors can affect EMC. It is recommended to take a sample periodically from the grain that the air first contacts to see how close it is to TMC. Then adjust the moisture setting accordingly.

Hysteresis (Drying and Rewetting differences.)

The same air that will dry grain to a given MC will not rewet grain to the same MC. This is called hysteresis. In corn this seems to be about 0.7%. It is unknown for other grains.

Large Temperature Fronts:

Moving large temperature fronts – more than 10° - through grain can set up a drying or rewetting front. Uniform temperature control with gradual changes is essential to uniform moisture control.