limits & Overrides

OPERATOR'S MANUAL FOR SENTRY PAC

Six limits are provided:

None are in effect in MANUAL ON.

Limits do not stop probe overrides 2 and 3. (Overrides must be turned off to prevent them form turning on the fans.)

                                                      Default

  1. Upper temperature limit……………………………………………………….……117°

  2. Lower temperature limit……………………………………………………………..…0°

  3. Upper humidity limit…………………………………………………………………..99°

  4. Lower humidity limit………………………………………………………………….…5°

  5. Upper target temperature limit…………………………………………………....…60°

  6. Lower target temperature limit………………………………………………………20°

These can be accessed by pressing the OPTIONS key.

The first four (upper and lower temperature and humidity) stop fan operation in all modes if the corresponding reading is beyond the limit.

 

Target temperature limits prevent the target temperature from equaling the average temperature if it moves beyond the limit.

Only the center of the temperature band stops at the target limit, so fan operation will occur at temperatures beyond this limit. (Up to the amount of the band range). A temperature limit may be set to stop fan operation at a specific point beyond the target limit.

Example: Set upper target limit to 60°.

Set upper temperature limit to 68°.

 The fans will run within the temperature band around 60° -even though average temperature is higher - , but not higher than 68° even if the band becomes greater than ± 8°.

A message will be displayed whenever a limit is stopping fan operation.

 The message will display only if the fans would be running except for the limit. If more than one limit is exceeded, both messages will be displayed.

limits

Three overrides may be activated by each probe.

Overrides may be turned off for each probe, leaving the temperature displayed.

A message will display whenever an override is in effect.

 All three are inactive in MANUAL OFF.

Override 1: Doubles budgeted hours.

Conditions:

  1. Probe temperature deviates from target temperature by 9° or more either warmer or cooler.

  2. Not in effect if the average temperature exceeds a target limit.

  3. Not in effect if backlog is greater than 300 hours.

  4. Active in Storage modes & Special 2.

Override 2: Turns fans on!

Conditions:

  1. Probe temperature above 50°.

  2. Probe temperature more than 15° above target temperature.

  3. Air temperature more than 10° below the probe temperature.

  4. Relative humidity below 90%.

  5. All modes except Special 1 & 2.

Override 3: Turns fans on!

Conditions:

  1. Probe temperature above 60°.

  2. Probe temperature more than 30° above target temperature.

  3. Air temperature more than 15° below the probe temperature.

  4. Relative humidity ignored.

  5. Active in all modes.

 

These three overrides are designed for normal maintenance of grain. They may be inappropriate for certain conditioning goals. Fan runtime triggered by a probe can introduce fronts that work against your goals.

 

Comments:

Override one is designed to increase the amount of backlog when a seasonal change of temperature is not getting through the grain mass. If the target limits are set properly for your location, this override should not go into effect in winter or summer, but only occasionally in spring and fall when sudden seasonal changes occur.

One can budget a little less runtime for economy and override one will respond when sudden seasonal changes occur. A note of caution: Setting the runtime too low can delay a cooldown enough so that even though the PAC doubles the setting, winter has moved in and condensation problems become greater.

Overrides 2 and 3 are designed to start fan operation when conditions indicate possible heating from grain going out of condition. If it is a false alarm triggered by attic heat, the probe should cool down in a few minutes without warming the bottom grain much. If either of these overrides comes on in summer often, check the top grain. If it is in good condition and probe is sensing attic heat only, bury the probe deeper.

overrides