Mode Change Hysteresis

| Overview

Equipment short cycling is one of the biggest challenges the 75F system has tried to address in all its ventures. It has already located such points during a system operation and has mitigated them by placing hysteresis-based checks.

There are relays' activation and deactivation hysteresis tuner parameters in place to avoid such short cycling of the equipment on the terminal side.

The system side equipment too had these hysteresis-based checks as in relay deactivation hysteresis in place within one type of conditioning or mode or operation (Heating/Cooling).

However, the system lacked a similar capability during conditioning or mode switching.

| Mode Changeover Hysteresis

The introduction of the modeChangeHysteresis tuner parameter addresses the above issue.

With this, the short cycling during the conditioning or mode switching of the system-level equipment is taken care of as below.

On VAV Systems, the operating mode changes to cooling when weightedAverageCoolingLoadMA > 0. This can result in unnecessary mode changes when one more zone is slightly off the desired temp cooling while many other zones have a much higher heating load.

With the ModeChangeoverHysteresis tuner parameter defaulted at 0.5, The VAV algorithms use the same to avoid unnecessary mode changes in the system operation.

When the system is in heating/off, the changeover to cooling triggers only when weightedAverageCoolingLoadMA > modeChangeHysteresis.

Similarly, when the system is cooling, a change over to heating triggers when

weightedAverageCoolingLoadMA drops to 0 & > 0

Note: The weightedAverageHeatingLoadMA is ignored since preference is given to cooling.

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| Overview

| Mode Changeover Hysteresis

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