Thermostat Schedule Set

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Hi Nadish,

Let’s summarise the question. You would like to cycle your system ON and OFF in both cooling and heating mode. The operation in the heating mode should be:

1. Keep the system running until the zone air temperature reaches the heating setpoint
2. Switch off the system and keep it off until the zone air temperature drops below the heating setpoint by Toffset
3. Switch on the system again.

Similarly, the operation in the cooling mode should be:

1. Keep the system running until the zone air temperature reaches the cooling setpoint
2. Switch off the system and keep it off until the zone air temperature rises above the cooling setpoint by Toffset.
3. Switch on the system again.

We can identify three control zones in the attached diagram.

• The crosshatched control zone (between heating setpoint and cooling setpoint) is a zone when the system is always OFF.
• The grey-shaded control zones (below (heating setpoint – Toffset) line and above (cooling setpoint + Toffset) line) are zones when the system is always ON.
• Control zones within Toffset from either heating setpoint or cooling setpoint are zones where system can be either ON or OFF depending on the previous operation. For example, if the heating setpoint is 21C and Toffset is 0.5C. When the zone air temperature reaches 21C the system should be stopped. The temperature in the zone starts dropping and in the next timestep it might be 20.7. It is still within the Toffset boundary and the system should remain OFF. If in the following timestep the zone air temperature drops below (heating setpoing – Toffset) the system will switch ON. Naturally, the zone air temperature will start rising, however it might not reash the heating setpoint within one timestep. This means that the system should remain ON. The behaviour is similar in the cooling mode.

The task is to apply this control login within EnergyPlus by using EMS. The crude way of achieving this is to override the system availability schedule (AvailabilityManager:Scheduled > Packaged Rooftop Air Conditioner Availability Manager).

In your example the system availability schedule (Always On Discrete) is used by many other objects. You need to create new schedule:constant (let’s name it Cycle) and apply it to the Packaged Rooftop Air Conditioner Availability Manager.

Schedule:Constant,Cycle,OnOff,1; ! New schedule object

AvailabilityManager:Scheduled, ! Updated Availability Manager
  Packaged Rooftop Air Conditioner Availability Manager, 
  Cycle;

To be able to create desired control logic you need to have three EMS sensors: Zone Mean Air Temperature, Zone Thermostat Heating Setpoint Temperature, and Zone Thermostat Cooling Setpoint Temperature.

EnergyManagementSystem:Sensor,
  AptTemp,
  Thermal Zone 1,
  Zone Mean Air Temperature;

EnergyManagementSystem:Sensor,
  hSP,
  Thermal Zone 1,
  Zone Thermostat Heating Setpoint Temperature;

EnergyManagementSystem:Sensor,
  cSP,
  Thermal Zone 1,
  Zone Thermostat Cooling Setpoint Temperature;

In addition to EMS sensors you need an EMS Actuator which will overwrite the “Cycle” schedule (basically switches system ON and OFF)

EnergyManagementSystem:Actuator,
  AvailSCH_Overwrite,
  Cycle,
  Schedule:Constant,
  Schedule Value;

The EMS Program Calling Manager specifies when the ERL program is executed ... (more)