This mode is intended for a complex 'on/off' mixed mode system where openings are controlled from a single zone's dry bulb temperature and a zone group's maximum temperature. The apertures are closed as the zone temperature or group maximum temperature exceeds a cut-off value, so mechanical cooling can be introduced through Internal Conditions. However, the set point for plant cooling can be below the control range for the aperture thus sending the zones of the zone group into a completely air conditioned state. The control bands overlap only allowing one control to be active at one time, this is achieved as follows. At the start of each day every active aperture type in this mode has each zone of its zone group flagged as 'plant inactive'. This ensures that even though the set points in Internal Conditions would indicate that the plant should be on, this is in fact overridden. During the simulation of the day if at any hour the zone exceeds its cut off temperature the aperture type will be flagged as inactive and the plant re-enabled for all the zones in the controlling zone group. This state will continue until the start of the following day when all flags are reset as described earlier. This mode requires the following parameters.
Parameter |
Description |
Zone |
The zone name whose dry bulb temperature will control the aperture. |
Override zone group |
The name of the zone group whose member zone with the maximum temperature is to be used as an additional cut-off control. |
Lower limit |
The aperture will be closed if the controlling zone dry bulb temperature is below this value. |
Upper limit |
The aperture will be fully open if the controlling zone dry bulb temperature is above this value. |
Cut-off |
The aperture will shut as the zone temperature rises above this value. AC will then be set active for all zones in the controlling group. |
Upper wind speed |
The aperture will start to close when the wind speed exceeds this value. The aperture will be fully closed at 0.5m/s above this value. |
For example, the automatic control function rdwom could have the parameters set as follows:
Zone: East Office
Override Zone Group: Offices
Lower limit: 22
Upper limit: 24
Cut-off: 25
Upper Wind Speed: 5.0
This would define the following strategy for aperture opening. As the dry bulb temperature in zone 5 rose above 22C the aperture would start to open. The aperture would be fully open at 24C and remain fully open until 25C when it would shut and the zones in zone group 3 would go into full AC mode. The aperture will also close if, at any time, the outside temperature is greater than the inside temperature. The aperture starts to close when the two temperatures are equal and will be fully closed when the outside temperature is one full degree above inside. The wind speed will also start to shut the aperture as it increases above 5m/s and be fully closed at 5.5m/s. Finally, the third zone group will be searched for the zone with the highest temperature. As this highest temperature rises above 25C the aperture will shut and all zones of zone group 3 will be placed into full AC mode. For a full description of how final aperture opening values are calculated please see the section: Aperture Type Functions.