HVAC tab in model data under Mechanical Ventilation header
With Compact HVAC, you can specify air-to-air heat recovery which is available between the relief air stream and the outside air inlet stream. Heat recovery is selected for Unitary multizone, CAV and VAV systems by checking Heat Recovery On under the Mechanical Ventilation header at building level. For Unitary single zone make the selection at the zone level.
Enter the type of air-to-air heat recovery. The choices are:
Enter the sensible heat recovery effectiveness. This is applied as a constant effectiveness at all conditions. The valid range is from 0.0 to 1.0, and the default is 0.70.
Enter the latent heat recovery effectiveness if Heat Recovery Type is Enthalpy. This is applied as a constant effectiveness at all conditions. The valid range is from 0.0 to 1.0, and the default is 0.65.
When no economiser is selected this data defines the heating setpoint temperature of the heat recovery device for Unitary and Unitary multizone systems. Note that the single value is applied throughout the year. For example enter 15°C to model a system which heats outside air up to 15°C and no higher. A high setpoint value will provide optimal heating but this may add to cooling loads in the summer.
Use this schedule to define the availability of the heat recovery device. Schedule values of 1 mean that heat recovery is available and values of 0 mean that it is not available and that the bypass is opened. You may want to use this control to bypass heat recovery in the summer for example.
If an economiser (free cooling) option is selected, the heat recovery is bypassed whenever the economiser operates and the heat recovery is always bypassed if economiser operation would be beneficial.
The heat recovery will operate when:
You can have heat recovery and no Economiser action by switching on Heat recovery and setting economiser to 1-None. In this case the heat recovery units heats outside air using the Heat recovery heating setpoint temperature above. It also cools outside air when return air temperature is lower than outside air temperature.
If the economiser is selected together with heat recovery then the Heat recovery heating setpoint temperature data is not shown and the effective heat recovery setpoint temperature is given by the lower economiser limit temperature.
When heat recovery is used with the 2-Full fresh air outside air mixing option in CAV/VAV systems, the heat recovery is by-passed when this is advantageous in reducing AHU heating/cooling coil loads. Otherwise, when using the 1-Recirculation option, the economiser must be selected in the interface for the heat recovery to be by-passed in this way.