VAV & CAV Heat Recovery

HVAC tab in model data under Mechanical Ventilation header - Compact HVAC

 

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 CAV and VAV systems by checking Heat Recovery On under the Mechanical Ventilation header at building level.

Heat recovery type

Enter the type of air-to-air heat recovery. The choices are:

 

Sensible heat recovery effectiveness

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.

Latent heat recovery effectiveness

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.

Heat recovery schedule

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.

Heat recovery + economizer

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.

 

When heat recovery is used with the 2-Full fresh air outside air mixing option 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.