.Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Modulations.Reliefs .Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Subsequences.Modulations.ReliefsThis is a multi zone VAV AHU economizer modulation block. It calculates the outdoor and return air damper positions based on the supply air temperature control loop signal. It is implemented according to Section 5.16.2.3.d, Figure 5.16.2.3-1 of ASHRAE Guideline 36, May 2020. Damper positions are linearly mapped to the supply air control loop signal.
When the economizer is enabled, the PI controller modulates the damper positions. Return and outdoor damper are not interlocked. When the economizer is disabled, the damper positions are set to the minimum outdoor air damper position limits.
The control charts below show the input-output structure and an economizer damper modulation sequence assuming a well configured controller. Control diagram:
Multi zone AHU economizer modulation control chart:
