ERV interaction - Johnson Controls - LIT-12011950 - Building automation software - Smart Equipment Controller - 5.0

Smart Equipment Controls Sequence of Operation Technical Bulletin

Johnson Controls
Product name
Smart Equipment Controller
Document type
Technical Bulletin
Document number
Revision date
Product status

The ERV function interacts directly with the exhaust control function. Only enable the ERV Interaction on VAV units equipped with exhaust VFDs.

Setpoints and related data

The setpoints and related data include the following items:

  • Power exhaust fan type (ExFType) variable frequency fan
  • Fan control type (FanCtlType) variable speed
  • ERV Enabled (ERV-En)
  • ERV Unoccupied Fan Enabled (ERVUnoccFan-En)
  • Operational Occupancy (OprOcc)


The outputs include the following items:

  • 2 to 10 VDC from EX VFD
  • 24 VAC from EX-FAN


The ERV function provides input to the exhaust control sequence by determining if energy recovery is installed and when it is active. The ERD state is determined based on Table 1.

Table 1. Energy recovery determination
ERV enabled ERVUnoccFan-En OprOcc State
Disable * * OFF
Enable Enable * ON
Enable Disable Occupied ON
Enable Disable Unoccupied OFF
* This state has no effect on the output.

When the ERV state is on, and applied to a VAV unit with exhaust VFDs, the EX VFD output is controlled by tracking the VFD OUTPUT of the supply fan.

When the ERV installed is disabled, the exhaust VFDs are controlled based on building static pressure. See Modulating power exhaust with VFD, for additional information.

When the ERV installed is enabled and ERV unoccupied fan is disabled, the exhaust outputs are turned off in the unoccupied mode.

On any unit without exhaust VFDs, the ERV installed parameter must be set to disabled.