Software Overview; Application Mode; Operational Modes - Emerson iPro.Genius Installation And Operational Manual

7

Software Overview

The DAC maintains space temperature setpoints
by modulating heating or cooling stages to maintain a
desired supply air temperature. For this reason, a
supply air temperature sensor must be connected to
the controller. The desired supply air temperature is
primarily determined by a setpoint and can be
automatically adjusted based on changes in building
load.

7.1. Application Mode

The DAC supports packaged HVAC control in
either Constant Air Volume (CAV) or Variable Air
Volume (VAV) applications. The main difference
between the two modes is how the variable speed fan
will be controlled. When CAV is selected, the
variable speed fan is modulated based on the number
of heating or cooling stages that are currently active.
When VAV is selected, the variable speed fan
modulates to maintain a static duct pressure. See
Section 7.5., Fan Control for more details.
Corresponding
Operating
Site Manager
Mode
Mode
0 Idle
1 Ventilation
2 CO2 Purge
3 Economizing
4 Make-up Air
5 Heating
6 Cooling
7 Dehum
8 Emergency
Shutdown
Table 7-1 - DAC Operational Modes with Corresponding Site Manager Mode
Discharge Air Controller (DAC) Manual
sensor to be connected to the controller. Instead, the
system terminal load is calculated by the E2 and is
sent over the network to the DAC so the operational
mode can be determined. Note that the primary
control of heating and cooling stages using the supply
air temperature sensor is identical for either CAV or
VAV mode.

7.2. Operational Modes

operation at any given time. All modes have different
priorities so if conditions warrant two modes to be
operational at the same time, one of the modes will
win and become active. In the table, the modes are
shown in ascending priority with the exception of
Cooling and Dehum. For example, Idle is the lowest
priority and Emergency Shutdown is the highest
priority, but if both cooling and dehumidification are
called for, the larger of the two calculated loads will
take priority and activate the proper mode of
operation.
Description
Default mode if no other modes are active
Space air recirculation only
Max CO2 level reached and fresh air must be
brought in to building
Outdoor air free cooling active
Exhaust Fan detected and make-up air must be
brought in to building
Heating is active
Cooling is active
Dehumidification is active
One of the following is active: Smoke
Detected, Phase Loss Active, Fan Proof
Failure
Also, VAV mode does not require a local space
The DAC will be in one of nine possible modes of
None
Indoor Fan
Indoor Fan, Outdoor Air Damper
Indoor Fan, Outdoor Air Damper
Indoor Fan, Outdoor Air Damper
Indoor Fan, Heat Stages, Modulat-
ing Heat
Indoor Fan, Cool Stages (Fixed or
Modulating),
Indoor Fan, Cool Stages or Dehum
Output, Reheat Output
None
Outputs Active
Software Overview • 15