Emerson E2 Air Handling Units, Temperature Control, Alternate Setpoints, System Log Report

11.5.6.3System Log Report

The System Log report provides a summary of all logged points for all applications in the system and a com- plete list of logged points for all applications in the sys- tem. Note that depending on the size of the configuration and the number of points logged, this may take a few sec- onds.

To display the System Log Report:

1.Press  for the Main Menu.

2.Press for System Configuration.

3.Press Logging Setup.

4.Press Display Logged Points.

NOTE: Depending on the number of points logged and the resolution setting, a limited amount of memory space is available for one-

year logging.

Figure 11-14- System Log Report Example

11.6Air Handling Units

(AHU)

11.6.1 Overview

The E2 BX supports the simultaneous control of up to six air handling units (AHU). AHU Control applications govern all aspects of an AHU’s operations, including heat- ing and cooling, dehumidification, fans, and economizer control.

Unlike rooftop control units (RTUs), AHUs are con- trolled directly by the E2 itself and not by a separate unit control board.

An AHU Control application actually consists of three separate control algorithms. The main control algorithm monitors the indoor temperature and activates heating and cooling stages when necessary to maintain the user- defined temperature setpoint. Another algorithm monitors the indoor humidity and uses a desiccant wheel or addi- tional AHU cool stages to reduce the humidity level. The third loop controls either a two-position (digital) or vari- able-position (analog) economizer damper based on the outside air conditions.

11.6.2 Temperature Control

In its most basic form, Temperature Control simply reads a control input value, compares it to the active tem- perature setpoint, and activates or deactivates heating or cooling stages in an effort to satisfy the setpoint. The majority of user setup that must be done in Temperature Control involves specifying which input is to be used as the control source, defining different setpoints for use in occupied, unoccupied, summer, and winter modes, and setting up the operating characteristics of the heating and cooling stages.

11.6.3 Alternate Setpoints

For both the heating and cooling setpoints, you may choose to use different setpoints during occupied or unoc- cupied building times, and different setpoints for summer and winter seasons. In other words, AHU Control may have four different pairs of heating and cooling setpoints, as shown in Table 11-9.

Cooling	Heating
SUMMER COOL OCC	SUMMER HEAT OCC
SUMMER COOL UOC	SUMMER HEAT UOC
WINTER COOL OCC	WINTER HEAT OCC
WINTER COOL UOC	WINTER HEAT UOC

Table 11-9- Possible Heating/Cooling Setpoints

AHU Control looks at the E2’s Global Data parameters to determine whether it should run in summer or winter mode. Refer to Section 10.17, Set Up Global Data, for information on how to set up summer/winter control parameters.

The AHU chooses occupied or unoccupied mode by reading an occupied state input, which is most commonly tied to the output of a Time Schedule application.

11-20 • E2 RX/BX/CX I&O Manual 026-1614 Rev 4 5-JAN-2013