Carrier 50LC 07, Service And Maintenance Instructions, Page: 54 / 100

54
Demand Control Ventilation —
If a space or return air CO
2
sensor is connected to the
Economize X control, a Demand Control Ventilation
strategy will operate automatically.
When the space CO
2
level is below setpoint DCV SET
(default 1100 ppm), the minimum ventilation position for
the outside air damper will be reset to lower settings
suited for offsetting CO
2
loads from space sources not
including people. The settings will vary according to
supply fan speed. When the supply fan speed is Low, the
DCV minimum ventilation point is VENTMIN L. When
the supply fan speed is High, the DCV minimum
ventilation point is VENTMAX H.
As the CO
2
level in the space increases above the setpoint
DCV SET (default 1100 ppm), the DCV ventilation
position of the outside air damper will be increased
proportionally, until the Maximum Ventilation setting is
reached. The settings will vary according to supply fan
speed. When the supply fan speed is Low, the DCV
maximum ventilation point is VENTMAX L. When the
supply fan speed is High, the DCV maximum ventilation
point is VENTMAX H.
DCV operation will float between its VENTMIN and
VENTMAX settings, never exceeding the VENTMAX
limit as the space CO
2
level varies according to changes
in people occupancy levels.
During concurrent demand for DCV and free cooling, the
outdoor--damper will follow the higher demand condition
from the DCV mode or from the free--cooling mode.
Setup and Configuration
Before being placed into service, the W7220 Economizer
module must be setup and configured for the installed
system according to project control specifications.
Inspect all wiring connections at the Economizer module’s
terminals, and verify compliance with the installation
wiring diagrams.
Initial Menu Display —
On initial start up, Honeywell displays on the first line and
Economizer W7220 on the second line. After a brief
pause, the revision of the software appears on the first line
and the second line will be blank.
Time--out and Screensaver —
When no buttons have been pressed for 10 minutes, the
LCD displays a screen saver, which cycles through the
Status items. Each Status items displays in turn and cycles
to the next item after 5 seconds.
IMPORTANT : During setup, the Economizer module is
live at all times.
Setup and configuration involves stepping through three
menus and enabling required functions and re--selecting
setpoints to meet project requirements. The menus used
are SYSTEM SETUP, ADV SETUP and SETPOINTS.
Obtain a copy of the project control specifications before
starting setup and configuration process.
NOTE : W7220 will be in the ”set up” mode for the first
60 minutes after powered. If a sensor for OA air or S--bus
device (sensor, actuator) is disconnected during the set up
mode, the W7220 will not alarm that failure. The SAT
sensor is a system ”critical” sensor, if the SAT sensor is
removed during the set up mode, the W7220 will alarm.
After 60 minutes the W7220 controller will change to
operation mode and all components removed or failed will
alarm in the operation mode.
For this application with the 2--speed supply fan option,
note that parameters EQUIPMENT, AUX2I and FAN
TYPE have required settings. Check that these parameters
are set at these required settings:
EQUIPMENT must be CONV
AUX2I must be W
FAN SPEED must be 2SPEED
Press the (EXIT) button to exit the SYSTEM SETUP
menu and return to top level menu. Scroll down to ADV
SETUP menu and press (ENTER) button to enter this
menu. Scroll down through the list of parameters and
adjust settings as required. Be sure that the message
CHANGE STORED appears with every change in
parameter setting.
Press the (EXIT) button to exit the ADV SETUP menu
and return to top level menu. Scroll down to SETPOINTS
menu and press (ENTER) button to enter this menu.
Scroll down through the list of parameters and adjust
settings as required. Be sure that the message CHANGE
STORED appears with every change in parameter setting.
SETPOINT Defaults: The default setpoint values
represent many years of successful experience with
economizing systems. Any changes that represent
significant deviations from the default values should be
well considered.
DCV SETPOINT:
The default value for DCV SET is
1100 ppm. It is recommended that this setpoint be
adjusted down to 500 ppm (or CO
2
level of outdoor air
plus 100 ppm, whichever is higher) to permit an earlier
initiation of the DCV mode as space occupancy increases.
Checkout
For checkout, review the Status of each configured
parameter by observing the scrolling display from the
Screensaver mode or by entering the STATUS menu.
Use the Checkout menu (see Table 9 on page 44) to test
the damper operation and any configured outputs. Only
items that are configured are shown in the Checkout
menu.