W7340 Only; Demand Control Ventilation (Dcv) Sensor Input (W7340 Only) - Honeywell Design and Application Technical Reference Manual

W7340 only

To measure enthalpy, the logic module
accepts signals from either:
• C7600C Humidity and 10K NTC
temperature sensors.
• or a C7400 Enthalpy Sensor.
• OR from the Trane controller via modified
Modbus communications link.
When using C7400 Enthalpy Sensors;
connect the enthalpy sensors to the humidity
sensor terminals; leave the temperature
sensor terminals empty.
• Use C7400A sensor with W7340A or
W7340B.
• Use a C7400C sensor with W7340C.
The local method (changing configuration from
Modbus) of configuring the Economizer for
enthalpy or humidity sensors is:
• Short out the external minimum damper
position terminals during the first three
seconds after boot-up will cause the LED to
go solid on within 5 seconds.
• Maintain the short for another 5 seconds will
cause LED to flash quick pulses, indicating
the type of configuration.
• 2 pulses between off periods indicates the
Economizer is configured for Humidity
sensors. 3 pulses means it is configured for
Enthalpy sensors.
The configuration can be toggled between
Humidity and Enthalpy by releasing the short
for approximately 5 seconds, until the LED
goes solid again, and then reapplying the
short for another 5 seconds.
The toggling is indicated by the new LED flash
sequence. This can be performed as many
times as desired, and the most recent
configuration will be saved when the short is
removed for over 10 seconds.
Section 10 - W7340 and W7345 Economizer Module
Demand Control Ventilation
(DCV) Sensor Input (W7340
only)
The DCV sensor can be any sensor that
provides a 2-10 Vdc output over a range of
500 to 1500 ppm of CO
modulates the outdoor damper to provide
ventilation based on occupancy.
The W7340A and B modules do not have the
ability to set the outdoor air damper to a
maximum position for DCV, they incorporate a
minimum position setting that defaults to 20%
but can be overridden using the on-board pot
or the modified Modbus communication link to
a maximum of 50% open.
The maximum position sets the damper
position to a position that the damper goes to if
the CO sensor fails. If the minimum position
2
set point is higher than the DCV maximum
position, on sensor failure, the damper goes to
the higher of the two of DCV maximum and
minimum position setting.
There is no limit on the damper position on a
call from the CO
100% open.
The W7340C DCV economizer logic module
has the ability to set DCV minimum damper
and minimum position. The DCV minimum
position is set to ventilate the building
contaminants and the minimum position is set
to ventilate for the building contaminants and
the building occupants. The installer sets the
damper DCV minimum position and the
minimum position based on the design
occupancy and cfm of outdoor air
requirements for the space. The damper will
modulate open between the DCV minimum
damper position and the minimum position
based on input from a CO
damper will not drive 100% open on a call for
ventilation, but can drive 100% open on a call
for cooling. If the CO
97
. The DCV signal
2
sensor (DCV). It can go
2
sensor. The
2
sensor fails the damper
2
Honeywell Economizers 63-8594-02