Section 10 - W7340 and W7345 Economizer Module
63-8594-02 Honeywell Economizers 96
W7340 and W7345 Components
The W7340 is a full enthalpy economizer used
in a Trane unit to provide a totally integrated
control system.
The W7345 provides temperature (OAT)
control only; it does not have an option for a
RAT, DCV sensor or exhaust control.
The W7340, when wired as shown below
responds to a signal from a modified Modbus
command. This system uses C7400 Solid
State Enthalpy Changeover Sensor(s). The
C7400 Enthalpy Sensors respond to both dry
bulb temperature and humidity, allowing use of
outdoor air at higher temperatures for free
cooling when humidity is low.
The logic module functions as a first stage of
cooling and provides maximum energy
savings during the cooling cycle. The logic
module automatically locks out free cooling
during heating and holds the outdoor air
damper at the DCV minimum setting.
Table 1 details the input/output (I/O) logic of
the W7340. The logic module energizes the
Unit Control and Indoor Fan contacts, and
operates according to Table 1.
Table 1. W7340 Economizer I/O Logic.
Inputs Outputs
DCV
Enthalpy
a
Y1
b
Y2
b
Compressor
Damper Outdoor Return Stage 1 Stage 2
Below set High Low On On On On Minimum position
On Off On Off
Low High On On On Off
Modulating
c
On Off Off Off
Above set High Low On On On On
Modulating
d
On Off On Off
Low High On On On Off Modulating
e
On Off Off Off
a
For single enthalpy control, the module compares outdoor enthalpy to the ABCDE setpoint.
b
If both stages of cooling are off, the system is off and the damper is:
— At DCV minimum position if DCV is below setpoint.
— Modulating if DCV is above setpoint.
c
Modulation based on mixed air sensor signal, modulating between DCV minimum position and 100% open.
d
Modulation based on DCV signal, limited by minimum position.
e
Modulation based on the greater of the DCV and mixed air sensor signals.
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