Specifications

6. SEQUENCE OF OPERATION
Modulating Economizer with Typical Electro -
Mechanical Thermostat
The Honeywell W7215 module, ML series actuators,
JCI damper sections, and factory wiring harness
comprise an integrated economizer. These
economizers are used to provide ventilation and free
cooling for the JCI Series of vertical, and horizontal,
air handlers.
The Honeywell W7215 can accept inputs from
additional optional sensors, including a return-air
enthalpy sensor (for differential enthalpy control) or
a CO
2
sensor (for Indoor Air quality strategies).
The economizer module also provides a provision
for remote damper position control. Min. and max.
damper position settings can be remotely controlled
using the P and P1, and Q and Q1 terminals on the
economizer module. For more information regarding
these features, consult the Honeywell W7215
manual included with the Economizer kit.
Powering the Thermostat (24vac) -
Power to the electromechanical thermostat is
provided from R terminal of the JCI unit’s low voltage
terminal strip. Electromechanical thermostats do not
require a 24vac common connection.
Powering the W7215 (24vac) -
The W7215 is powered from the JCI unit’s
microprocessor board at the G-Out pin whenever the
fan of the evaporator section is operating. To ensure
that the W7215 is continuously powered, the fan
switch on the thermostat sub-base should be left on
at all times.
High Enthalpy Sequence:
When the outside air enthalpy exceeds the enthalpy
set-point, the economizer W7215 module terminals
1 and 2 are closed and economizer will be forced
into the minimum damper position setting. The JCI
unit’s microprocessor board will control cooling
requirements.
Low Enthalpy Sequence:
When the outside air enthalpy is below the enthalpy
set-point, W7215 economizer terminals 1 and 2 are
opened and free cooling is activated. The JCI unit’s
microprocessor board turns off compressor
operation.
Damper Modulation:
On all JCI units' the C7046 temperature sensor
should be located in the discharge air duct. Locating
the sensor in the discharge air provides effective
'low-limit' sensing and control. The outside-air
damper remains at minimum position if the
discharge air temperature is below 50
0
F or 10
0
C. If
the discharge air temperature is between 50
0
to 56
0
F (10
0
to 13.3
0
C) the outside air damper will
modulate between minimum position and fully open.
Above 56
0
F (13.3
0
C) the outside air damper will
remain in the fully open position.
Occupied:
The OCCUPIED harness terminal is not connected
to the economizer controller. It has been provided if
site conditions require field connection of an
Occupied function. Consult the Honeywell W7215
Economizer Controller Manual for more information.