4
ec1: outdoor temperature reference
The economizer controller positions the mixing box
dampers to achieve 55° F mixed temperature when
the thermostat calls for cooling AND the outdoor air
temperature is below the economizer
setpoint. If outdoor air temperature is
between 55° F and the economizer
setpoint, the dampers will modulate
to the 100% outdoor air position.
Above the setpoint, the outdoor
air damper is held at the minimum
position. The setpoint is field
adjustable and the outdoor air sensor
is factory mounted.
The economizer controls package enables free cooling using outdoor air. All EC options include a modulating
actuator for controlling outdoor and return air dampers, and a minimum outdoor air positioner. During a call for
heating the economizer is locked out and the outdoor air damper holds at the minimum position.
MB1: Minimum outdoor air Positioner
The MB1 option includes a modulating
actuator and potentiometer that control
the outdoor air and return air damper
positions. When the unit is energized,
the dampers will travel to the position
corresponding to the potentiometer
setting, providing the desired amount of outdoor air.
When the unit is powered off, the outdoor air damper
closes to prevent backdrafting. To adjust the damper
settings, simply dial the potentiometer (shown above) to
desired operating position of the outdoor air damper.
MB2: 2-10 Volt external signal
The MB2 option includes a modulating actuator that is
controlled by an external 2-10 volt signal. This option
is appropriate for applications that call for a building
automation system that will control the mixing box
dampers.
MB3: 4-20 ma external signal
The MB3 option includes a modulating actuator that is
controlled by an external 4-20 mA signal. Like the MB2
option, this option is appropriate for applications that
call for a building automation system that will control the
mixing box dampers.
MB4: Manual Quadrant
The MB4 option consists of a manual
quadrant that enables the outdoor air
and return air dampers to be secured
into a single position. The primary
function is to introduce the specified minimum outdoor
air volume during operation. Dampers remain in the
same position when the unit is powered off.
In addition to the EC options described above, Greenheck offers four MB mixing box control options for
applications where a factory provided economizer package is not desired.
The mixing box (shown at right) includes
outdoor air and return air low leakage
control dampers in a face and bypass
configuration. Either two inch pleated
or aluminum mesh filters are available
within the mixing box section. Double wall
construction is optional.
A mixing box control option must be
specified for every IGX-HV unit. Greenheck
offers eight mixing box control options
that accommodate a wide variety of
applications. The four EC and four MB
options are described below. Specify only
one control box option per unit.
ec2: outdoor enthalpy reference
Same as EC1, except economizer setpoint is based on
outdoor air
enthalpy
.
ec3: airstream temperature reference
The economizer controller compares the temperatures
of the outdoor air and return air when the thermostat
calls for cooling. The mixing box dampers are then
positioned to maximize the
airflow of the cooler airstream.
When outdoor air temperature
is sufficiently cool, the mixing
box dampers will modulate to
provide 55° F mixed air. The
outdoor air sensor is factory
mounted. The return air sensors
are field installed.
ec4: airstream enthalpy reference
Same as EC3, except airstream
enthalpy
values are
compared.
MIXInG BoX controLs
Mixing Box controls with economizer cooling
Mixing Box controls (no economizer)
Supply
Return Air
Outdoor Air
