Enabling Economizer And Settings; Free Cooling Compressor Lockout Mode And Low Ambient Set Point - Lennox Core Unit Controller Setup Manual

10.3. Enabling Economizer and Settings

The economizer, when configured, controls:
• Damper position, which determines how much outdoor
air is used to meet free cooling or indoor air quality
requirements, and
• Optional power exhaust fans.
On a cooling demand, outdoor air is used for free cooling
instead of first-stage compressor(s) when outdoor air is
suitable.
To enable the economizer if installed:
Go to SETUP > INSTALL
When reaching Configuration ID 1, position 2 will need to
be set to the applicable type of economizer. Valid types are:
• M = Motorized Outdoor Air Damper Only
• T = Economizer - Temperature (Note: Used for both set
point and offset temperature control.)
G = Economizer - Global
•
S = Economizer - Single Enthalpy
•
D = Economizer - Dual Enthalpy
•
10.3.1. Damper Feedback Calibration
Use the following procedure to perform a damper feedback
calibration.
Go to SETUP > TEST & BALANCE > DAMPER > IS DAMPER
This drives the damper to the fully closed position. Visually
inspect that the damper has stopped moving in the closed
position, and answer YES to calibrate damper closed
position feedback value.
Then the next screen will ask IS DMPR FULL OPEN?
This will drive the damper to fully open position. Visually
inspect that the damper has stopped moving in the full open
position, and answer YES to calibrate damper full open
position feedback value.
10.3.2. Damper Operation During Free
Cooling
These are operating profile options for the economizer
damper (Parameter 164 - ECONOMIZER PROFILE) during
free cooling when any compressor is on and can be selected
as follows:
Damper opens to its max open position (Parameter 131 -
FREE CL MAX DAMPER) when any compressors start.
NOTE: When using Option 1 and after the compressor is
stopped, the M3 shall resume damper modulation.
10.4. Free Cooling Compressor Lockout
Mode and Low Ambient Set Point
Go to SETTINGS > RTU OPTION > EDIT PARAMETER > COOLING =
285 (FRCL COMP LCKOUT MD).
Default value is 2. Range is 0 to 2.
• 0 = Disable Compressor Lockout
• 1 = Lockout Compressor if outdoor air is suitable
regardless of outdoor air temperature.
CLOSED?
2 = Lockout Compressor if outdoor air temperature is
•
below Parameter 108 setting and Outdoor Air is Suitable
(Default).
Go to SETTINGS > RTU OPTION > EDIT PARAMETER = 108
(FREE LO AMB LCKT SP).
Default value is 55.0°F. Range is 45.0 to 80.0°F.
10.4.1. Outdoor Air Suitable for Free
Cooling
The CORE Unit Controller displays the outdoor air suitability
information on the status screen.
The appropriate sensors are provided when the economizer
is factory-configured. When the economizer is field-installed
and configured, the single or dual enthalpy modes require
additional field-provided sensor(s).
10.4.2. Enthalpy Set Point
This setting pertains to the single enthalpy free cooling mode
only. The CORE Unit Controller will enable free cooling
when outdoor air enthalpy (A7) is less than the enthalpy set
point (Parameter 162 - ECON FREECL ENTH SP). Figure
6 shows the approximate enthalpy sensor output at various
temperatures and percentage of relative humidity.
100
90
80
70
60
50
40
30
20
10
40°F 50°F
Figure 31. Enthalpy Sensor Output Current
Honeywell C7400
10.4.3. Free Cooling Damper Maximum
Position
Damper Maximum position for free cooling is by default set
to 100%. To modify this settings, use the following path:
SETTINGS > RTU OPTION > EDIT PARAMETER > AIR FLOW >
131 (FREE CL MAX DAMPER)
10.4.4. Minimum Damper Position
Use the following menu path to modified the minimum
damper positions for both high and low operations.
SETUP > TEST & BALANCE > DAMPER > CLOSING DAMPER >
OPEN DAMPER > TURN BLOWER ON > MIN DAMPER POSITION
BLOWER ON HIGH = .%
SETUP > TEST & BALANCE > DAMPER > CLOSING DAMPER >
30
60°F 70°F 80°F 90°F 100°F