Page 41
507232-04 7/2017
1.2. 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:
Option 0: Damper continues to modulate while
compressors are on, but the effect of mechanical cooling
may force the damper closed to its minimum position. After
compressor starts, the free cooling set point is lowered to
fixed temperature setting of 45°F.
Option 1: Damper opens to its maxopen 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.
Option 2: Is as follows:
Holdsoff compressor on Y2 call until damper has
modulated to maximum position (Parameter 131 -
FREE CL MAX DAMPER) for three minutes.
After three minutes, the compressor starts and the free
cooling set point is lowered to 45°F. Damper is not
locked at maximum open while compressor is on, but
modulates to maintain 45°F discharge air temperature.
When Y2 is satisfied, compressor goes off and free
cooling set point is restored to 55°F (Parameter 159 -
FREE COOL SUPPLY SP).
Option 3: Same as Option 2, but with a ten-minute delay
instead of a three-minute delay.
1.3. Free Cooling Compressor Lockout
Mode and Low Ambient Set Point
Go to SETTINGS > RTU OPTION > EDIT PARAMETER =
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.
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.
1.4. Outdoor Air Suitable for Free Cooling
The M3 Unit Controller displays the outdoor air suitability
information on the status screen.
The appropriate sensors are provided when the
economizer is factory-configured. See figure 35 and 36 for
factory-installed sensor locations. When the economizer is
field-installed and configured, the single or dual enthalpy
modes require additional field-provided sensor(s).
California Title 24 Compliance
For California Title 24 compliance, adjust the free cooling
setpoint based on:
-The climate zone where the unit is installed. See table 19.
-The setpoint requirement published by the California
Energy Commission. See Section 140.4 - Prescriptive
Requirements for Space Conditioning Systems of the
2013 Building Energy Efficiency Standards.
Note - Values in the referenced standard will supersede
values listed in table 19.
To Next Page
Loading...
Need help?
General
