83
YORK INTERNATIONAL
FORM 100.50-NOM1 (604)
5
The following parameters are used to set up an eco
2
unit
for Flexsys operation.
• Under the Configuration key of the OptiLogic
Control the “
Unit Type”
must be set to “Flexsys”.
• Under the Setpoints key of the OptiLogic Control
the
“VAV Cool High Temp”
must be set. This is
the setpoint for the temperature of the air off the
evaporator coil, which the Primary Unit Controller
will use to stage the economizer and mechanical
cooling.
• Under the Setpoints key of the OptiLogic Control
the “
VAV Cool Low Temp”
must be set. This is
the setpoint of the temperature of the air off the
evaporator coil that the Primary Unit Controller
uses to stage the mechanical cooling if the under
ß
oor temperature and humidity approaches the dew
point.
• Under the Setpoints key of the OptiLogic Control
the “
Flexsys MSAT Setpoint”
must be set. This is
the setpoint of the temperature of the air the eco
2
unit will try to deliver to the under
ß
oor system.
• Under the Setpoints key of the OptiLogic Control
the “
Flexsys Min Dewpt Diff”
must be set. When
the dew point of the under
ß
oor space gets within
this number of degrees of the actual dewpoint the
Primary Unit Controller switches to the “
VAV Cool
Low Temp”
setpoint.
• Under the Unit Setup key of the OptiLogic Control
the “
Flexsys Dewpt Reset”
must be set to ON if an
under
ß
oor temperature and humidity sensor is being
used to reset the supply air temperature.
A modulating damper is used to vary the amount of
Return Air By-passed from the Return air Duct to the
fan section of the rooftop unit.
• The damper is direct acting (0 VDC – bypass
damper 100% open, 10 VDC – bypass damper
closed.
• During Unoccupied Modes of operation and dur-
ing Morning Warmup, the bypass damper is com-
manded 100% open (10 VDC).
• During the Occupied Mode of operation, the by-
pass damper is controlled to maintain the
“Flexsys
MSAT"
Setpoint.
• The minimum time for the by-pass damper to go
from full open to closed or closed to full open will
be approximately 15 minutes.
• The Primary Unit Controller will calculate a by-pass
damper set point using formula 1 in Figure 45:
• The Primary Unit Controller will calculate the Ac-
tive By-pass Percentage using formula 2 in Figure
45:
• The by-pass damper will be controlled as follows:
◦
If the Actual By-pass Percentage is > = to the
(By-pass Percentage Se 2.5
0
F) the By-
pass damper will close until the Actual By-pass
Percentage is equal to the By-pass Percentage
Setpoint
◦
If the Actual By-pass Percentage is < = to the
(By-pass Percentage Setpoint - 2.5
0
F) the By-
pass damper will open until the Actual By-pass
Percentage is equal to the By-pass Percentage
Setpoint.
Flexsys MSAT Setpoint – Supply Air Temperature Setpoint
Return Air Temperature – Supply Air Temperature Setpoint
By-pass Percentage Setpoint =
Actual By-pass Percentage =
Current MSAT Temperature – Current Supply Air Temperature
Current Return Air Temperature – Current Supply Air Temperature
Formula 1
Formula 2
FIG. 45 –
BY-PASS DAMPER FORMULAS
