York MILLENNIUM Y22, Installation Manual

Page: 76 / 140

102777-YIM-E-0206
76 Unitary Products Group
14. When the space temperature rises above the Unoccu-
pied cooling setpoint, the control enables optional duct
pressure control and optional power exhaust system;
power is applied to the airflow proving switch (APS) and
to the coil of starter 5M to engage the supply fan motor. If
the supply fan operates correctly (proper rotation) the
pressure difference between the heating section and the
supply fan section increases and APS closes to allow
mechanical cooling operation. The unit operates as
though it were in the Occupied mode (see above) until
the space temperature falls below the cooling setpoint or
Occupied mode is engaged.
15. Duct Pressure Control - Inlet Guide Vane Option: The
duct pressure controls are powered with a call for the
supply fan. Once powered, the pressure transducer DPS
provides a voltage signal input to the Simplicity control.
The control calculates a 2-10VDC signal to the inlet
guide vane actuator.
16. Duct Pressure Control - VFD (Variable Frequency
Drive) Option:
The duct pressure controls are powered
with a call for the supply fan. Once powered, the VFD
responds to a VDC control signal from the DPS (Duct
Pressure transducer). In the heating mode the VDC,
DPS pressure signal forces the fan to full volume. VAV
boxes should be tied to the H1 terminal to signal the
boxes to full open.
17. Electronic Economizer Option: The control directly
controls the position of the outside air / return air damp-
ers through a 2-10 VDC signal to ACT1 (economizer
actuator). The economizer is powered only after supply
fan operation has been verified (APS closed) and the
unit is in Occupied or Recovery mode. When the control
is not powered or is in Unoccupied mode, the outside air
dampers spring return closed. When in Occupied or
Recovery mode and there is no Y1 call or if free cooling
is unavailable, the Simplicity control opens the econo-
mizer dampers to the minimum position setting made in
the parameters.
With a Y1 call where the outside air is appropriate for
free cooling (see below), the control modulates the
vanes for free cooling in place of first stage cooling.
(Please see the compressor staging chart above.) The
control modulates the economizer dampers to maintain a
Mixed Air Temperature (Return Air / Outside Air Mixture,
sensed between the filters and the DX coil) between
50
°
F and 55
°
F (adjustable between 40
°
F and 65
°
F).
The Simplicity control uses one of three methods to
determine when free cooling is available. The method
used is determined by the option selection.
Dry Bulb: The control refers to input from the OAT, and
will allow free cooling when the outdoor temperature falls
below the Economizer First Stage temperature setpoint.
Free cooling will be available until the outdoor tempera-
ture rises above the temperature setpoint.
Single Enthalpy: the control will consider, along with
outside temperature, outside air humidity [OAH sensor;
parameter must be set to ON] in enabling free cooling.
The outside air enthalpy setpoint parameter [BTU per
pound] must also be set.
Dual Enthalpy (Comparative/Differential Enthalpy):
Both the Outdoor Air Enthalpy and the Return Air
Enthalpy [RAH sensor, option parameter must be set to
ON] are connected to the control. The setpoint when the
outdoor air enthalpy is less than the return air enthalpy,
free cooling is available. The rules in the control will lock
out free cooling and force mechanical cooling when the
outside air temperature exceeds setpoints.
18. Power Exhaust Option with Modulating Dampers:
The power exhaust controls are enabled in Occupied
mode. The building pressure sensor [BSP] provides a
signal to the control. The exhaust dampers are modu-
lated by a 2-10VDC signal from the control, proportional
to the pressure sensed, to the damper actuator. When
the actuator opens the damper more than the parameter
“Exhaust Damper Position for Exhaust Fan to Turn ON”
setting, the Simplicity control powers the 10M starter to
engage the power exhaust fan motor. When the dampers
reach the ”Exhaust Damper Position for Exhaust Fan to
Turn OFF” setting, the control turns the motor off. When
the power exhaust is disabled, the control closes the
exhaust dampers.
19. Non-Modulating Power Exhaust Option: The power
exhaust controls are enabled by the Simplicity control.
The control powers the exhaust fan motor by monitoring
the position of the economizer damper vanes [“Econo-
mizer Damper Setting for Exhaust Fan to Turn ON
[OFF]”]. The outlet pressure of the power exhaust fan
forces the barometric relief dampers open. Exhaust Fan
operation is continued until the economizer reaches the
% set in the parameter Gravity closes the barometric
relief dampers when the exhaust fans are off.
20. Power Exhaust Option with Variable Frequency Drive
(VFD):
The power exhaust controls are enabled through
the Simplicity control. The variable frequency drive is
controlled by a signal from the control, based on the
Building Pressure sensor (BPS), located in the control
box, which translates the building pressure signal to a
VDC signal. Fine tuning is accomplished by setting
parameters in the VFD [ref: separate instruction].
NOTE: Modulated exhaust: Pressure-tap tubing must be
run from an appropriate location in the building to
the "high" port on the BPS transducer. Dampers on
the VFD power exhaust are gravity-closed and are
not modulated. The BPS signal is proportional with
the difference between outside ambient pressure
and building pressure. The VFD is set for a mini-
mum speed of 33% and a maximum of 100%. The
VFD parameters are factory set, specific for each
control system, and are detailed on a sticker by the
drive. The drive manual is shipped with the unit.