York MILLENNIUM Y22 Installation Manual page 108

ter uses a one BTU/LB hysteresis on each side of the limit.
The limit is preset to 27 BTU/ LB with an adjustable range
from 10 to 50 BTU/LB.
Return Air Humidity (RAH) Sensor enable - (OFF) - This
tells the control that it will compare Outside Air Enthalpy (cal-
culated from Outside Air Temperature and Outside Air Rela-
tive Humidity sensed values) and Return Air Enthalpy
(calculated from Return Air Temperature and Return Air Rela-
tive Humidity sensed values). The control will use the air
stream with the lower enthalpy for cooling.
The control is self-configuring to the best available decision
strategy for free cooling availability. For example, if it detects
that OAT and OAH and RAT and RAH sensors are all con-
nected and reliable, will self-configure for Differential
Enthalpy operation. If one of the return air sensors should fail,
the control will stop using rules that involve RAH and set an
alarm.
If the RAH Sensor Enable option is turned ON (and sup-
ported by installed sensors), Differential Enthalpy Operation
can be enabled. If the appropriate sensors are not installed,
or one of them failed, a sensor failure alarm is set. The RAH
alarm can be turned off by turning off the RAH Sensor Enable
option. Thus, the option setting is used to reflect the desired
operation and mainly to control sensor failure alarms.
Economizer Loading to Control SAT - (ON) - This tells the
control if it is going to use Economizer Loading to control
excessive SAT [supplying warmer outside air to keep SAT
from going too low]. This parameter is only applicable outside
the normal Economizer operation. During the Economizer
operation, the loading function is always performed and is an
integral part of the control algorithm.
Duct Static Setpoint - (1.5"WG) - This parameter is applica-
ble only to VAV mode of operation. This is the pressure set-
point that the control will maintain when operating the fan in a
VAV unit. This setpoint is adjustable between 0"WG and
5"WG with the default set to 1.5"WG.
Duct Static High Limit Setpoint - (4.5"WG) - This parame-
ter is applicable only to VAV mode of operation. This tells the
control at what Static Pressure to shut down the unit due to a
Fan control failure. This setpoint is to insure that we don't
continue to operate the Fan with an Inlet Guide Vane or VFD
problem that could cause the ductwork to fail from duct pres-
sure. When the Static Pressure reaches this setpoint
(4.5"WG default), the control will drive the supply fan control
output to zero. If the static pressure does decrease below the
"Duct Static High Limit Setpoint" within 3 seconds after
decreasing the supply fan control output to zero, the control
will resume normal operation. If there is no change in static
pressure after 3 seconds, the control will generate a High
Duct Static alarm, shut down all the outputs including the Fan
and shut down the unit. The alarm is written to the Error His-
tory Buffer and will trigger storing a snapshot of Points
108
Screen data along with a date and time stamp. In networked
applications, the alarm flag is readable by the network. This
parameter can be adjusted from 0"WG to 5"WG with the fac-
tory default set to 4.5"WG.
The customer must be aware of the duct pressure design
limit, and what the duct pressure sensor will be reading when
the peak pressure is reached [the pressure pickup tube may
not have been located at the place of highest pressure in the
system].
The alarm must be reset (after the problem that caused the
alarm is corrected) by resetting the controller by turning
power to the unit off and back on, or by reset command
issued by an external connection.
Morning Warm Up - Is inferred from the entries in Occu-
pied/Unoccupied
Occupied - (from settings in Weekly Schedule and Holi-
day Schedule Tables 44 and 45.) - See discussion in
Sequence of Operation.
Unoccupied - (from settings in Weekly Schedule and Hol-
iday Schedule Tables 44 and 45.) - See discussion in
Sequence of Operation.
VAV High Temperature SAT Setpoint for Cooling - (60°F) -
The control will maintain this SAT when operating in VAV
mode with a thermostat that is calling for first stage cooling.
This parameter may be adjusted from 40°F to 70°F with 60°F
set as the default value.
VAV Low Temperature SAT Setpoint for Cooling - (55°F) -
The control will maintain this SAT when operating in VAV
mode with a thermostat that is calling for second stage
cooling. This parameter may also be adjusted from 40°F to
70°F with 55°F set as the default value.
VAV SAT Reset Setpoint - (72°F) - This parameter is used
only in VAV mode with a Space Sensor. The control will
switch from the VAV Lower Cooling SAT Setpoint to the VAV
Upper Cooling SAT Setpoint when this Space Temperature
Setpoint minus 0.5°F is reached. The control will switch from
High setpoint back to Low setpoint when the space tempera-
ture gets 2°F above this setpoint. This is SAT reset based on
Space Temperature. The reset occurs in both Occupied and
Unoccupied modes and may be adjusted from 40°F to 85°F.
The factory default is 72°F.
VAV Occupied Heating - (OFF) - This option applies in VAV
mode with a Space Sensor and does not affect VAV Occu-
pied heating if requested by a thermostat. When this option is
toggled on, a VAV unit is able to operate heating in the occu-
pied mode as long as it is operating with a Space Sensor. If
the Space Temperature drops to 2°F below the VAV SAT
Reset Setpoint the control will read the RAT. If the RAT is
below the Morning Warm Up RAT Setpoint the unit will enter
102777-YIM-E-0206
Unitary Products Group