Carrier 48TC*D08 - Manual (Page 77)

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Routine No. 2: If DXLOCK (or DX Cooling Lockout is
disabled) < OAT ≤ 68_F when Y1 input is energized, the
economizer will be modulated to maintain SAT at SASP =
SATLO1 + 3_F. If the SAT > SASP + 5_F and the
economizer position > 85% then the economizer will
close the to minimum position for three minutes or until
the SAT > 68_F. The economizer integrator will then be
reset and begin modulating to maintain the SASP after
stage one has been energized for 90 seconds.
When Y2 is energized, the economizer will be modulated
to control to a lower supply air setpoint SASP= SATLO2
+ 3_F If the SAT > SASP + 5_F it will close the
economizer to minimum position for 3 minutes, reset the
integrator for the economizer, then start modulating the
economizer to maintain the SASP after the stage two has
been on for 90 seconds. This provides protection for the
compressor against flooded starts and allow refrigerant
flow to stabilize before modulating the economizer again.
By using return air across the evaporator coil just after the
compressor has started allows for increased refrigerant
flow rates providing better oil return of any oil washed out
during compressor start--up.
Routine No. 3: If the OAT > 68_F and the enthalpy is low
and the OAT < SPT then the economizer will open to
100% and compressors 1 and 2 will be cycled based on
Y1 and Y2 inputs respectively. If any of these conditions
are not met the economizer will go to minimum position.
If there is no call for heating or cooling, the economizer,
if available, will maintain the SASP at 70_F.
Heating — For gas or electric heat, HS1 and HS2 outputs
will follow W1 and W2 inputs respectively. The fan will
also be turned on if it is configured for electric heat.
Heating may also be energized when an IAQ sensor
installed and has overridden the minimum economizer
damper position. If the OAT < 55_F and an IAQ sensor is
installed and the IAQ minimum position > minimum
damper position causing the SAT to decrease below the
SPT -- 10_F, then the heat stages will be cycled to temper
the SAT to maintain a temperature between the SPT and
the SPT + 10_F.
Auxiliary Relay configured for Exhaust Fan — If the
Auxiliary Relay is configured for exhaust fan (AUXOUT
= 1) in the CONFIG configuration table and Continuous
Power Exhaust (MODPE) is enable in the SERVICE
configuration table then the output (HS3) will be
energized whenever the G input is on. If the MODPE is
disabled then output will be energized based on the Power
Exhaust Setpoint (PES) in the SETPOINT table.
Indoor Air Quality — If the optional indoor air quality
(IAQI) sensor is installed, the PremierLink controller will
maintain indoor air quality within the space at the
user--configured differential setpoint (IAQD) in the
CONFIG configuration table. The setpoint is the
difference between the IAQI and an optional outdoor air
quality sensor (OAQ). If the OAQ is not present then a
fixed value of 400 ppm is used. The actual space IAQ
setpoint (IAQS) is calculated as follows:
IAQS = IAQD + OAQ (OAQ = 400 ppm if not present)
As air quality within the space changes, the minimum
position of the economizer damper will be changed also
thus allowing more or less outdoor air into the space
depending on the relationship of the IAQI to the IAQS.
The IAQ algorithm runs every 30 seconds and calculates
IAQ minimum position value using a PID loop on the
IAQI deviation from the IAQS. The IAQ minimum
position is then compared against the user configured
minimum position (MDP) and the greatest value becomes
the final minimum damper position (IQMP). If the
calculated IAQ Minimum Position is greater than the IAQ
maximum damper position (IAQMAXP) decision in the
SERVICE configuration table, then it will be clamped to
IAQMAXP value.
If IAQ is configured for low priority, the positioning of
the economizer damper can be overridden by comfort
requirements. If the SAT < SASP --8_F and both stages of
heat are on for more then 4 minutes or the SAT > SASP +
5_F and both stages of cooling on for more then 4 minutes
then the IAQ minimum damper position will become 0
and the IQMP = MDP. IAQ mode will resume when the
SAT > SASP --8_F in heating or the SAT < SASP + 5_F in
cooling.
If the PremierLink controller is configured for 1 stage of
heat and cool or is only using a single stage thermostat
input, this function will not work as it requires the both
Y1 and Y2 or W1 and W2 inputs to be active. In this
application, it is recommended that the user configure
IAQ priority for high.
If IAQ is configured for high priority and the OAT < 55_F
and the SAT < (SPT --10_F), the algorithm will enable the
heat stages to maintain the SAT between the SPT and the
SPT + 10_F.
CCN SENSOR MODE — When the PremierLink
controller is configured for CCN control, it will control
the compressor, economizer and heating outputs based its
own space temperature input and setpoints or those
received from Linkage. An optional CO
2
IAQ sensor
mounted in the space or received through communications
can also influence the economizer and heating outputs.
The PremierLink controller does not have a hardware
clock so it must have another device on the CCN
communication bus broadcasting time. The controller will
maintain its own time once it has received time as long as
it has power and will send a request for time once a
minute until it receives time when it has lost power and
power is restored. The controller will control to
unoccupied setpoints until it has received a valid time.
The controller must have valid time in order to perform
any broadcast function, follow an occupancy schedule,
perform IAQ pre--occupancy purge and many other
functions as well. The following sections describe the
operation for the functions of the PremierLink controller.
48TC