HEATING.UNITSWITHECONOMISER2,PREMIERLINK
CONTROLANDATHERMOSTAT-- Whenthethermostat
c_dlsforheating,terminalWI isenergized.ThePremierLink
controlwillmovetheeconomizerdampertotheminimumpo-
sitionifthereisacallforGandclosedifthereisacallforWI
withoutG Inordertopreventthermostatfromshortcycling,
theunitislockedintotheheatingmodeforatleast10minutes
whenWI isenergized.
Onunitsequippedfortwostagesofheat,whenadditional
heatisneeded,W2isenergizedandtheelectricheat(if used)
comeson.WhenthethermostatissatisfiedandWI isdeener-
gized,theIFMstops.
COOLING. UNITS WITH ECONOMISER2, PREMIER-
LINK CONTROL AND A ROOM SENSOR -- When free
cooling is not available, the compressors will be controlled by
the PremierLink controller using a PID Error reduction c_flcula-
tion as indicated by Fig 41.
The PremierLink controller will use the following informa-
tion to determine if free cooling is available:
• Indoor fan has been on for at least 30 seconds.
• The SPT. SAT. and OAT inputs must have valid readings.
• OAT must be less than 75 F.
• OAT must be less than SPT.
• Enthalpy must be LOW (may be jumpered if and
enthalpy sensor is not available).
• Economizer position is NOT forced.
When free cooling is available, the outdoor-air damper is po-
sitioned through the use of a Proportional Integral (PlD) control
process to provide a calculated supply-air temperature into the
zone. The supply air will maintain the space temperature be-
tween the heating and cooling set points as indicated in Fig. 42.
The PremierLink control will integrate the compressol.s
stages with the economizer based on simiku logic as the three
routines listed in the previous section. The SASP will float up
and down based on the error reduction calculations that com-
ptue space temperature and space set point. The reversing
valves will be energized.
When outdoor-air temperature conditions require the econo-
mizer to close for a compressor stage-up sequence, the econo-
mizer control integrator is reset to zero after the stage-up se-
quence is completed. This prevents the supply-air temperature
from &opping too quickly and creating a freeze condition that
would make the compressor turn off prematurely.
The high space set point is used for DX (direct expansion)
cooling control, while the economizer space set point is a
c_dculated value between the heating and cooling set points.
The economizer set point will always be at least one degree
below the cooling set point, allowing for a smooth transition
from mechanical cooling with economizer assist, back to
economizer cooling as the cooling set point is achieved.
The compressors may be used for initkfl cooling then the
PremierLink controller will modulate file economizer using an
enor reduction calculation to hold the space temperature
between the heating and cooling set points. See Fig. 42.
The controller uses the following conditions to determine
economizer cooling:
• Enthalpyis Low.
• SAT reading is available.
• OAT reading is available.
• SPT reading is available.
• OAT < SPT
• Economizer Position is NOT forced.
If any of the above conditions are not met, the economizer
submaster reference (ECSR) is set to maximum limit and the
dmnper moves to minimum position. The operating sequence
is complete. The ECSR is recalculated every 30 seconds.
If an optional power exhaust is inst_dled, as the outdoor-air
dmnper opens and closes, the power exhaust fans will be
energized and deenergized.
If field-installed accessory CO2 sensors tue connected to
the PremierLink control, a PID-controlled demand ventilation
strategy will begin to operate. As the CO2 level in file zone
increases above the CO2 set point, the minimum position of the
damper will be increased proportionally. As the CO2 level
decreases because of the increase in fresh all: the outdoor-air
damper will be proportionally closed.
HEATING. UNIT WITH ECONOMISER2, PREMIERLINK
CONTROL AND A ROOM SENSOR -- Every 40 seconds
the controller will calculate the required heat stages (maximum
of 3) to maintain supply-air temperature (SAT) if the following
qu_difying conditions are met:
• Indoor fan has been on for at least 30 seconds.
• COOL mode is not active.
• OCCUPIED, TEMRCOMPENSATED START or HEAT
mode is active.
• SAT reading is available.
• Fire shutdown mode is not active.
If all of the above conditions me met, the number of heat
stages is c_dculated; otherwise the required number of heat
stages will be set to 0.
If file PremierLink controller determines that heat stages are
required, the economizer dmnper will be moved to minimum
position if occupied and closed if unoccupied.
Staging should be as follows:
If Heating PID STAGES=2
• HEAT STAGES=I (75% capacity) will energize HSI
• HEAT STAGES=2 (100% capacity) will energize HS2
In order to prevent short cycling, the unit is locked into the
Heating mode forat least 10 minutes when HSI is deenergized.
On units equipped for two stages of heat, when additional heat
is needed, it may be provided by electric heat (if supplied).
When the space condition is satisfied and HSI is deenergized
the IFM stops. The fan will mn continuously in the occupied
mode as required by national energy and fresh air standards.
75,
W
744
_: 734
££
nm 724
714
I-
w 704
o
694
co 68 J
TEMPERATURE CONTROL
TIME
...... SET POINT
I TEMPERATURE
NOTE: PremierLinkTM control performs smart staging of 2 stages of
DX cooling and up to 3 stages of heat.
Fig. 41 -- DX Cooling Temperature
Control Example
W
OC
W
w
W
o
69
TEMPERATURE CONTROL
75
74 1_.__
73
72 ......... _ .................................... ------COOL SETPO[NT
711 \ /j __ -- TEMPERATURE
704 ........ _v_ .......................... --- HEAT SETPOINT
J
69
68
TIME
Fig. 42 -- Economizer Temperature
Control Example
34
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