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Above50Fsupply-airtemperature,thedmnperswillmodu-
latefrom100%opentotheminimumopenposition.From50F
to 45F supply-airtemperature,the&tmperswill maintain
attheminimumopenposition.Below45Fthe&lmperswill
becompletelyshut.Asthesupply-airtemperaturerises,the
damperswillcomebackopentotheminimumopenposition
oncethesupply-airtemperatmerisesto48IF.
If optionalpowerexhaustisinst_dled,astheoutdoor-air
damperopensandcloses,thepowerexhaustfanwillbeener-
gizedanddeenergized.
If field-installed accessory COz sensors are connected to the
EconoMiSerIV control, a demand controlled ventilation strate-
gy will begin to operate. As the CO2 level in the zone increases
above the CO2 set point, the minimum position of the &_mper
will be increased proportionally. As the CO2 level decreases
because of the inclease in fresh aik the outdoor-air damper will
be proportionally closed. Daraper position will follow the high-
er demand condition from DCV mode or free cooling mode.
Damper movement from full closed to lifll open (or vice
veLsa) will take between 11/2and 21/: minutes.
If free cooling can be used as determined from the appropri-
ate changeover command (switch, diy bulb, enthalpy curve,
differential dry bulb, or differential enthalpy), a call for cooling
(YI closes at the thermostat) will cause the control to modulate
the &tmpeLs open to maintain the supply air temperature set
point at 50 to 55 E
As the supply-air temperature diops below the set point
range of 50 to 55 E the control will modulate the outdoor-air
dampers closed to maintain the proper supply-air temperature.
HEATING, UNITS WITH ECONOMISERIV -- When the
room thermostat calls for heat, the heating controls are ener-
gized as described in the Heating, Units Without Economizer
section. When the indoor fan is energized, the economizer
damper moves to the minimum position. When the indoor fan
is off. the economizer dmnper is fully closed.
COOLING. UNITS WITH ECONOMISER2, PREMIER-
LINK TM CONTROL AND A THERMOSTAT -- When free
cooling is not available, the compressoLs will be controlled by
the PremierLink control in response to the YI and Y2 inputs
from the thermostat.
The PremierLink control will use the following information
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 Sir[ '.
• Enthalpy must be LOW (may be jumpered if an enthalpy
sensor not available).
• Economizer position is NOT forced.
Pre-cooling occurs when the is no call fi_m the thermostat
except G Pre-cooling is defined as the economizer modulates
to provide 70 F supply air
When free cooling is available the PremierLink control will
control the compressors and economizer to provide a supply-
air tempemtme determined to meet the YI and Y2 c_dls from
the thermostat using the following three routines. The three
control routines are based on OAT.
The 3 routines ;ue based on OAT where:
SASP = Supply Air Set Point
DXCTLO = Dilect Expansion Cooling Ix_ckout Set Point
PID = Proportional Integral
Routine 1 (OAT < DXCTLO)
YI energized - economizer maintains a SASP =
(SATLOI + 3).
Y2 energized - economizer maintains a SASP =
(SATLO2 + 3).
Routine 2 (DXCTLO < OAT < 68 F)
• If only YI energized, the economizer maintains a SASP
= (SATLOI + 3).
• If SAT > SASP + 5 and economizer position > 80%,
economizer will go to minimum position for 3 minutes or
until SAT > 68 IF.
• First stage of mechanical cooling will be energized.
• Integrator resets.
• Economizer opens again and controls to current SASP
after stage one on for 90 seconds.
• With YI and Y2 energized economizer maintains an
SASP = SATLO2 + 3.
• If SAT > SASP + 5 and economizer position >80%,
economizer will go to minimum position for 3 minutes or
until SAT > 68 E
• If compressor one is on then second stage of mechanical
cooling will be energized. Otherwise the first stage will
be energized.
• Integrator resets.
• Economizer opens again and controls to SASP after
stage one on for 90 seconds.
Routine 3 (OAT > 68)
• Economizer is opened 100%.
• Compressors 1 and 2 are cycled based on YI and Y2
using minimum on and off times and watching the sup-
ply air temperature as compared to SATLOI and
SATLO2 set points.
If optiomd power exhaust is installed, as the outdoor-air
&tmper opens and closes, the power exhaust fans will be ener-
gized and deenergized.
If field-installed accessory CO2 sensors me connected to the
PremierLink control, a PlD-controlled demand ventilation
strategy will begin to operate. As the CO2 level in the zone
increases above the CO2 set point, the minimum position of the
&_mper will be increased proportionally. As the COz level
decreases because of the increase in fresh air, the outdoor-air
&tmper will be proportionally closed.
HEATING, UNITS WITH ECONOMISER2, PREMIERLINK
CONTROL AND A THERMOSTAT -- When the thermostat
calls for heating, terminal Wl is energized. The PremierLink
control will move the economizer damper to the minimum
position if there is a call for G and closed if there is a call for
WI without G In order to prevent thermostat from short cy-
cling, the unit is locked into the heating mode for at least
10 minutes when WI is energized. The induced-di'aft motor is
then energized and the burner ignition sequence begins.
On units equipped for two stages of heat, when additional
heat is needed, W2 is energized and the high-fire solenoid on
the main gas valve (MGV) is energized. When the thermostat
is satisfied and WI is deenergized, the IFM stops after a
45-second time-off delay unless G is still maintained.
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 Enor reduction calcula-
tion as indicated by Fig. 46.
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 E
• 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
positioned through the use of a Proportional Integral (PID)
control process to provide a calculated supply-air temperature
37