Carrier 48TJ016-028 - Manual (Page 37)

Above 50 F supply-air temperature, the dampers will modu­
late from 100% open to the minimum open position. From 50 F
to 45 F supply-air temperature, the dtunpers will maintain
at the minimum open position. Below 45 F the diimpers will
be completely shut. As the supply-air temperature rises, the
dampers will come back open to the minimum open position
once the supply-air temperature rises to 48 F.
If optional powei' exhaust is installed, as the outdoor-air
damper opens and closes, the power exhaust fan will be ener­
gized and deenergized.
If field-installed accessoiy CO 2 sensors are connected to the
EconoMi$erIV control, a demand controlled ventilation strate­
gy will begin to operate. As the CO
2 level in the zone increases
above tlie CO
2
set point, the minimum position of tlie damper
will be increased proportionally. As the CO 2 level decreases
because of the increase in fresh air, tlie outdoor-air damper will
be proportionally closed. Damper position will follow the high­
er demand condition from DCV mode or free cooling mode.
Damper movement from full closed to full open (or vice
verea) will tiike between 1V
2
and
2
V
2
minutes.
If free cooling can be used as determined from the appropri­
ate changeover command (switch, diy bulb, enthalpy curve,
differential diy bulb, or differential entlialpy), a call for cooling
(Yl closes at the thermostat) will cause the control to modulate
the clamper open to miiintain the supply air temperature set
point at 50 to 55 F.
As tlie supply-air temperature di'ops below the set point
range of 50 to 55 F, the control will modulate the outdoor-air
dampers closed to maintain the proper supply-air tempeiature.
HEATING, UNITS WITH ECONOMI$ERIV -- 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. Wlien the indoor fan
is off, the economizer diunper is fully closed.
COOLING. UNITS WITH ECONOMI$ER2. PREMIER-
LINRi^' CONTROL AND A THERMOSTAT — When free
cooling is not available, the compressoi's will be controlled by
the PremierLink control in response to the Yl and Y2 inputs
from the thermostat.
Tlie 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 SPT,
• 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 from the themiostat
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 temperature determined to meet the Yl and Y2 ctills from
the thermostat using the following tliree routines. Пае three
control routines are based on OAT
Tlie 3 routines ш'е based on OAT where:
SASP = Supply Air Set Point
DXCTLO = Direct Expansion Cooling Lockout Set Point
PID = Proportional Integral
Routine 1 (OAT < DXCTLO)
• Yl energized - economizer maintains a SASP =
(SATLOl -I- 3),
• Y2 energized - economizer maintains a SASP =
(SATL02 -I- 3).
Routine 2 (DXCTLO < OAT < 68 F)
If only Yl eneraized. the economizer maintains a SASP
= (SATLOl -1-3).
If SAT > SASP -I- 5 and economizer position > 80%,
economizer will go to minimum position for 3 minutes or
until SAT > 68 F.
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 Yl and Y2 energized economizer maintains an
SASP = SATL02
-I- .3.
If SAT > SASP -I- 5 and economizer position >80%,
economizer will go to minimum position for 3 minutes or
until SAT > 68 F.
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 Yl and Y2
using minimum on and off times and watching the sup­
ply air temperature as compared to SATLOl and
SATL02 set points.
If optional power exhaust is installed, as the outdoor-air
damper opens and closes, the power exhaust fans will be ener­
gized and deenergized.
If field-installed accessoiy CO
2
sensors tti'e connected to the
PremierLink control, a PID-controlled demand ventilation
strategy will begin to operate. As the CO
2 level in the zone
increases above the CO 2 set point, the minimum position of the
damper will be increased proportionally. As the CO 2 level
decreases because of the increase in fresh air, the outdoor-air
damper will be proportionally closed.
HEATING UNITS WITH ECONOMI$ER2. PREMIERLINK
CONTROL AND A THERMOSTAT—-When the tliermostat
calls for heating, terminal W1 is energized. Tlie PremierLink
control will move the economizer damper to the minimum
position if there is a call for G and closed if tliere is a call for
W1 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 W1 is energized. The induced-di'aft motor is
tlien energized and the burner ignition sequence begins.
On units equipped for two stages of heat, when additional
heat is needed, W2 is energized and tlie high-fire solenoid on
tlie main gas valve (MGV) is energized. When the thermostat
is satisfied and W1 is deenergized, the IFM stops after a
45-second time-off delay unless G is still maintained.
COOLING UNITS WITH ECONOMI$ER2. 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 calcula­
tion as indicated by Fig. 46.
The PremierLink controller will use the following informa­
tion to detennine 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
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