Carrier 50TFQ004 Installation, Start-Up And Service Instructions Manual page 43

Heating —
To start the unit, turn on the main power supply.
Set the system selector switch at the HEAT position, and set
the thermostat at a setting above room temperature. Set the fan
at the AUTO position.
The first stage of the thermostat energizes the indoor fan,
compressor, and outdoor fan; the second stage energizes the
electric heater elements, if installed. Check heating effects at
the air supply grille(s).
If the electric heaters do not energize, reset the limit switch
(located on indoor-fan scroll) by pressing the button located be-
tween terminals on the switch.
TO SHUT OFF UNIT — Set the system selector switch at the
OFF position. Resetting the thermostat at a position below
room temperature temporarily shuts the unit off until the space
temperature falls below the thermostat setting.
Safety Relief —
A soft solder joint at the suction line
fitting provides pressure relief under abnormal temperature and
pressure conditions.
Ventilation (Continuous Fan) —
tem selector switches at the ON and OFF positions, respective-
ly. The indoor fan operates continuously to provide constant air
circulation.
Operating Sequence
COOLING, UNITS WITHOUT ECONOMIZER — When
thermostat calls for cooling, terminals G and Y1 are energized.
The indoor-fan contactor (IFC), reversing valve solenoid
(RVS1) and compressor contactor no. 1 (C1) are energized and
indoor-fan motor, compressor no. 1, and outdoor fan starts. The
outdoor-fan motor(s) run continuously while unit is cooling.
HEATING, UNITS WITHOUT ECONOMIZER — Upon a
request for heating from the space thermostat, terminal W1 will
be energized with 24 v. The IFC, outdoor-fan contactor (OFC)
and C1 will be energized. The reversing valve switches posi-
tion and the indoor fan, outdoor fan, and compressor no. 1 are
energized.
If the space temperature continues to fall while W1 is ener-
gized, W2 will be energized with 24 v, and the heater contac-
tor(s) (HC) will be energized, which will energize the electric
heater(s).
When the space thermostat is satisfied, W2 will be deener-
gized first, and the electric heater(s) will be deenergized.
Upon a further rise in space temperature, W1 will be
deenergized, and the reversing valve solenoid (RVS1) will be
energized.
COOLING, UNITS WITH ECONOMI$ER IV — When free
cooling is not available, the compressors will be controlled by
the zone thermostat. When free cooling is available, the
outdoor-air damper is modulated by the EconoMi$er IV
control to provide a 50 to 55 F supply-air temperature into the
zone. As the supply-air temperature fluctuates above 55 or be-
low 50 F, the dampers will be modulated (open or close) to
bring the supply-air temperature back within the set point limits.
Integrated EconoMi$er IV operation on single-stage units
requires a 2-stage thermostat (Y1 and Y2).
For EconoMi$er IV operation, there must be a thermostat
call for the fan (G). This will move the damper to its minimum
position during the occupied mode.
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 dampers will maintain at
the minimum open position. Below 45 F the dampers will be
completely shut. As the supply-air temperature rises, the damp-
ers will come back open to the minimum open position once
the supply-air temperature rises to 48 F.
If optional power exhaust is installed, as the outdoor-air
damper opens and closes, the power exhaust fans will be ener-
gized and deenergized.
EconoMi$er IV control, a demand controlled ventilation strate-
gy will begin to operate. As the CO
above the CO
will be increased proportionally. As the CO
because of the increase in fresh air, the outdoor-air damper will
be proportionally closed. Damper position will follow the high-
er demand condition from DCV mode or free cooling mode.
versa) will take between 1
ate changeover command (switch, dry bulb, enthalpy curve,
differential dry bulb, or differential enthalpy), a call for cooling
(Y1 closes at the thermostat) will cause the control to modulate
the dampers open to maintain the supply air temperature set
point at 50 to 55 F.
range of 50 to 55 F, the control will modulate the outdoor-air
dampers closed to maintain the proper supply-air temperature.
Set the fan and sys- HEATING, UNITS WITH ECONOMI$ER IV — When the
room temperature calls for heat, the heating controls are ener-
gized as described in the Heating, Units Without Economizer
section. When the thermostat is satisfied, the economizer
damper moves to the minimum position.
COOLING, UNITS WITH ECONOMI$ER2, PREMIER-
LINK™ CONTROL AND A THERMOSTAT — When free
cooling is not available, the compressors will be controlled by
the PremierLink control in response to the Y1 and Y2 inputs
from the thermostat.
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
• Economizer position is NOT forced.
except G. Pre-cooling is defined as the economizer modulates
to provide 70 F supply air.
control the compressors and economizer to provide a supply-
air temperature determined to meet the Y1 and Y2 calls from
the thermostat using the following three routines. The three
control routines are based on OAT, where:
Routine 1 — (OAT < DXCTLO)
• Y1 energized — economizer maintains a SASP =
• Y2 energized — economizer maintains a SASP =
Routine 2 — (DXCTLO < OAT < 68 F)
• If only Y1 energized, the economizer maintains a SASP
• If SAT > SASP + 5 and economizer position > 80%,
• First stage of mechanical cooling will be energized.
• Integrator resets.
• Economizer opens again and controls to current SASP
• With Y1 and Y2 energized economizer maintains an
43
If field-installed accessory CO
set point, the minimum position of the damper
2
Damper movement from full closed to full open (or vice
1
/ and 2
2
If free cooling can be used as determined from the appropri-
As the supply-air temperature drops below the set point
The PremierLink control will use the following information
sensor not available).
Pre-cooling occurs when the is no call from the thermostat
When free cooling is available the PremierLink control will
SASP = Supply Air Set Point
DXCTLO = Direct Expansion Cooling Lockout Set Point
(SATLO1 + 3).
(SATLO2 + 3).
= (SATLO1 + 3).
economizer will go to minimum position for 3 minutes or
until SAT > 68 F.
after stage one on for 90 seconds.
SASP = SATLO2 + 3.
sensors are connected to the
2
level in the zone increases
2
level decreases
2
1
/ minutes.
2