Carrier 50HJQ004 Installation, Start-Up And Service Instructions Manual page 54

Compressor restart is accomplished by manual reset at the
thermostat by turning the selector switch to OFF position and
then to ON position.
Allow unit to operate a minimum of 10 minutes before checking
refrigerant charge.
STEP 10 —HEATING
To start unit, turn on main power supply.
Set system selector switch at HEAT position, and set thermostat at
a setting above room temperature. Set fan at AUTO position.
First stage of thermostat energizes the indoor fan, compressor,
and outdoor fan; second stage energizes electric heater elements,
if installed. Check heating effects at air supply grille(s).
If electric heaters do not energize, reset limit switch (located on
indoor-fan scroll) by depressing button located between terminals
on the switch.
To Shut Off Unit - - Set system selector switch at OFF position.
Resetting thermostat at a position below room temperature
temporarily shuts off unit until space temperature falls below
thermostat setting.
STEP 11 —SAFETY RELIEF
A soft solder joint at the suction line fitting provides pressure
relief under abnormal temperature and pressure conditions.
STEP 12 —VENTILATION
Set fan and system selector switches at ON and OFF positions,
respectively. Indoor fan operates continuously to provide constant
air circulation.
STEP 13 —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 (RVS) and compressor contactor are energized and
indoor-fan motor, compressor, and outdoor fan starts. The
outdoor fan motor runs 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), C1, and C2 will be energized. The indoor fan, outdoor
fan, and compressor no. 1 and compressor no. 2 are energized.
The RVS is deenergized and switches position.
If the space temperature continues to fall while W1 is energized,
W2 will be energized with 24 v, and the heater contactor(s) (HC)
will be energized, which will energize the electric heater(s).
When the space thermostat is satisfied, W2 will be deenergized
first, and the electric heater(s) will be deenergized.
Upon a further rise in space temperature, W1 will be
deenergized.
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
below 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 modulate
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 dampers
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 energized and
deenergized.
If field-installed accessory CO
EconoMi$er IV control, a demand controlled ventilation strategy
will begin to operate. As the CO
above the CO set point, the minimum position of the damper
2
will be increased proportionally. As the CO
because of the increase in fresh air, the outdoor-air damper will be
proportionally closed. Damper position will follow the higher
demand condition from DCV mode or free cooling mode.
Damper movement from full closed to full open (or vice versa)
1 1
will take between 1 / and 2
2
If free cooling can be used as determined from the appropriate
changeover command (switch, dry bulb, enthalpy curve,
differential dry bulb, or differential enthalpy), a call for cooling
(Y1 closes at the thermostat) will cause the control to modulate
the dampers open to maintain the supply-air temperature set point
at 50_ to 55_F.
As the supply-air temperature drops below the set point range of
50_ to 55_F, the control will modulate the outdoor-air dampers
closed to maintain the proper supply-air temperature.
HEATING - - UNITS WITH ECONOMI$ER IV
When the room temperature calls for heat, the heating controls are
energized 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-
LINKt 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.
The PremierLink control will use the following information to
determine if free cooling is available:
S Indoor fan has been on for at least 30 seconds.
The SPT, SAT, and OAT inputs must have valid
S
readings.
S OAT must be less than 75_F.
S OAT must be less than SPT.
S Enthalpy must be LOW (may be jumpered if an
enthalpy sensor not available).
S Economizer position is NOT forced.
Pre-cooling occurs when there is no call from 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
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.
The 3 routines are based on OAT where:
SASP = Supply Air Set Point
DXCTLO = Direct Expansion Cooling Lockout Set Point
PID = Proportional Integral
Routine 1 (OAT < DXCTLO)
S Y1 energized – economizer maintains a SASP =
(SATLO1 + 3).
S Y2 energized – economizer maintains a SASP =
(SATLO2 + 3).
54
sensors are connected to the
2
level in the zone increases
2
level decreases
2
/ minutes.
2