Carrier 50HJQ004-016 Product Data page 185

CONTROLS (CONT)
Sequence of operation — 50TFQ004-012,
50HJQ004-012, and 50HEQ003- -006
Cooling, units without economizer- -- -When thermostat calls for
cooling, terminals G and Y1 are energized. The indoor-fan
contactor (IFC), reversing valve solenoid (RVS1 for sizes
004-007) (RVS1 and RVS2 for sizes 008-012) 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 fans, and compressor no. 1,
and compressor no. 2 are energized and reversing valves are
deenergized and switch 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, unit 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 mixed-air temperature into the zone. As the mixed-air
temperature fluctuates above 55 or below 50_F, the dampers will
be modulated (open or close) to bring the mixed-air temperature
back within control.
If mechanical cooling is utilized with free cooling, the
outdoor-air damper will maintain its current position at the time
the compressor is started. If the increase in cooling capacity
causes the mixed-air temperature to drop below 45_F, then the
outdoor-air damper position will be decreased to the minimum
position. If the mixed-air temperature continues to fall, the
outdoor-air damper will close. Control returns to normal once the
mixed-air temperature rises above 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$er IV control, a demand controlled ventilation strategy
will begin to operate. As the CO
above the CO set point, the minimum position of the damper
2
will be increased proportionally. As the CO
because of the increase in fresh air, the outdoor-air damper will be
proportionally closed.
For EconoMi$er IV operation, there must be a thermostat call for
the fan (G). If the unit is occupied and the fan is on, the damper
will operate at minimum position. Otherwise, the damper will be
closed.
When the EconoMi$er IV control is in the occupied mode and a
call for cooling exists (Y1 on the thermostat), the control will first
check for indoor fan operation. If the fan is not on, then cooling
will not be activated. If the fan is on, then the control will open
the EconoMi$er IV damper to the minimum position.
On the initial power to the EconoMi$er IV control, it will take the
1
damper up to 2 / minutes before it begins to position itself. Any
2
change in damper position will take up to 30 seconds to initiate.
Damper movement from full closed to full open (or vice versa)
1 1
will take between 1 / and 2 /
2 2
If free cooling can be used as determined from the appropriate
changeover command (switch, dry bulb, enthalpy curve,
differential dry bulb, or differential enthalpy), then the control
sensors are connected to the
2
level in the zone increases
2
level decreases
2
minutes.
will modulate the dampers open to maintain the mixed-air
temperature set point at 50 to 55 F.
If there is a further demand for cooling (cooling second stage —
Y2 is energized), then the control will bring on compressor stage
1 to maintain the mixed-air temperature set point. The
EconoMi$er IV damper will be open at maximum position.
EconoMi$er IV operation is limited to a single compressor.
Heating, units with Economi$er- -- -When the room temperature
calls for heat through terminal W1, the indoor (evaporator) fan
contactor (IFC) and heater contactor no. 1 (HC1) are energized
and the reversing valve(s) deenergize and switches position. On
units equipped for 2 stages of heat, when additional heat is
needed, heater contactor no. 2 is energized through W2. The
economizer damper moves to the minimum position. When the
thermostat is satisfied, the damper moves to the fully closed
position.
Cooling, units with EconoMi$er2, PremierLink] control and a
- - - -
thermostat
When free cooling is not available, the compressors
will be controlled by the PremierLink control in response to the
Y1 and Y2 inputs from the thermostat.
The PremierLink control will use the following information to
determine if free cooling is available:
S Indoor fan has been on for at least 30 seconds.
The SPT, SAT, and OAT inputs must have valid
S
readings.
S OAT must be less than 75_F.
S OAT must be less than SPT.
S Enthalpy must be LOW (may be jumpered if an
enthalpy sensor not available).
S Economizer position is NOT forced.
Pre-cooling occurs when the is no call from the thermostat except
G. Pre-cooling is defined as the economizer modulates to provide
70_F supply air.
When free cooling is available the PremierLink control will
control the compressors, energize the reversing valve(s) and
economizer to provide a supply-air temperature determined to
meet the Y1 and Y2 calls from the thermostat.
If optional power exhaust is installed, as the outdoor-air damper
opens and closes, the power exhaust fans will be energized and
deenergized.
If field-installed accessory CO
PremierLink control, a PID-controlled demand ventilation
strategy will begin to operate. As the CO
increases above the CO set point, the minimum position of the
2
damper will be increased proportionally. As the CO
decreases because of the increase in fresh air, the outdoor-air
damper will be proportionally closed.
Heating, units with EconoMi$er2, PremierLink control and a
thermostat- -- -When the thermostat calls for heating, terminal W1
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 W1 without G. In order to prevent thermostat
from short cycling, the unit is locked into the heating mode for at
least 10 minutes when W1 is energized. The reversing valve
solenoid(s) deenergizes and switches position.
On units equipped for two stages of heat, when additional heat is
needed, W2 is energized and the electric heat (if used) comes on.
When the thermostat is satisfied and W1 is deenergized, the IFM
stops.
Cooling, units with EconoMi$er2, PremierLink control and a
room sensor- -- -When free cooling is not available, the
185
sensors are connected to the
2
level in the zone
2
level
2