Carrier WEATHERMASTER 50HJQ004-016 Product Data page 165

If field-installed accessory CO
the PremierLink control, a PID-controlled demand ventila-
tion strategy will begin to operate. As the CO
zone increases above the CO
position of the damper will be increased proportionally. As
the CO level decreases because of the increase in fresh
2
air, the outdoor-air damper will be proportionally closed.
Heating, units with EconoMi$er2, PremierLink con-
trol and a thermostat — When the thermostat calls for
heating, terminal W1 is energized. The PremierLink
control will move the economizer damper to the minimum
position if there is a call for G and closed if there is a call
for W1 without G. In order to prevent thermostat from
short cycling, the unit is locked into the heating mode for
at least 10 minutes when W1 is energized. The reversing
valve solenoid(s) deenergizes and switches position.
On units equipped for two stages of heat, when addition-
al heat is needed, W2 is energized and the electric heat (if
used) comes on. When the thermostat is satisfied and W1
is deenergized, the IFM stops.
Cooling, units with EconoMi$er2, PremierLink con-
trol and a room sensor — When free cooling is not
available, the compressors will be controlled by the Premier-
Link controller using a PID Error reduction calculation.
The PremierLink controller will use the following infor-
mation 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 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 tempera-
ture into the zone. The supply air will maintain the space
temperature between the heating and cooling set points.
The PremierLink control will integrate the compressors
stages with the economizer based on similar logic as the
three routines listed in the previous section. The SASP will
float up and down based on the error reduction calcula-
tions that compare space temperature and space set point.
The reversing valves will be energized.
If an 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
the PremierLink control, a PID-controlled demand ventila-
tion strategy will begin to operate. As the CO
zone increases above the CO
sition of the damper will be increased proportionally. As
the CO level decreases because of the increase in fresh
2
air, the outdoor-air damper will be proportionally closed.
Heating, unit with EconoMi$er2, PremierLink con-
trol and a room sensor — Every 40 seconds the con-
troller will calculate the required heat stages (maximum of
sensors are connected to
2
level in the
2
set point, the minimum
2
sensors are connected to
2
level in the
2
set point, the minimum po-
2
3) to maintain Supply Air Temperature (SAT) if the follow-
ing qualifying conditions are met:
• Indoor fan has been on for at least 30 seconds.
• COOL mode is not active.
• OCCUPIED, TEMP.COMPENSATED START or HEAT
mode is active.
• SAT reading is available.
• Fire shutdown mode is not active.
If all of the above conditions are met, the number of heat
stages is calculated; otherwise the required number of heat
stages will be set to 0.
If the PremierLink controller determines that heat stages
are required, the economizer damper will be moved to
minimum position if occupied and closed if unoccupied.
Defrost (50TFQ004-007 and 50HJQ004-007) —
As frost builds up on the outdoor coil, the coil temperature
drops below 28 F. When this outdoor-coil temperature
drop is sensed by the defrost thermostat (DFT) and the de-
frost timer is at the end of a timed period (adjustable at 30,
50, or 90 minutes), the unit operates in a defrost cycle
controlled by the defrost timer and thermostat. During this
cycle, the reversing valve solenoid (RVS) is energized and
the outdoor fan shuts off. The electric heaters (if installed)
will be energized.
The unit continues to defrost until the coil temperature
as measured by DFT reaches 65 F, or the duration of de-
frost cycle completes a 10-minute period.
At the end of the defrost cycle, the electric heaters (if in-
stalled) and the reversing valve will be deenergized, and the
outdoor-fan motor will be energized. The unit will now op-
erate in the Heating mode.
If the thermostat is satisfied during a defrost cycle, the
unit will continue in the Defrost mode until the time or tem-
perature constraints are satisfied.
Defrost (50TFQ008-012 and 50HJQ008-012) —
When the temperature of the outdoor coil drops below 28
F as sensed by the defrost thermostat (DFT2) and the de-
frost timer is at the end of a timed period (adjustable at 30,
50, or 90 minutes), reversing valve solenoids (RVS1 and
RVS2) are energized and the OFC is deenergized. This
switches the position of the reversing valves and shuts off
the outdoor fan. The electric heaters (if installed) will be en-
ergized.
The unit continues to defrost until the coil temperature
as measured by DFT2 reaches 65 F, or the duration of de-
frost cycle completes a 10-minute period.
During the Defrost mode, if circuit 1 defrosts first, RVS1
will oscillate between Heating and Cooling modes until the
Defrost mode is complete.
At the end of the defrost cycle, the electric heaters (if in-
stalled) will be deenergized; the reversing valves switch and
the outdoor-fan motor will be energized. The unit will now
operate in the Heating mode.
If the space thermostat is satisfied during a defrost cycle,
the unit will continue in the Defrost mode until the time or
temperature constraints are satisfied.
165