95
If field-- installed accessory CO
2
sensors are 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
setpoint, 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, unit with EconoMi$er2, PremierLink
control and a room sensor
Every 40 seconds the controller will calculate the required
heat stages (maximum of 3) to maintain Supply Air
Temperature (SAT) if the following qualifying conditions
are met:
S Indoor fan has been on for at least 30 seconds.
S COOL mode is not active.
S OCCUPIED, TEMP.COMPENSATED START or HEAT
mode is active.
S SAT reading is available.
S 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
When the temperature of the outdoor coil drops below
28_F(--2_C) as sensed by the defrost thermostat (DFT2)
and the defrost timer is at the end of a timed period
(adjustable at 30, 60, 90 or 120 minutes), reversing valve
solenoids (RVS1 and RVS2) are energized and the OFC is
de--energized. This switches the position of the reversing
valves and shuts off the outdoor fan. The electric heaters
(if installed) will be energized.
The unit continues to defrost until the coil temperature as
measured by DFT2 reaches 65_F(18_C), or the duration
of defrost 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
installed) will be de--energized; 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.
Automatic changeover
When the system selection switch is set at AUTO.
position, unit automatically changes from heating
operation to cooling operation when the temperature of
the conditioned space rises to the cooling level setting.
When the temperature of the conditioned space falls to the
heating level setting, unit automatically changes from
cooling to heating operation (with a 3°F deadband in
between).
Continuous air circulation
Turn unit power on. Set system control at OFF position.
Set fan switch at ON position. The indoor fan contactor is
energized through the thermostat switch and the indoor
fan runs continuously.
Emergency heat
When the switch is on (thermostat is set to the EM HT
position), compressor circuit and outdoor thermostats are
bypassed, and the second stage of thermostat energizes the
indoor blower and the electric resistance heaters.
50TCQ
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