Automatic Operation (Auto) Mode; Operating Fault Diagnosis; Microprocessor Control Operation - Carrier 40QNB018 Installation, Start-Up And Service Instructions Manual

Automatic Operation (Auto) Mode —
is selected, the system automatically switches the operating
mode from heating (heat pump system only) to cooling, or
from cooling to heating (heat pump system only) depending
on the selected temperature.
NOTE: Between the cooling cycle and the heating cycle there
is a neutral zone of approximately 2° F above and 2° F be-
low the selected temperature when only the fan is operating.
Operating Fault Diagnosis —
an automatic diagnosis feature which is activated under
difficult or unacceptable operating conditions. If such con-
ditions occur, the system stops automatically, the operating
fault signal appears (green ''UNIT ON'' light on the front of
the fan coil unit flashes), and an analysis of the system op-
erating conditions is initiated. The system will then be re-
started automatically, as soon as normal conditions have been
restored, or it will remain off. If the system does not start
again, the green ''UNIT ON'' light will flash an error code.
Microprocessor Control Operation —
tem is controlled by a microprocessor designed to give op-
timum levels of comfort and operating efficiency. The con-
trol is located in the 40QN unit. To operate the unit, the factory-
supplied remote controller is required.
There are 9 (QNB systems) or 11 (QNE systems) oper-
ating modes (including the off mode) for the unit. Each mode
operates as follows:
• Off Mode — When the unit is in the off mode, all func-
tions (compressor, outdoor fan, indoor fan, and air sweep)
are off, except the reversing valve (QNE only), which will
stay energized if the unit was last operated in the cooling
mode.
• Air Circulation Mode (Fan Operation Only) — When air
circulation mode is selected, the indoor fan will operate
continuously in the selected speed (high, medium, low, or
auto.). If the auto. mode is selected, the indoor fan will
operate at low speed. The compressor and outdoor fan are
off. The reversing valve (QNE only) will remain in the
last operating mode.
• Cooling Mode — When the cooling mode is selected, the
indoor fan will operate continuously at the selected speed
if the speed is high, medium, or low. If the indoor fan is
in auto. mode, the fan will change operating speeds de-
pending on the difference between the room temperature
and the set point. The reversing valve (QNE only) will be
on. The compressor cannot run for 3 minutes from the time
the system starts up or for 3 minutes from the time the
compressor last operated. When the temperature of the room
is equal to or greater than the selected temperature, the
compressor and outdoor fan will operate until the room
temperature is 2° F below the set point, and then shut off.
When the room temperature is less than the selected tem-
perature, the compressor and outdoor fan remain off.
• Maximum Dehumidification Mode — When the dehu-
midification mode is selected, the indoor fan will operate
continuously at the selected speed if the speed is high, me-
dium, or low. If the indoor fan is in auto. mode, the fan
will change operating speeds depending on the room tem-
perature. If the room temperature is below the set point,
the indoor fan will run at ultra-low speed, and the com-
pressor could run for up to 4 minutes. (Ultra-low speed is
a control-driven speed [not user configurable] used to sample
the space when the fan would normally be off.) The re-
versing valve (QNE only) will be on. The compressor can-
not run for 3 minutes from the time the system starts
up or for 3 minutes from the time the compressor last
operated.
If auto mode
The system includes
This sys-
11
Initial Operation — When the mode is first selected, one of
the following occurs:
1. If the room temperature is above or equal to the selected
temperature, the unit will operate for 16 minutes, and the
compressor and outdoor fan will operate. The indoor fan
will operate as in the cooling mode. After 16 minutes of
operation (or when the room reaches 2° F below set point),
the unit switches to normal dehumidification operation.
2. If the room temperature is below the selected tempera-
ture, the unit will operate for 8 minutes as follows: the
compressor and outdoor fan will operate for 3 minutes.
The indoor fan will operate in low speed, and 30 seconds
after the compressor stops, the indoor fan stops. The unit
remains off for 1 minute, and then the indoor fan starts in
ultra-low speed for 30 seconds. The unit then switches to
normal dehumidification operation.
Normal Operation — One of the following will take place:
1. When the temperature of the room is equal to or greater
than the selected temperature (by not more than 3° F), the
unit will operate for 8 minutes as follows: the compres-
sor and outdoor fan will operate for 3 minutes. The in-
door fan will operate in low speed, and 30 seconds after
the compressor stops, the indoor fan stops. The unit re-
mains off for 1 minute, and then the indoor fan starts in
ultra-low speed for 30 seconds. The normal dehumidifi-
cation operation is repeated for the newly sensed room
temperature.
2. If the room temperature is equal to or greater than the
selected temperature, but not by more than between 4° F
and 6° F, the compressor and outdoor fan operate for
4 minutes. The indoor fan will run at ultra-low speed and
will stop 30 seconds after the compressor stops. After
3 minutes, the indoor fan runs at ultra-low speed for
30 seconds. The normal dehumidification operation is re-
peated for the newly sensed room temperature.
3. When the room temperature is equal to or greater than
4° F below the selected temperature, the system operates
as follows: The compressor and outdoor fan operate for
3 minutes. The indoor fan will operate at ultra-low speed
and will stop 30 seconds after the compressor stops. Af-
ter 4 or 5 minutes, the indoor fan starts in ultra-low speed
for 30 seconds. The normal dehumidification operation is
repeated for the newly sensed room temperature. If the
room temperature is still 4° F below the selected tem-
perature, the compressor, outdoor fan, and indoor fan re-
main off. After 7 1 ⁄ minutes, the indoor fan operates at
2
ultra-low speed for 30 seconds. The normal dehumidifi-
cation operation is repeated for the newly sensed room
temperature.
• Heat Pump Heating Mode (Heat Pump Systems Only) —
When the heat pump mode is selected, the indoor fan will
operate at the selected speed if the speed is high, medium,
or low, unless overridden by the coil temperature (to pre-
vent cold drafts). If the indoor fan is in auto. mode, the fan
will change operating speeds depending on the difference
between the room temperature, the set point, and the coil
temperature. The reversing valve will be off. The com-
pressor cannot run for 3 minutes from the time the system
starts up or for 3 minutes from the time it last operated.
When the temperature of the room is 8° F below the se-
lected temperature, the unit will operate in heat pump mode
until the temperature is 6° F above the selected tempera-
ture, or the compressor runs for 40 minutes (whichever
comes first). If the temperature of the room is less than
7° F below or equal to the selected temperature, the unit
operates in heat pump mode until the selected set point
temperature plus 2° F is reached.
• Demand Defrost Mode (Heat Pump Systems Only) — This
unit uses a demand defrost system to remove frost from
the outdoor coil during heating operation. The indoor and
outdoor fans are shut off during defrost mode.