20
EN
Programmable Functions, Ranges, and Factory Defaults
Universal Air Conditioning Unit
The fan response differential can be adjusted from 1/4°
to 4°, in 1/8° increments. All program functions must be
adjusted in °F even if the temperature display is changed
from Fahrenheit to Celsius. Refer to “2: Fahrenheit,
Celsius, or Auto Selection” on page 19.
The fan speed range is divided by the Q3 control system
into five equal increments. If the fan response differential
is set at 1/2°, then the fan speed will change 20% for
each 1/2° of temperature deviation from the set point.
Lowering the fan speed differential will cause the fan
to change speeds more frequently as the temperature
changes. Raising the fan speed differential will result
in slower fan speed changes for a given temperature
change. The factory setting of 1/2° is ideal for most
applications.
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If the compressor restart and the fan response
differentials are both set to the factory default or a
comparable range and the Auto fan mode is on,
then the fan will not run at high speed unless the
conditioned space temperature rises 3 °F
(-16 °C) above the set point.
5: Low Fan Speed
You can adjust the lowest fan speed to suit individual
preferences. For instance, you may wish to decrease the
low fan speed setting to minimize fan noise.
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For the most efficient operation of your system,
you should keep the low fan speed at the highest
possible setting, consistent with a comfortable
noise level. Running the fan speed too low may
have an adverse effect on the system and may cause
the evaporator coil to freeze and shut down on low
pressure.
6: High Fan Speed
A blower will often reach its highest speed at a voltage
lower than full line voltage. For example, at a line voltage
of 115 VAC, the blower might reach its fastest speed at
110 VAC. At higher voltages, the blower speed will not
increase significantly.
The high fan speed adjustment allows you to set the
maximum high-speed voltage to the threshold of the
blower high-speed response. The Q3 control system
divides the fan speed voltage steps into five equal
increments (between the low-speed and high -speed
adjustments).
Accurately setting the high and low fan speed
adjustments can help ensure that each fan speed
increment step results in a noticeable change of fan
speed.
• While in programming mode, listen to the fan noise
level and use the Up button to raise the displayed
value past the point that you can hear an increase in
the fan noise level.
• Press the Down button to lower the voltage until
you hear a drop in the fan speed. Raise that number
by two or three to ensure that it is set at the highest
speed.
7: Fan Mode
You can select continuous or intermittent fan operation.
Select “C” and the fan will run continuously while the
system is on. Select “I” for intermittent operation and the
fan will cycle on and off with the compressor.
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If you select intermittent fan operation, you should
relocate the thermistor from the return-air grille to a
conditioned space wall where it can best sense the
average room temperature. Check with your dealer
or call Dometic for more information.
8: AC Line Voltage Calibration
The unity control board assembly has a built-in voltmeter
that senses AC line voltage and this feature displays
the voltage being read. The unity control board
automatically responds to sustained low-voltage or high-
voltage conditions by shutting down the air conditioning
system to prevent compressor damage. At installation,
the unity control board voltmeter should be calibrated to
line voltage within ± 1 %. To check or re-calibrate the AC
line voltage:
• Line voltage will be displayed as the last two digits of
the voltage. On 115 VAC systems, 95 VAC appears as
“95”, 100 VAC as “00”, and 115 VAC as “15”.
• To check accuracy or to calibrate, turn off all on-
board AC loads and measure the line voltage with an
accurate voltmeter.
• Press the Up or Down buttons to recalibrate the value
as required.
