Service manual

11-3
CONTROL SYSTEM
SM DUO38 1-E.1 GB
11.4 Indoor Fan Control
10 Indoor fan speeds are determined for each model. 5 speeds for cool/dry/fan modes and
5 speeds for heat mode.
When user sets the indoor fan speed to a fixed speed (Low/ Medium/ High), unit will
operate constantly at set speed.
When Auto Fan is selected, indoor unit controller can operate in all speeds. The actual
speed is set according to the cool/heat load.
11.4.1 Turbo Speed
The Turbo speed is activated during the first 30 minutes of unit operation when auto fan
speed is selected and under the following conditions:
• Difference between set point and actual room temperature is bigger then 3 degrees.
• Room temperature > 22 for cooling, or < 25 for heating.
11.5 Heating Element Control
Heating element can be started if LOAD > 0.8 * MaximumNLOAD AND Indoor Coil
temperature < 45.
The heating element will be stopped when LOAD < 0.5 * MaximumNLOAD OR if Indoor
Coil temperature > 50.
11.6 Outdoor Fan Control
7 outdoor fan speeds are determined for each model. 3 speeds for cool and dry modes,
and 3 speeds for heat mode, and a very low speed.
Outdoor fan speed is a function of compressor frequency and outdoor air temperature
(OAT).
4 routines for fan control are determined. The control routine selection depends on
operation mode, compressor speed, and outdoor air temperature (OAT) and heat sink
temperature (HST).
Routine Conditions
A
Heating with OAT < 15
0
C
or
Cooling with OAT > 20
0
C, or HST > 50
0
C
or
Faulty OAT
B Cooling with 20
0
C > OAT > 7
0
C
C Cooling with 7
0
C > OAT
D Heating with OAT > 15
0
C
Compressor Frequency (CF)
Outdoor Fan Speed
Routine A Routine B Routine C Routine D
CF = 0 OFF OFF OFF OFF
10 ≤ CF < OFLowFreq
Low Low Very Low Low
OFLowFreq ≤ CF < OFMedFreq
Medium Low Very Low Low
OFMedFreq ≤ CF
High Low Low Medium
When compressor is switched to OFF and the heat sink temperature is above 55 degrees,
the outdoor fan will remain ON in low speed for up to 3 minutes.
CONTENT