Willis WST12MC16S Service Manual page 26

Temperature sensor malfunction detection
(1) Indoor temperature sensor
Detect malfunctions of temperature sensor any time.
(2) Indoor pipe temperature sensor
In defrosting period, the temperature sensor malfunction will not be detected. 5 min after finishing defrosting, the system begins to detect the temperature
sensor malfunction. In other times, the temperature sensor malfunction will be detected.
(3) Protection of temperature sensor
1. When short-circuit occurs to the temperature sensor for 30s:
The temperature sensor overheats. In this case, the complete unit will stop for protection. At the same time, the temperature protection and temperature
sensor malfunction will be shown.
2. When break-circuit occurs to the temperature sensor for 30s:
The unit will stop and the temperature sensor malfunction will be displayed
Frequency Control
<Outline>
When starting the compressor, or when conditions are varied due to the change of the room, the frequency must be initialized according
to the D value of the indoor unit and the Q value of the indoor unit.
Q value: Indoor unit output determined from indoor unit volume, air flow rate and other factors.
1. P control
Calculate D value in each sampling time (20 seconds), and adjust the frequency according to its difference from the frequency
previously calculated.
2. I control
If the operating frequency is not change more than a certain fixed time, adjust the frequency up and down according to the
obtaining the fixed D value.
When the D value is small...lower the frequency.
When the D value is large...increase the frequency.
3. Frequency management when other controls are functioning
When frequency is drooping;
Frequency management is carried out only when the frequency droops.
For limiting lower limit
Frequency management is carried out only when the frequency rises.
4. Upper and lower limit of frequency by PI control
The frequency upper and lower limits are set depending on indoor unit.
When low noise commands come from the indoor unit or when outdoor unit low noise or quiet commands come from indoor unit, the
upper limit frequency must be lowered than the usual setting.
3-minutes Standby
Prohibit to turn ON the compressor for 3 minutes after turning it off.(except when defrosting)
Compressor Protection Function
When turning the compressor from OFF to ON, the upper limit of frequency must be set as follows. (The function must not be used when
defrosting.)
32
FCG 3 88
FCG 2 64
FCG 1 48
TCG1 240
TCG2 360
TCG3 180
Frequency
FCG3
FCG2
FCG1
TCG 1sec
Function and Control
Time
TCG 2sec TCG 3sec
D value,