Airwell ONG3-17 R410A, Service Manual

Page: 41 / 127

CONTROL SYSTEM
Service Manual-CN Fixed RPM series
12-6
12.3.3 OFAN operation
Min time interval between OFAN ON/OFF state change is 30 sec.
In general, OFAN starts together with COMP.
12.3.4 HE operation
Minimum Heaters ON or OFF time is 30 sec.
Heaters can be activated only if IFAN is on.
In RH group, HE-1 and HE-2 will be activated only when COMP is not
operating, except in Dry Mode.
12.3.5 Protections
High pressure protection is applicable to all operating modes.
Deicing control is valid in Heat and Auto Heat Mode only.
Defrosting control is valid in Dry, Cool, Heat and Auto Modes.
No reset after protection modes.
12.3.6 Thermistors operation
Return air Temp. is detected by RAT (RT1) in normal Mode, or by RCT (R/C sensor) in
I-FEEL Mode.
Indoor Coil Temp. is detected by ICT (RT2).
Outdoor Coil Temp. is detected by OCT (RT3).
Similarly, in the Indoor Units of a WMQ/T system, 4.7k Ohm (5%) resistors must be connected
to the OCT ports to disable the “Thermistor Temp reading doesn’t change” error checking.
Definition of thermistor faults:
a. Thermistor is disconnected -
The thermistor reading is below -30
o
c.
b. Thermistor is shorted -
The thermistor reading is over 75
o
c.
c. Thermistor Temp reading doesn’t change (irrelevant for RT1) -
(i) This test is performed only once after a unit is switched from OFF/STBY to
operation. At the first occurrence of 10 min continuous COMP operation,
the current ICT & OCT are compared with those when the COMP was
switched from OFF to ON 10 min before. If the
'
T is less than 3
o
c, the
thermistor is regarded as defective.
(ii) The ICT and OCT no-change error can be disabled together by connecting a
4.7 k or 3.9 k ohm resistor (5%) to the OCT connector. These resistors are
equivalent to a thermistor at 43+/-1
o
c and 48+/-1
o
c respectively.
(iii) Connecting a 4.7k resistor to the ICT connector will disable the ICT
no-change error only.