Troubleshooting By Alarm Code (Related To Tank) - Hitachi YUTAMPO Series Service Manual

6 Troubleshooting
Indoor unit

6.2.2 Troubleshooting by alarm code (related to tank)

03
Alarm code
• This alarm is displayed when an Outdoor unit is not detected for three minutes after the normal transmission between
the indoor units and the outdoor units. Also an abnormal transmission is maintained for 30 seconds after the micro-
computer is Power ON. The alarm is displayed when the abnormal transmission is maintained for 30 seconds from
the starting of the outdoor unit.
16
Alarm code
• This alarm code is displayed when the thermistor is short-circuited (greater than 100ºC) or cut (less than -10ºC) when
DHW is enabled.
• This alarm forces all operations to stop (Outdoor & Indoor Units).
• The unit should be stopped to release the alarm.
Is THM connected to
DHWT
CN4 (pin 3 and pin 4)?
Yes
Is resistance of
THM between 0.25
DHWT
kΩ and 21 kΩ?
Yes
Is the
temperature of
THM between 100ºC
DHWT
and -10ºC?
Yes
Faulty PCB (Check
PCB)
80
72,05
70
60
50
40
30
20
10
0
-30 -25 -20 -15 -10
72 SMGB0135 rev.0 - 06/2020
Abnormal transmission between the indoor unit and the outdoor unit
No
No
No
Thermistor resistance characteristics
37,92
20,96
12,10
7,26
4,51
2,89
-5 0 5 10 15 20 25 30 35
Temperature (ºC)
DHW tank thermistor abnormally (THM
1,91
1,29
0,63
0,89
0,46 0,34
40 45 50 55 60 65 70 75 80 85 90 95
Temperature (ºC)
)
DHWT
Connect it
Faulty thermistor
(Change it)
Check correct position
of THM and correct
DHWT
it
0,25 0,15 0,13
0,19
100 105 110 115 120 125 130