Mitsubishi EHST20C-VM2C Service Manual page 76

Part Name
Flow sensor
Flow signal V
5V DC
Booster heater
Thermostat (90°C) and thermal cut out (121°C)
121 °C
Thermal
cut-out
9
10
2 kW heater (230 V, 1 phase)
2 + 4 kW heater (230 V, 1 phase)
2kW
1
3 + 6 kW heater (400 V, 3 phase)
1kW
1kW
1 2
3 + 6 kW heater (230 V, 3 phase)
1kW
1kW
1 2
Earth leakage circuit breaker for heater
Relay for heater
R S T A1 A2
U V W
OCH570C
1
4
CN1A
90 °C
Manual reset
water
thermostat
2kW
1 2
2kW
2kW
2 3 4
2kW
1kW 2kW 2kW
3 4 5 6
1kW
2kW 2kW
2kW
3
4 5 6
Check Points
Flow signal
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.35V
0.0
0 20 40
Flow [l/min]
Measure the resistance between the terminals with a tester.
Terminal
9–10 110(±35) mΩ
Terminal Normal
1–2 26.5(+3/−1.3) Ω
Terminal
1–2 26.5(+3/−1.3) Ω
3–4 13.3(+1.5/−0.6) Ω
Terminal Normal
1−2=2-3=1−3 105.8(+11.8/−5) Ω
4−5=5-6=4−6 52.9(+5.8/−2.5) Ω
Terminal Normal
35.3(+3.9/−1.8) Ω
1−2=2-3=3−1
4−5=5-6=6−4 17.6(+1.9/−0.9) Ω
If a short circuit occurs on the booster heater, immersion heater, or each power
line, a short-circuit breaker will trip and power source will be blocked.
Eliminate the causes of short circuit and then turn on the breaker again.
When the applied voltage is not 230 V AC across the terminals A1-A2, check
the terminals R-U, S-V, and T-W are open.
When the applied voltage is 230 V AC across the terminals A1-A2, check the
terminals R-U, S-V, and T-W are short.
76
60 80 100
Normal Abnormal
Open or Short
Abnormal
Open or Short
Normal Abnormal
Open or Short
Open or Short
Abnormal
Open or Short
Open or Short
Abnormal
Open or Short
Open or Short