Mitsubishi Electric EHSD-MED Service Manual page 56

Part Name
Earth leakage circuit breaker for heater
Relay for heater
R S T
U V W
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)
1
2 + 4 kW heater (230 V, 1 phase)
2 kW
1 2
3 + 6 kW heater (400 V, 3 phase)
1 kW
1 kW 1 kW
1 2 3 4
3 + 6 kW heater (230 V, 3 phase)
1 kW 1 kW
1 kW
1 2 3 4
OCH712C
A1 A2
90 °C
Manual reset
water
thermostat
2 kW
2
2 kW
2 kW
3 4
2 kW
2 kW 2 kW
5 6
2 kW 2 kW
2 kW
5 6
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 VAC across the terminals A1-A2, check the terminals
R-U, S-V, and T-W are open.
When the applied voltage is 230 VAC across the terminals A1-A2, check the terminals
R-U, S-V, and T-W are short.
Measure the resistance between the terminals with a multimeter.
Terminal
9–10 80(±20) mΩ
Terminal
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
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
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
56
Checkpoints
Normal Abnormal
Open or Short
Normal Abnormal
Open or Short
Normal Abnormal
Open or Short
Open or Short
Normal Abnormal
Open or Short
Open or Short
Normal Abnormal
Open or Short
Open or Short