Mitsubishi Electric EHST20C-VM6HB Service Manual page 66

Part Name
Booster heater
Thermostat (90 °C) and thermal cut out (11 °C)
121 °C
Thermal
cut-out
9
kW heater (0V, 1 phase)
 + 4kW heater (0V, 1 phase)
2kW
2kW
3
 + 6kW heater (400V,  phase)
2kW
4 5
Earth leakage circuit breaker for heater
Relay for heater
R S T A1 A2
U V W
Flow switch
Flow
OCH531
90 °C
Manual reset
water
thermostat
10
2kW
2
1
2kW
4 1 2
2kW 1kW
2kW 1kW 1kW
6 1 2 3
1
2
3
Check Points
Measure the resistance between the terminals with a tester.
Terminal
110(±35)mΩ
9-10
Terminal Normal
26.5(+3/-1.3)Ω
1-
Terminal
26.5(+3/-1.3)Ω
1-
13.3(+1.5/-0.6)Ω
-4
Terminal Normal
105.8(+11.8/-5)Ω
1-=-=1-
52.9(+5.8/-2.5)Ω
4-5=5-6=4-6
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 230V AC across the terminals A1-A2, check the
terminals R-U, S-V, and T-W are open.
When the applied voltage is 230V AC 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 tester.
State of moving part
Paddle vertical (Flow < 5.5 l/min)
Paddle inclined (Flow > 5.5 l/min)
66
Normal Abnormal
Open or Short
Abnormal
Open or Short
Normal Abnormal
Open or Short
Open or Short
Abnormal
Open or Short
Open or Short
Normal Abnormal
Open Other than open
Short Other than short