Booster Heater; Earth Leakage Circuit Breaker For Heater; Relay For Heater; 3-Way Valve - Mitsubishi Electric EHST17D-VM2D Service Manual

Booster heater

Thermostat (90°C) and thermal cut out (121°C)
121 °C
Thermal
cut-out
9
2 kW heater (230 V, 1 phase)
2 + 4 kW heater (230 V, 1 phase)
3 + 6 kW heater (400 V, 3 phase)
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

3-way valve

<DHW> <Heating>
Motor
Valve
A AB A
B
B
OCH714A
Part Name
90 °C
Manual reset
water
thermostat
10
2kW
1 2
2kW
2kW 2kW
1 2 3 4
1kW 2kW
1kW 2kW 2kW
3 4 5 6
1kW 2kW 2kW
2kW
3 4 5 6
<DHW>
Motor
Valve
AB
A
B
AB
Measure the resistance between the terminals with a tester.
Terminal
9–10
Terminal
1–2
Terminal
1–2
3–4
Terminal
1−2=2-3=1−3
4−5=5-6=4−6
Terminal
1−2=2-3=3−1
4−5=5-6=6−4
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.
(1) Check the movement of the red indicator. The red indicator normally
points to A in DHW mode and to B in Heating mode as shown to the left.
<Heating>
(2) If each indicator position is correct but the 3-way valve does not work
properly, the motor may not fit onto the valve securely, so remove the
motor by pressing the release button, and reinstall it.
A
B
AB
62
Checkpoints
Normal Abnormal
110(±35) mΩ Open or Short
Normal Abnormal
26.5(+3/−1.3) Ω Open or Short
Normal Abnormal
26.5(+3/−1.3) Ω Open or Short
13.3(+1.5/−0.6) Ω Open or Short
Normal Abnormal
105.8(+11.8/−5) Ω Open or Short
52.9(+5.8/−2.5) Ω Open or Short
Normal Abnormal
35.3(+3.9/−1.8) Ω Open or Short
17.6(+1.9/−0.9) Ω Open or Short