Motor Heater Damage Inspections


1) Motor Coil Inspections
1. Turn power of unit off.
2. Use tester unit to measure resistance range (Ω)
3. Measure resistance of U1 ~ V1, U1 ~ W1, V1 ~ W1. (see left illustration for reference)
4. If all three phases have the same resistance (Ω), the motor coil is normal.
* If the resistance values are unbalanced, the motor coil is defective.
Note: Even if the resistance of the motor coil is normal, thermal relay may trip depending of hardness of motor shaft bearing.
* Motor pumps will require overhaul.

2) Motor Relay Inspections
1. Turn power of unit off.
2. Remove U1, V1, W1 on motor lines from thermal relays.
3. Set motor thermal relays.
4. Use tester to measure AC voltage range.
5. Turn power on and turn MS-1 relay on.
6. Measure voltage of U1 ~ V1, U1 ~ W1, V1 ~ W1. (see left illustration for reference)
7. If all three phases have AC-200 running, the motor coil is normal.
* If the AC voltage values are unbalanced, the relay or the thermal relays are defective.

3) Heater Inspections
1. Turn power of unit off.
2. Use tester unit to measure resistance range (Ω).
3. Measure resistance of H1 ~ H2, H1 ~ H3, H2 ~ H3. (see left illustration for reference)
4. If all three phases have the same resistance (Ω), the heater coil is normal.
* If the resistance values are unbalanced, the heater coil is defective.

4) Heater Relay Inspections
1. Use tester to measure AC voltage.
2. Turn power on and turn the MC-1 relay on.
3. Measure voltage of H1 ~ H2, H1 ~ H3, H2 ~ H3. (see left illustration for reference)
4. If all three relay phases of H1, H2 and H3 have AC-200 running, the heater relay is normal.
* If the AC voltage values are unbalanced, the relays are defective.