DZ20LE MCCB Molded-Case-Circuit-Breaker 160A-630A with transparent case

2. Use and Routine Maintenance of Residual Current Circuit Breaker

(1) During wiring, the residual current circuit breaker must strictly distinguish between the neutral wire and the protective earthing wire. When connecting a 3-pole 4-wire or 4-pole residual current circuit breaker, the neutral wire shall be connected to the N pole of the circuit breaker. The output terminal of the neutral wire of the residual current circuit breaker shall not be used as a protective earthing wire again (i.e., no repeated earthing or connection to equipment casing), and can only be used as a current-carrying neutral wire. If a protective earthing wire needs to be connected, it must be connected before the input terminal of the residual current circuit breaker. Otherwise, the residual current circuit breaker cannot operate normally.

(2) When the operating handle of the residual current circuit breaker shows the “ON” position, it indicates that the circuit is closed and connected; when the handle shows the “OFF” position, it indicates that the circuit is open and disconnected.

(3) After installation and before closing, the operating handle of the residual current circuit breaker shall be in the “OFF” or “O” position before closing.

(4) A separately installed residual current circuit breaker should be easy to operate and maintain, and the recommended height from the ground is generally 1500mm.

(5) After installation and a certain period of use, the residual current circuit breaker shall press the “Test Button” to check whether the earth leakage protection performance is normal. If the residual current circuit breaker can break normally when the “Test Button” is pressed, it indicates that the earth leakage protection characteristic is normal; if the residual current circuit breaker cannot break when the “Test Button” is pressed, it indicates that the earth leakage protection function has failed, and it should be removed for replacement or sent to the manufacturer for maintenance in time.

(6) The overload, short-circuit and earth leakage protection characteristics of the residual current circuit breaker are all set by the manufacturer and cannot be disassembled and adjusted arbitrarily during use. Otherwise, you will be responsible for all consequences.

(7) If the residual current circuit breaker breaks due to earth leakage in the protected circuit or earth leakage caused by insulation damage during use, the operating handle will be in the tripped position (middle position). The cause should be identified and the fault eliminated. Then, first flip the operating handle downward to “reset” the operating mechanism before closing and using it again. Otherwise, the residual current circuit breaker cannot operate normally.

3. Selection of Residual Current Circuit Breaker

(1) When selecting the rated residual operating current value of the residual current circuit breaker, full consideration shall be given to the normal leakage current value of the protected circuit and various equipment. If possible, the normal leakage current value of the circuit and equipment can be measured on site.

(2) When selecting the rated residual non-operating current value of the residual current circuit breaker, it shall not be less than twice the maximum normal leakage current value of the circuit and equipment.

(3) When selecting the rated current of the residual current circuit breaker, the appropriate rated current, rated residual operating current and breaking time shall be selected according to the specific requirements of the protected object. Otherwise, the correct protection effect cannot be achieved.

4. Troubleshooting of Common Faults

Correct selection and installation of the residual current circuit breaker is an important link to achieve normal protection. If installed improperly or wired incorrectly, the residual current circuit breaker cannot operate normally, and may even malfunction or refuse to operate.

(1) Main Causes and Solutions for Malfunction

① Malfunction caused by earthing of the neutral wire on the load side of a 3-pole 4-wire residual current circuit breaker:

Earthing of the neutral wire on the load side will make the vector sum of the currents flowing into the zero-sequence current transformer non-zero, causing the residual current circuit breaker to malfunction.

Troubleshooting: Remove the earthing of the neutral wire on the load side. If you must connect the protective earthing wire, please use a three-phase five-wire power supply, because only the non-current-carrying earthing wire can achieve real earthing protection.

② Malfunction caused by using single-pole load on the load side of a 3-pole residual current circuit breaker:

3-pole residual current circuit breakers are mostly used for motor (delta connection) protection, and the neutral wire does not pass through the zero-sequence current transformer. Therefore, the residual current circuit breaker will break as long as a single-phase load is used.

Troubleshooting: When both three-phase load and single-phase load are needed in a three-phase power supply, be sure to use a three-phase four-wire or four-pole residual current circuit breaker.

③ Malfunction caused by excessive normal leakage current of the circuit and equipment:

Excessively long wires on the load side of the residual current circuit breaker will increase the normal leakage current, which may cause the residual current circuit breaker to malfunction; or the insulation of the equipment decreases, and the earth leakage current increases, causing the residual current circuit breaker to malfunction.

Troubleshooting: Minimize the length of the wires, perform insulation maintenance on the equipment, or select a residual current circuit breaker with an appropriate earth leakage operating current after actually measuring the leakage current value.

④ Malfunction caused by the connection of neutral wires of two residual current circuit breakers on the branch:

When there is an unbalanced load, the unbalanced current cannot all return along this branch, and part of the unbalanced current must return along other branches, causing the two residual current circuit breakers to malfunction.

Troubleshooting: Connect the neutral wire on the power supply side of the residual current circuit breaker.

(3) Electrical Equipment with and without Earth Leakage Protector

When electrical equipment with and without earth leakage protector share a set of earthing device, if an earth leakage fault occurs on the equipment without earth leakage protector, the dangerous touch voltage will be transmitted to the equipment with earth leakage protector through the common earthing device. When touching the equipment casing, the electric shock current does not pass through the earth leakage protector, thus losing the earth leakage protection function and causing electric shock hazard.

Troubleshooting: The earthing protection devices of electrical equipment with and without earth leakage protector shall be earthed separately.

Ordering Information

Users shall specify the following contents when placing an order:

1. Name and model of the residual current circuit breaker;

2. Rated current (A) of the residual current circuit breaker;

3. Rated residual operating current (mA) of the residual current circuit breaker;

4. Residual current breaking time: standard type or time-delay type;

5. Protection type;

6. Pole number and quantity.

Note: If users have other special requirements for ordering, please contact the manufacturer.

Example: Ordering CDZ20L-400 residual current circuit breaker, rated current 400A, rated residual operating current 200mA, for distribution use, total 100 units.

It should be written as: CDZ20L-400/3N300, 400A, 200mA, 100 units.