MCB Connection Diagram with MCCB and Wiring Procedure

Hey, in this article, we are going to see the connection diagram between MCB and MCCB with wiring procedures. MCBs are commonly used to protect individual branch circuits in residential and commercial electrical distribution panels. They offer protection for lower current circuits. On the other hand, MCCBs are suitable for higher current circuits, often found in industrial settings. In a distribution panel, you might have a combination of MCBs and MCCBs, each protecting circuits of different sizes and current ratings.

In industrial installations, MCCBs are used to protect larger feeder circuits that supply power to various parts of a facility. These feeders can then distribute power to smaller branch circuits protected by MCBs.

Figure 01: 3 Pole MCCB Connection with Single Pole MCBs

Here, in the below diagram, a 3-pole MCCB is used as the main circuit protection for an entire distribution board or an electrical sub-panel. It provides overcurrent protection for the entire panel, and from there, individual circuits can be protected by the single pole MCBs.

Wiring Procedure

1. Connect the three phases of the power source(L1, L2, L3) to the respective input line terminals on the MCCB.
2. For each MCB, connect the input line terminal of the MCB to the output load terminal of the MCCB. Here, we have connected one MCB for each phase.
3. Connect the output load terminal of the MCB to the respective load (e.g., lighting circuit, outlet circuit).
4. Connect the neutral terminal directly to the load. Use a neutral link for neutral wire distribution purposes.

Figure 02: A 4 Pole MCCB Connection with a Three-Pole MCB and Three Single-Pole MCBs

Here, in the below diagram, the 4-pole MCCB is used as the main incoming circuit breaker for an entire distribution board or an electrical sub-panel. The three-pole MCB is used to control the Three-phase load and the single-pole MCBs are used for controlling smaller branch circuits or smaller loads.

Wiring Procedure

When we use a four-pole MCCB, we need to connect all three phases and neutral from the power source to the MCCB. Before starting the connection identify all the input, output, line, and neutral terminals of the MCCB and MCBs. Because your device terminal may not same as shown in this diagram. If your device is also the same as the above diagram then follow the below procedure,

1. Connect the three phases of the power source (L1, L2, L3) and Neutral(N) to the respective input line terminals on the MCCB.
2. For three-pole MCB, connect the input of the 3-pole MCB to the output of the MCCB(only line connection required)
3. Connect the output of the 3-pole MCB to the three-phase load(e.g., motor).
4. For each single-pole MCB, connect the input line terminal of the MCB to the output load terminal of the MCCB. Here, we have connected one MCB for each phase.
5. Connect the output load terminal of the MCB to the respective single-phase load (e.g., lighting circuit, outlet circuit).
6. Connect the output neutral terminal from the MCCB directly to the single-phase loads. Use a neutral link for neutral wire distribution purposes.

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