How to expand and modify your energised Low-Voltage Switchboard?

As energy requirements change over time, the requirement to add new equipment to meet these changing needs may arise and sometimes the extension of a LV switchboard has to be carried out under voltage because complete disconnection of the switchboard is not possible. 

To add additional feeders to an existing switchboard care must be taken to ensure that:
  • Sufficient spare space is available.
  • Certain criteria are met for modifying the live switchboard (Service Index, IP and Forms).

If you want to extend your Comeca LV switchboard discover our LV switchboards extension service solutions.

Available spare space

The first step is to assess the space needed for the new feeder(s) to be added and check the space available in the existing installation.
Depending on the modularity of the feeders to be added and the available space, it may be necessary to modify the existing switchboard configuration.


You need to add a 2-module feeder while your panel only has 1-module reserve slots.
In this case, it is possible to transform 2 contiguous 1-module slots into a single 2-module slot in order to accommodate the new feeder. The modification consists of removing the separating sheet, and equipping the slot thus formed with:

  • power connectors to establish the link with the vertical busbar
  • power connection block
  • auxiliary connection block

Once the modification is complete, the new feeder can be inserted into its slot. It must be checked that the plug-in connection is correct and stress-free.
The reverse operation is also possible.

The above transformations can be carried out in service only if the design of the switchboard allows it (Service Index). This work must be carried out by authorised personnel or by COMECA Services in compliance with safety regulations. 
Feeders of the same size and gauge are interchangeable. The installation of a mechanical interlocking system will prevent an unsuitable drawer from being inserted in the wrong place.

GALAXIS and TITAN switchboards are designed to allow the easy installation, replacement or addition of additional feeders.

adding extra feeders Titan

What is the service index of my equipment? Does it allow an evolution in service?

To know or define the modalities in terms of evolution of your switchboard it is necessary to check the 3rd figure of the service index.
If you need the switchboard to be extended while it is energised the service index must be either the number 2 or 3 for the upgrade.

Evolution: What is the difference between the number 2 and 3?

2: It is possible to add equipment according to the existing spare sockets. The addition or replacement of sockets requires the complete disconnection of the switchboard.

3: It is possible to add live equipment to the existing spare volume. The modularity of the existing slots can be changed. The busbar connection systems allow equipment to be added or removed in service.

IS333 withdrawable drawer technology

This solution offers maximum flexibility for adding additional equipment and modifying existing slots.

From an available spare slot, it is sufficient to equip the compartment with:

  • a partition
  • power connectors for connection to the vertical busbar
  • power terminal block
  • auxiliary connection block
  • plug in the new feeder

The modification of an existing configuration is done, without disconnecting the panel, by adding or removing the above mentioned equipment.
The IS333 withdrawable drawer has a test position allowing its operation to be tested without having connected the power.

Comeca offers 2 IS333 type switchboards in its range:

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IS223 disconnectable technology or IS233 withdrawable technology

This technology offers the possibility of adding additional equipment to a live switchboard.

From an available spare slot, it is sufficient to equip the box tier with:

  • a separation plate
  • power connectors to establish the link with the vertical busbar
  • power terminal block (only for IS233)
  • an auxiliary terminal block (only for IS233)
  • plugging in the board

The modification of an existing configuration is done, without disconnecting the switchboard, by adding or removing the equipment mentioned above.

The IS223 and 233 mounting panel does not have a test position.
When working on the IS223 board, the cables connected directly to the circuit breaker must be removed.

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Is my equipment safe for workers?

When considering the extension of an LV switchboard, and even more so when extending it under voltage, the emphasis must be on the safety of the operators. 

Safety through forms

The screens placed inside the installation play a key role in protecting workers. 
The forms of the switchboard define the separations (screens, partitions) placed inside the Low Voltage switchboard. They determine the protection of people and the possibility of intervening or not under voltage.

To ensure the modification and/or extension of the live switchboard safely, at least a type 3 is recommended, ideally a type 4. 

In some cases, it will be necessary to use additional removable protections to remove the danger (e.g. insulating layer).

Recommended Forms :

Safety with the protection index (IP)

The protection index is a classification of the level of protection offered by an installation against the penetration of solid and liquid bodies. It is composed of 2 digits and can be completed by a letter indicating the level of protection of the personnel independently of the protection of the equipment against the penetration of solid foreign bodies. 

In order to provide increased protection for the worker, it is important that the design of the switchboard provides an XXB open door protection rating
The letter B accompanying the index corresponds to the protection of persons against access to dangerous (live) parts with the finger of the hand.

More information to help you choose your LV equipment: How to choose your LV equipment ? Download the guide


In summary

It is possible to add extra feeders to a switchboard in service if the following conditions are met:

  • There is sufficient spare space available.
  • Check that the Service Index: have a type of 2 or 3 for the evolution part, The Protection index for the open door is XXB, the used forms are type 3 or 4 associated with «b» in order to be sufficiently protective for operators.


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