LV installation systems: internal organisation (1/2)

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Let’s go one step forward on our way to choose a Low Voltage Electrical Distribution (LV ED) panel for our small or medium size building. Until now we concentrated on functions and modularity. It’s time to get more technical, and take a look at some more detailed aspects.

There are multiple internal organisations possible for the LV ED panel. Experience shows that some of them are better than others. The goal is to optimise maintenance tasks, protection of people and property, footprint, and costs.

We will try now to describe very synthetically what we believe are the best choices for the internal organisation of LV panels for both types of installation: Floor-Standing and Wall-Mounted.

In this article we will concentrate on Floor-Standing panels and in the next one we will concentrate on Wall-Mounted ones.

What do we mean by “internal organisation”?

We call “internal organisation” the relative positioning of the different components of the LV Panel internal to its enclosure.

The main elements are:

  • The Bus Bars.
    • The Horizontal Bus Bars (HBB).
    • The Vertical Bus Bars (VBB).
  • The Power Cables or Busways.
  • The Access.
  • The Grounding.
  • The Control Power, the Auxiliary Wiring, the Communications Network, the I/O, and the like.

Additionally, some elements may depend on local habits.

We will illustrate these internal organisations with very rough sketches in order to make them clear. In these sketches we will use the following symbols:

Floor-Standing (FS) Panels

The preferred internal architecture for FS panels would be the following:

  • The Bus Bars.
    • The HBB can be installed either at the TOP, at the MIDDLE or at the BOTTOM of the panel.
    • The VBB will be preferably installed on the LEFT or on the RIGHT (LATERAL installation).
  • The Power Cables or Busways.
    • Incoming can be both at the TOP AND at the BOTTOM.
    • Horizontal Outgoings require SEPARATE CABLEWAYS.
  • The Access is preferably both FRONT AND REAR, unless local habit allows for FRONT ONLY Access.
  • Grounding should be easily modified, i.e. independent from the main Bus Bars location (HBB).
  • Control Power, Auxiliary Wiring, Communications Network, I/O, and the like: EMC constraints respected. Preferably, at a certain distance from power distribution, and in any case not parallel to it, unless there is a metallic barrier in between.
  • The most widespread local habit consists of a dedicated cubicle for the incoming switchgear.

Why LATERAL installation of the VBB is preferred to BACK installation?

Almost all of these preferences are due to common sense and help with obtaining maximum flexibility for installation and late decision taking. The one which is not so obvious is the preference for LATERAL installation of the Vertical Bus Bars (VBB).

The alternative installation of the VBB would be at the back of the panel. Considering that positioning of VBB Laterally (whether left or right) is more costly – it requires more steel and copper – than positioning them at the Back, why do we claim that Lateral positioning is the best choice?

There are several strong reasons for this preference:

  • Access to the VBB and to the connection of the devices is easier.
  • Active parts can be installed in a dedicated zone, separated from the devices zone. This means less possible damage of the functional units (FU) in case of a short circuit onto the busbars (electro-dynamic forces).
  • The possibility to perform infrared thermography.

Of course, the ultimate decision will be taken based on the allocated footprint. With VBB installed laterally the panel will be longer and less deep. At the opposite, back VBB will make the panel shorter but deeper.

Example of a Floor-Standing LV panel: Front access, Top HBB, Lateral VBB
Example of a Floor-Standing LV panel: Front access, Top HBB, Lateral VBB


Example of a Floor-Standing LV panel: Front access, Bottom HBB, Lateral VBB
Floor-Standing LV panel: Front access, Bottom HBB, Lateral VBB


Example of two Floor-Standing LV panels: Front access, Top HBB, Back VBB (you can click to see full size)

Writtent by Frederic Waterlot and Daniel Barstz