How to Choose the Right Low Voltage Switchgear for Your Project

Ask ten engineers how to choose low voltage switchgear and you will get ten versions of the same answer: it depends on the load, the fault level, and how long you can tolerate a shutdown. The phrase “it depends” gets a bad reputation, but in this case it is doing real work. The differences between switchgear types are not marketing noise — they show up in the price tag and in how the equipment behaves the first time a drawer fails at 3am.

This is a practical walk through the factors that actually decide the choice, in the order we tend to think about them when a client sends us a load list.

Start with what the site can tolerate

Before any current ratings, before any standards, answer one question: what happens to your operation when the board has to come down for maintenance?

For a data center or a continuous process plant, an outage is measured in lost revenue per minute. That answer points straight at withdrawable switchgear — MNS or GCS — where a failed unit is pulled and replaced in minutes without dropping the board. For a warehouse running one shift, a scheduled shutdown is a planning detail, not a crisis, and a fixed GGD board saves 30-40% on first cost.

This is the fork in the road. Everything else follows from it.

Then the numbers: current and fault level

Two numbers drive most of the specification.

Main busbar current. Total your connected load, then add headroom — 20-30% is the figure we usually recommend, because upgrading busbar later means pulling the whole board apart. The ranges sort themselves out: GGD and GCK top out around 3150A, GCS at 5000A, MNS at 6300A. If your site is pulling more than that, the choice is already made for you.

Short-circuit withstand (Icw). This is the number that keeps the panel intact when a fault happens downstream and the upstream protection takes a moment to clear. For industrial installations you are typically looking at 50-80kA. Get this wrong and the panel does not just trip — it can physically distort. This is one of the things IEC 61439 now requires to be proven on a real specimen, not calculated on paper.

Do not forget to confirm the prospective fault level at your site with the utility. It varies by location and transformer size, and guessing at it is how boards end up under-specified.

Environment decides the enclosure

The IP rating is easy to get wrong because it is easy to ignore. A clean, dry electrical room is happy with IP30. The moment the panel sits in a dusty workshop, a humid coastal plant, or anywhere near process chemicals, you want IP54 with gasketed doors. The cost difference is modest; the cost of accelerated contact corrosion and mystery nuisance trips is not.

Altitude is another quiet factor. Above roughly 1000 meters, air density drops and equipment needs de-rating. If your project is up in the mountains — common in parts of Africa and the Middle East — mention it early rather than discovering the issue at commissioning.

Protection that works together

A switchboard is only as good as the protection coordination across it. The incoming breaker, the feeder breakers, and the loads downstream all need to be graded so that a fault in one branch trips only that branch.

On a real installation, three things matter:

• Arc flash containment — compartmentalized construction that stops an internal arc from spreading through the board and endangering operators. This is where the barriers between compartments earn their keep.
• Interlocking — on a withdrawable panel, the drawer physically cannot be withdrawn while the breaker is closed. Simple, but it prevents a whole category of human error.
• Earth leakage protection — essential in wet or conductive environments, where a small leak that would be harmless in a dry room becomes a shock hazard.

Think about growth before you sign

Most factories grow. The board you spec today will likely feed more loads in five years. A few cheap decisions now avoid expensive ones later:

• Size the busbar for 20-30% more than today’s load
• Prefer modular designs where new drawers slot into existing compartments
• Leave a couple of spare outgoing compartments in the initial layout
• Give yourself cable space — running out of termination room is a common and infuriating retrofit

The total cost conversation

The sticker price is not the cost. The math that matters looks like this: withdrawable carries a 20-40% premium, but a single avoided shutdown in a high-value plant can cover that difference many times over. Fixed type is cheaper to buy and simpler to maintain, but every intervention means downtime.

We have seen both calculations go the right way. The clients who get it wrong are the ones who only looked at the sticker.

The quick version

If you are working through this for a specific project, send us the load list and fault level — the decision usually becomes obvious once the numbers are on the table.