This is the third post in our LV Panel Engineering Series. Part 1 covers the governing standards. Part 2 explains Form of Separation. This post covers three more topics that connect directly: how well an enclosure keeps things out, who can safely access it, and how cables get in.
An LV panel’s enclosure does two jobs. It keeps the outside world out. It lets the right people safely in. The IP rating measures ingress protection. The IK rating measures impact resistance. And how the panel gets cabled on site directly affects how much current it can carry. This post covers all three.
LV Panel IP Ratings
IEC 60529 defines the IP (Ingress Protection) code. IEC 61439-1/2 references it directly in clause 10.3 — part of the design verification table from Part 1. The code always has two digits. Each digit protects against something different.
First digit — protection against solid objects
| Digit | Protects against |
|---|---|
| 0 | No protection |
| 1 | Objects larger than 50mm — basic protection against accidental hand contact |
| 2 | Objects larger than 12mm — fingers |
| 3 | Objects larger than 2.5mm — tools, wires |
| 4 | Objects larger than 1mm |
| 5 | Dust — some ingress occurs, but not enough to affect operation |
| 6 | Total protection against dust |
Second digit — protection against liquids
| Digit | Protects against |
|---|---|
| 0 | No protection |
| 1 | Vertically dripping water (e.g. condensation) |
| 2 | Water dripping at up to 15° from vertical |
| 3 | Rain falling at up to 60° from vertical |
| 4 | Water splashing from any direction |
| 5 | Water jets from any direction |
| 6 | Powerful water jets, similar to waves |
| 7 | Temporary immersion (typically up to 1m, limited time) |
| 8 | Continuous immersion |
Take IP54 as an example. The “5” protects against dust that could affect operation. The “4” protects against splashing water from any direction. An outdoor panel facing wind-blown sand and rain might need IP66 instead — fully dust-tight, and protected against powerful water jets. The two digits work independently. That’s why you’ll sometimes see combinations like IP20: touch-safe internal barriers, but no liquid protection at all. This is normal for equipment that sits inside a separate, sealed outer enclosure.
The IK Code: A Different Kind of Protection
IP ratings say nothing about physical impact — a dropped tool, an accidental knock from nearby equipment. The IK code covers that. It runs from IK00 (no protection) to IK10, using a standard test hammer to deliver a defined impact energy at each level.
| IK rating | Impact energy (Joules) |
|---|---|
| IK00 | Not protected |
| IK01 | 0.14 |
| IK02 | 0.20 |
| IK03 | 0.35 |
| IK04 | 0.50 |
| IK05 | 0.70 |
| IK06 | 1.00 |
| IK07 | 2.00 |
| IK08 | 5.00 |
| IK09 | 10.00 |
| IK10 | 20.00 |
The scale isn’t linear. IK10 withstands twenty times the impact energy of IK06. Manufacturers usually reserve IK08–IK10 for enclosures without glazed doors, since high impact energy tends to rule out glass viewing windows. If a panel sits near vehicle or forklift traffic, specify the right IK rating alongside the IP rating — it matters just as much.
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Accessibility: Who Can Open What
IEC 61439 also defines accessibility — who can open a compartment, and under what conditions:
- Ordinary persons — front fascia items only, no tool needed, usually interlocked.
- Skilled persons — compartments that need a key or tool. This applies to most MCC starter compartments and main busbar chambers.
- Instructed persons — an in-between category, like an operating handle that works without opening a door.
These rules shape the panel’s interlocking scheme. A door interlock stops you opening a compartment while its breaker stays on. A racking interlock stops you pulling a withdrawable unit out while it’s energized. Key-exchange interlocks stop two breakers from closing at the same time when they shouldn’t. Accessibility works together with Form of Separation from Part 2: a high Form gives a skilled person safe access to one compartment without exposing the busbar or any other circuit.
Cable Entry — and Why It Affects the Panel’s Rating
This part looks like a mechanical detail. It isn’t. It directly affects how much current the panel can carry.
Entry configuration.
Cables enter from the top or the bottom, depending on how they’re routed. Bottom entry suits floor-standing boards fed from underfloor trenches. Top entry suits cables running from overhead trays. Either way, cables need their own dedicated compartment, separate from the busbar and devices. This preserves segregation and allows proper bending radius — especially where several parallel runs land on one large incomer.
Gland plates.
Size every gland correctly for its cable. Plug every unused hole. Skip this, and the enclosure’s IP rating breaks the moment it’s commissioned — no matter what it was designed for.
The thermal link.
Here’s the connection that matters most. IEC 61439-1 requires the assembly’s temperature rise to stay within defined limits. That verification depends on assumptions about cable quantity, arrangement, and the heat they inject through their terminations. Cables packed too tightly, or squeezed into an undersized compartment, restrict airflow and add localized heat at the terminals. If the site’s actual cable arrangement doesn’t match what the panel was verified for, its real current-carrying capacity can drop below the nameplate rating. That’s a derating the panel builder never planned for.
This is why a panel’s rated current isn’t just a busbar ampacity figure from a datasheet. It’s a value verified for one specific combination of enclosure, ventilation, and cable arrangement. Change the cable arrangement significantly after that verification, and the rating no longer strictly applies.
The practical lesson: finalize cable schedules — sizes, quantities, entry points, routing — before the panel builder starts thermal design or heat-run testing. A late change, like extra parallel runs or larger cable sizes, is one of the most common causes of non-conformance once a panel reaches site.
How SEC’s Own Standard Fits In
Part 1 covered this pattern: Saudi Electricity Company’s own Material Standard Specification for auxiliary AC/DC panels — SEC-MSS-131-02 — sits on top of IEC 61439 rather than replacing it. Alongside IEC 60529 and IEC 61439’s clause 10.3, it sets project-specific minimum requirements for enclosure ingress protection, matched to the panel’s installation environment. It ties into the same design-verification framework from Part 1: degree of protection is one of the twelve characteristics that must be formally verified, by testing or by assessment. This shows how a utility standard works in practice — it doesn’t invent new concepts. It takes the IEC framework and pins down the exact values for that utility’s equipment.
Up next in this series: Inside an LV Panel: Switching, Control & Measuring Devices Explained, covering what actually sits inside these compartments — from air circuit breakers to protection relays and metering — and how each device type is selected and coordinated.