Short answer: an IP rating is two numbers, and only two numbers. The first digit is protection against solid objects and dust (0–6), the second is protection against water (0–8, plus 9K for high-pressure hot-water jet cleaning). The digit describes the enclosure as tested, closed, with the correct cable entries — not the switchboard you build inside it. So IP65 on the box does not mean IP65 on the installation, and it says nothing about corrosion, UV, impact or the heat that a sealed box traps around your breakers.
This page explains how to read the code, which digits actually matter for a low-voltage distribution board, and where the specification usually goes wrong. We are an independent trading company — not a manufacturer, and not an appointed distributor of any brand — so certificates and ratings here are always quoted against the exact ordering code, never against a whole family.
Reading the two digits
IEC 60529 is the standard behind the code. The letters IP are followed by two digits; sometimes a letter suffix appears (IP20B, IPX4, IP44), and sometimes a third digit for mechanical impact is written separately as IK under IEC 62262. Those are different tests and should not be merged into one number on a quotation.
| First digit | Protection against solid objects | What it means in a panel |
|---|---|---|
| 0 | No protection | Open frame; only acceptable inside a larger enclosure. |
| 1 | Objects ≥ 50 mm | Back of the hand. Not a safety claim for terminals. |
| 2 | Objects ≥ 12.5 mm, jointed finger | “Finger-safe”: the classic IP2X requirement for accessible live parts. A 12.5 mm sphere must not touch live metal. |
| 3 | Objects ≥ 2.5 mm (tools, thick wires) | Better than finger-safe, still not dust-tight. |
| 4 | Objects ≥ 1.0 mm (thin wires, screws) | Common on industrial terminal blocks; stops wire clippings bridging terminals. |
| 5 | Dust-protected | Dust may enter but not in a quantity that interferes with operation. |
| 6 | Dust-tight | No dust ingress at all in the test. The usual requirement for desert and cement-plant jobs. |
| Second digit | Protection against water | Where it is normally asked for |
|---|---|---|
| 0 | None | Indoor, dry, climate-controlled rooms. |
| 1 | Dripping water, vertical | Covered outdoor positions with no wind-driven rain. |
| 2 | Dripping water, enclosure tilted 15° | Rarely specified on its own. |
| 3 | Spraying water up to 60° from vertical | Sheltered walkways, canopies. |
| 4 | Splashing water from any direction | The realistic minimum for an outdoor wall box in a rainy climate. |
| 5 | Water jets (6.3 mm nozzle) | Hose-down areas, food and beverage, vehicle bays. |
| 6 | Powerful water jets (12.5 mm nozzle) | Deck wash, heavy washdown, exposed coastal sites. |
| 7 | Immersion 1 m for 30 min | Pits, sumps, flood-prone basements. |
| 8 | Continuous immersion, conditions agreed | Submersible pumps and similar; the depth and duration must be agreed in writing. |
| 9K | High-pressure, high-temperature jet (ISO 20653) | Car wash and steam cleaning. Not an IEC 60529 digit. |
Two traps live in that second table. First, IPX4 is not “outdoor rated” — it is splash-resistant, and wind-driven rain at 30° off vertical on an exposed wall hits harder than the test. Second, IP67 is not “better than IP66” for a ventilated board: if the box is genuinely sealed, it also holds in heat and condensation, and the water that gets in through a gland never gets out.
What the rating is tested on — and what you actually install
An enclosure is type-tested as a closed box, usually with the entries sealed by the manufacturer’s own blind plugs. On site, three things change the result:
- Cable entries. A 25 mm hole with a plain cable through it is not IP54, whatever the door says. Correct size gland, correct sealing washer, correct tightening torque. An unused knockout must be fitted with a matching blind plug.
- The door and the seal. A gasket that is pinched, painted over, or missing a corner is the most common cause of a “leaking IP65 box”. Sealing depends on compression, so overtightening the screws distorts the lid and opens a gap.
- Field modifications. Every hole you drill for a cable, a breather, a DIN-rail bracket or a mounting bolt is a new, untested penetration. If the job needs instrumentation cable, plan the entries before you drill.
Then there is the part IP ratings deliberately do not cover: corrosion, UV ageing, impact and thermal management. A polycarbonate box on a Dubai roof can be IP66 and still fail in two summers as the polymer embrittles. A steel box on a West African coast can be IP65 and rust through at the gland plate. Specify material and finish separately: IK08/IK10 for impact, a UV-stabilised polymer or coated steel for sun, stainless fixings for salt.
Heat: the cost of a sealed box
This is the point that gets missed most often in a quotation. A breaker is calibrated at a reference ambient — for MCBs to IEC/EN 60898-1 that is 30 °C, and for many MCCBs to IEC/EN 60947-2 it is 40 °C — and the catalogue carries a derating table for higher ambient. Put an IP66 sealed enclosure in direct sun and the internal air can run well above the outside temperature. The result is nuisance tripping in the afternoon and a customer who blames the breaker.
The fix is not a bigger breaker chosen by guesswork. It is decided at specification stage: size the enclosure for the heat load rather than only the ways count; use a metal body where ambient is high and mount it out of direct sun; where the site allows, fit a pressure-compensating breather drain so the box breathes without taking water; and apply the ambient derating to the real internal temperature, recording that assumption on the quotation.
| Location | Sensible target | What to specify besides the IP digits |
|---|---|---|
| Indoor apartment riser, dry plant room | IP20 to IP40 | Finger-safe (IP2X) live parts, 9 mm modular interior, removable gland plate. IP20 is normal and honest here. |
| Workshop with dust and metal particles | IP54, first digit 5 minimum | Dust-protected rather than dust-tight is often enough — but metal swarf needs first digit 4 or better plus a lockable door. |
| Outdoor wall, temperate, under eaves | IP54 to IP65 | UV-stabilised polymer, correct glands, drain/breather, IK08. |
| Coastal or desert, direct sun | IP65/IP66, metal body | Corrosion class of the coating, sun shield, internal temperature derating, stainless fixings. |
| Washdown bay, food plant | IP65/IP66, slope top | Hose-proof glands, no water trap on the lid, 9K only if steam cleaning is actually used. |
| Pit, sump, flood-prone basement | IP67 or relocated | Immersion rating plus a mounting height rule; a floating board is better than a deep-rated one. |
Matching the enclosure to the interior
In the CHINT range the usual starting point for terminal distribution is the DB2 terminal box, an IEC-system enclosure in flush and surface versions built around 9 mm modular devices, which pairs directly with the NB1/NXB miniature circuit breakers and the NL1/NB1L residual current devices. For domestic consumer units the NX2 family runs from small ways counts up to 36 ways with a flame-retardant ABS/PC cover, and for harsher positions there are wall enclosures such as the NXW1-3/5 series rated IP65.
Those three examples are enough to make the selection logic concrete: the interior dictates the module width and the busbar system, and the enclosure then has to be chosen for the environment. Sizing the board itself — circuits, maximum demand, incomer, spare ways — is a separate exercise, covered in how to size a distribution board.
One discipline saves arguments later: state the IP rating for the assembled board, not the empty box. If we supply a populated board, the rating we can defend is the one that holds with our glands, entries and door seal as delivered. If you populate it yourself, the enclosure rating is where our responsibility ends and your workmanship begins; both are legitimate claims, and they should be written differently on the order.
FAQ
Q: Is a higher IP rating always better?
A: No. A sealed box traps heat and condensation, and it costs more. For an indoor dry riser, IP20 with finger-safe terminals is the correct answer. Specify the environment first, then the digit that matches it.
Q: What does IP2X or IPXXB mean?
A: The X is a digit that was not tested or is not claimed — IP2X means protection against 12.5 mm objects was verified but water protection was not. The suffix B refers to the jointed test finger (IP20B), which is the standard “finger-safe” claim for accessible live parts.
Q: Does IP65 mean the box can be hosed down?
A: No. IP65 is a 6.3 mm nozzle jet test. Hose-down and steam cleaning sit at IP66 and IP69K. Also check that the glands and any breather fitted are rated at least as high as the enclosure.
Q: Is an IP rating the same as a NEMA type?
A: No, they are different standards with different tests, and the commonly published equivalence tables are approximate. If a project specifies NEMA 4X, treat it as its own requirement — including the corrosion-resistance part, which IP does not test at all.
Q: Can a breaker be installed in a sealed IP66 box without derating?
A: Only if the internal temperature stays at the calibration reference. In practice a sealed box in sun runs hotter than the outside air, so the catalogue ambient derating applies. We quote the derated rating and the assumption behind it.
Q: Does the IK rating come with the IP rating?
A: They are separate tests under separate standards (IEC 60529 for IP, IEC 62262 for IK) and must be specified separately. A high IP rating says nothing about resistance to a knock from a trolley.
What to send us for a quotation
Enclosure type (flush or surface, ways or module width), the devices going inside, the installation location and environment, the IP and IK you need, material preference, and the destination country. You get unit price, packing data (pcs per carton, gross weight, CBM) and the certificate document for the exact ordering code. Request a quotation.
Related: Distribution boards and enclosures · Miniature circuit breakers · How to size a distribution board · SPD, ATS and isolators · How to verify genuine product · Cross-reference · FAQ