"Waterproof" is a marketing word. Engineers don't get to use it on a control plan. The control plan needs an IP rating — and IP67 is the rating that gets specified for chassis‑mount PDBs on heavy trucks that meet salt, road spray, monsoon water and standing water at the wheel arch. Depot wash‑down is a related duty but a separate test, and this page keeps the two apart rather than folding one into the other.
If you're writing a spec for a waterproof central distribution box on a heavy‑truck program, here's the version of the conversation that goes inside an OEM engineering team.
The immersion rating this chassis box is built to
On this page, IP67 means a dust-tight enclosure that has passed a static immersion test — not a jet test. The two digits, the IEC 60529 method, and why a jet pass does not imply an immersion pass are on the IP ratings guide. What follows is the chassis-PDB consequence: wheel-arch standing water is an immersion duty, and a gasket alone does not produce that rating.
Why heavy‑truck chassis programs specify IP67
Three reasons in particular:
- Wheel-spray and road-water during heavy rain. A box mounted near the wheel arch sees not just spray but standing water during deep puddle crossing.
- Wash‑down at depots and ports. Depot cleaning drives water into cavities that then hold standing water against the connector seal long after the lance has moved on. Note the distinction, though: a room-temperature jet is an IP66 question, and a hot high-pressure lance is a different test again — IPX9K in ISO 20653, commonly written “IP69K”. Neither is an IP67 question. If a box is routinely hit directly by a pressure washer, that duty and its test method belong in the specification alongside the IP67 line, not inside it.
- Salt-spray on coastal routes and winter roads. Salt-laden water is not just a sealing problem; it accelerates corrosion at the connector pin and gasket interface, so the seal needs to keep its integrity over many years.
How the NBX‑971 is designed to IP67
The NBX‑971 Waterproof Central Distribution Box is the IP67 reference design in the NBX family. The IP67 rating is a coordinated outcome of several design choices, not a single feature:
- Continuous gasket seal at the split-line. The enclosure halves are designed with a continuous gasket groove and controlled compression. The gasket compound is selected to retain elasticity across the full −40 to +85 °C working range, not just at room temperature.
- Sealed automotive connectors. The harness exit uses sealed automotive connectors with matching wire-side seals. The standard NBX‑971 build is three Deutsch harness-side housings — two DT06-12S and one HDP26-24-18PS; Bussmann, Tyco/AMP Superseal or Delphi GT are specified where a programme already stocks them. An IP67 enclosure with a non-sealed connector is not IP67. There is no shortcut here.
- Pressure-equalising vent membrane. A perfectly sealed enclosure has a pressure-differential problem under thermal cycling: warm air expands, cold air contracts, and the gasket sees stress every cycle. A semi-permeable ePTFE pressure-equalising vent membrane equalises internal pressure without admitting water.
- Validated, not assumed. IP67 status comes from testing to IEC 60529 with traceable equipment, a documented sample configuration and agreed pass criteria. Our in-house environmental lab handles dust-ingress screening and environmental preconditioning; the programme validation plan assigns the immersion test itself to the appropriate qualified facility. Where independent evidence is required, testing is completed by a qualified third-party laboratory. Results can be included in the PPAP package when a programme calls for one.
What IP67 does not give you
It helps to see the boundary explicitly. IP67 is a precise statement about two things — and silent about four others that teams sometimes assume it covers:
| Protection aspect | Covered by IP67 | What it means / validate separately |
|---|---|---|
| Dust ingress (solids) | First digit "6" — dust-tight, nothing solid gets in. | |
| Water immersion | Second digit "7" — 30 min with the lowest point 1 m below the surface, per IEC 60529. | |
| High-pressure / high-temperature washing | Its own test — IPX9K in ISO 20653, IPX9 in IEC 60529, sold as “IP69K” — at roughly 80 °C and 80–100 bar. | |
| Corrosion / salt | Not an IP property — needs separate salt-spray validation. | |
| Vibration / mechanical | Ingress only — validated separately (see NBX‑961). | |
| UV / sustained sunlight | Needs UV-stabilised material — e.g. Middle East rooftop installs. |
The table is the PDB-side cut. Why those four sit outside the number, and what evidence to ask for instead, is on the IP ratings guide. An excavator boom still needs its own vibration line — see the NBX‑961 excavator integrated box.
When you should specify something other than IP67
IP67 is right when the enclosure can see immersion. If it never can — for example, a body-cavity install on a heavy truck — then IP67 is over-spec, IP54 or IP65 is enough, and you save cost on connectors and seals. See the NBX‑957 for body-cavity body-central PDB use cases, or the NBX‑953 (47-way) for high-circuit-count body harnesses.
For chassis-rail placement that sees water jets but not immersion, IP65 is often the right specification — see the NBX‑969 chassis distribution box at IP65. The job is to match the rating to the actual environment, not over-spec. If you are working through that trade-off across a whole vehicle rather than one box, which IP level does each mounting position actually need? sets out the five zones and the evidence to request behind any rating.
Matching the rating to where the box actually lives, at a glance:
| Installation scenario | Minimum IP | Reference product |
|---|---|---|
| In-cabin / body cavity, no water exposure | IP54 | NBX‑957 body-central PDB |
| High-circuit-count body harness, sheltered | IP54 | NBX‑953 (47-way) |
| Chassis rail — water jets, not immersion | IP65 | NBX‑969 chassis box |
| Chassis-mount / near-wheel — can see immersion | IP67 | NBX‑971 waterproof PDB |
What to send to a supplier when you need IP67
- The installation location on the vehicle (chassis, body cavity, under-floor, near-wheel).
- The working temperature range (−40 to +85 °C or specific target).
- The connector standard required by the harness drawing.
- The circuit count and current rating (or alternatively the harness drawing itself).
- Any region-specific approval requirements (e-Mark / ECE, SASO, FCC) — these are available upon project requirement, not blanket-claimed.
- Mass-production volume, sample timing, target launch.
Buyer-side digits and mounting zones: IP ratings for commercial-vehicle electronics. Supplier-side design and validation: IP65 / IP67 protection.
To request drawings or a sealing strategy quote against your harness, please use the contact page or WhatsApp — typical reply within one business day.