Tunnel distribution boxes
- Environment: IP65 + anti-condensation heater (thermostat-controlled) — no condensation despite large day-night temperature swings
- Enclosure: 304 stainless steel or hot-dip galvanized steel with powder coating, resistant to exhaust gas and moisture corrosion
- Circuits: lighting / jet fan / monitoring / maintenance reserved per tunnel system, clearly labeled
- Entry and exit: bottom or side exit toward the cable trench, sealed with cable glands
- Markings: reflective markings + impact-resistant base (required for in-tunnel and portal placement)
Specifications
The table below covers 80% of factory distribution room cases. Anything outside it we can still build — those are engineered items, quoted separately, with an indicative price the same day.
| Enclosure type | Outdoor wall-mount / floor-standing (concrete foundation + impact-resistant base) |
|---|---|
| Standard dimensions (W×H×D) | 600×800×300 to 1000×1400×400 mm, custom builds available |
| Enclosure material | 304 stainless steel / hot-dip galvanized sheet steel with powder coating (per corrosion class) |
| IP rating | IP65 (jet water and dust protection), double-gasket door seal |
| Anti-condensation | Anti-condensation heater + humidity/temperature controller — no condensation inside the cabinet |
| Impact protection and markings | In-tunnel placements get an impact-resistant base; reflective markings and number plates |
| Rated voltage | AC 380V / 400V, 50 Hz |
|---|---|
| main breaker | Molded case circuit breaker + surge protective device (SPD, mandatory in high-lightning areas) |
| Circuit configuration | Tunnel lighting / jet fan / monitoring and communications / maintenance socket circuits |
| Lighting control | Time / photocell / remote (tunnel management platform) — optional |
| Metering & monitoring | Current and voltage monitoring; meters supplied to the operator's specification |
| Cable entry | Cable entry from the bottom or side of the cable trench, sealed with cable glands |
| Component brands | Schneider / ABB / Chint, self-procured and shipped to factory accepted |
| In-tunnel lighting sub-distribution box | Sectioned lighting circuits with photocell and time control; enhanced lighting at the portal |
|---|---|
| Fan distribution box | Jet fan circuits (soft start / direct-on-line depending on fan); reversing optional |
| Monitoring & communication box | Power supply for monitoring, communication and detection equipment; UPS provision reserved |
| Roadside equipment box | Power take-off along the route for guardrail lighting / variable message signs / weather stations |
| Utility tunnel type | Utility tunnel fire, drainage and lighting sub-circuits (supply scope to be confirmed per project) |
| Assembly standard | GB/T 7251.1 / IEC 61439-1 |
|---|---|
| Ingress protection verification | IP65 spray test on a sampling basis + door seal check on every unit |
| Routine tests (every unit) | Insulation resistance, dielectric withstand, circuit-by-circuit energization and heater commissioning |
| Anti-corrosion inspection | Weld and opening sealing inspection on stainless steel / galvanized enclosures |
| Documents with shipment | System diagram, terminal schedule, BOM, test report |
Five steps to specify your run
A configuration summary is generated as you go. It travels with your inquiry, saving a round of confirmation.
Build details
Systems have been in service for decades, and the failure points are always the same few: poor busbar contact, water ingress at the door seal, high temperature rise in the correction cabinet, and mis-phased outgoing feeders. The six hard rules below are written for exactly these points — every cabinet can be traced to them.
Thermostat-controlled heater on/off
Tunnel temperature swings between day and night are wide, and condensation inside the box damages components more than rain does: thermostat-controlled heater cycling plus a breather valve to equalize pressure means no water droplets when the door is opened in the morning.
Welds and openings all sealed
Welds on stainless steel enclosures are ground and sealed, and cable entries use glands instead of punched-out holes — corrosion starts at welds and openings, and nothing is skimped here.
Box number matches chainage
Enclosure numbers correspond to tunnel chainage, and nameplates match the as-built drawings, so O&M crews can find the right box by chainage without guessing.
Two-stage protection in high-lightning areas
Mountain tunnels see frequent lightning, so surge protection is configured in two stages (incoming line + lighting circuits), with optional event logging to back up inspections after a strike.
IP65 is proven by testing
Spray testing is sampled from every batch plus a door-seal visual check on every unit; any batch that fails is reworked in full — outdoor enclosure protection is backed by test data.
System diagram inside the door
A laminated system diagram and circuit schedule are mounted inside the door, so inspectors see the drawings the moment they open the box instead of going back to the office for documentation.
Photos & enclosure construction
Below are photos taken in our own shop — from the complete unit down to the internal busbars and secondary wiring. Every build detail can be checked item by item.
Image key: 01–05 are shop photos (the numbers match the shot list). The line drawing shows the front elevation of the enclosure; dimensions match the specification table above.
Where these cabinets go
These are the routine applications — we can talk scheme and configuration directly. For the industry view, see the industry pages.
Highway and railway tunnels
Sectional power supply for in-tunnel lighting, fans and monitoring.
Highway corridors
Power takeoff for guardrail lights, variable message signs and weather stations.
Bridges and ramps
Landscape lighting and maintenance circuits.
Utility tunnels
In-tunnel lighting / drainage / maintenance circuits (confirmed per project requirements).
Toll plazas and service areas
Plaza lighting and equipment boxes.
Mine roads and adit entrances
Outdoor power distribution in dusty and damp environments.
Commercial terms
Specification dated September 2026; quotations follow this.
| Drawings & design | Free |
| MOQ | 1 unit (5 or more recommended for production) |
| Production lead time | 15-25 days after drawing approval |
| on-time delivery | 98% |
| Warranty | 12 months |
| Loading port | Ningbo / Shanghai, China |
| Component brands | Schneider / ABB / Siemens / Chint |
| Factory visit & dispatch confirmation | Factory visits welcome; finished-cabinet photos and video before dispatch |
| Capacity | 5,800+ units / year |
Documents for your engineering team
Selection manual, outline dimensions and RFQ checklist — for the customer's electrical engineer. All three documents are being organized by product line; download links go live once complete.
Six questions procurement and electrical engineers ask most
How is a tunnel box different from an ordinary outdoor box?
Three things: environment (moisture + exhaust gas corrosion + day-night temperature swings → IP65 + stainless steel / galvanized + anti-condensation heater), placement (impact protection inside the tunnel, reflective markings, numbering by chainage), and system (lighting / fan / monitoring circuits reserved per the tunnel system, not the generic circuits of an ordinary distribution box).
Does the anti-condensation heater draw much power?
Very little: thermostat-controlled on/off (typically only turns on below a threshold inside the box), a few dozen watts per unit, a few dozen yuan a year in electricity; the component life and reliability gained far outweigh that cost. Strongly recommended for boxes at tunnel portals with wide day-night temperature swings.
Can it be configured for remote monitoring?
Yes: current and voltage monitoring, breaker status, door access and water ingress signals are reported to the tunnel management platform through a gateway (Modbus / Ethernet depending on the platform); fiber relay is used in tunnel sections without signal coverage, and the scheme is issued according to the platform protocol.
What is special about the fan circuits?
Jet fans draw high power and cause a large starting surge: direct-on-line or star-delta starting for low power, soft starter or VFD for high power; forward/reverse (bidirectional jet) circuits are configured per fan requirements. Fan circuits and lighting circuits are placed in separate boxes or separate compartments so maintenance on one does not affect the other.
How do you protect against lightning in mountainous areas?
Two-stage surge protection (Type 1 at the incoming line + Type 2 at branch circuits) plus solid grounding (grounding resistance per code, with a dedicated ground electrode for the portal box); SPDs are replaceable-module type with a status window so degradation is visible at a glance during inspection.
How do you ensure consistency across a batch of dozens of units?
Units are numbered sequentially by chainage, checked one by one against the drawings, and each box ships with its factory test report; batch deliveries include a master schedule (chainage - box number - circuit configuration) so units can be installed on arrival without sorting.
Other cabinet types in the same main circuit
Related products use color-block placeholders for now (product photos not yet complete; they will be replaced together). Internal links will be filled in once live URLs are confirmed.
Send the tunnel system diagram or branch circuit requirements and we will reserve accordingly
Send the tunnel system diagram or branch circuit requirements (lighting / fans / monitoring) and we will provide an enclosure design free of charge · quote within 24 hours. Direct from the source factory, MOQ 1 unit, 15–25 day delivery, 1-year warranty.
ISO 9001:2015 · CE(LVD+EMC) · CQC · IP65
When you write, include: single-line diagram or primary scheme, switch room layout, load list, and component brand requirements. You do not need complete drawings — capacity and cabinet type are enough to start.