PLC control cabinets
- PLC: Siemens S7-1200 / S7-1500, Schneider M241 / M580, Mitsubishi FX / Q series, selected to match process and budget
- I/O: DI / DO / AI / AO modules configured by point count with about 15% spare points, terminal blocks numbered to match the point list one for one
- Power: 24V switching power supply sized at 1.5× the load, with separate supply circuits for PLC, sensors and loads
- Wiring: DI / DO color-coded, analog on shielded twisted pair grounded at one end, power and signal cables in separate ducts
- Testing: 100% point-to-point check on every cabinet, verified against the point list and actual hardware, then powered commissioning before shipment
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.
| Type | Floor-standing control cabinet / wall-mounted control box, single or double door |
|---|---|
| Standard sizes (W×D×H) | Floor-standing 800×600×1800 / 2000 mm; wall-mounted 600×500×250 / 800×600×300 mm, custom sizes available |
| Enclosure construction | 1.5–2.0 mm cold-rolled carbon steel, bent and welded with reinforcing ribs, electrostatic powder coated |
| Surface treatment | Degrease → derust → phosphating → electrostatic powder coating 60-80 μm, baked at 200 °C for 30 minutes |
| IP rating | IP54 standard / IP65 optional (GB 4208 / IEC 60529) |
| Mounting plate | Galvanized mounting plate, height adjustable; PLC, relays and terminals laid out in separate rows |
| Cable entry | Bottom cable entry with gland plate, or bottom wireway / cable tray entry |
| Door and lock | Single door with 180° hinges and multi-point lock; optional clear viewing window for PLC indicator lights |
| PLC CPU | Siemens S7-1200 / S7-1500, Schneider M241 / M580, Mitsubishi FX / Q (brand and model can be specified) |
|---|---|
| I/O modules | DI / DO 16 or 32 points, AI / AO configured by channel count, with about 15% spare channels reserved |
| Analog input types | 4–20 mA / 0–10 V / PT100 / thermocouple, with optional signal isolators |
| Communication | Ethernet / Profinet / Modbus RTU / Modbus TCP / CANopen |
| HMI | Optional 7 / 10 / 15 in. touchscreen, flush-mounted in the door |
| Control power supply | DC 24V switching power supply (Mean Well / CHINT / Schneider), sized at 1.5 times the load |
| interposing relays | Schneider / Omron / CHINT, for isolated DO output drive |
| Terminals and wire marking | Weidmüller / Phoenix-style terminals, with wire markers showing the point number at both ends |
| Standalone local control | One PLC + I/O set per machine, in a local control box, with pushbuttons and indicator lights on the door |
|---|---|
| Centralized process line control | I/O from multiple stations centralized in the main cabinet, or distributed as a main cabinet plus remote I/O sub-cabinets |
| Closed-loop analog control | Temperature / pressure / flow / level 4–20 mA input + PID control output |
| VFD and servo integration | PLC controls the VFD / servo via communication or analog setpoint; VFDs mounted in a separate compartment for heat dissipation |
| Supervisory monitoring | PLC connects to the host computer / SCADA over Ethernet; space reserved in the cabinet for a switch and gateway |
| Safety circuit | E-stop, safety door and ESD hardwired shutdown chain, routed independently of the PLC program |
| Reference standards | GB/T 7251.1 / IEC 61439-1 (assemblies); GB/T 5226.1 (electrical safety of machinery) |
|---|---|
| Clearance & creepage | Meets pollution degree 3 and overvoltage category III requirements |
| Control circuit voltage | AC 220V or DC 24V |
| Insulation resistance | ≥1 MΩ (500V megohmmeter) |
| Power frequency withstand voltage | Control circuit 1500V / 1 min, main circuit 2500V / 1 min |
| Routine tests (every unit) | Loop resistance, insulation resistance, dielectric withstand, grounding continuity, point-to-point I/O verification, powered functional test |
| Documents with shipment | Electrical schematic, terminal wiring table, I/O list, BOM with brand and model, test report, factory photos |
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.
Point-by-point I/O channel verification
Before shipment, every DI / DO / AI / AO channel is tested point by point against the I/O list, so drawings, terminals and program all line up. Skip this step and your engineers will be tracing wires one by one on site.
Wire markers on both ends
Both ends of every wire get a ferrule, numbered to match the drawing point number. During troubleshooting you find the wire by reading the drawing — no need to buzz out every core with a meter.
Four wire classes, routed separately
Input, output, power and analog wiring are color-coded, with power and signal cables run in separate ducts. Circuit type is obvious at a glance inside the cabinet, and rewiring is far less likely to land on the wrong terminal.
Single-ended grounding for analog shields
The shield on shielded twisted pair is grounded at one end only, inside the cabinet, so no circulating current develops between two ground points — that current shows up as jitter on the 4–20 mA signal.
Headroom on the 24V supply
Switching power supplies are sized at 1.5x the actual load, with separate feeds for PLC, sensors and relays. Adding a solenoid valve on site won't drag the supply down into a brownout and restart.
Spare I/O reserved
Roughly 15% spare channels are reserved against the process point count, with terminal blocks already wired. Adding a signal later doesn't mean replacing the cabinet — land the wire and it works.
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.
Water treatment and pumping stations
Level, pressure and flow acquisition with multi-pump duty rotation, integrated with online water quality instruments.
Production Lines & Packaging Machinery
Multi-station sequence control, cycle time control and interlocking between stations.
HVAC & Refrigeration
Temperature and humidity acquisition, damper and valve modulation, unit rotation and fresh air control.
Dust Collection & Environmental Equipment
Pulse-jet cleaning sequence, differential pressure monitoring and fan interlocking.
Mining & Heavy Equipment
Start/stop interlocking and overload protection for crushers, conveyors and hoists.
Central Monitoring Retrofit for Legacy Equipment
Add PLC-based status acquisition and connect to the supervisory system over Ethernet.
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
Can you use the PLC brand and model we specify?
Yes. Siemens, Schneider, Mitsubishi, Omron and Inovance are all available, with brand and model written into the contract. You can also buy the hardware yourselves and ship it to our plant — we inspect it on receipt (appearance, model, serial number, power-up) and only install it after it checks out.
Who writes the program? Do you do that?
Two options. If you have an electrical engineer writing the program, we build the enclosure, wiring, terminals and point list, then run point-to-point checks against your list before shipment. If you don't, we also handle the process logic and factory commissioning. The two scopes are priced differently — just say which one you need in your inquiry.
How do I count I/O points? How many should I specify?
Work from the equipment list and the action sequence: every pushbutton, limit switch and sensor counts as one input; every contactor, solenoid valve and indicator light counts as one output; continuous values such as temperature, pressure, flow and level count as analog. If the count is uncertain, send us the process flow and equipment list and we will build the point list for you.
My analog signals keep jumping. What should I do?
Three things inside the cabinet: single-ended shield grounding, separate ducts for analog and power wiring, and an isolator on the analog input front end (or isolated input modules). On site, use shielded cable for the VFD output and ground it properly — that usually settles it.
Can the cabinet be expanded later if we add points?
Yes. We typically reserve about 15% spare I/O channels and leave mounting space on the DIN rail and terminal blocks. If a major change is expected later, we recommend sizing the enclosure one step up and the power supply for higher capacity — doing it once is cheaper than rebuilding the cabinet.
What do I need to provide for a quote?
An equipment list and a description of the process sequence. An electrical schematic or I/O point list is ideal; if you have no drawings, the process flow is enough. Please also confirm: enclosure dimensions and mounting method, ingress protection (IP) rating, PLC brand, whether an HMI is needed, and the cable entry/exit arrangement.
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.
Have a process to control? Let's start with the I/O list.
Send us your equipment list or process flow and we will provide a free I/O list and cabinet design · quote within 24 hours · build-to-drawing customization supported. Direct from the factory, MOQ 1 unit, 15–25 day lead time, 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.