Engineering

Control Cabinet Layout

A control cabinet layout is the physical order that makes power, isolation, protection, control power, logic, switching and field wiring readable and serviceable. In industrial engineering, the same internal arrangement is also commonly described as a control panel layout. A strong layout reduces unnecessary wire length, controls heat and EMC routing, keeps labels and terminals accessible, and lets technicians follow faults in the same order as the circuit.
DIN rail zoneswire routingterminal accessthermal spaceservice order
Layout is an engineering orderPlace devices so the cabinet can be read from supply entry to field terminals. When the physical order matches the drawing order, inspection is faster and accidental misreading is less likely.
Functional control cabinet layout with power, protection, control and terminal zones
A readable layout separates functions while keeping the circuit path visible.

The Answer in One Minute

A good control cabinet layout follows energy, heat and service flow — not visual symmetry. Keep supply entry and isolation easy to identify; group protection by feeder; give power-conversion and switching devices their required clearances; keep PLC, I/O, analogue and communication equipment away from unnecessary heat and high-energy wiring; and treat field terminals as a deliberate interface near cable entry.

No universal DIN-rail pattern is correct for every cabinet. Manufacturer spacing, thermal data, EMC requirements, conductor routing, protective bonding, cable bend radius, service access and the adopted project standard all have to survive the final arrangement after trunking and field wiring are installed.

Read energy firstSupply → isolation → protection → conversion/switching → control → field interface.
Design for the finished cabinetCheck clearances with wires, duct covers, labels and site cables in place.
Separate unlike problemsHeat, high-energy switching, sensitive signals and field termination need different layout priorities.
Make service work obviousA technician should be able to identify the next safe test point without tracing unrelated wiring.

Start with functions before physical placement

Use this sequence as a design-reading order, not as a mandatory left-to-right backplate geometry.

From incoming energy to the field interface

The physical cabinet can be vertical, horizontal or split across mounting plates. A control panel layout should therefore preserve functional boundaries, service access and equipment requirements rather than follow a fixed visual pattern. What matters is that each functional boundary remains visible and serviceable.

  1. SourceSupply entry & PE bond

    Incoming conductors, protective earth and any upstream-live area are identifiable before downstream wiring obscures them.

  2. BoundaryMain isolation

    The service isolation point and door-handle/mechanical relationship remain obvious and accessible; also verify what can remain live after the main disconnect is OFF.

  3. ProtectionBranch protection

    Fuses or breakers are grouped so each feeder and downstream load can be followed without crossing unrelated circuits.

  4. Energy conversionPower conversion & switching

    PSUs, transformers, drives and contactors get thermal clearance, cable space and replacement access.

  5. Sensitive controlPLC, I/O & interfaces

    Logic and signal devices sit away from avoidable heat and high-energy routes, with ports and labels visible.

  6. InterfaceField terminals & cable exit

    External conductors terminate in an order that matches drawings, cable numbers or machine areas.

Design rule: the isolation boundary, protective bonding path and field interface should remain understandable after every trunking cover and field cable is fitted. A neat empty backplate is not the final condition.

Example A vs Example B: same parts, very different serviceability

The comparison is intentionally schematic. It shows design logic rather than a mandatory physical orientation.
Example A · weak layout

Placement follows spare space

  1. 1Incoming power is visually buried. The route to the main disconnect passes behind unrelated control wiring.
  2. 2Hot and sensitive devices are mixed. A drive or power supply crowds PLC/I/O and leaves little room for manufacturer clearance.
  3. 3Ducts become shared traffic lanes. Power, control and field conductors run together because the shortest free route wins.
  4. 4Terminal access is an afterthought. Site cables cover markers, shields and test points.

Result: the cabinet may look compact, but fault tracing, thermal verification, EMC control and later modifications all become harder.

Example B · serviceable layout

Placement follows function and maintenance

  1. 1Supply and isolation are immediately readable. The upstream-live area and service boundary are not hidden by downstream wiring.
  2. 2Protection and power devices form a coherent energy path. Heat-producing equipment keeps the clearances required by its manufacturer.
  3. 3Logic and sensitive signals have cleaner routes. Unavoidable crossings are short and shield/bonding strategy remains inspectable.
  4. 4Field terminals remain a usable interface. Cable entry, bend radius, markers, PE and shield termination can all be reached.

Result: the physical layout supports the schematic, the service sequence and the thermal/EMC constraints at the same time.

Real-cabinet inspection: five checks in one view

Use the numbered photograph and the matching checklist together. The points are inspection prompts, not pass/fail declarations from the photograph alone.
Control cabinet used to inspect supply, protection, PLC and I/O, wiring routes and field terminals
The same numbered points appear immediately beside the photograph on desktop and directly below it on mobile.
  1. Supply & isolation

    Check the incoming path, PE bonding and service boundary remain obvious after wiring.

  2. Branch protection

    Labels and feeder-to-load relationships should remain visible and accessible.

  3. PLC & I/O

    Keep labels, ports and indicators visible and avoid unnecessary thermal crowding.

  4. Wiring routes

    Check bend space and EMC routing against the project and equipment guidance.

  5. Field terminals

    Verify numbering, PE/shield points and test access remain usable after field wiring.

Engineering limit: exact compliance still depends on the schematic, conductor data, component instructions, enclosure design and adopted standards.

Separate power, control and field wiring by purpose

Power, 24 V DC control, safety, analogue, communication and field wiring do different jobs, so the layout should keep those functions readable rather than forcing unrelated circuits into the same congested route.

Higher-energy devices need space for clearance, bend radius, heat and service access; PLC, signal and communication devices need clean routes and protection from unnecessary heat and noise. Where groups must cross, keep the crossing short and obvious. For the detailed routing logic, see control cabinet wire routing.

Routing matrix

What each wiring group needs from the layout

Separate power, control and field wiring by purpose table
Wiring groupLayout priorityCommon mistake
Incoming powerClear route from cable entry to isolation and protection.Hidden behind control wiring or trunking.
24 V DC controlReadable distribution from power supply to loads and I/O.Multiple unlabelled take-off points.
Analogue / communicationShort, identifiable routes with shield handling visible.Long parallel runs beside switching or drive wiring.
Safety circuitsTraceable path between devices, contacts and reset points.Mixed into general control wiring without clear identification.
Field wiringTerminals close to cable entry and ordered to match the drawing.External cables landed directly on internal devices.

Thermal and EMC zoning should be visible in the backplate

Separation is not a fixed distance copied from a generic diagram. It comes from the actual devices, wiring, enclosure and project requirements.

High-energy / heat-producing zone

Examples include drives, transformers, power supplies, braking equipment, contactors and heavily loaded protective devices.

  • Preserve manufacturer ventilation and spacing.
  • Plan conductor bend radius and replacement space.
  • Keep switching and motor/output routes identifiable.
  • Do not block enclosure airflow paths with full ducts.
Controlled separation

Sensitive control / signal zone

Examples include PLC/I/O, analogue interfaces, communication devices, signal isolators and low-level instrumentation.

  • Avoid unnecessary exposure to hot devices.
  • Keep shield, PE/FE and reference connections inspectable; for drive-specific screen termination, see VFD cable shield grounding.
  • Limit long parallel routing beside high-energy conductors where the project requires separation.
  • Keep diagnostic ports and status indicators accessible.
Do not turn EMC into a cosmetic ruleThere is no universal cabinet-wide spacing number that makes every mixed-voltage or signal problem disappear. Apply the cable, drive, PLC, enclosure and project documentation to the actual geometry. The layout should make compliance with those instructions possible rather than contradicting them.

The mounting plate can be part of the EMC path

In EMC-sensitive cabinets, mechanical mounting and high-frequency bonding are often the same physical problem.

Bare-metal or galvanised contact surfaces

A conductive mounting surface can help create a low-impedance, large-area bond between drives, filters, shield clamps and the cabinet structure when the equipment manufacturer expects that installation method.

  • Keep designated contact areas conductive and clean.
  • Use the mounting method specified for the device.
  • Preserve protective-earth requirements separately from EMC bonding needs.

Painted or insulated surfaces

Paint, powder coating and anodised layers can interrupt a high-frequency contact path. Where a conductive bond is required, use approved contact hardware, prepared bonding points or other manufacturer-defined measures rather than assuming a bolted joint is electrically equivalent.

  • Check whether toothed washers or prepared contact points are specified.
  • Do not remove coatings indiscriminately.
  • Restore corrosion protection where the design requires it.

PE conductor ≠ complete EMC strategy

A protective conductor remains essential for safety, but a round PE wire alone may not provide the same high-frequency behaviour as a short, wide or large-area bonding connection. Treat protective bonding and EMC bonding as related functions with different performance concerns.

  • Keep shield termination short and inspectable.
  • Avoid long pigtails where 360° termination is specified.
  • Follow the exact drive, filter and enclosure instructions.
Engineering limit: a galvanised or bare-metal mounting plate is not automatically “better” in every cabinet. The correct surface preparation, bonding hardware and corrosion treatment depend on the enclosure system, environment and equipment instructions.

Practical design ranges: useful starting points, not universal limits

Numbers can help during the first layout pass, but they must never override the exact device, cable, enclosure or project requirements.
Practical control cabinet layout starting points and their limitations
Layout questionUseful starting pointHow to use it correctly
Future expansionIf future expansion is a project requirement, a documented target such as roughly 20–25% usable DIN-rail, terminal or duct capacity may be chosen.Treat this as a design allowance, not an IEC/NFPA requirement. Reserve space where it can actually be wired, labelled and serviced.
Power-to-sensitive-signal separationPublished equipment-manufacturer examples can fall in roughly the 150–300 mm range.Use the selected drive, PLC, cable and EMC documentation as the governing value. Different equipment can require different distances.
Unavoidable cable crossingA short crossing at about 90° is a common EMC layout practice.It reduces parallel coupling; it does not replace required segregation, shielding, bonding or manufacturer instructions.
Wire-duct loadingPlan from the real conductor bundle, bend radius, heat/ampacity conditions and duct geometry — not a universal 40–50% number.Leave enough usable space for covers, ferrules, additions and inspection, then verify the project and product rules that apply.
Why the ranges are labelled this way: they are early-layout aids, not compliance claims. Final spacing, capacity and thermal decisions belong to the exact manufacturer instructions, adopted standards and verified cabinet design.

Terminal blocks should be designed as the field interface

Terminal blocks are not only a place to join wires. They are the boundary between the built cabinet and the machine, skid, conveyor, pump set or external installation. In a serviceable control panel layout, terminal blocks remain a deliberate field interface rather than unused space at the edge of the mounting plate. A strong layout treats terminal blocks as a readable interface, not as spare space at the bottom of the panel.

The terminal strip should tell a logical story. It may follow cable numbers, machine zones, motor groups, instrument loops, I/O card order or a site standard. What matters is that the terminal order is easy to compare with the drawing and cable schedule.

Leave enough room for site cable bend radius, shield termination, earth conductors, wire markers, test access and component replacement. A crowded terminal strip can look acceptable before site wiring arrives, then become the hardest part of the cabinet to inspect.

Terminal layout

Checks before the layout is frozen

Terminal blocks should be designed as the field interface table
QuestionWhy it matters
Can the terminal number be read after field wires are installed?Labels that disappear under cable bundles slow down commissioning and maintenance.
Does terminal order match the drawing or cable schedule?A logical order reduces wrong landings and makes fault tracing easier.
Are PE, shield and screen termination points visible?Hidden bonding or screen points create inspection problems and can mask installation errors.
Is there space for trunking covers and ferrules?A layout that only works with covers removed is not a serviceable layout.
Are spare terminals grouped and labelled?Unmarked spare points are often misread during panel changes.

Heat must be allowed for in the layout

Control cabinets are often judged by wiring neatness, but heat is just as important. Power supplies, contactors, drives, braking resistors, dense electronic modules and closely packed protection devices can raise local temperature. Heat does not spread evenly across a backplate, so component grouping matters.

Heat-producing devices need space around them according to their manufacturer data and the enclosure design. Crowding a power supply beside another hot device may not fail immediately, but it can shorten service life and create intermittent faults that appear only during warm operation. Where a DIN-rail supply is mounted in a non-standard orientation, check the specific power-supply mounting and derating guidance rather than assuming the nameplate output remains available.

Thermal layout also affects the location of sensitive electronics. PLC modules, communication equipment and analogue signal devices should not be placed where they receive unnecessary heat from drives, transformers or dense power devices. The layout should leave a visible path for air movement, inspection and cleaning. Enclosure size, mounting surface, dissipation and cooling strategy should be checked together; the related control cabinet enclosure selection reference covers that enclosure-level decision.

Control cabinet showing a readable path from supply entry to field terminals
Heat, wiring and diagnostic order should be considered before the first device is fixed to the backplate.
Thermal ruleA compact layout is useful only when it still gives hot components enough clearance, keeps labels reachable and leaves airflow paths open after wiring duct covers are fitted.

Two useful first-order thermal relationships

These equations are useful for an early engineering sense-check. They are not a substitute for device loss data, enclosure calculations or IEC TR 60890 verification.

Conductor and contact loss

Power loss equals current squared multiplied by resistance.

Resistive loss increases with the square of current, which is why heavily loaded conductors, terminals and connections deserve thermal attention even when their resistance is small.

I — current through the resistive pathR — effective resistance of that pathPloss — heat produced in watts

First-pass enclosure heat flow

Heat flow approximately equals heat transfer coefficient multiplied by surface area multiplied by temperature difference.

A simple wall-loss relationship helps explain why enclosure area, material, ambient temperature and allowed internal temperature rise affect passive heat rejection.

k — effective heat-transfer coefficientA — effective enclosure surface areaΔT — inside-to-ambient temperature difference

Total cabinet heat load

Total internal loss approximately equals the sum of component losses.

For a practical first pass, start from manufacturer loss data for drives, power supplies, transformers, contactors and other devices, then consider conductor losses and the enclosure's ability to reject that heat.

Use real loss data where available.Check mounting orientation and derating.Verify the final enclosure, not just the empty backplate.
Do not treat these as the IEC TR 60890 method. The standard method is more detailed and application-specific. These relationships are only early-stage engineering checks that help expose obviously unrealistic layouts before formal thermal verification.

Three failure paths created by a poor layout

These are not separate “tidiness” issues. Each one changes how the cabinet behaves or how safely it can be diagnosed.
1 · Thermal bottleneck
  1. Heat sources are crowded because DIN-rail space is treated as the only constraint.
  2. Air paths and specified clearances shrink after ducts and wiring are installed.
  3. Local temperature rises and component derating or service life becomes harder to verify.
Review: power loss, enclosure cooling surface, ventilation and manufacturer spacing before drilling the backplate.
2 · Diagnostic bottleneck
  1. Functional zones are mixed and the physical order no longer matches the schematic.
  2. Labels and test points become hidden by cross-routed conductors and full trunking.
  3. Fault tracing takes more interventions because the next measurement point is not obvious.
Review: walk through the expected fault sequence with covers, field wiring and replacement access in mind.
3 · EMC / service bottleneck
  1. High-energy and sensitive routes share space because physical separation was not planned early.
  2. Shield, bonding or cable-routing instructions become difficult to implement after the cabinet is wired.
  3. Intermittent signal problems are harder to isolate and modifications disturb more wiring than necessary.
Review: reserve the routing and termination geometry before component density removes the option.

Component placement matrix

This matrix gives a practical layout logic for common cabinet components. Always apply the project standard, manufacturer instructions and local electrical rules.
Component placement matrix table
Component groupGood placement logicInspection risk if placed poorly
Main switch or isolatorNear supply entry, mechanically aligned with door operation where required, and clearly separated from downstream circuits.The service boundary becomes hard to identify and upstream live parts may be misread.
Fuses and circuit breakersGrouped by feeder or function, with labels visible and downstream wiring easy to follow.Technicians may remove or test the wrong branch during fault-finding.
24 V DC power supplyClose to control distribution, with heat clearance and a readable DC output path.Voltage drop, overheating and unclear DC branching become harder to diagnose.
PLC and I/O modulesPlaced where module labels, field wiring and communication ports remain accessible.Signal tracing becomes slow and online work may be blocked by cable congestion.
Relays and contactorsGrouped by machine function or load group, with coil and contact wiring easy to identify.Control and load wiring become mixed, which increases tracing errors.
Analogue and communication devicesAway from unnecessary heat and high-energy switching routes, with shield and screen handling visible.Noise, hidden shield problems and unclear signal references become more likely.
Terminal blocksNear field cable entry and ordered by cable, drawing, I/O group or machine area.Site wiring hides labels and makes documented additions difficult.

What to verify before the cabinet layout is frozen

A layout drawing is only convincing when the evidence behind the spacing, routing and service assumptions can be checked.
Control cabinet layout design evidence checklist
EvidenceWhat to confirmWhat it prevents
Manufacturer mounting & clearance dataOrientation, minimum spacing, ventilation zones, surrounding temperature and any derating conditions for the exact device.Treating free DIN-rail space as proof that a component can be mounted there.
Power-loss / thermal dataExpected losses, enclosure cooling method, internal temperature target and whether natural or forced ventilation assumptions are valid.A visually neat cabinet with unverified hot spots.
Cable and conductor requirementsBend radius, conductor size, terminal entry direction, duct capacity and separation/routing instructions for power and signals.Routes that only work before real cable sizes and ferrules are fitted.
PE, bonding and shield strategyProtective bonding path, shield/screen termination points and any functional-earthing requirements in the equipment documentation.Hidden or inaccessible bonding and ad-hoc EMC fixes during commissioning.
Field cable scheduleCable entry location, terminal order, spare terminals, shield/PE points and realistic service loops.Field cables covering labels or landing directly on internal devices without a readable interface.
Maintenance task reviewAccess to isolation, fuses/breakers, test points, removable modules, connectors, filters, fans and replaceable parts.A layout that is compliant on paper but requires disturbing unrelated wiring for routine work.

Digital design tools should verify the physical layout, not just draw it

Modern ECAD and enclosure tools can expose routing, clearance and thermal problems before the backplate is drilled.
3D ECAD

EPLAN Pro Panel

Useful for 3D mounting layouts, routing paths, virtual wiring and manufacturing data. Its value is strongest when the schematic, device geometry and physical wire routes are kept in the same engineering data model.

Selection / dimensioning

Siemens TIA Selection Tool / Electrical Designer

Useful for electrical main-circuit dimensioning, device selection, cable sizing and short-circuit verification within the Siemens engineering workflow. It supports pre-engineering, but final cabinet spacing, wiring, thermal and EMC decisions still come from the exact installed products and project requirements.

Enclosure / thermal

Rittal RiPanel and RiTherm

RiPanel supports enclosure configuration and manufacturing data; RiTherm supports enclosure thermal calculation and climate-control selection. These tools are useful checks before a compact layout becomes expensive to change.

Workflow rule: software can improve consistency and catch geometry problems, but it does not turn an unverified layout into a compliant one. The final design still has to match the adopted standards, equipment instructions and actual installation environment.

Standards Context

These documents define different layers of the problem. None of them supplies one universal backplate drawing that is correct for every control cabinet.
IEC 60204-1

Electrical equipment of machines

IEC 60204-1:2016+A1:2021 provides the machine-level framework for electrical equipment, including supply, protection, protective bonding, wiring, EMC considerations, documentation and verification. Layout decisions should make those requirements practical to implement and inspect.

IEC 61439-1 / -2

Low-voltage assemblies

IEC 61439-1:2020 and IEC 61439-2:2020 cover construction, characteristics and verification of applicable low-voltage switchgear and controlgear assemblies. The assembly context matters when assessing temperature rise, clearances, internal separation and incorporation of devices.

IEC TR 60890

Temperature-rise calculation

IEC TR 60890:2022 provides a method for calculating air temperature rise inside certain enclosed low-voltage assemblies. It is useful thermal evidence, not a generic instruction to place a particular device on a particular rail.

IEC TR 61000-5

EMC installation guidance

IEC TR 61000-5-1:2023 gives general EMC installation and mitigation guidance, while IEC TR 61000-5-2 addresses earthing and cabling. These support a layout that leaves routing, bonding and shielding strategies physically achievable.

NFPA 79 · 2024

North American machinery context

NFPA 79 addresses electrical equipment of industrial machinery, including disconnecting means, protection, wiring, marking, documentation and verification. It should be read using the edition adopted by the project or jurisdiction.

UL 508A

Industrial control panels

UL 508A is central to many North American industrial control panels. UL component guidance requires applicable components to be installed within ratings and according to manufacturer instructions, including mounting, wiring routing, ventilation and required spacing.

NEC Article 409

Panel installation context

NEC Article 409 addresses industrial control panels, including important marking and short-circuit-current-rating context. It does not replace the equipment standard or manufacturer instructions with a single universal cabinet-layout geometry.

Project rule

Adopted edition + exact device data

Use the standards adopted by the project and jurisdiction, then apply the exact component and enclosure instructions. A cabinet layout is defensible when the final wired assembly can still satisfy those requirements — not when it merely resembles a reference picture.

Technical basis

Reference documents used for the layout logic

  • IEC 60204-1:2016+A1:2021 — Safety of machinery — Electrical equipment of machines — General requirements.
  • IEC 61439-1:2020 + COR1:2021 + COR2:2023 — Low-voltage switchgear and controlgear assemblies — General rules.
  • IEC 61439-2:2020 — Power switchgear and controlgear assemblies.
  • IEC TR 60890:2022 — Method of temperature-rise verification by calculation.
  • IEC TR 61000-5-1:2023 and IEC TR 61000-5-2:1997 — EMC installation, mitigation, earthing and cabling guidance.
  • NFPA 79 (2024 edition) — Electrical Standard for Industrial Machinery.
  • UL 508A, Third Edition and current UL component guidance, including Supplement SA (October 2025).
  • NFPA 70 (NEC), Article 409 — Industrial Control Panels, using the edition adopted in the jurisdiction.

Inspection and pre-build review

Common faults

Layout defects seen during inspection

Layout defects seen during inspection table
DefectWhy it causes trouble
No visible functional zonesThe cabinet cannot be read quickly from supply to field wiring.
Overfilled wiring ductLabels, ferrules and conductors become hard to inspect without disturbing wiring.
Hot devices grouped togetherLocal heat rises and intermittent faults may appear under load.
Terminal strip too close to cable entryField wiring bend radius and marker visibility suffer after installation.
PLC hidden by trunking or relaysStatus LEDs, connectors and module labels become hard to read.
Uncontrolled spare spaceUndocumented changes are squeezed into the nearest gap instead of a readable zone.

Inspection sequence before a panel is built

A layout review should happen before drilling, cutting wire or fixing trunking permanently. At that stage, mistakes are still cheap to correct. Once the backplate is drilled and the wire duct is full, even small corrections can become slow.

A control panel layout should be reviewed against the schematic, thermal data, EMC requirements, cable schedule and expected maintenance tasks before the mounting plate is drilled. Check whether a person can follow the supply path without removing unrelated covers. Check whether a field cable can be terminated without covering labels. Check whether a hot component has clearances that still exist after wire duct and neighbouring devices are installed.

The best review is practical. Ask what the next person must see first during a fault: incoming voltage, isolator position, branch protection, 24 V DC output, PLC status, relay state, terminal number or field cable. The cabinet layout should make that first check obvious.

Power LibraryIsolation LibraryProtection LibraryEngineering Library

Layout checklist

The layout is ready to freeze only when the energy path, service access, thermal clearances, wiring separation, terminal interface and documented expansion space still work in the fully wired cabinet. Review the finished condition, not just the empty backplate.

Readable pathSupply entry, isolation, protection, conversion, control distribution and terminals can be followed in order.
Service accessLabels, test points, terminals, covers, locking points and replaceable devices remain reachable.
Thermal spaceHeat-producing devices have clearance and do not crowd sensitive electronics.
Wiring separationPower, control, signal, communication, safety and field wiring are routed by purpose.
Terminal logicTerminal order matches the drawing, cable schedule or machine area clearly enough for site work.
Expansion marginSpare DIN rail, duct capacity and labelled terminal space are kept as documented reserve, not as random empty space.

Common Questions

What is the best starting point for control cabinet layout?

Start with function, not component count. Define incoming supply, isolation, protection, power conversion, control power, switching, I/O and field terminals before placing devices on the backplate.

Should power wiring and control wiring share the same duct?

They should be routed according to the project standard and the requirements of the connected equipment. Avoid forcing high-energy and sensitive circuits into long shared routes merely because one duct is convenient; where groups must cross, keep the route clear and inspectable.

Where should terminal blocks be placed in a cabinet?

Field terminal blocks should be near the relevant cable entry and arranged in an order that matches the drawing, machine area or cable schedule. They must remain reachable after field cables, trunking covers, shields and protective conductors are installed.

Why does heat matter in cabinet layout?

Power supplies, drives, contactors, transformers and dense protection devices create local heat. Layout affects airflow, enclosure temperature, component derating and service life, so manufacturer clearances and a thermal verification method should be considered before the mounting plate is fixed.

How should a VFD be positioned relative to PLC and signal wiring?

Use the drive manufacturer's installation and EMC instructions. Give the drive its required thermal clearance, keep motor/output and other high-energy routes identifiable, and avoid unnecessary parallel routing beside sensitive analogue or communication wiring.

Is a neat cabinet always a good cabinet?

No. Neatness helps inspection, but a good layout must also support isolation, protection, thermal management, EMC routing, protective bonding, readable labels, measurement access, terminal service and component replacement.

How much spare space should a cabinet layout leave?

There is no universal percentage that is correct for every panel. Reserve usable DIN-rail, duct and terminal capacity according to the expected design changes, and keep that reserve reachable and documented rather than leaving random empty corners.

Which standards matter for control cabinet layout?

For machinery, IEC 60204-1 is a key international reference; applicable assemblies can also involve IEC 61439 and IEC TR 60890, while EMC installation guidance can involve the IEC 61000-5 series. In North America, NFPA 79, UL 508A and NEC Article 409 can be relevant. The adopted edition and exact equipment instructions govern the project.