System Integration

System integration means combining controllers, drives, sensors, networks, panels, software and people into one machine or process that does what the customer specified, safely and repeatably. Most problems at commissioning come from decisions made (or not made) much earlier: unclear requirements, an incomplete I/O list, an undersized power supply, a panel that overheats, noise, missing documentation. This guide follows a project from the first requirement to handover and beyond, in ten pages: requirements and stages, architecture and selection, power distribution, wiring, panel layout and heat, grounding and noise, machine safety, HMI and cybersecurity, testing and commissioning, and documentation and lifecycle. Every worked number is computed so that you can check your own project against it. The detail of the parts is in PLC and Logic Control, Industrial Communication, Motion Control and Actuators, Sensors and Field Devices and Industrial Robotics.

Start here: what do you need?

I need to…	Go to
write a specification, count the I/O, plan the stages or manage change	Requirements, Specification and Project Stages
choose a platform, size a controller, or decide between a central panel and remote I/O	System Architecture and Component Selection
size the 24 V supply, protect a motor circuit or work out a fault level	Power Distribution and the Control Supply
work out voltage drop, choose a cable, or lay out a 4–20 mA loop	Wiring, Cables and Voltage Drop
lay out a panel, size a fan or an air conditioner, or choose an enclosure rating	Panel Layout, Heat and Enclosures
earth a system, route cables, terminate a shield or cure noise	Grounding, Shielding and Noise
assess risk, set a performance level, wire an emergency stop or validate a safety function	Machine Safety Systems
design operator screens, manage alarms, log data or secure the network	HMI, Alarms, Data and Cybersecurity
test, commission, run an acceptance test or hold a FAT and SAT	Testing, Commissioning and Acceptance
document, hand over, hold spares, manage versions or troubleshoot	Documentation, Handover and Lifecycle

A suggested order

Start with Requirements, Specification and Project Stages and System Architecture and Component Selection, because every later decision follows from them. Then design the hardware: Power Distribution and the Control Supply, Wiring, Cables and Voltage Drop, Panel Layout, Heat and Enclosures and Grounding, Shielding and Noise. Machine Safety Systems runs alongside the whole design and is never an afterthought. HMI, Alarms, Data and Cybersecurity covers the human and network side; Testing, Commissioning and Acceptance and Documentation, Handover and Lifecycle close the project and keep the machine running.

1. Requirements, Specification and Project Stages: The functional specification, the I/O list, project stages and effort, change control, FAT and SAT, and what makes projects late.
2. System Architecture and Component Selection: Choosing the platform, sizing the controller and its scan time, remote I/O, network topology, redundancy and standardizing.
3. Power Distribution and the Control Supply: Main isolators, branch protection, motor circuits, trip curves and coordination, sizing the 24 V supply and ride-through.
4. Wiring, Cables and Voltage Drop: Voltage drop, current rating, conductor colors, terminals and ferrules, 4–20 mA loop budgets and cable selection.
5. Panel Layout, Heat and Enclosures: Layout zones, enclosure ratings, heat dissipation and fan or air-conditioner sizing, short-circuit rating and labeling.
6. Grounding, Shielding and Noise: Protective earth and functional earth, how noise couples, routing and separation, shield termination and suppressing loads.
7. Machine Safety Systems: Risk assessment, performance levels and safety integrity, emergency stops and stop categories, safety circuits, and validation.
8. HMI, Alarms, Data and Cybersecurity: Operator screens, alarm management and its numbers, recipes and user levels, logging, and securing the control network.
9. Testing, Commissioning and Acceptance: Insulation and earth tests, I/O and loop checks, drive and safety tests, fault injection, FAT, SAT and acceptance criteria.
10. Documentation, Handover and Lifecycle: Schematics and tags, program backups, spares, training, change control, obsolescence and a troubleshooting table.

The stages of a project

Stage	Main outputs	Where to look
Specify	Functional description, I/O list, risk assessment, budget and schedule	Requirements, Specification and Project Stages
Design	Architecture, schematics, panel layout, bill of materials, safety design	System Architecture and Component Selection, Power Distribution and the Control Supply, Wiring, Cables and Voltage Drop, Panel Layout, Heat and Enclosures, Grounding, Shielding and Noise, Machine Safety Systems
Build and FAT	Assembled panel, programs, workshop tests, factory acceptance	HMI, Alarms, Data and Cybersecurity, Testing, Commissioning and Acceptance
Install, commission, SAT	Installed machine, tested I/O and loops, tuned drives, accepted	Testing, Commissioning and Acceptance
Handover and life	As-built drawings, backups, spares, training, change control	Documentation, Handover and Lifecycle

Quick reference: formulas and rules

Topic	Formula or rule	Page
24 V supply	rating ≥ (sum of loads) × 1.25, then round up; run below about 80 %	Power Distribution and the Control Supply
Motor current	I = P ÷ (√3 V η cos φ)	Power Distribution and the Control Supply
Fault level	Isc = V ÷ (√3 Z)	Power Distribution and the Control Supply
DC voltage drop	ΔV = 2 L I ρ ÷ A (ρ = 0.0172 Ω·mm²/m)	Wiring, Cables and Voltage Drop
Enclosure temperature rise	ΔT = P ÷ (k A), k ≈ 5.5 W/m²K	Panel Layout, Heat and Enclosures
Fan airflow	V (m³/h) = 3.1 P ÷ ΔT	Panel Layout, Heat and Enclosures
Earth-fault loop	Zs ≤ U0 ÷ Ia	Grounding, Shielding and Noise
Performance level	PFHd of the parts add; PL e is below 10⁻⁷ per hour	Machine Safety Systems
Alarm rate	at most about 1 alarm per 10 minutes on average (ISA-18.2)	HMI, Alarms, Data and Cybersecurity
Insulation test	500 V DC, at least 1 MΩ (IEC 60204-1)	Testing, Commissioning and Acceptance
Spare I/O	15 to 20 % spare points, panel space and power	Requirements, Specification and Project Stages

Related guides and tools

• PLC and Logic Control: the program, scan cycle and I/O wiring.
• Industrial Communication: networks, protocols and security for the architecture.
• Motion Control and Actuators and Sensors and Field Devices: the devices being integrated.
• Industrial Robotics: integrating robot cells.
• Electronics Fundamentals: the circuits behind supplies, protection and noise.
• Analog Scaling Tool and Motor Torque and Inertia Matching Calculator.

Safety and responsibility

• Safety is designed in, not added at the end, and it is a legal requirement: a documented risk assessment and protective measures matched to the risk (see Machine Safety Systems).
• Mains and stored energy are dangerous: work on a panel only when it is isolated, locked out and proved dead, and only if you are competent to do so.
• The numbers in this guide are typical. Use the manufacturers’ data and the standards and codes of the country where the machine will run; have electrical and safety work done and signed off by competent people.
• Responsibility is written down: who supplies, who designs, who wires, who programs, who validates safety (see Requirements, Specification and Project Stages).

FAQ

What is the difference between FAT and SAT?

The factory acceptance test (FAT) is done at the supplier’s premises before shipping, to show that the equipment meets the specification. The site acceptance test (SAT) repeats the important checks after installation, with the real field wiring, utilities and process. See Testing, Commissioning and Acceptance.

How much spare capacity should I leave?

A common target is 15 to 20 % spare I/O, plus free panel space, power supply and wire-duct capacity. It costs little at the start and a lot to add later. See Requirements, Specification and Project Stages.

Who is responsible for machine safety?

The machine builder is responsible for the risk assessment, design and validation of the machine’s safety functions; the integrator must follow the law and standards and document it. A safety function changed on site needs to be validated again. See Machine Safety Systems.

Where did the old System Integration sections go?

All of them are in this guide with much more depth: the stages, requirements, architecture, power, wiring, grounding, safety, HMI, documentation, testing and troubleshooting each have a place in the ten pages.

References

• IEC 60204-1, Safety of machinery: electrical equipment of machines (wire colors, stop categories, testing); IEC 60364 and the local electrical code; UL 508A for industrial control panels.
• ISO 12100, ISO 13849-1, IEC 62061 and IEC 61508 (risk assessment and safety-related control); ISO 13850 (emergency stop); IEC 62443 (industrial cybersecurity).
• ISA-18.2 (alarm management) and ISA-101 (HMI); IEC 61131-2 (programmable controller equipment); IEC 61082 and IEC 81346 (documentation and reference designations).

Last reviewed: October 2026. This guide is an introduction, not a substitute for the standards and legal requirements that apply to your machine and country: confirm them before design, and have safety functions designed and validated by competent people.