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  • Alex Mathers

Start up and Commissioning: What's the Difference?

In the world of complex projects commissioning plays a vital role in ensuring that equipment, a system, facility, or process is fully prepared to function efficiently and effectively before final verification. Whether it's a new manufacturing plant, laboratory, data center, hospital or office, the operational readiness that commissioning provides is the steps that bridges the gap between construction and turnover.

What is Operational Readiness?

Operational readiness means different things to different people. Operational readiness for commissioning is the systematic process of verifying and ensuring that all elements required for an operation to function smoothly are in place, tested, and ready for use. It encompasses a wide range of activities that validate not only the design aspects but also the application specific aspects of the system operation.

There are a number of key tasks that must be completed between equipment installation and final functional testing. More often than not, these tasks are not included in the project schedule. The project schedule only includes a single line item for “Startup and Commissioning”:

Startup and commissioning are often used together or interchangeably, but they represent distinct stages in the process of bringing a project to life. There are key differences but both provide the best practices to ensure a smooth transition from construction to operation.

Startup vs. Commissioning: What's the Difference?

Before we delve deeper into the individual aspects of startup and commissioning, it's crucial to understand the fundamental distinctions between the two.


· Startup refers to the initial phase where equipment or systems are powered up for the first time. It primarily focuses on making sure everything turns on, runs, and operates as expected.

· During startup, there is limited testing and validation of system functionality, and it mainly deals with checking if individual components are functional. For example, are electrical phases connected correctly. Is the fan or pump spinning in the correct direction or are there any shorts or blown fuses.

· The goal of startup is to get the equipment or system running, but it does not necessarily guarantee that it will operate optimally or safely.


· Commissioning is a process, not a point in time.

· Commissioning is a more comprehensive and systematic process that occurs, not just after startup, but from all the way back in the planning phase of the project.

· The functional testing phase of commissioning that everyone likes to just call “Commissioning” ensures that all equipment, systems, and components work together as an integrated whole, meeting safety, performance, and regulatory standards.

· Commissioning is not just the functional testing task. It also involves documenting and verifying the system's performance, conducting functional tests, and addressing any issues that arise during the process.

Even on small projects, one or two weeks for “Start up and Commissioning” is a tight schedule. Here are some if not all the tasks that are assumed in the line item:

· Factory Witness Testing

· Controls and Automation Bench Testing

· Equipment Installation

· DALT (Duct Air Leakage Testing)

· Piping Pressure Test

· NETA Testing

· Megger Testing

· Ground Resistance Testing

· Electrical Installation Checklists (Pre-Energization)

· Power On

· Electrical Adjustable Trip Setting

· Feed and Bleed / Fill and Flush

· Plumbing Sanitization / Disinfection / Chlorination

· Equipment Startup

· Electrical Walkdown and Testing (Post-Energization)

· NFPA 110 Testing

· Plumbing System Balance

· Controls Point to Point (PTP) Checkout including I/O checking, sequence checking, and loop checking

· Controls Sensor Calibration

· Controls Graphics Checkout

· HVAC Test, Adjust, and Balance (TAB) - Wet Side

· HVAC Test, Adjust, and Balance (TAB) - Dry Side

· Controls Trending Setup

· Controls Alarming and Remote Notification (RENO) Setup

· Controls SAT

· Mechanical Acceptance Testing

· Lighting Acceptance Testing

· Equipment and Systems SAT

· Pre-Functional Checklists (PFCs)

· Pre-Verification Testing (PVTs)

· Readiness Documentation Review

Some of these tasks shown on a timeline looks something like this:

Most, if not all of these tasks must be completed prior to final Functional Testing (i.e. “Commissioning”) which itself is another step in the overall commissioning process.

Functional Testing is the continuance with more comprehensive functional testing, including interlocks, alarms, and control sequences where the CxA verifies that the system operates within specified parameters. Functional testing also includes performance testing where the CxA conducts performance tests to evaluate the system's efficiency, capacity, and overall performance and ensures that the system meets design specifications and regulatory requirements. Safety checks are conducted to verify that all safety systems are functioning correctly and that emergency procedures are in place.

Startup and commissioning are parts of the whole. While startup gets things up and running, commissioning takes a comprehensive approach to ensure that everything works harmoniously and meets performance and safety standards. By understanding the differences and following best practices in these phases, industries can minimize risks, maximize efficiency, and lay the foundation for a successful operational future.

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