BMS commissioning, step by step: from factory test to witnessing

Commissioning is where a BMS goes from a collection of panels and cables to a system that actually runs the building. It’s also where projects most often run out of time, so the commissioning gets squeezed and the building’s first year is spent fixing things that should have been caught.

Doing it in a clear order, with evidence at every stage, is what makes it go smoothly.

Plan it first

Before anyone sets foot on site with a laptop, you need:

• an agreed points schedule and control strategy (description of operation)
• the network design, with IP addresses, device instances and MS/TP trunks
• a commissioning programme that fits around the mechanical and electrical trades
• test sheets for each type of plant, ideally agreed with the client’s commissioning manager in advance

Industry commissioning codes, such as CIBSE Commissioning Code C for automatic controls, are a useful framework for what a thorough commissioning process should cover.

Off-site testing

A lot can be tested before anything goes to site. Panels can be checked at the panel builder’s: wiring against the drawings, power-up, controller I/O. Software can be loaded and simulated, so the logic is run through with forced inputs to check it does what the strategy says. Graphics can be reviewed with the client before the system goes live.

A factory acceptance test, or FAT, at this stage catches problems when they’re cheap to fix.

Pre-commissioning: the dead checks

Once panels and field devices are installed, and before anything is powered up properly:

• Check the installation against the drawings: device locations, cable routes, labelling, containment.
• Check continuity and polarity on every circuit.
• Check terminations at both ends, including screens.
• Confirm the mechanical side is ready: valves fitted the right way round, dampers free to move, systems filled and vented.

The electrical installation testing has to be done safely and without damaging the electronics. There’s more in testing and calibrating a BMS installation.

Point-to-point checks

With power on, every single point gets proven from the field device to the front end.

• Inputs. Change the real condition and check the BMS sees it. Warm a sensor, operate a switch, trip a fault contact. Check the value and the scaling against a reference.
• Outputs. Drive each output from the BMS and check the right device responds the right way. Does 0% close the valve and 100% open it? Does the start command start the right pump?

Tick off every point on the points schedule as it’s proven. It’s tedious, and it’s the step most often rushed. Skipping it is why so many “commissioned” sites have sensors labelled as the wrong room.

Functional testing

With all the points proven, test the strategy itself, plant by plant:

• start-up and shutdown sequences
• each control loop holding setpoint, with the tuning recorded
• interlocks and safety functions: fire alarm stops, frost protection, pump proving
• duty/standby changeover and fault responses
• schedules, optimum start, and any seasonal modes
• every alarm, from the field device right through to the front end and its notifications

Use PID tuning properly here rather than leaving loops on default settings.

Integration

Third-party systems such as chillers, boilers, VRF, meters, lighting and fire alarm interfaces all need their own testing: every mapped point checked, values scaled correctly, writes that work, and sensible behaviour when the link fails. See testing third-party integrations.

Witnessing

The client, or their commissioning manager, will want to witness a sample of tests, or sometimes every test on critical plant. Make it easy for them:

• agree the witnessing scope and dates well in advance
• have completed test sheets ready, so witnessing is confirmation rather than discovery
• demonstrate from the front end and in the plant room
• record anything that fails, fix it, and re-test

Handover

A system isn’t finished until the documentation is. At handover the client should get:

• the as-built control strategies and points schedule
• network drawings and IP and device schedules
• completed commissioning and test records
• software backups and licence details
• user training for the people who’ll run the building

See what should be in your BMS O&M manual.

Seasonal commissioning

Some things can only be tested properly in the right weather. Heating at full load needs winter, cooling at full load needs summer. A seasonal visit after occupation, where trends are reviewed and loops and setpoints adjusted under real conditions, catches a lot of issues that a summer handover can’t. It’s well worth building into the contract.