Preparing a heating circuit for commissioning: cleaning, filling, venting and soundness checks in the specified sequence.
Clean before you commission
Clean a new or reworked system by the procedure appropriate to its condition and the appliance and treatment instructions before final commissioning. Installation debris, flux and swarf can cause noise, blockages and corrosion. The process can include an initial flush, circulation of a suitable cleaner and a final thorough flush. Manage the flow through every affected branch: one clear outlet does not mean the whole circuit is clean.
England’s 2021 Approved Document L calls for cleaning and flushing existing primary circuits before a new heating appliance is installed, followed by suitable inhibitor, with preparation and commissioning to BS 7593. Protect the new appliance from old-system debris. A model can permit a different sequence for a wholly new circuit: the Greenstar 8000 Life instructions allow its use during cleaning of a new system with the specified return filter. This does not authorise flushing an old dirty circuit through a new boiler. In hard-water areas, apply the required scale-control measures to water-heater feeds and the hot-water side of combis.
Fill and vent
Fill the system slowly so air is pushed ahead of the water rather than trapped. Vent radiators and high points, and confirm the automatic air vents are working. On a sealed system bring it up to the specified cold water fill pressure (commonly around 1.0 to 1.5 bar) and top up as trapped air is released.
Soundness
Before firing, prove the system is sound. Inspect every joint, then pressure test for leaks, holding the test pressure for the period given in the relevant standard and the manufacturer instructions. Rectify any weep before going further — it is far easier with the system cold and accessible.
Inhibitor
Once clean and sound, dose the system to the specified inhibitor concentration and fit in-line filtration under the applicable treatment and appliance guidance. A magnetic collector removes magnetic particles; combined devices may capture other debris too. Filtration supports cleaning and treatment rather than replacing them. Record the products, dose and test results.
Check the concentration again after filling, and after any later work that adds water, such as new radiators or a drain-down. Fresh water dilutes the treatment, so the dose may need topping back up to the manufacturer's figure. Fit any magnetic filter, and other directional components such as valves, with the flow arrow on the body pointing the way the water flows. Leave the filter reachable so trapped debris can be cleaned out later.
Notifying that commissioning is complete in England
Under the 2021 Approved Document L guidance, the building control body must also receive a commissioning notice confirming that the fixed building services were commissioned. Where a building notice or full plans route was used, or the work is overseen by a registered building control approver, that notice is due within five days of finishing the commissioning. Where a Competent Person Scheme member self-certifies the work instead, the notice is due within 30 days. Building control can withhold the completion certificate until it arrives.