Commissioning and Handover
This domain tests the handover: proving the system works, is safe and is documented.
Before commissioning
Flush and clean. Chlorinate new or altered pipework to the specified concentration and contact time, then neutralise and flush. Pressure-test and record. Check that valves are open, strainers clean, controls wired and sensors installed.
Commissioning
Balance heating circuits to design temperature drop; record pump settings; set the cylinder stat; confirm the relief valve discharge is safe and visible; check expansion vessel pre-charge against static pressure; record inhibitor concentration; commission gas appliances only if registered.
Handover
Provide O&M information, commissioning certificates, a benchmark-style record, Building Energy Rating where required, and demonstrate controls to the user. Confirm legionella sampling where new water systems demand it.
Worked example
A new unvented cylinder and system boiler. Fill and vent; pressure-test; set the expansion vessel pre-charge to the incoming static pressure; set the cylinder stat to 60 °C; confirm the temperature and pressure relief valve and its discharge route; balance radiators to an 11 °C drop; record inhibitor at the correct concentration; demonstrate the programmer and TRVs. If the pre-charge is set high, the vessel accepts little expansion and the relief valve will pass - the reasoning, not the checklist, earns the marks.
Traps that cost marks
Handing over without flushing; leaving the expansion vessel at factory pre-charge; no record of inhibitor; demonstrating controls only to your own satisfaction; forgetting the discharge pipe route.