Heat Pump Commissioning Checklist UK 2026

Before the heat pump runs operationally, the installer must:

• Fill the hydronic circuit with the correct water + inhibitor mix (typically Fernox F1 or equivalent at 1-2% concentration).
• Pressure-test the system to 3.0 bar minimum, hold for 30 minutes, confirm zero pressure drop.
• Bleed all radiators + check for any leaks at joints, valves, or pipe runs.
• Document the pressure-test result on the commissioning paperwork.

What you should see: the engineer running the pressure test in your presence, showing you the pressure gauge readings. Ask for the leak-test reading to be recorded on the commissioning certificate.

The heat pump's first operational run validates that:

• Outdoor unit starts cleanly + reaches steady-state operation within 10-15 minutes.
• Flow temperature matches the design (typically 35-45°C for UFH-equipped properties, 45-55°C for radiator-based systems).
• Indoor temperature rises measurably + radiators heat up across all rooms.
• No fault codes displayed on the controller.

What you should see: the controller display showing live flow temp + return temp readings, plus the outdoor unit fan running steadily. Ask the engineer to point out where the design flow temperature is set in the controller - this is the most important number for your system's efficiency.

The hot water cylinder reheat test:

• Set the cylinder to cold start (drain or use the night's standing-cold position).
• Run the heat pump in hot-water-priority mode until cylinder reaches target temp (typically 50-55°C for legionella safety + comfort).
• Time how long the reheat takes - compare against the manufacturer spec for your specific cylinder + heat pump pairing.

Typical 200L cylinder reheat from 15°C to 55°C: 60-90 minutes for a 7kW heat pump. If it takes significantly longer (2+ hours), there's either a sizing mismatch (cylinder too large or heat pump too small) or a control system issue. Flag this immediately.

The COP (Coefficient of Performance) measurement captures the system's real-world efficiency at install:

• Outdoor temperature at the test time.
• Flow temperature being delivered.
• Electrical power draw (kW).
• Heat output (kW) - measured via flow rate × temperature differential.
• Calculated COP at this operating point.

Get this number recorded on the commissioning certificate. It's the baseline for future efficiency comparisons - if your COP measurably drops in year 2-3 (sensor faults, refrigerant leak), this number is the reference point.

Typical commissioning COP for a 2026 R290 heat pump at A7/W35: 4.0-4.8. Lower than this at commissioning suggests installation issues; investigate before signing off.

The installer should program the controller with:

• Your preferred indoor temperature ranges (typically 18°C overnight, 20-22°C daytime).
• Weather compensation curve (slope + offset matching your property's heat loss).
• Hot water schedule (when to reheat, how often, target temp).
• Holiday mode setup (frost protection only, hot water off).
• Smart-home integration if applicable.

Don't let the engineer leave with the default factory programming - your household's specific usage patterns matter for both comfort + efficiency. Ask the engineer to walk through the programming on screen so you understand how to make future adjustments yourself.

For Cosy Octopus, Intelligent Octopus Go, or other smart-tariff households:

• Confirm the heat pump controller is talking to the Octopus tariff API (some manufacturer apps need separate setup steps).
• Verify the off-peak window is recognised + the controller schedules pre-heat / hot-water reheat during the cheap window.
• For Home Assistant + Modbus integration: confirm the Wi-Fi Modbus adapter (Waveshare or similar) is paired + Home Assistant can read state.
• For MELCloud / myVAILLANT / ViCare apps: confirm Wi-Fi connection + mobile app shows live data.

This is the step most likely to be skipped or done badly - installers focus on the hardware install + treat smart-home integration as 'figure it out yourself'. Push back if your install quote included tariff-aware setup but the engineer isn't verifying it works.

Annual servicing is a warranty condition for almost every UK heat pump manufacturer. Lock in the first annual service appointment:

• Schedule for approximately 12 months from commissioning date.
• Confirm whether it's included free in your install package (most large installers include the first year service).
• Get the future service cost in writing (typically GBP 130-280; some installers offer 3-year service plans).
• Note the engineer's preferred contact channel for service booking (typically online portal or direct phone).

The MCS commissioning certificate is the single most important document from commissioning day. It confirms:

• Install was completed to MCS standards.
• System performance was tested + meets specifications.
• BUS grant final payment can be released to the installer.
• Manufacturer warranty is activated.

You should receive a signed copy - typically PDF emailed within 48 hours of commissioning, plus a paper copy if you request it. Keep this document forever (digital + paper) - it's needed for:

• Manufacturer warranty claims throughout the warranty period.
• House sale documentation.
• Insurance claims involving the heat pump.

The manufacturer warranty period (typically 5-10 years depending on brand) starts from the commissioning date - but only if your unit is registered with the manufacturer. The engineer should:

• Register your heat pump serial number with the manufacturer (Vaillant Advance, MELCloud, ViCare, Octopus Cosy etc.).
• Provide you with a copy of the warranty registration confirmation.
• Confirm the warranty period start date matches the commissioning date.

Unregistered units default to a much shorter warranty period (often 1-2 years) - confirm registration is complete before signing off.

Don't let the engineer rush out the door. Use the last 20-30 minutes for:

• Controller operation walkthrough - daily-use features + how to make adjustments.
• Fault code reference - which codes are minor + which require call-out.
• Outdoor unit care - keeping the area around it clear of leaves/snow/obstructions.
• Hot water expectations - recovery times, peak-demand handling, off-peak optimisation.
• Tariff coordination - when the heat pump will run during off-peak vs peak hours.
• What to do if something goes wrong - engineer's direct contact for first 30 days, manufacturer support line afterwards.

Take notes during this walkthrough - your first cold week with the heat pump generates dozens of small questions that are easier answered now while the engineer is on site.