Heat Pump Maintenance Checklist for Owners UK 2026

1. Outdoor unit visual inspection (2 min):

• Walk around the outdoor unit.
• Check for: leaves/debris in fan area; ice buildup not clearing via defrost; visible damage (storm impact, fallen branch); unusual sounds (knocking, grinding).
• Clear loose debris by hand (NOT inside the unit casing).

2. Manufacturer app review (2 min):

• Open manufacturer app (Vaillant Connect, Daikin Onecta, Octopus app, MELCloud, myUplink).
• Check: fault codes (should be none); current SCOP (7-day rolling); aux heater hours (should be small percentage of total); recent defrost cycles (3-15/day normal in damp +0-5C weather).
• Note any anomalies for next professional service visit.

3. Condensate drainage check (1 min):

• Look under outdoor unit for water drainage path.
• Confirm water draining away (to soakaway, surface drain, or splash pad).
• Concerning: water pooling, ice buildup, water running toward building.
• If issue, call installer - drainage problems cause defrost-cycle failures.

Five minutes monthly catches 80% of emerging issues before they become expensive repairs.

Spring (March-April):

• Clear winter debris from outdoor unit (leaves, twigs, animal nests).
• Gentle hose-down of outdoor unit fins (low pressure water; never pressure washer).
• Check anti-vibration mounts under outdoor unit (visible cracks or compression = replace).
• Confirm condensate drainage flowing freely after winter freeze.
• Review winter SCOP performance via manufacturer app.

Summer (June-July):

• Outdoor unit may run less; check for spider webs / wasp nests in vents.
• Trim back vegetation if growing within 1m of outdoor unit (airflow obstruction).
• Test cooling mode (if reverse-cycle enabled) - verify cooling delivery.
• Cylinder Legionella weekly cycle - verify running (should auto-fire weekly to 60C).

Autumn (September-October):

• Pre-winter readiness check - all components working before peak heat demand.
• Condensate drain heat-trace cable check (cold-climate properties).
• Annual MCS service typically scheduled now (before winter peak).
• Smart tariff verification - confirm Cosy/Intelligent Go schedule still active.

Winter (December-February):

• Watch for ice buildup not clearing via normal defrost cycle.
• Monitor aux heater hours (should remain small percentage even during cold snaps).
• Cylinder reheat times normal (2-3 hours from cold).
• If unusual symptoms: log immediately, call installer if persistent.

1. Outdoor unit deep clean. Gentle hose; remove cumulated debris; trim vegetation 1m+ from unit; verify no animal nests in vents.
2. Refrigerant pipework insulation inspection. Walk pipework run from outdoor unit to indoor; check for damaged insulation (cracks, gaps, missing sections). Re-insulate damaged sections (GBP 30-100 self-fit) - prevents efficiency losses + freeze damage.
3. Electrical isolator switch test. Locate outdoor unit isolator (usually within 2m of unit); confirm switch accessible + functional. If suspected loose connection, call electrician.
4. Cylinder thermostat verification. Check cylinder thermostat setpoint (55-60C typical). Verify cylinder reaches setpoint within normal reheat time (2-3 hours).
5. Manufacturer app data export. Export 12-month SCOP, aux heater hours, defrost cycle counts. Share with MCS engineer at annual service.
6. Photo log update. Photograph outdoor unit, indoor cylinder, controller for records. Compare with install-completion photos for any visible change.
7. Manufacturer warranty registration check. Confirm warranty still valid via manufacturer website using serial number.

1. Refrigerant top-up / recharge. F-gas certified technician required. DIY refrigerant work violates F-gas regs + can damage compressor.
2. Compressor service or repair. Specialised work; warranty implications.
3. Electrical panel modifications. Consumer unit / isolator switch work needs qualified electrician.
4. Cylinder coil cleaning. Internal cylinder work; specialised tools + scale risk.
5. Controller firmware updates beyond standard manufacturer app. Engineer-mode access required for some manufacturers.
6. Weather compensation curve tuning during fault state. If system showing fault codes, don't tune; call engineer for diagnosis.
7. Hydronic system flushing. Power flush specialised; risk of damage to heat pump if done incorrectly.
8. Outdoor unit relocation. Refrigerant work + structural mounting + commissioning - full re-install effectively.

Annual MCS service (GBP 150-250) covers F-gas inspection + comprehensive system check. DIY supplements but never replaces this.

1. Fault codes on controller or app. Not all codes are emergencies but all warrant prompt diagnosis. Note code + call installer within 24 hours.
2. Loud knocking, grinding, or rapid clicking noises. Compressor, fan, or refrigerant pipework issue. Stop using + call immediately.
3. No hot water + DHW priority enabled. Cylinder coil fouled OR heat pump not heating cylinder. Call within day.
4. Indoor temperatures consistently 3+C below target despite heat pump running. Sizing, WC, or refrigerant issue. Call within day.
5. Visible refrigerant leak. Pipework damage or compressor seal failure. Don't touch refrigerant; call immediately.
6. Outdoor unit failing to start. Electrical or fault state. Check isolator switch + consumer unit MCB before calling, but escalate quickly.
7. Bills 30%+ above installer estimate sustained over 2+ months. Indicates real problem - undersizing, controller fault, aux heater stuck on. Call within week.

Manufacturer warranty conditions typically require:

• Annual MCS-certified service (skipping voids warranty for subsequent claims).
• F-gas leak inspection compliance.
• Repairs by certified engineer only.
• No unauthorised modifications.

DIY maintenance acceptable to manufacturer:

• Visual inspection + cleaning per manufacturer guide.
• Trim vegetation around outdoor unit.
• App-driven schedule + setpoint changes.
• Manufacturer app firmware updates (standard updates only).

If in doubt: ask manufacturer support or installer before any DIY beyond visual inspection + surface cleaning. Better to over-call than void warranty.