Summary

Commissioning is the final stage of a heat pump installation and the point at which all previous design and installation work is verified. A properly commissioned system will perform as designed; a poorly commissioned system may short-cycle, fail to heat the property, cause premature component failure, or void the manufacturer warranty and MCS certification.

For MCS-certified installers, commissioning is a compliance obligation, not an optional final check. The commissioning record is required for BUS grant claims and must be issued to the customer.

Key Facts

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  • MCS Commissioning Record — the formal document required by MCS 007 to evidence commissioning; records system pressure, flow rate, flow/return temperatures, outdoor temperature at commissioning, inhibitor type and pH, controls settings, and installer signature
  • System pressure — the heating circuit must be filled to the manufacturer's specified cold fill pressure (typically 1.0–1.5 bar); check the pressure gauge reading at commissioning and record
  • Pressure test — after filling and bleeding, the system must hold pressure for at least 1 hour with no drop; a pressure drop indicates a leak that must be located and rectified before commissioning proceeds
  • Minimum flow rate — the heat pump manufacturer specifies a minimum water flow rate through the primary circuit (typically 0.3–0.8 l/s for an 8–12kW ASHP); verify using a commissioning valve (integral flow meter) or external ultrasonic flow meter; record in commissioning documentation
  • Flow and return temperatures — at steady state operation (after 30–60 minutes run time), measure and record the flow and return temperatures and the differential (ΔT); typical ΔT for an ASHP is 5–10°C; a low ΔT indicates excessive flow rate; a high ΔT may indicate insufficient flow or oversized heat output
  • Inhibitor and pH — system water must contain a suitable corrosion inhibitor (Fernox F1, Sentinel X100, or equivalent) at the manufacturer's recommended dosage; pH should be within the heat pump manufacturer's specification (typically 6.5–8.5); check with a calibrated pH meter or test strips; record product and dosage
  • Outdoor temperature at commissioning — record the outdoor air temperature at the time of commissioning; used as context for the flow temperature and COP data in the commissioning record
  • Weather compensation — verify the weather compensation curve is configured and operational; confirm the outdoor temperature sensor is reading correctly (compare to a reference thermometer); record the heating curve settings
  • DHW setpoints — set the DHW cylinder target temperature (typically 50–55°C); configure the legionella pasteurisation schedule (60°C, weekly); record both settings in the commissioning documentation
  • Zone control — test each zone valve or actuator opens and closes correctly; test each room thermostat or zone controller; confirm the heat pump responds to zone demand
  • Defrost operation — if commissioning in cold conditions (<5°C outdoor), observe the defrost cycle to confirm it operates correctly and the system recovers smoothly; record if observed
  • BUS documentation — for BUS grant claims, the MCS commissioning record is a required document; ensure it is completed correctly — errors or omissions can delay or invalidate the grant claim

Commissioning Checklist

Pre-Commissioning Checks

  • All pipework connections complete and visually inspected for leaks
  • All electrical connections complete; power supply checked against manufacturer specification
  • Outdoor unit base secure; anti-vibration pads fitted; clearances correct per siting requirements
  • Outdoor temperature sensor sited correctly (north-facing, shaded, away from heat sources)
  • DHW cylinder connections complete; immersion heater element checked; wiring correct
  • Magnetic filter fitted on heating circuit return; filter body accessible
  • System flushed and refilled with clean water + inhibitor (record product name, dosage)

Hydraulic Commissioning

  • System filled to cold fill pressure (record: _____ bar)
  • All radiators and heat pump bled; no air in system
  • Pressure held for 60 minutes; no drop observed
  • Flow rate measured and recorded (record: _____ l/s; manufacturer minimum: _____ l/s)
  • pH checked and recorded (record: _____; acceptable range: 6.5–8.5 or per manufacturer)
  • Inhibitor type and dosage recorded

Controls Commissioning

  • Heat pump controller powered on; initial setup complete
  • Weather compensation curve configured (record cold-end: _____°C flow at _____°C outdoor; warm-end: _____°C flow at _____°C outdoor)
  • Outdoor temperature sensor reading verified against reference thermometer
  • Room thermostat(s) set to correct setpoint and operating correctly
  • Zone valves/actuators tested — all zones opening and closing on demand
  • DHW target temperature set (record: _____°C)
  • Legionella pasteurisation schedule configured (record: day _____, time _____, target 60°C)
  • DHW priority mode confirmed active

Operational Verification

  • Heat pump started; self-diagnostic completed with no fault codes
  • System run for 30–60 minutes to reach steady state
  • Flow temperature at steady state recorded (record: _____°C)
  • Return temperature at steady state recorded (record: _____°C)
  • ΔT calculated (record: _____°C; typical 5–10°C)
  • Outdoor temperature at time of commissioning recorded (record: _____°C)
  • Defrost cycle observed (if outdoor temp <5°C): operating correctly Y/N
  • No fault codes active at completion of commissioning

DHW Verification

  • DHW cylinder heating cycle initiated
  • Flow and return temperatures at DHW coil recorded
  • Cylinder reaches target temperature (record: time to heat from cold _____hrs)
  • T&P relief valve and expansion vessel checked (unvented cylinder)
  • Thermostatic blending valve (TMV) set and outlet temperature verified (record: _____°C at tap)

Documentation and Handover

  • MCS Commissioning Record completed and signed
  • MCS certificate issued to customer
  • Building control notification submitted (self-certification via MCS scheme)
  • Equipment log completed (if split ASHP / F-Gas applicable)
  • Customer handover pack prepared (see below)

Customer Handover Pack

Provide to the customer at completion:

  • MCS Commissioning Record (signed copy)
  • MCS certificate / Microgeneration Certification
  • Heat pump manufacturer's user guide and quick-start card
  • Warranty documentation (manufacturer warranty; any extended warranty)
  • Inhibitor dosage label affixed to the filling loop or near the heat pump
  • Emergency contact information (installer, emergency heating cover)
  • Brief written guide: how to adjust setpoint, what to do if the heat pump shows a fault code, when to call for service
  • Service schedule recommendation (annual service recommended; manufacturer warranty may require it)

Frequently Asked Questions

What if the system pressure drops during the 60-minute hold test?

A pressure drop means a leak is present. The leak must be found and rectified before commissioning proceeds. Common locations: radiator valves not fully tightened, compression fittings on new pipework, the heat pump's own connections. Use leak detection spray or a soap solution at all connections. Do not sign the commissioning record if a pressure drop is present — the system is not commissioned.

What if the flow rate is below the manufacturer's minimum?

Check first that all zone valves are open and all radiators are bled. If flow rate is still insufficient, the system may have excessive restriction (undersized pipework, partially closed valves, blocked filter). Clean the magnetic filter, check all isolation valves are fully open, and recheck. If the problem persists, the pipework design may need review. Do not commission a system below the manufacturer's minimum flow rate — it risks damage to the heat pump's internal components.

Does weather compensation have to be enabled at commissioning for MCS compliance?

MCS 007 requires weather compensation to be configured and operational at commissioning. It is a core efficiency requirement of the MCS standard — not optional. If the customer subsequently disables it, that is outside the installer's control, but the commissioning record must show it was configured at handover.

Regulations & Standards