A mechanical ventilation with heat recovery system must be balanced and commissioned after installation, with measured supply and extract rates recorded for each room. Maintenance means changing filters regularly and cleaning valves and ductwork.
Commissioning is not optional. Without measured and balanced flow rates the system will not deliver the design ventilation, and an unbalanced unit can pressurise or depressurise the dwelling.
Ask for the commissioning sheet showing measured rates at each terminal against the design values. Keep it with the handover documents alongside the maintenance schedule.