How an ASHP actually works
Refrigerant in the outdoor unit evaporates at very low temperatures, absorbing heat from outside air. A compressor pressurises the gas, raising its temperature. The hot refrigerant transfers heat to your central heating water via a plate exchanger, then expands and cools, repeating the cycle. The 'COP' is the ratio of heat delivered to electricity consumed.
Brands we install
Mitsubishi Ecodan, Daikin Altherma, Vaillant aroTHERM plus and Samsung EHS — all monobloc R32 or R290 units. We are accredited installers for each, meaning extended warranties and direct technical support.
Sizing — the critical first decision
MCS requires a room-by-room heat-loss calculation using actual u-values and CIBSE temperature data for the Darlington area. We size to peak demand at -2°C external (the regional design temperature) and verify against measured oil/gas consumption from your last 12 months.
Emitter strategy
ASHPs run most efficiently at flow temperatures of 35–45°C. Existing radiators sized for an 80°C gas boiler are typically 40–60% undersized at 45°C. We will quote upsized radiators or, where feasible, switch a downstairs zone to underfloor heating for the lowest flow temperatures and highest SCOP.
Cylinder & hot water
ASHPs require an indirect unvented cylinder with a high-surface-area coil (3.0–4.0 m²). We install 200–300L cylinders depending on household size and incorporate a weekly anti-Legionella cycle automatically.
Tariffs and running cost
Pair the install with Octopus Cosy or Intelligent Octopus, which give 7p/kWh during off-peak windows. We program the heat pump to charge hot water and pre-heat the home during cheap windows, dropping running costs by another 20–30%.
Planning, noise & permitted development
Most domestic ASHPs fall under permitted development rules provided the unit is >1m from boundary and below 0.6 m³ in volume. We model the noise at boundary using MCS-020 calculations — your neighbours never hear it.