Viessmann announced on 4 July 2023 that it has added three lower output variants to its Vitocal 150-A/151-A domestic air source heat pump range. The new 4, 6 and 8 kW models complement the existing 10, 13 and 16 kW heat pumps launched in 2022, which the company says gives a wider choice of outputs for heating modernisation projects across a broader range of properties1.
All models in the range provide both heating and cooling, and are available for connection to a single-phase electricity supply. Three-phase versions are available only for the 10 to 16 kW variants. The units use R290 natural propane refrigerant, which Viessmann gives a Global Warming Potential of 0.021.
The range is offered as the wall-mounted Vitocal 150-A and the floor-standing Vitocal 151-A, the latter available with an integral 190-litre domestic hot water cylinder. Both have a maximum flow temperature of 70 °C. Viessmann states that, subject to system design requirements and seasonalised efficiency calculations, it may be possible to retain existing radiators depending on the heat loss from the house, a calculation it says the installer is required to undertake1.
The single-fan outdoor unit of the new lower output models is half the height of the 10, 13 and 16 kW units, at 800 mm high. Viessmann quotes a sound pressure level of 33.5 dB(A) at three metres for the 6 kW outdoor unit, installed against one wall in standard heating mode. The One Base control platform includes an Integrated Energy Management System, which the company says gives customers transparency on energy consumption and costs1.
"The arrival of the 4, 6 and 8 kW models provides our installers with added flexibility to select the appropriately-sized product for homes with low heat losses, such as smaller or newer homes, or perhaps whole house retrofits."
Viessmann was founded in 1917 as a heating technology manufacturer and is now part of Carrier1. The company's wider UK heat pump range is covered in the Viessmann Vitocal heat pump range guide.
Why it matters for households
Heat pump output has to match a home's heat loss, and a unit that is too large will cycle on and off rather than run steadily. The addition of 4, 6 and 8 kW models extends the range downwards into the sizes that suit smaller, newer or better insulated homes, and into whole house retrofits where a boiler is being replaced. That matters for energy independence because a correctly sized electric heat pump is the main route by which a household can move its space heating and hot water off gas and onto a supply it can increasingly generate itself.
Two details bear on practical installation. The 70 °C maximum flow temperature is high for a heat pump and is the figure that determines whether existing radiators can stay, though Viessmann ties that to a heat loss calculation the installer must carry out. The 800 mm outdoor unit height and the quoted 33.5 dB(A) sound level are the kind of figures that matter where space outside is tight or where a neighbour's wall is close, and they are relevant to permitted development and planning questions in Scotland and elsewhere.
The propane refrigerant has a very low global warming potential compared with older synthetic refrigerants, which reduces the direct emissions associated with the unit itself. The control platform's stated ability to integrate solar PV, battery storage, mechanical ventilation with heat recovery and EV chargers points to a system that can be added to over time rather than replaced.
What happens next
Viessmann says that by the end of 2024 it will have launched all of these additional elements, and that all will be visible to the homeowner within the ViCare app and to the installer via the ViGuide app, which offers remote monitoring, maintenance and troubleshooting1. No UK pricing or eligibility for government grant schemes is given in the announcement.
Sources1 cited
- Viessmann launches lower output Vitocal ASHP | Viessmann UK, viessmann.co.uk