Strebel heat pumps in cascade installation
Air source heat pumps are now a popular heating and hot water solution for a wide range of decarbonisation projects in commercial properties, as the building sector seeks to meet the UK’s net zero commitments.
Established boiler manufacturer, Strebel Ltd, added heat pumps to their product portfolio in 2018. Several product development and enhancements have followed the initial launch and further improved the previous high levels of performance.
The new S-ASX-21 air to water heat pump is available with heating capacities ranging from 60kW to 100kW. The units are suitable for multiple installations of up to 16 units operating in cascade. Seasonal co-efficiency of performance (SCOP) is a key performance measure for all heat pumps and the S-ASX-21 offers a favourable SCOP up to 4.41 at 35⁰C and 3.52 at 55⁰C.
This range benefits from an enhanced vapour injection (EVI) design that, along with a well-matched compressor and refrigerant combination, helps to achieve flow temperatures of up to 65⁰C. EVI also ensures that heat output degradation is minimised when ambient temperatures drop to lower than 0⁰C. Unlike many other rival heat pumps the S-ASX-21 unit can deliver 65⁰C even when ambient falls to minus 22⁰C.
Other standard features include compressor soft start, ModBus connectivity and an integrated fully modulating pump allowing close matching of heat demand to delivery. S-ASX-21 units are of monobloc design, suitable for outdoor installation and integral dampers provide low acoustic performance.
“We saw growth in demand for our heat pumps in 2021 and the early signs are that this will increase further in 2022. The recent performance upgrades we have made provide design engineers, contractors and end users with a high-performing heat pump solution” says Strebel UK National Sales Manager, Adrian Walker.
“The efficiency of a heat pump is of particular importance in keeping running costs at reasonable levels; that’s especially important for businesses and organisations who have traditionally had heating and hot water systems powered by gas-fired products” he added.
Heat pump demand in the non-domestic market sector has been driven by decarbonisation programmes, from both public and private sector clients, where air to water heat pumps have replaced fossil-fuel boiler heating systems.
Hybrid systems
Ultra-low NOx boilers installed as part of hybrid system provides a cost-effective, low carbon option
Whilst heat pumps are particularly suited to new-build projects, a hybrid heat pump and high efficiency gas boiler system can provide a good solution for retrofit in existing buildings. In such instances the heat pumps can be designed to provide the bulk of the heating load with gas boilers providing back-up when outside temperatures fall.
A hybrid system would not always require the upgrading of heat emitters or heating circuits and therefore can provide a cost-effective solution, when compared to a heat pump only system. Not only would such a system reduce initial capital cost, but a well-designed hybrid system will maximise the operational efficiency of the heat pumps, which will assist in keeping running costs under control, while helping to provide major reductions on carbon emissions.
Where gas boilers are to be used, it also makes sense to minimise harmful NOx emissions and install ultra-low NOx boilers as part of the hybrid system. High efficiency boilers such as the Strebel S-FX floor standing or S-CBX wall or frame mounted models both have NOx emissions lower than 24mg/kWh and qualify for the maximum 2 credits on BREEAM projects.
There is little doubt that heat pumps will continue to be at the forefront of the quest towards net zero carbon, but high efficiency, ultra-low NOx gas boilers can also be part of a step-based approach. They also provide the possibility of burning hydrogen or at least a hydrogen blend in the future, which will also provide a further low carbon option.
Strebel UK was established in 1970 since when its products have provided heating and hot water solutions for commercial applications such as schools, university buildings, hospitals, care homes, offices, and multi-residential buildings.
