Baxi
The Baxi Assure HP55 is an R290 monobloc heat pump offering up to 13.5kW output, a 5.34 SCOP at 35°C, and a 75°C maximum flow temperature for UK domestic retrofits.
The Baxi Assure HP55 is a high-temperature monobloc air-source heat pump range designed for the UK domestic market. Utilizing R290 refrigerant, the series offers nominal outputs from 4.4kW to 13.5kW across single and three-phase variants. With a maximum flow temperature of 75°C and an A+++ ErP rating at both 35°C and 55°C, these units are engineered for both new builds and retrofit applications where higher water temperatures may be required for existing emitters.
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Full technical specifications extracted from the manufacturer brochure. Empty sections are hidden.
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The Baxi Assure HP55 series represents a significant shift toward natural refrigerants in the UK heating sector. By employing R290 (propane), which has a Global Warming Potential (GWP) of just 3, this monobloc range achieves high efficiency while meeting stringent environmental standards. The lineup includes seven distinct variants, ranging from the entry-level 4.4kW model (Assure HP55-4-1-PHMB) to the high-capacity 13.5kW three-phase unit.
Performance metrics are notable for the UK climate. The system maintains operation down to outdoor temperatures of -25°C. At a 35°C flow temperature, the unit achieves a Seasonal Coefficient of Performance (SCOP) of 5.34, while at 55°C, it maintains a SCOP of 3.99. These figures ensure the range carries an A+++ ErP rating across both low and medium-temperature applications. The ability to reach a 75°C maximum flow temperature is particularly relevant for retrofit projects where radiator sizing might otherwise limit heat pump feasibility.
Physical installation requirements for the outdoor unit involve a chassis measuring 1301mm in width, 725mm in height, and 426mm in depth. The unit weighs 94kg and requires specific clearances: 500mm at the sides, 1000mm at the front, and 300mm behind the unit to ensure adequate airflow. For hydraulic integration, Baxi specifies that both a buffer tank and a volumiser are required to maintain system stability and defrost performance. The defrost mechanism utilizes a reverse cycle method, which is automated based on system requirements.
Electrical configurations vary by model. The standard residential units operate on a single-phase 230V supply with a recommended 16A MCB rating for the smaller capacities. For larger domestic or light commercial loads, 11kW and 13.5kW three-phase (380-415V) variants are available. Control is managed via the Baxi ASHP Control or the uSense 2 Smart Thermostat, with full OpenTherm compatibility for enhanced modulation.
The range is MCS certified and eligible for the Boiler Upgrade Scheme (BUS) grant. Sound performance is a key consideration for planning; the unit produces a sound power level of 48 dB(LwA) and a sound pressure level of 40 dB at one meter. A quiet mode is also available to further reduce noise during sensitive hours. Standard warranty coverage is two years, extendable to seven years subject to manufacturer terms and registration.
Common questions from engineers and homeowners about the Baxi Assure HP55.
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Specifications on this page are extracted from the manufacturer brochure. Always cross-check against the latest datasheet before commissioning or quoting. Last updated 30 April 2026.