Baxi
The Baxi HP60/HP55 is a monobloc air source heat pump with a nominal capacity of 4.4 kW, using R290 refrigerant, and achieving an A+++ ErP rating at both 35°C and 55°C.
The Baxi HP60-4-1-PHMB and Assure HP55-4-1-PHMB are monobloc air source heat pumps designed for domestic heating in the UK. This page provides a comprehensive technical overview for heating engineers, covering detailed specifications, performance data, and installation considerations. Homeowners researching heat pump options will also find essential information regarding efficiency, sound levels, and compatibility. BoilerTag aims to be the definitive reference for these Baxi models, ensuring accurate and up-to-date information for both installation and servicing.
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Full technical specifications extracted from the manufacturer brochure. Empty sections are hidden.
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The Baxi HP60-4-1-PHMB and Assure HP55-4-1-PHMB are monobloc air source heat pumps specifically engineered for domestic heating applications across the UK. These units are distinguished by their use of R290 (propane) refrigerant, which possesses an ultra-low Global Warming Potential (GWP) of 3, with a refrigerant charge of 0.7 kg. This environmentally conscious choice aligns with stringent F-Gas regulations and ensures the system is future-proofed against evolving environmental standards.
According to the manufacturer's technical datasheet, the nominal heating capacity at an outdoor air temperature of 7°C and a water flow temperature of 35°C (A7W35) is 4.4 kW. It is important to note that while the model numbers might imply higher outputs, the performance table within the documentation indicates this specific capacity. The heat pump demonstrates versatility by being capable of delivering a maximum flow temperature of 75°C, making it a viable option for integration with various emitter systems, including existing radiator setups that may require higher temperatures.
Efficiency is a core attribute of these Baxi models, evidenced by a Seasonal Coefficient of Performance (SCOP) of 5.34 at 35°C and 3.99 at 55°C. These high SCOP values contribute to an A+++ ErP rating for both low and medium temperature applications, signifying exceptional energy performance over an entire heating season. This translates directly into reduced operational costs for the end-user.
From a physical installation perspective, the outdoor unit measures 725 mm in height, 1301 mm in width, and 426 mm in depth, with a total weight of 94 kg. Precise installation requires specific minimum clearances: 500 mm to the sides, 1000 mm to the front, 300 mm above, and 500 mm behind, ensuring adequate airflow and service access. The unit operates on a standard 230V, 50Hz single-phase electrical supply, necessitating a 16A MCB for protection. Hydraulic connections are designed for 25.4 mm (1 inch) pipework, with the system capable of handling a maximum operating pressure of 3 bar.
Sound emissions are carefully managed to minimise disturbance. The unit has a sound power level (LwA) of 48 dB and a sound pressure level of 40 dB at 1 metre. Furthermore, a quiet mode is available, allowing for reduced noise operation during specific periods, which can be particularly beneficial in residential areas or during night-time hours. For user control and monitoring, the heat pump is compatible with the Baxi START App, offering modern connectivity. An extended warranty of 7 years is provided, subject to specific terms and conditions, offering long-term assurance and peace of mind for homeowners and installers alike. Compatibility extends to Baxi ASHP Pre-plumbed Cylinders and other dedicated ASHP Cylinders, facilitating seamless system integration for domestic hot water production.
Common questions from engineers and homeowners about the Baxi HP60-4-1-PHMB and Assure HP55-4-1-PHMB.
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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.