PHAM NEWS | MAY 2026 Hybrid HeatingSystems


It’s the little things that matter


Reliable performance of hybrid heating systems depends on correct system design and the use of supporting components to manage fl ow, protect against freezing and maintain effi ciency across mixed technologies. Ed Morris from Altecnic explains how ancillary components improve system performance and resilience.


heating systems are becoming an increasingly practical option for domestic properties. By combining air source heat pumps with traditional gas boilers, hybrid systems off er homeowners fl exibility, effi ciency and reassurance during periods of high demand or low ambient temperatures. However, achieving reliable


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performance from a hybrid system relies on more than just the heat sources themselves. Correct system design and the selection of appropriate ancillary components play a critical role in protecting equipment, managing mixed fl ow temperatures and ensuring long-term effi ciency. Heat pumps typically operate


at lower fl ow temperatures, while boilers are designed to deliver higher temperatures to meet peak demand. This variation places additional demands on the system, making eff ective control, protection and hydraulic balance essential. Without suitable ancillaries in place, issues such as ineffi cient heat transfer, uneven fl ow rates, contamination and freezing can all compromise system performance.


Stopping freezing One of the most important considerations when supporting a heat pump within a hybrid system is protection against freezing. External pipework and heat pump connections are particularly vulnerable during colder weather, especially when systems are exposed to prolonged low temperatures. Anti-freeze valves are designed


to safeguard these components by discharging system water when temperatures fall to a critical level, preventing damage caused by freezing. For hybrid


s the UK heating market continues its transition towards low-carbon solutions, hybrid


installations where higher system temperatures may be present, selecting the correct specifi cation is essential. To address this requirement,


Ed Morris Technical manager at Altecnic


Altecnic off ers the iStop High Temperature anti-freeze valve, specifi cally engineered for applications where elevated fl ow temperatures are expected. Installed on the external fl ow and return pipework, the valve opens at temperatures below 3°C to safely discharge system water, preventing ice formation and protecting both the heat pump and associated pipework. Once


temperatures rise above 4°C, the valve automatically closes to avoid unnecessary water loss. By selecting a high-temperature


rated solution, installers can ensure reliable freeze protection without compromising system compatibility or performance.


Flow and effi ciency Hybrid systems also require accurate fl ow control to accommodate varying demands across diff erent heating circuits. An automatic dynamic balancing valve is particularly benefi cial in these installations, ensuring that each emitter receives the correct fl ow rate regardless of pressure fl uctuations within the system. Using a fl ow-settable,


...performance from a hybrid system relies on more than just the heat sources themselves


Caleffi XF semi- automatic


self-cleaning magnetic dirt separator


pressure-independent thermostatic radiator valve (TRV) allows precise hydraulic balance to be maintained across the system. This not only improves comfort levels within the property but also reduces stress on the heat pump compressor, helping to extend its working life and maintain effi ciency. Altecnic’s Dynamical TRV


provides installers with a reliable solution for managing fl ow rates within hybrid systems, supporting stable operation across mixed temperature circuits.


Keep it clean Contamination from dirt and air is another key challenge in hybrid heating systems. Debris circulating within the system can accumulate on heat exchangers and internal components, reducing heat transfer effi ciency and increasing energy consumption. Trapped air can also cause noise, corrosion and uneven heating performance. The installation of a combined


Caleffi Dynamical thermostatic radiator valves provide a reliable solution for managing fl ow rates within hybrid systems


dirt and air separator is therefore essential. In heat pump applications, particular attention must be paid to fl ow rates to


ensure optimal separation without excessive pressure loss. The Caleffi XF heat pump


magnetic fi lter, available from Altecnic, has been designed with heat pump and hybrid installations in mind. Adjustable by-pass options on larger sizes allow installers to manage fl ow rates eff ectively, while the unit’s design enables maintenance to be carried out without shutting down the system.


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Caleffi iStop Anti-Freeze Valve featuring 1" threaded connections designed to protect heat pump systems from freezing


Long term performance Hybrid heating systems off er a practical pathway towards lower- carbon heating, combining the effi ciency of heat pumps with the reliability of traditional boilers. However, their success depends on careful system design and the correct selection of supporting components. By incorporating high-quality


ancillaries such as high- temperature anti-freeze valves, dynamic balancing valves and dirt and air separators, installers can improve effi ciency, protect key components and extend system lifespan. As hybrid systems continue to gain traction across the UK, ancillaries will remain a vital element in delivering reliable, effi cient and futureproof heating solutions. ◼ phamnews.co.uk/526/37


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