PHAM NEWS | APRIL 2025 28 Radiators & Towel Warmers


Optimising radiators to work with heat pumps


With the increasing push towards energy-effi cient heating solutions, heat pumps are becoming a popular alternative to traditional gas and oil boilers. However, for a heat pump to work eff ectively, the entire heating system, especially the radiators, must be optimised to operate at low temperatures. John Klee from BestHeating looks at some of the key things to consider.


S


tandard radiators designed for high- temperature systems may not provide adequate heat output


when paired with a heat pump, meaning thought must be given to radiator size, material, and system balancing. So what should be the key considerations when fi tting new radiators for a heat pump system?


Size and surface area One of the biggest diff erences between a traditional boiler system and a heat pump is the fl ow temperature. Installers will know that conventional boilers typically operate at fl ow temperatures of 70–80°C, whereas heat pumps run at much lower temperatures, generally between 35–45°C depending on the external conditions. Since heat output is directly


related to temperature diff erence (Delta T), it’s important to educate customers that radiators need to be larger to compensate for the lower temperatures. However, while heat pumps do operate at lower fl ow temperatures, existing radiators can still provide suffi cient heating if they are appropriately sized and matched to the heat pump’s output. When designing a radiator


system for a heat pump, work with customers to calculate the required radiator size based on Delta T20 to ensure the radiator supplies suffi cient heat output at a fl ow temperature of around 40°C, with a return temperature of 30°C. This typically requires increasing the radiator surface area by two and a half times compared to a system designed for a traditional boiler. There is also the option to upgrade to low-temperature radiators, such as aluminium models or fan-assisted convectors, to further improve effi ciency.


Radiator materials The material of a radiator signifi cantly impacts its heat output and responsiveness. Traditional cast iron radiators, while aesthetically pleasing, have a high thermal mass and take longer


to run smoothly and keep homes warm and comfortable.


Additional considerations Beyond radiator selection and system balancing, there are a few other key considerations to ensure a successful installation:


John Klee Heating technology expert at BestHeating


to heat up and cool down. This can be ineffi cient when used with heat pumps, which work best with radiators that can respond quickly to changes in demand. Aluminium radiators are an


excellent choice for heat pump systems due to their superior thermal conductivity and many customers are opting for these now anyway in light of a growing trend. They heat up quickly, distribute heat evenly, and work well at lower fl ow temperatures. Steel panel radiators are also a good option, off ering a balance between cost and effi ciency. Helping customers choose the right radiator material can eff ortlessly enhance system performance and improve overall comfort.


System balancing To get the best performance from a heat pump system, it’s important to have a well-balanced heating system. Unlike traditional boilers, which can overcome poor system balancing by running at higher temperatures, heat pumps require precise water fl ow rates to distribute heat evenly across all radiators. A heating professional can


adjust radiator valves to ensure each room gets the right amount of warmth, preventing cold spots and ineffi ciencies. In some cases, upgrading pipework may be necessary to maintain proper fl ow rates, helping the heat pump


Insulation and heat loss Heat pumps work best in well insulated homes so ensuring adequate insulation and minimising heat loss will help maintain comfort without overloading the heat pump.


Thermostatic and smart controls Using thermostatic radiator valves (TRVs) and smart heating controls can optimise heat distribution and improve energy effi ciency by adjusting temperatures based on occupancy and room usage.


Fan-assisted radiators In some cases, particularly in smaller homes, fan-assisted radiators can be used to boost heat output without requiring larger radiator sizes. These models contain small fans that enhance convection and improve heat transfer at lower fl ow temperatures.


Underfl oor heating If space is a concern, combining radiators with underfl oor heating can provide an eff ective solution for heat pump systems, distributing warmth more evenly throughout the home.


Planning ahead In summary, for a heat pump system to work at its best, there needs to be careful planning to ensure compatibility with the lower fl ow temperature characteristic of heat pumps. Increasing radiator size, selecting effi cient materials like aluminium or steel, ensuring proper system balancing, and optimising fl ow rates are all critical factors for success. By taking these steps, installers can create an effi cient, comfortable heating system that maximises the benefi ts of heat pump technology. ◼ phamnews.co.uk/425/40


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