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Heat pumps are one of the leading alternatives to the gas boilers that are gradually being phased out across the UK and Europe. Since they are a fairly new product, many questions still exist around their use, requirements and compatibility with radiators. We are happy to offer more clarity by answering the 5 most frequently asked questions we received from our customers about combining a heat pump with radiators.

Are your radiators suitable for heat pumps?

The short answer to this question is yes. The slightly more nuanced answer is that the suitability of the radiators depends on the flow temperature of the heat pump system. When the flow temperature drops below 45°C the type of radiator that is suitable to combine with a heat pump changes since there is less natural convection below this temperature level. This leads us seamlessly to the next question.

Which radiators are suitable to use with a heat pump?

When a new heat source is installed and the system temperatures are lowered, it is important that the heat emitters are matched to the new temperature regime. For flow temperatures above 45°C modern panel radiators and designer radiators offer a perfect match for a heat pump in modern buildings. Thanks to technical developments and design measures taken in recent years, radiators are now much more efficient.
For flow temperatures below 45 °C, emitters such as the iVector S2 fan convector or the Ulow E2 heat pump radiator should be used. Their integrated technology supports the natural convection of the radiator to ensure a high heat output, an even heat distribution and optimal indoor climate comfort at all times.

How do I size radiators for a heat pump?

Sizing radiators for a heat pump is no different to sizing radiators for a boiler. First of all it’s important to calculate the heat demand of the various rooms in the building. You can then combine this with other parameters such as the system temperatures and desired room temperature to determine the correct size of the radiator(s).
Delta T plays an important role in ensuring that the emitters are matched perfectly to the heat source and the heat pump system is able to work optimally. 

How much bigger do heat pump radiators need to be?

A general guideline is sometimes enforced that a heat pump radiator needs to be 2.5 times larger than a traditional radiator. However, we would advise against the use of such a guideline as a heating system, including the heat source and the emitters, must be tailored to the building it is installed in and its use.
Naturally the radiators need to be large enough to provide sufficient heat output. Yet modern panel radiators are already very efficient thanks to their innovative design. And if the flow temperatures drop below 45°C, a heat pump radiator or fan convector features the necessary technology to boost heat output, making a larger format unnecessary.

What should I keep in mind when renovating an old building with a heat pump and fan convectors?

The heat demand is a vital factor in the renovation of the heating system with a heat pump. If the insulation of the building has not been optimised prior to the installation of the heat pump, the same heat output must be achieved with lower system temperatures for the heat pump to work efficiently. This is possible with a fan convector. The fan convector operates with a small delta t and requires a high volume flow. Therefore it is important to ensure that the existing pipe network is able to cope with the larger volumes of water so that the fan convector can deliver the required output.

If you have any other questions about combining a heat pump with radiators or would like our advice for setting up a heat pump system in your project(s), don’t hesitate to get in touch with our experts. We are happy to help in any way we can.