Can Air Source Heat Pumps Work With Radiators?

Air source heat pumps are now a popular source of heating in many homes. Prospective buyers often want a confirmation of the output temperatures these units can reach and whether or not they can work with radiators.

Air source heat pumps can work with radiators. However, the number and size of radiators used in conjunction with an air source heat pump must be calculated to ensure that the heat is released efficiently into a home.

Our home uses a combination of radiators and underfloor heating to release the heat generated by our air source heat pump.

The heat pump was installed when the house was built and so the right number and size of radiators were designed and installed. Heat pump systems extract and release heat more slowly compared to traditional heating systems and so correctly designing the radiator system is important.

Air Source Heat Pump
Our air source heat pump works with both radiators and underfloor heating across the home for maximum heating efficiency

We explain more about how air source heat pumps can work with radiators in more detail below.

Can Air Source Heat Pumps Work With Radiators?

Air to water heat pumps will need to be accompanied by radiators and/or underfloor heating with large surface area as part of a central heating system to release the heat most effectively into a home. Small radiators with low surface area may not be adequate.

Air to water heat pumps extract heat from the outside air and transfer that heat to the central heating system, and also potentially to a hot water cylinder for use as domestic hot water.

This heat circulating around a house within the central heating system must be released into a home through an efficient means.

Depending on the outside temperature, air source heat pumps (ASHP’s) may produce lower temperature water and so to be as effective as traditional boiler central heating systems they must be coupled with large surface area appliances such as underfloor heating and modern radiators.

Air to water heat pumps therefore not only work with radiators but radiators are required to release the heat into a home if not using underfloor heating.

For our home, our air to water heat pump works alongside a central heating system that uses both underfloor heating and numerous (and large) radiators to disperse the heat.

Air Source Heat Pump Water Heater Tank
Our air source heat pump delivers heat energy to the indoor components such as this hot water tank before being released across the home through the form of large radiators and underfloor heating
Air Source Heat Pump Radiator
Our heat pump system uses large surface area radiators on the upper floor of our home

If you’re looking to install an air source heat pump into a home with an existing radiator setup, then the installer will help you to understand whether your radiators will need to be upgraded in size or whether more radiators will need to be added.

Air to air heat pumps transfer warm air into a home through a series of blowers and/or ducts and may not work with radiators. See our article comparing air to water and air to air heat pumps for more information.

Explaining The Air Source Heat Pump And Radiator Relationship

Radiators transfer heat from one medium to another. They are designed to draw heat from steam or water, using the heat to warm up the surrounding air. If the radiator is the right size, it can effectively heat a room with this approach.

Radiators are one of the most effective ways of heating a home. They’re still popular in many homes because of their simplicity and how they provide even heating in a space.

On the other hand, air to air source heat pumps are more modern units that work like your standard air conditioner, but in reverse. They bring hot air from the outside and use it to raise your home’s temperature.

An air source heat pump can work harder in situations where the temperature difference the inside and outside is larger.

To help combat using more electricity in such situations when an ASHP is working harder and therefore to help maximize efficiency, air source heat pumps should be coupled with radiators with larger surface area.

Air Source Heat Pump Water Heater Control Panel
The heating in our home is more efficient and effective with the use of large and numerous radiators with large surface area

Small radiators with lower surface area will need higher temperature water for the same heating effect and so a heat pump will need to work harder and use more electricity as a result, reducing the coefficient of performance (COP).

Underfloor heating can also be used alongside radiators, or instead of, when using an air source heat pump as they have a large surface area as standard. See our article on using air source heat pumps with underfloor heating for more information.

Combining air source heat pumps with the right size and number of radiators maximizes even and effective heating across each room.

Combining Air Source Heat Pumps With Radiators

Some installers erroneously believe that air source heat pumps can only work if you have under-floor heating and total insulation in the home. They don’t believe the units can work with radiators and have thus influenced many homeowners with that line of thought. However, this isn’t the reality.

However, many installers know how to combine air source heat pumps outputting temperatures between 40-60 °C (100-140 °F) with radiators to build an efficient heating system.

These professionals calculate your heating needs in line with your home’s R-value to come up with the right radiator and heat pump configuration. Using a scattergun approach in the installation approach can lead to energy wastage.

By combining your air source heat pump with the right size and number of radiators, you can increase the lifespan of the various components. Your heat pump and radiators won’t need to work as hard to maintain your desired temperature as a result.

Air Source Heat Pump Radiator

In general, a heat pump’s primary flow temperature is set to 120 °F (50 °C), so it can supply radiators. Existing radiators may require re-sizing to adequately match the heat pump’s temperatures. The correction factor will vary depending on the size of the radiator.

Can Your Old Radiators Work With An Air Source Heat Pumps?

Existing radiators can work with an air source heat pump. However, they may be too small to complement the system. In this scenario, an installer can recommend a bigger heat pump, increasing radiator size, and adding more radiators to get the desired efficiency level.

Each installation will vary, so it’s best to allow the installer to decide what works for your specific case.

In some cases, adding a second radiator may be more cost-efficient than combining an air source heat pump and a radiator. A professional survey will show you the available options, and the installer will offer advice on the best option to choose.

Remember, the goal is to ensure your home heating is enough to provide just the right amount of heat you need to stay warm, with little to no energy wasted. Also, the perfect arrangement will ensure your units won’t work too hard.

Your air source heat pump has a few moving parts. If it must strain too much to keep your home warm, these parts will wear out much quicker than they should.

Maintaining Radiators For Use With Air Source Heat Pumps

You’ll need to regularly maintain your radiators to ensure it’s at its most efficient. Ideally, you should maintain them once a year. There are a few aspects of maintenance you should carry out:

Bleed the Radiator Air

The pipes in a radiator are closed, but air can escape from the water once in a while. The air will rise to the top of the unit since it’s lighter than water.

You’ll need to periodically get rid of the air to ensure it won’t interfere with the radiator’s heating process. Here’s how to complete the process:

  • Turn off the system and wait for it to cool. This won’t be ideal if you’re in the middle of winter, so you’re better off completing the maintenance before winter arrives.
  • Open the valve on top of the radiator. Opening this valve will release the air. You’ll need a bleed key to open the valve. You can order one at any hardware store. Alternatively, you can use a flathead screwdriver if possible.
  • Put a bowl or rag below the valve. Once you turn the bleed key, you’ll hear the air escaping. As soon as some water starts trickling into the bowl, close off the valve to complete the process. The water in the bowl can look dirty, but that can be no cause for concern.

Check The Pressure

When you’re done bleeding the boiler, the next step is to check the system pressure. It’s best to check the pressure before turning on the unit, as the temperature will alter it.

You can find a gauge for pressure next to the one for temperature in the service panel area.

Air Source Heat Pump Pressure Gauge

Can Air Source Heat Pumps Work With Radiators?

Air source heat pumps can work with radiators. The configuration will come down to variables such as the size of the radiator and the maximum temperature delivered by the air-source heat pump.

Larger sized radiators with greater surface area are most beneficial when coupled with an air source heat pump as the pump can need to work harder when used with smaller sized radiators to increase water temperature for the same heating effect, thus increasing energy costs.

Further Reading

How An Air Source Heat Pump Works

Parts Of An Air Source Heat Pump Explained

Air Source Heat Pumps & Underfloor Heating

Using An Air Source Heat Pump To Provide Hot Water

Do You Need A Hot Water Tank With An Air Source Heat Pump?