Central Heating Radiators

Need help choosing a central heating radiator? From radiator types to BTU output and heat pump compatibility, these FAQs cover the key things to know before choosing one.

 

What are central heating radiators?

Central heating radiators connect to a wet heating system, where hot water flows through pipework to each radiator and then back through the system. 

The water may be heated by a boiler or another compatible heat source, such as a heat pump. 

Convector radiators are one type of central heating radiator and use fins to increase the surface area available to warm the surrounding air.

 

What's the difference between Type 11, Type 21 and Type 22 radiators?

The number tells you how many panels and convector fins the radiator has:

• Type 11 Radiators (K1): Single panel, single row of fins. These are slimmer, making them a good choice for rooms with limited space.
• Type 21 Radiators (P+): Double panel, single row of fins. They provide higher heat output without significantly increasing depth.
• Type 22 Radiators (K2): Double panel, double row of fins. These offer greater heat output, making them suitable for larger or cooler rooms.

 

How many central heating radiators do I need?

The number of radiators you need depends on each room’s size and heat requirements. 

Smaller rooms may only need one radiator, while larger rooms or spaces with higher heat loss may benefit from more. 

Calculate the total BTU output needed for each room, then choose radiators that provide enough heat for the space.

Check out our BTU calculations guide if you’re not sure where to start.

 

What size central heating radiator do I need?

The right size radiator depends on the heat output your room needs, rather than the room's dimensions alone. Factors such as room size, insulation, windows, external walls and ceiling height can all affect the required BTU output. 

Once you've calculated the required output, choose a radiator that provides enough BTUs, while still fitting comfortably on your room’s available wall space.

 

Are convector radiators efficient?

Convector fins increase the radiator's surface area, helping transfer heat into the room. How well the heating system performs overall also depends on whether the radiator is the right size for the space, the water temperature, and how the heating is controlled. 

Thermostatic radiator valves can help you control individual room temperatures and avoid heating rooms more than necessary.

 

Can central heating radiators work with a heat pump?

They can, but the radiator needs to give out enough heat at the lower water temperatures commonly used by heat pumps.

As the water temperature drops, so does the radiator's heat output, which means an existing convector radiator may need to be replaced with a larger or higher-output model. Check the room's heat loss and the radiator's output at the temperatures your system will use.

 

How long do central heating radiators last?

There isn't a fixed lifespan for every central heating radiator. How long one lasts depends on the radiator itself, the condition of the heating system and how well it's maintained. 

Rust, leaks or damage may mean replacement is needed, while cold spots or uneven heating can sometimes be caused by trapped air, sludge or another system issue rather than the radiator reaching the end of its life.

We have many radiator maintenance guides on our blog, including how to bleed a radiator and our radiator balancing tutorial.