What is the difference between a Type 11, Type 21 and Type 22 radiator?

When you’re buying a compact central heating radiator, there are three common ‘types’ – to heat your room correctly and efficiently, it’s important to understand the difference.  If you’re not a plumber or heating engineer, you’ve probably not heard of the different ‘types’ of convector you can buy, but if you’re replacing an existing radiator or having a new one installed, now is a good time to make sure you’re buying the right one.

What’s a convector radiator?

One of the most common types of radiator you’ll find in British homes today is the convector radiator.  Either behind the front panel, or in between the front and back panels are a series of metal ‘fins’ which are heated by the radiator panel, and transfer heat to the air within and around the radiator.  This air then rises, and the process continues.  Many convector radiators now have a grille at the top, so you’ve probably not even noticed the fins before.

Type 11 Radiator

Type 11 Radiator diagram

The slimmest of the three sizes is the Type 11, which has a front panel and one set of fins behind.  Sometimes called a K1 type, this design gives out the lowest heat, but is also much thinner than type 21 and type 22 radiators, so is perfectly suited to rooms where space is a premium.  They’re also useful when you don’t need a high heat output – such as in a cloakroom or ensuite bathroom, or as a secondary radiator in a large room.

View our Type 11 radiators

Type 21 Radiator

Type 21 Radiator diagram

Similar to a type 11 radiator, the type 21 has a single set of fins, but this time they’re encased between two panels – one at the front and one at the back.  This gives a higher heat output than the type 21, but increases the depth of the radiator.  Type 21 radiators are great for bedrooms, where you’ll usually need a good heat put (look for the BTU ratings on our website), but where you need to keep an eye on the depth of your radiators so they don’t eat too much into the space.

View our Type 21 radiators

Type 22 Radiator

Type 22 Radiator diagram

With two sets of fins, and both front and back panels, the Type 22 convector radiator gives the highest heat output of the three sizes.  It’s also the widest size, usually being around 30mm wider than a type 21, and is most suited to larger rooms with more space to heat.  This size might look bulky or clunky in a small room, but on larger walls you’ll rarely notice the difference.  If depth is a concern, consider a type 21 radiator but in a slightly longer or higher size to match the heat output.

View our Type 22 radiators


    • Manissa Limited on November 13, 2022 at 8:52 pm

      Type 11 radiators are single panels with a convector on the back
      Type 21 radiators are double radiators with a single convector on the back
      Type 22 radiators are double radiators with 2 convectors on the back