Type 11, 21 & 22 Radiators - What's The Difference?
- Feb 19, 2024
- 4 min read
Updated: 2 days ago
The difference between type 11, 21 and 22 convector radiators is important to know to ensure you're buying the correct radiator to heat your room properly.
Type 11, Type 21, and Type 22 are all different configurations of central heating radiators, distinguished by the number of panels and fins they possess. The "Type XX" designation typically describes the number of panels and fins within the radiator.
Before going into the differences between Type 11, 21 and 22 radiators, it is also important to know what we mean when we talk about convector radiators and convection heating.
What is a Convector Radiator & Convection Heating?
Convection heating is the indirect transfer of heat to an area via the movement of liquid or gas, which in the case of home heating, relies on the movement of air. Warm air rises and displaces the cold air in the room down towards the radiator. This cold air is then heated, which then rises, repeating the cycle.
Convector radiators are any radiator that heats a room by this method of convection, achieved by 'sandwiching' layers of fins between panels in various arrangements.
These types of radiators heat these fins, which then heat the body of air within the radiator. This warm air then escapes through vents at the top of the radiator itself, heating the room in the process.
Radiator Types & Trade Names: At a Glance
Industry Standard | Pro/Trade Name | Description | Width/Depth Profile |
Type 11 | K1 | Single Panel, Single Convector | Slimmest (ideal for halls) |
Type 21 | P+ | Double Panel, Single Convector | Mid-range depth |
Type 22 | K2 | Double Panel, Double Convector | Deepest (max heat output) |
What is a Type 11 (K1) Radiator?
This radiator has one panel and one set of fins and is the simplest configuration.
The single panel allows for a relatively slim profile, making it suitable for spaces where wall space is limited.
While it may be less powerful in terms of heat output compared to radiators with more panels and fins, it's often chosen for its space-saving design.
What is a Type 21 (P+) Radiator?
Type 21 radiators feature one set of fins between two panels.
The extra panel increases the heat output compared to Type 11 radiators, making it more suitable for larger rooms or rooms with greater heat loss.
It still maintains a relatively slim profile compared to radiators with more panels and fins.
What is a Type 22 (K2) Radiator?
This radiator has two panels and two sets of fins.
With the additional set of fins, Type 22 radiators offer even greater heat output compared to Type 21 radiators.
They are suitable for larger rooms or spaces where more heat is required, but they are bulkier compared to Type 11 and Type 21 radiators.
Frequently Asked Questions about Radiator Types
Can I replace a Type 11 with a Type 22?
Yes, as long as you have enough wall clearance. A Type 22 is significantly deeper (thicker) than a Type 11. While the pipe centres (width) might be the same, the radiator will sit further out into the room. Always check the "projection from wall" measurement before upgrading.
Is a Type 21 warmer than a Type 11?
Yes. Because a Type 21 has an extra water panel, it has a larger surface area and typically a higher BTU output. It will provide more heat than a Type 11 of the same physical height and width.
Which radiator type is best for a small hallway?
A Type 11 (K1) is usually best for hallways. Because hallways are often narrow, the slim profile of a single-panel radiator prevents it from becoming an obstruction while still providing enough heat for a transitional space.
Do Type 22 radiators use more water?
Yes, Type 22 radiators hold more water than Type 11 or 21 models because they have two internal panels. This means your boiler will work slightly harder to heat the initial volume of water, but the radiator will also stay warm for longer once the heating is turned off.
The choice between these types of radiators depends on factors such as the size of the room, the level of insulation, and the desired heat output. Type 11 radiators are often preferred in smaller spaces or where a sleeker design is desired, while Type 21 and Type 22 radiators are usually chosen for larger rooms or areas with greater heating requirements.
