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ANSWERED: How Does a Hydronic Heating Radiator Panel System Work

hydronic heating radiator panel diagram

How Does a Hydronic Heating Radiator Panel System Work

The aim of this article is to help you understand

  • What controls a hydronic heating panel system
  • What a boiler does within a radiator system
  • How we size panels
  • How we choose a panel from many options

A centrally located thermostat of which there is a range of choices is the brains behind a hydronic heating system. When a thermostat control detects that the room temperature has become lower than the target temperature set by programming your control unit Рit will call for heat from the boiler to be pumped through the system until the target temperature is met.


immergas hydronic heating internal gas boiler

The Role of a Hydronic Heating Boiler

In this case, the Immergas internal hydronic heating gas boiler is going to turn on much like an instantaneous hot water system. By burning gas it transfers heat energy into the water.

With panel heating the boiler is set to raise the water temperature to 70C. The boiler has an internal pump which circulates the hot water through the flow and return pipes.

Hydronic Heating Pipework

The flow and return pipes run from and to the boiler, generally down the centre of the home. Each panel then branches off of the flow and return pipes.

The flow and return pipes are much thicker that the branch pipes.

As the water temperature heats up inside the radiator panels, the heat energy is exchanged from the water into the steel panels then radiates into the room.

hydronic heating panel convection diagram

Heat Convection Increases Efficiency

Panels such as our standard range that have convection fins increase the efficiency of the heat energy conversion by creating convection.

Where cool air is drawn up through the fins heating it in the process.

When sizing a panel for a room we need to take into consideration the kW’s required to heat the space, the wall space available, general aesthetics and sometimes stock availability.

How we Size a Hydronic Heating Panel for a Room

From the dimensions of the room we can calculate the kW’s required to adequately heat it.

With the known kW requirement we can now consult our sizing table. There is a sizing table for every type and design of a hydronic heating panel. Each kW rating could match to a large range of panel sizes even in a similar design.

hydronic heating sample panel sizing sheet

At the top of each table you can see that there is a Type number.

  • Type 11 | 1 Radiator Panel + 1 Convection Fin
  • Type 21 | 2 Radiator Panels + 1 Convection Fin
  • Type 22 | 2 Radiator Panels + 2 Convection Fins
  • Type 33 | 3 Radiator Panels + 3 Convection Fins

As you can see from the sizing sheet the same dimensions with different panel type give a large difference in kW output.

The most common size used is a 22 at 600mm high due to its high output without being too bulky. So from the sheet we can see that we would usually choose a 800mm wide unit.

Other considerations are to consider the placement of the panel – how much wall space do you have, is there a good spot under a window.

  • Type 11 – Used in smaller rooms where being slim is the aim
  • Type 21 – Ideal where a higher heat is required but space is at a premium such as entry ways and halls
  • Type 22 – Most commonly used as they aren’t too bulky and give a great output without being too high and wide
  • Type 33 – When a lot of heat is required to meet a kW rating or to get a high rating with the smallest width and height such as under a window or desk where depth isn’t an issue

Each panel has a simple on off valve. So a spare room panel could be turned off for example.

It is ideal to have a thermostatic head on radiator panels in bedrooms.

Feel free to visit our showroom / selection centre

18 De Havilland Rd, Mordialloc 3195

If you have any questions please write them in the comments section so that we can help you and others with similar questions into the future.
2017-09-07T13:26:03+00:00