Underfloor Heating Pressure Drop

The temperature of the water in the underfloor heating pipes is determined by the room temperature that must be achieved at a certain q-value.  This temperature is the mean water temperature.

Underfloor heating systems are normally designed for a temperature drop across the pipe loop of 10 to 15 degree C.  A low temperature drop through the pipe loop provides an even floor temperature.

The water in the underfloor heating system must flow in order to convey heat to the floor.  The size of the water flow is determined by the amount of heat to be conveyed and the designed water temperature drop.

Depending on the interior design of a house, the rooms are different sizes.  This means that the heat requirement will be proportional to the area of each room.  In an underfloor heating system the pipe loops will have different lengths.  Normally, the largest room will have the highest water flow.

In a house there might be different rooms with different heat requirements depending on the location of the rooms, number of outer doors and windows.

In order to dimension the underfloor heating pump capacity for the underfloor heating system, data about total pressure drop and flow must be available.

The total pressure drop can be obtained by adding the pressure drop across:

1. Underfloor heating pipes.

2. Manifolds.

3. The supply and return pipes.

4. Boiler, valves, etc.

An underfloor heating installation with different pipe loop lengths and water flow requirements will have different pressure drops for the different loops.  In order to achieve an even heat distribution between the rooms in the installation the pressure drop of the different loops must be balanced.

In our underfloor heating system this can be done by means of the ‘lockshield’ valves provided on the return manifold.

View our technical documents page for further information or contact us here to discuss your underfloor heating options.