Unit 317 Session 4a Underfloor heating systems

​The working principles of underfloor central heating system pipework and components

​As we have already seen, underfloor heating works by distributing heat in a series of pipes laid under the floor of a room.
To do this, certain components are required to distribute the flow of heat to ensure that the system warms the room.

​This is achieved by the use of:

● manifolds

● a thermostatic blending valve

● a circulating pump

● various pipework arrangements to suit the floor and

its coverings

● the application of system controls – time and

temperature – to space heating zones.

​The use of manifolds

​In technical terms, the manifold is designed to minimise the amount of uncontrolled heat energy from the underfloor pipework.

The manifold is at the centre of an underfloor heating system.

It is the distribution point where water from the heat source is distributed to all of the individual room circuits, and as such, should be positioned as centrally in the property as possible.

​Typical underfloor heating manifold

​Room temperature is maintained via thermostatic motorised actuators on the return manifold whilst the correct flow rate through each coil is balanced via the flow meters on the flow manifold.

​The thermostatic mixing (blending) valve

The thermostatic mixing or blending valve is designed to mix the flow and return water from the heat source to the required temperature for the underfloor heating circuits.

The circulating pump

The circulating pump is situated between the thermostatic mixing valve and the flow manifold to circulate the blended water through every circuit. Most models are variable speed.

​Underfloor heating circulating pump/blending valve module

​Underfloor heating pipework arrangements

​The success of the underfloor heating system depends upon the installation of the underfloor pipework and the floor pattern installed.

There are many variations Underfloor heating pipework arrangements of pipe patterns based upon two main pattern types.

These are:

● the series pattern

● the snail pattern.

​The series pattern

The series pattern (also known as the meander pattern) is designed to ensure an even temperature across the floor especially in systems incorporating long pipework runs.

It is often used in areas of high heat loss.

​The snail pattern

The snail pattern (also known as the bifilar pattern) is used where an even uniform temperature is required such as under hardwood floors and vinyl floor tiles.

Multiple Choice

Can you name the underfloor heating pipework pattern shown in the picture?

• Snail pattern

• Series pattern

• Snake pattern

• Manifold pattern

Multiple Choice

Can you name the underfloor heating pipework pattern shown in the picture?

• Snail pattern

• Series pattern

• Snake pattern

• Manifold pattern

​Pipework arrangements (cabling)

There are many variations to these two basic layouts.

The pattern should be set out in accordance with the orientation and the shape of the room.

Window areas may be colder and may require the bulk of the heat in that area.

Other considerations include the type of floor construction and the floor coverings.

The pipework should be laid in one continuous length without joints.
It is recommended that no loop should exceed 100 m.

​Solid floor

There are many types of underfloor heating installation techniques for a solid floor.

The drawing above shows one of the more common types using a plastic grid where the underfloor heating pipe is simply walked into the premade castellated grooves. Another popular method is the use of plastic clips/staples.

​Research task

Open Ended

Research how we install underfloor heating in suspended timber floors, please use images to back up your work.

​As seen in the video, installation under a poured screed floor is the most common method of underfloor heating, however there are methods that allow installation under Suspended timber floors.

​Suspended timber floor

This system is designed for use under timber suspended floors. It uses aluminium double heat spreader plates to transmit heat evenly across the finished floor surface.

This system is suitable for any timber suspended floor with joist widths up to 450 mm.
The heat plates are simply fixed to the joists using small flat headed nails or staples.
A layer of insulation must be placed below the plates to prevent the heat penetrating downwards.
Where the pipework must cross the joists, the joists must be drilled in accordance with the Building Regulations.

Multiple Choice

What is the central distribution point where water from the heat source is distributed to individual room circuits in an underfloor heating system?

• Thermostatic blending valve

• Circulating pump

• Manifold

• Pipework arrangements

Multiple Choice

The purpose of the thermostatic mixing (blending) valve in an underfloor heating system is to:

• Mix the flow and return water for the heat source

• Control the room temperature

• Circulate water through every circuit

• Balance the flow rate

Multiple Choice

The success of an underfloor heating system depends on:

• The type of floor construction

• The floor pattern installed

• The circulating pump model

• All of the above

Multiple Choice

Which pattern type is designed to ensure an even temperature across the floor, especially in systems with long pipework runs?

• Series pattern

• Snail pattern

• Serial pattern

• Bifilar pattern

Multiple Choice

The snail pattern is often used under which types of floor coverings?

• Hardwood floors

• Ceramic tiles

• Carpeted floors

• Suspended floors

Multiple Choice

What is the recommended maximum length for an underfloor heating loop?

• 50 m

• 75 m

• 100 m

• 150 m

Multiple Choice

For timber suspended floors, what is used to transmit heat evenly across the finished floor surface?

• Plastic clips

• Castellated grooves

• Aluminium double heat spreader plates

• Plastic grid

Multiple Choice

What must be placed below the heat spreader plates in a timber suspended floor to prevent heat penetration downwards?

• Insulation

• Vapor barrier

• Joists

• Radiant barrier

Using the drawing given (Also on the next slide)
Draw a suitable underfloor layout, remember you cannot cross pipework runs.
The manifold is to be installed in the 1m² 'St' area near the centre of the bungalow.

Once you have designed the pipework layout, produce an estimate for the system including the manifold and all required components.
Assume the pipework feeding the manifold is already present.