Underfloor Heating Controls

Where the boiler plant is being used to provide energy for other services, then it will usually be necessary to mix down the temperature of the water to the underfloor heating system.

This is because underfloor heating operates at temperatures below 65 degree C which is the temperature required to produce water for domestic use or for other forms of heating such as radiators.

On large constructions such as sports halls and similar buildings it is sometimes better to provide a boiler just for the underfloor heating which can then be operated at the required lower water temperatures.

These types of boilers needs to be constructed to operate at temperatures below 50 degree C and are referred to as Condensing boilers.  These Condensing boilers when operating with underfloor heating can return between 95 % and 100 % efficiency on a continual basis throughout the heating season.

If these types of boilers are only serving the underfloor heating system then the controls can be further simplified since there is no need for a mixing valve to reduce the temperature.

Clearly any form of boiler can be used for underfloor heating and the control requirements will vary.  The essence of a good underfloor heating control system must be to combine with the following elements:

- To maintain the desired space temperature

- To maintain the required water temperature

- To maintain periods of operation as required

- To eliminate waste of energy

- To protect buildings against frost damaged

- To ensure full safety in operation

There are many forms of control systems available on the market of which are suitable for the control of our water underfloor heating system.

Underfloor Heating Controls

A value of – 1 degree C for areas in the south of the UK is usually assumed for the hours between 6 am and midnight.  This means that the resulting surface temperature will only be 3 degree C to 5 degree C above the required space temperature.

This much lower temperature is a result of better insulated buildings.  Warm water underfloor heating takes advantage of this to provide a much greater degree of comfort at lower operating costs than more conventional heating.

We must remember that radiant heating is the most natural form of heating and also the simplest.  This means that the heating controls can be considerably simplified and can be applied to whole buildings.

Overheating is far less of a problem with underfloor heating at lower operating temperatures.  This is because a rise in the internal space temperature reduces the temperature difference between the floor surface and the air temperature.

By adding a simple mixing circuit to the underfloor heating system we can further improve the situation by:

1.  Reducing the water circulating temperature when the space temperature increases.

2. Increasing the water circulating temperature when the space temperature declines.

In this way we can fine tune the underfloor heating systems to meet the precise needs of the building irrespective of the space temperature required which can be set independently.

To this mode of underfloor heating control we can also add additional items such as:

- Temperaure sensors

- Timeclocks

- Programmers

- Energy Management Systems

This can extend all the way up to full Building Energy Management Systems (BEMS for short).

All of our standard underfloor heating systems will also have individual zone control to ensure that individual zones or areas can be controlled at different tempertaures or at different times of the day.

Underfloor Heating Response Time

Different factors, all interrelated, affect the response time of an underfloor heating installation:

1. Climate conditions

Climatic conditions vary in different parts of the world.  Water underfloor heating systems are designed to cope with the temperatures of the coldest months of the year.  This implies that the underfloor heating system is designed to work properly during the winter seasons.  The response will, however, be more rapid during the other intermediate months in the beginning and the end of the coldest season.  There will be capacity reserve to improve the response time.

2. Design of the Building

The insulation of a building, the U-value, will complement the performance of the underfloor heating system.  If the building is poorly insulated, which causes indeed a waste of energy, the response time will be affected by the losses.

The floor structure also affects the response time.  In houses with concrete screeded floors, the screed store energy.  There will be an initial retardation of the response time in comparison with wooden suspended floors.

In public buildings the storage effect can be used to save energy at night or during the weekends.  A temperature drop can be accepted when the buidlings are not occupied.  The underfloor heating system can be controlled by programmable digital room thermostat to allow for the system response.

In houses with wooden suspended floors or floating floors, the response time will be rapid since wood has a low thermal mass.  The underfloor heating system should be provided with an infill in order to achieve an even floor temperature on the whole surface of every room.

3. Design and installation of the underfloor heating system

The correct design and installation is crucial as to whether the underfloor heating system will operate satisfactorily or not.  Design aspects such as loop configuration, pipe size, pitch and depth are the base for a correct operation.

Other aspects having influence on the underfloor heating systems performance are the calculated values such as water temperature and required flow rate.  Finally a correct installation and balancing of the loops will ensure the efficient performance of the underfloor heating system.

Underfloor Heating Materials

A standard underfloor heating quote from Underfloor Heating Systems would include;

• Multilayer pipe 16 x 2 mm – PEX/AL/PEX – Made by HENCO in Belgium, one of the largest mulitlayer manufacturer in the World.
• High quality Manifold(s) with flow regulators, on/off valves, filling valves and ball valves.  The manifolds are made in Germany by DUMSER/WATTS to the highest quality possible.
• Control Pack(s) for mixing the water temperature to the underfloor heating system with 6 mGrundfos pump and a Highflow RWC mixing valve. Made in the UK by Reliance Water Controls.
• Heatmiser PRT programmable digital individual room thermostats.  We can also offer Heatmiser PRT Touch Screen room thermostats, wireless room thermostats, etc.  The Danfoss TP5000 Si is available as a surface mounted programmable digital room thermostat for our underfloor heating systems.
• Thermal 230 V actuators to fit on our underfloor heating manifolds.
• Heatmiser UH3 wiring centre will work with both Heatmiser room thermostats and the Danfoss room thermostats.
• Clips for fitting the pipe to the insulation.
• Pipe fittings for connecting to the manifolds.
• Calibration tool and a pipe cutter .

Underfloor Heating Design

A complete underfloor heating installation design includes;

- Specification of the underfloor heating material required.

- Pipe hand sketch drawing.

- Technical information.

The first step before beginning the design and the calculations is to check that all necessary information is at hand:

- Legible and clear drawing of the building, indicating scale.

- Indication where the boiler is placed in the building.

- Underfloor heating manifold position(s).

- How many programmable digital room thermostats are required.

The underfloor heating manifold(s) can serve up to 12 loops.  Manifolds can be located in a cupboard, box-room, below a sink or recessed in a wall with a cupboard cover.

The floor structure must follow the applicable national regulations and standards.  The thickness of the underfloor heating insulation must be homogeneous on the whole area.  Suspended floor structure must be insulated as well.  Always follow the instructions from the manufacturer of the floor covering material.

Design criteria for our warm water underfloor heating systems are normally;

- Inside air temperature is 20 degree C.

- Heat requirement of the house is less than 100 W/sqm.

- Temperature drop across the loop of the pipe is approximately 10 – 20 degree C.

- Pipe centres c/c 250 mm – c/c 200 mm.

- Henco mulitlayer underfloor heating pipe, 16 x 2 mm, PEX/AL/PEX Pipe.

Underfloor Heating

The human foot could be called the body’s thermostat.  In areas with cold winters human beings have been concerned about the floor temperature since ancient times.  This can be observed by the use of rudimentary underfloor heating or covering materials with high specific heat, such as wood floors or carpets.

A basic temperature of 21 degree C on the floor surface gives a comfort feeling.  According to the International Standards Associations ISO7730, the most comfortable range is between 19-26 degree C but underfloor heating systems may be designed for 29 degree C.  It is acceptable to design with higher temperatures in specific areas such as bathrooms and limited areas adjacent to walls.

The essence of a good underfloor heating control system must be to combine the following elements;

- To maintain the desired  space temperature.

- To maintain the required water temperatures.

- To maintain periods of operation as required.

- To eliminate waste of energy.

- To protect building against frost damage.

- To ensure full safety in operation.

There are many forms of control systems available on the market many of which are suitable for the control of our underfloor heating system.

One of the most important thing to remember is that warm water underfloor heating requires much lower temperature than most other forms of heating and in many cases this will mean reducing the temperature from the boiler using our underfoor heating mixing control pack.

Underfloor Heating Installations

Modern underfloor heating installations demand high standards of workmanship backed by a thorough understanding of these systems concept and how it’s principles should be applied in different situations.

Heating engineers used to installing conventional central heating systems will be accustomed to working with radiators, convectors and copper pipes.

Installing underfloor heating is different, for although the boiler or heat source remains unchanged, the materials and methods of heat distribution are completely different.

1. There is a central distribution point, the manifold, at which the copper, plastic or steel connections to the boiler interface with the plastic tubing of the underfloor heating system.

2. Warm water underfloor heating operates with a low temperature water flow and return, unlike radiators or convectors, and this means different controls and pumps.

3. Underfloor heating employs the whole floor as the heating medium, replacing radiators or convectors completely.

Moreover, although, the use of plastic pipes makes the installers physical task much easier, laying an underfloor heating system to be buried in concrete means that his responsibilities are increased immensely, for once the job is completed it is virtually impossible to alter in any way.  Therefore a pressure test of the underfloor heating system is vital before the screed is laid.

The overall efficiency of the underfloor heating system is inherent in it’s design.  However, the installer is solely responsible to the client for ensuring that the design and system criteria are followed to the letter.  Only by adopting a responsible attitude can this be achieved.

Underfloor Heating Temperatures

Since 50 % of the comfort effect is a result of radiation, air temperatures can be little lower with warm water underfloor heating than with other heating methods.  As an example an air temperature of 19 degree C feels very comfortable with underfloor heating, i.e. 2 degree C lower than accepted norm with other heating systems.  Since 1 degree C reduction will normally save as much as 6 % in energy consumption, a 2 degree C could save 10-12 % on the heating bill.

The temperature of the floor surface obviously affects the rate of convection.  If it is only a few degrees above air temperature, the warm air will rise gently and naturally.  Compare this to a radiator system where the surface temperature of each radiator could reach 80 degree C to achieve an air temperature of 20 degree C.  The velocity of hot air rising from such a radiator would be high, sufficient in fact to create dust laden air currents that encourage draughts.  Radiators are inherently dirty, staining walls and prone to creating hot and cold spots within the building they serve.

Underfloor heating is clean, creating low velocity air convection and distributing heat evenly across the entire floor area of the building, eliminating hot and cold spots forever.

By eliminating high velocity convection, underfloor heating cuts out the stratification of heat above head level that prevails with other heating methods.  There is no hot air bulge with underfloor heating.  The vertical temperature gradient created by the system rises evenly to the ceiling and is almost identical to the ideal gradient.

The elimination of this high air temperature above head level can reduce energy consumption by up to 26 % in normal domestic situations.

Underfloor Heating Information

Since the 19th century we have built open grate fires from which most of the energy is directed up the chimney.  We have built cast iron stoves which offered dangerously hot surfaces and often added more than just a little smoke to the room’s atmosphere.  Electric fires have also been used despite the obvious potential danger and the substantial cost required to operate them.  The wall mounted radiator has been around for over 100 years and has been joined more recently by convectors and night storage heaters.

All these systems operate on the somewhat curious assumption that the heat travels sideways.  Incredible though it may seem we have even developed ceiling heating systems designed to heat downwards.

But we forgot a lot more than physics.  The old Roman hypocaust system also offered the benefits of invisibility, silence, true integration with the building and wall to wall warmth without taking up any floor space.  Instead, we have opted for modern systems that are obtrusive, ugly, inefficient and sometimes downright dangerous.  They are expensive to operate and require regular maintenance if their working life is to run into double figures.

The effect in terms of comfort with underfloor heating is completely different from that acheived by any other type of heating system.  Underfloor heating provides 1:1 ratio of convected and radiated warmth, giving a healthier and more pleasurable indoor environment.

Underfloor heating installers

Due to our continuing success and growth we are always looking for potential new  underfloor heating installers.

It can possible feel easy to sell products when the customers know they get reliable high quality products for good prices. However, with a limited number of competent approved installers – and installers not yet covering the complete country – we can only see it a benefit in adding you to our list of approved underfloor heating installers.     Would you be experienced and talented enough to help us install our high quality water underfloor heating systems in your region?

We currently need installers in the North East in particular, however please contact us for more available regions and for  more information about our underfloor heating systems (would you not yet have installed one).