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UFH System Basics The majority of modern UFH systems are warm water systems, which integrate high tech plastic pipe either within or just below the floor. Normally, water at a temperature of 47-62°C is circulated through this pipe and this warms the floor to a surface temperature of 25-28°C, about the same temperature as the palm of your hand. The heat generated by radiators is transferred from a small surface area far hotter than the space it is heating. By comparison, UFH transfers heat from a very large surface area, which is only slightly warmer than the room. Modern UFH systems are economical to run, virtually maintenance free and utilise effective controls. They provide the most comfortable all round warmth of any heating system. In concrete floors, it is usual to set out the heating pipe or cable on top of insulation before the screed covers the pipe and completes the floor construction. Hot water is pumped from the boiler to the Speedfit Pump Pack, where the water is mixed to approximately 50°C via the unique mixing valve before being pumped to the manifold. The Speedfit PEX pipe is connected to the manifold from where it runs out to the heating circuits. The pipes are embedded into the solid screeded floor, which can be covered with almost any finish. The system is controlled by one or more thermostats, which signal the Pump Pack when heat is required.
How Does Underfloor Heating Work? Underfloor Heating is not new, the principles go back to Roman times. In Europe it is the system of choice and in some countries accounts for 70% of new heating installations. A radiator system transfers energy into the room largely by convection. This convection results in the floor being the coolest part of the room and leaves a mass of warm air at ceiling level. It also picks up fine dust from the floor and distributes it into the air and over the furnishings. This can mean that much of the energy, which had been put into the room, is wasted and not in the area you want it to be.
A UFH system heats mainly by radiation. This is the most natural and comfortable form of heating - just like the sun. Radiant energy emitted by the floor is partly reflected by each surface and partly absorbed. Where it is absorbed, that surface becomes a secondary emitter. After a while, all surfaces become secondary emitters. Furnishings themselves radiate energy and the room becomes evenly and uniformly warmed. The energy reaches into every corner of the room - no cold spot, no hot ceilings and no cold feet.
When compared to other forms of heating, the overall effectiveness of a UFH heating system can be seen below. The heat is concentrated where it is most needed for human comfort and energy efficiency.
Features & Benefits The Speedfit Underfloor Heating System offers many benefits to the consumer. Some of these are shown below. Installation It is simple to install, requiring the minimum of effort and little maintenance. Comfort The system uses radiant heat, which is the most comfortable form of heating. Space The system is unobtrusive and space saving which means that every square metre of floor and wall space can be fully utilised giving freedom of interior design. Noise Compared to radiator systems the UFH system is virtually silent running. Health Dust is minimised and reduces house dust mites. Reduced numbers of hot surfaces and sharp edges reduce the risk of burns or injury. Economy The system reduces energy consumption and the loss of heat from the building surface is reduced. Control The system is easy to control and the small temperature difference between the floor and the air means that the system is virtually self-regulating. Environment Underfloor heating is suitable for use with the most energy efficient and environmentally friendly heating systems including condensing boilers, solar power and heat pumps.
DESIGN Solid Floor Installation Principles The Speedfit Underfloor Heating System is designed to be installed into a solid floor with a screed. Because the screed is in direct contact with the heating pipes there is excellent heat transfer, an even distribution of heat and reduced temperature fluctuation. A typical installation will consist of:
The floor insulation is an integral part of any UFH installation in a solid floor. Speedfit recommend that expert guidance be obtained to ensure the products used are suitable for underfloor heating and comply with current regulations. For assistance, please refer to the section of this site referring to the Speedfit Technical Advisory Service.
Design Considerations The design and calculations for a UFH System in a solid floor should be conducted in accordance with BS EN 1264 and the details given on this site are based upon this standard. There are a number of important issues relating to the Speedfit Underfloor Heating System which should be considered before commencing a project:
These are described below. Heat Sources Due to the lower flow temperatures used in UFH, typically 47° - 62°C, a variety of heat sources other than a standard wall mounted boiler can be considered. These include Solar Power, Heat Pumps or Geothermal Systems and Speedfit recommend specific advice be sought from relevant manufacturers. Additional pumps may affect some boilers - check compatibility with the boiler manufacturer prior to installation. Manifold Location The installation and balancing of an underfloor heating system is easier if the manifold is located near to the centre of the building. This will mean circuit loops are as equal as possible. Heat Outputs and Floor Temperatures Due to the number of different floor construction methods, it is difficult to provide precise heat outputs. Current standards maintain the maximum output for any UFH system laid into a solid floor is approximately 11 Watts/m²/K, where K is the difference in temperature between the surface of the floor and the desired room temperature. This takes into account human medical limits and sensitivity to heat of the building's occupants. Practically, with the Speedfit Underfloor Heating System, an output of approximately 100 Watts/m² can be achieved from a floor surface temperature of 29°C with an air temperature of 20°C. In certain cases, it is possible to allow higher floor surface temperatures such as in bathrooms (33°C), infrequently used rooms or perimeter zones (35°C). Screeds The screed is an important and integral part of a UFH system and it is used to transfer the energy from the pipes to the heated area. This thermal mass, as it is referred to, will respond to the heating demand depending on its depth and make up. Generally, most hand applied traditional sand/cement screeds are 65 - 75mm thick. However, when advising on a specific project, details of the type and depth of screed, if known, will be required. More modern pumped screeds are available which offer advantages in terms of speed of application and curing time. It is also possible that screed depths can be reduced and this will assist in the performance of the underfloor heating system. Speedfit advises that expert guidance is obtained from a screed supplier to ensure that the correct products are specified and used for your underfloor central heating system. For assistance, please refer to the section of this site referring to the Speedfit Technical Advisory Service. Floor Finishes & Covering The Speedfit Underfloor Heating System is suitable for almost any floor finish including ceramic tiles, carpet, vinyl and laminate. Since the floor covering is essentially part of the heating system, the thermal resistance or insulation ability of the floor finish will affect the output from the floor. The higher the resistance, the lower the heating effect and the longer the warm up time. The most suitable coverings are those with low thermal resistance, normally referred to as the R-value or TOG value. The recommended maximum R-value is 0.15m²K/W (1.5 TOG) and the table below gives some typical values.
Ceramic Floor Tiles Ceramic Tiles work well with UFH as they provide minimal resistance to heat transfer. To avoid cracking of the tiles flexible adhesive and edge joints should be used to accept the expansion. Check that the adhesive is suitable for use with UFH. Carpets Carpet and underlay represent higher levels of resistance to heat transfer. Avoid the use of felt, corks and thick rubber underlay as their insulation properties reduce the heat output of the system. If carpet adhesive is to be used, make sure it is suitable for temperatures up to 40°C. Plastic/Vinyl Tiles Plastic based flooring also works well with UFH as there is generally minimal resistance to heat transfer. It is important that the covering and adhesive used are suitable for use up to 40°C. This reduces the risk of softening and loss of adhesion. Timber/Wooden Floors Timber floor coverings work well with UFH. However, as a natural material, it is important to follow the recommendation of the floor manufacturer regarding installation and initial start up. Timber floors should generally have a moisture content greater than 10% and when installing with a screeded floor the screed must be fully cured before the covering is installed. Following curing the system should be run for approximately 2 weeks with the materials in the area before installation occurs. This reduces the moisture in the area and allows the material to acclimatise. We advise that specific information should be obtained from the proposed covering supplier or manufacturer to assess the suitability of the covering for underfloor heating. Perimeter Areas Under certain circumstances, it is possible to achieve higher floor temperatures and therefore higher outputs than are normally permissible. This may be in an unused living space or an area permanently covered by furniture. This is achieved by reducing the pipe spacing to approximately 100mm along the perimeter of the room (to an approximate width of 1 metre). For example, the perimeter pipe spacing could be used where the external wall of the room has a high proportion of windows, which may give a higher local heat loss. Controls As with all heating systems, suitable controls are required to achieve comfort condition, maintain economic operation and to comply with Building Regulations and British Standards. Underfloor heating systems can be used as the sole heating system or be linked to other appliances such as radiators. There are many ways to control an underfloor heating system and almost any boiler can be used including combination and condensing types. Manufacturers' installation advice should be sought on specific boilers. Whilst UFH has many advantages over traditional systems they are not quite as responsive. As they are most efficient in constant operation, it is good practice to provide controls which can "set-back" the temperature in an area by 4 - 5°C during periods of low demand such as night time rather than turning the system completely off. Normally, room thermostats are used to control the actuator valves on the Speedfit manifold, these in turn control the flow of water in each loop. Controls can be split into 3 main categories: 1. Flow Temperature Controls Unless a condensing boiler with a low temperature control is being used, for most underfloor heating systems the water temperature from the boiler, normally 82°C, is reduced to the required temperature using a mixing valve. More advanced controllers, called weather compensators, use an external sensor and programmer to adjust flow and temperature to compensate for outside conditions. It is important to have a device to control the boiler and pump to prevent flow temperature exceeding safety limits. The Speedfit Pump Pack is fitted with an integral limit thermostat. 2. Comfort Controls Room thermostats are used to control the air temperature in a room or area and are wired back to the control centre to enable individual pipe circuits to be opened or closed and to turn the pump/boiler on or off as required. Rooms can be controlled individually or in zones of 2 or more rooms. There are a wide variety of room thermostats suitable for underfloor heating systems. These include electro mechanical, digital and programmable. Models can be hard-wired or controlled by radio frequency. All types of controls are suitable for connection to the Speedfit Control Centre. Programmable Room Thermostats offer total control of the UFH system. Each zone or room can be set with its own requirement and individual occupation patterns can be taken into account. These types of stats also offer the ability to use a "set-back" mode for maximum efficiency. As most control systems operate with 240v power, for control in a wet area such as a shower or bathroom we recommend the use of a remote sensor or slaving from another room. 3. Boiler and pump controls The UK Building Regulations require a link between the control systems and the boiler to ensure that the boiler does not operate when no heat has been demanded from the system. The Speedfit Controller has provision for this connection. To discuss the options for individual projects, please contact the Speedfit Technical Help Desk on 01895 425333.
Design Guide The design of Speedfit Underfloor Heating System is a straightforward process consisting of 6 main steps:
Heatloss Calculations To establish the amount of heat required for each room or area, heatloss calculations must be undertaken. If the specifier is not familiar with the calculation, the Institute of Building Services Engineers (CIBSE) and the Heating and Ventilating Contractors Association (HVCA) have documents on the subject. It may be possible on certain projects for a Speedfit Engineer to assist in this process. Please contact the Technical Advisory Service on 01895 425333 for further information. For the purposes of an underfloor heating system the heatloss through the ground floor is generally ignored, as the floor will be warmer than the room temperature. Practically, there will be some heatloss through the floor and therefore a 10% margin is added to the total when calculating the boiler load. The actual heat output needed for the room is calculated by dividing the heat requirement obtained from the heatloss calculations by the total floor area. In areas such as under kitchen units or permanent fixtures pipework is not generally required and should be excluded from the calculation. This generates a heat requirement figure in Watts per m² which can then be referred to the Speedfit System Output tables when selecting pipe spacing and flow temperatures. Example: From the drawing plans, a heatloss for a room has been calculated at 1200 W and the area of floor has been measured at 20m². The UFH system performance required is therefore: Heat Loss (W) / Floor Area (m²) = Required Output (W/m²)
It should be noted, if a heatloss of greater than 100 W/m² is calculated, it may be necessary to provide supplementary heating to achieve comfort levels. This can, for example, be the case in a space with a high level of glazing such as a conservatory. Water Flow Temperature & Pipe Spacing The JG Pump Pack, connected to the manifold, has an integral proportional blending valve to regulate the water temperature from the primary supply. Normally this is set between 47° - 62°C depending on the requirements of the system and the flow temperature would remain the same for each circuit. Having calculated the required heat loss above, select the appropriate Speedfit output table based on the floor covering being used. Select a flow temperature and pipe spacing, based on the desired room temperature and a maximum floor temperature of 26° - 29°C. Example: - From above, a minimum performance requirement of 60W/m² is required from the UFH system. Using Table 1 - Textile Floor Covering, the following can be determined. At 55°C flow, 20°C Room Temp and a 200mm pipe spacing the output of the system is 80W/m² at a floor temperature of 27°C, which is within the acceptable performance limits. (It is normal not to exceed 200mm pipe centres for domestic applications in living rooms and a floor temperature of 29°C should not be exceeded.) If coverings are specified which are not mentioned in the tables specific calculations may need to be carried out. Resistance details for specific floor coverings should be obtained from the manufacturer prior to installation of the UFH system. It may be possible on certain projects for a Speedfit Engineer to assist in this process. Please contact the Technical Advisory Service on 01895 425333 for further information. Manifold Position & Circuit Lengths The unique Speedfit Manifold is available in a 4, 8 or 12 port configuration and Speedfit UFH pipe is supplied in 120 metre and 150 metre coiled lengths to allow for the flow and return connections to the manifold. The choice of manifold configuration will depend upon the number of circuit loops and temperature zones you require. For example you may wish to have a different temperature in the kitchen to the lounge area. The number of circuits in each area will depend upon the size of the area and the pipe centres chosen from the Speedfit Output Tables. To avoid excessive pressure drops in the pipework, the maximum loop length is limited to 100 metres and the amount of pipe required can be calculated from the table below:
Example: If a 18sqm lounge is to be heated at 200mm pipe centres the length if pipe required would be approximately 90m. However, if the distance to the manifold is 11m, giving an additional requirement 22m, then 2 loops would be required (e.g. 90m + 22m = 112m). Having determined the number of loops and, therefore, manifold configuration, the pipe layout can be planned. The circuit loop length must include the tails to connect to the manifold. Pipe Layout UFH piping layouts are based on two main considerations that must be effectively balanced. The pipe should be laid out in such a way as to provide an even spread of heat and a relatively even surface temperature across the area. Pipes should be laid in a continuous length, connections must not be made in the area to be screeded. The layout needs to allow for the increased heat required against colder exterior surfaces. The pipe loops can be laid out in various patterns depending on the nature of the specific project, taking into account the external walls and windows where the highest heatloss will occur. The optimum pipe layout is normally achieved by mixing the flow and return pipes so that the pipe with the highest flow temperature is adjacent to the pipe with the lowest return temperature. This is commonly referred to as a reversed return or counter spiral layout. Whatever layout is used, pipes must not cross over in the floor and must run to the corresponding port on the manifold. Therefore, it is advisable to prepare a pipe layout drawing before installation takes place. Some layout patterns are referred to by name as:
In practice, the pipe layouts can be combined or mixed in order to meet the heat requirements. Examples of these patterns can be seen below: Serpentine Patterns Serpentine patterns allow for the hottest water to border the exterior perimeter (highest heatloss areas). The water temperature is highest at the coldest walls and will decrease as it flows through the pipe towards the centre of the room.
Counter Flow Counter flow patterns differ from serpentine in that the supply and return pipes are laid out next to each other, creating an average temperature between them. Connection Areas In areas close to the manifold, such as the hall, several pipes may be in close proximity to each other as the circuit's flows and returns meet. This will contribute to the heat requirement of the room. It is common to either insulate these pipes or use the pipes to heat the area concerned. Therefore, consider and design these areas after all other rooms, loops and manifolds are known. Pressure Loss and Pump Duty Providing the limits of circuit length and area are adhered to, the total pressure loss in the system is within the capability of the pump supplied with the Speedfit Manifold. Speedfit Technical Data
Output Tables The following 4 tables are designed to assist in the specification of the UFH system and show different sets of data depending on floor finish, as defined BSEN 1264. The figures are for guidance only and are based on specific data. If you need further information or need to discuss a specific project please contact the Speedfit Technical Help Desk on 01895 425333. Table 1 Textile Floor Covering
Table 2 Tiles/Hardwood
Table 3 Wood Strip/Thick Linoleum
Table 4 Bare Concrete
Temperatures indicated in red exceed maximum permissible floor temperatures. In non-habitable areas or perimeter areas, temperatures above 29°C may be permitted.
INSTALLATION Installation Considerations There are several requirements to be taken into account prior to installation:
Speedfit Manifold The Speedfit Manifold and Pump Pack are supplied pre-assembled and individually boxed. They are supplied complete with installation, wiring and commissioning instructions. Balancing To ensure the flow of water to each circuit is approximately equal, the valves on the manifold should be adjusted and balanced in accordance with instructions supplied with the Manifold Pack. Fixing Details Make sure the site floor is clean, free from debris and free from irregularities. If required overlay the whole floor with polythene to act as a vapour barrier and lay edge insulation on all outer and inner walls. The insulation can be either roll or rigid type. Lay floor insulation panels starting close to the wall and proceeding in a brick bond fashion. If the insulation has printed gridlines ensure they are uppermost, this will assist the laying of the pipe circuits. Butt panels firmly together and tape all joints. Where necessary, carefully cut the insulation panels to fit around columns, drains, etc. Fit the Speedfit Manifold to the wall in the chosen position. Make sure the manifold is level and high enough to accept the pipe. Cut a short length of conduit (min 500mm) and slide over the pipe end. This will protect the pipe where it enters the screed. Repeat this on the return pipe. Pipe may also require sleeving across construction joints in floor and where it passes through doorways, etc.
Connections should not be made in the area to be screeded. From the manifold, start laying the pipe in the pre-designed configuration. The pipe is secured to the insulation by stapling the pipe to the insulation using the staple gun. Position the gun over the pipe and push down firmly to engage a staple. Allow the handle to travel back before moving on to the next staple. Staples should be set at intervals of 400mm and fixed to maintain a minimum bend radius is no tighter than 175mm. Fixing Details It is important to note when installing pipe in doorframes, through holes in the construction or in areas where expansion joints are needed in the screed, the pipe should always be sleeved with a section of conduit to allow for movement. Once the first loop has been laid, lay the pipe back to the manifold and connect as before to the corresponding return connection. When all loops have been installed, complete the installation of the control pack and follow the instructions for filling and pressure testing. If added security is required, a collet clip can be fitted to each pipe connection of the manifold. Filling and Pressure Testing To fill the system the following procedure can be followed:
The system should be pressurised at 2 BAR for 10 minutes followed by 10 BAR for 10 minutes. After this time the pipework and fittings should be visually checked for evidence of a leak. Once completed the system should be left pressurised throughout the screeding and curing process. BS EN 1264 Part 4 recommends a minimum of 6 Bar. Screeding The screed should be laid as soon as possible after laying the pipe circuits and completion of a pressure test. The system should be left pressurised throughout the screeding and curing process. The screed must be placed so that it is in good contact with the pipes without any air pockets. If standard sand & cement screed, which is normally 65 - 75mm thick, is being used, this should be installed and allowed to dry naturally in accordance with the screed, the manufacturer's instructions and British Standard requirements. Special low thickness screeds are available and contact should be made with the screed manufacturer for information with regard to their use with UFH. Manufacturers' quoted drying times will vary. However, under no circumstances should the UFH system be used to speed this process along. Initial Start Up In accordance with BS EN 1264, the start-up procedure following installation should be as follows:
Under no circumstances should the underfloor heating be used to speed up the screed drying time in excess of this schedule. Commissioning Following the initial start up period, the system should be commissioned with all floor coverings laid to ensure the system could be correctly balanced. Ensure the complete central heating system, including radiators if present, is working to required operational temperature. Each circuit can then be slowly adjusted via the valves on the manifold to ensure an even flow and heat up is achieved. Check installation details supplied with the manifold. Electrical General Notes The Speedfit UFH electrical control pack which includes a Manifold Controller (with or without set back time periods), room thermostats and actuators is a permanently live system operating independently and constantly 24 hrs (a stand-alone system). It will not control the main boiler and system pump, therefore if the main boiler and system pump are not on, no heat will enter the UFH system. In order to individually control heated water to the UFH system, a two-port zone valve fitted on the supply pipework to the UFH system must be wired into a spare channel on the existing time clock programmer. If there is no facility on the clock then the two-port zone valve must be wired into an additional time clock/programme. Both of these are requirements under Part L of the Building Regulations. If the existing system already has a three-port zone valve (mid-position, Y plan), then this must be replaced by 2 x two-port zone valve (S plan). In doing this the existing system may require a pipework by-pass. If the UFH system is installed with its own dedicated heat source it still requires a two-port zone valve and a time clock/programme which could be a part of the boiler or remote. This clock would operate the zone valve, which in turn would turn on the heat source (boiler) and system pump if fitted. The UFH electrical system would still be operated independently and constantly 24 hrs. For further advice contact your local IEE approved electrician. Installation Checklist 1. Floor Construction
2. Heat Requirement
3. Manifold Position
4. Pipe Requirement
5. Do not join pipes in the screeded floor. 6. Boiler Sizing
7. Flow & Return Pipe Sizing
8. Floor Finishes
Technical Advisory Service A full Technical Advisory Service is available from JG Speedfit. For further information please call the Technical Help Desk on 01895 425333. All JG Speedfit products are available through a network of stockists and advice can be offered on both system design and installation. JG Speedfit also maintains a preferred contractor and installer listing. For specific advice on insulation products, please contact Celotex Limited on 01473 820888 or email technical@celotex.co.uk For specific advice on screeds, please contact Optiroc Limited on 01928 515656.
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