Cablewarm® Electric Underfloor Heating Cable Installation Guide For Tile Floors 

Please ensure that your browser is set to print backgrounds and images in order to see all the diagrams on the printed version of this page.

Cablewarm® Electric Heating Cable Description

Cablewarm® underfloor heating cables are manufactured from multi-strand copper, twin heating conductors with a PTFE outer insulation, high tensile film screen, copper braid earth shield with an outer protective jacket of high temperature PVC (melt point of 105ºC); to form a twin conductor heating cable.

Cablewarm® underfloor heating cables are totally waterproof, making them perfectly suited for installations in wet areas.

The resulting thin profile heating cables are extremely safe, durable and robust.

Measuring Up Cablewarm® Heating Cables

It is important to measure the room correctly and avoid all permanent fixtures such as baths, showers, kitchen and bedroom units. Avoid thermally blocking the heated area as this will result in localised heat build up and possible damage to the floor covering or units.

From the total area you are planning to heat, deduct a further 10% to make an allowance for the perimeter.

Use the table below to determine your requirements.

Cablewarm® Heating Cables - Sizing Guides and Technical Data

Cablewarm® Heating Cables @ 15 Watts per Linear Metre - Variable Power Output W/m² 

To calculate cable spacing, use the following formula:  Area (m²) ÷ Cable Length  X 1000 = cable spacing (mm)

Please note: Floor Heating Ltd heating cables are based on a higher output of 15 watts per linear metre

For greater areas individual cable lengths can be joined in any configuration and connected in parallel.  

A contactor can be used where a single thermostat is required to control a total area of underfloor heating exceeding a 13amp fused spur supply. The contactor will control up to a maximum of 146m2 of heating cable or 24amps total loading.

For more information on contactors click here.

NOTE: Ampage loading is based on 230 Volts 

If in any doubt contact Floor Heating for advice

Planning the Installation of Cablewarm® Heating Cables

The diagram below illustrates a kitchen floor 5m x 3.2m, which equates to a total area of 16m2. However, due to the fixed units and island the total usable area available to heat is reduced to 11.3m2. After deducting a further 10% perimeter allowance, this leaves a total heated area of 10.2m2: from the Cablewarm® cable heating range, the CWC15-2000 has been selected.

This example highlights the advantage of the Cablewarm® twin conductor floor heating cable, requiring connection to the electricity supply at one end only, removing the need to design the layout to get the cable back to the original start point.

Cablewarm® Heating Cables - Installation of Larger Areas

Illustrated below is a 25m2 area with both corners missing, representing either fixed units or angular walls in a Victorian design conservatory. After making an adjustment for the corners of 1m2; deduct the standard 10% perimeter allowance, leaving a total heated area of 21.6m2: from the Cablewarm® heating cable range, the FHC3400 has been selected - a combination of two Cablewarm® heating cables. 
 
Using the larger of the two Cablewarm® heating cables, run this out from the termination point to the opposite end of the room: check the remaining floor area will accommodate the additional Cablewarm® heating cable. Lay the additional Cablewarm® heating cable around fixed units, odd shapes, corners and previously laid cable. Remember, never overlap the Cablewarm® heating cables as this will cause localised overheating, leading to eventual failure and invalidation of the manufacturer’s guarantee.

The thermostat sensor must be positioned centrally between the heating cable loops – see the Thermostat and Floor Sensor section below.

NOTE: Never cut the cable, this will invalidate the manufacturer’s guarantee.

Laying Cablewarm® Underfloor Heating Cables

The heating cable should be no closer than 50mm from the walls and any other fixed obstruction. NEVER bury or try to hide the cable, if necessary start again.  If you have ordered the wrong size of cable contact Floor Heating Ltd. Provided that the cable has not been cut, laid or damaged in any way, then it can be exchanged.

Having now planned the layout of the heating cable to obtain the best fit within the floor area, the cable now requires to be fixed down on to the Fastwarm® insulation, or wood/cement sub-floor if no insulation has been laid. Fastwarm® fixing tape is used to hold the cable firmly in place prior to applying tile adhesive or pouring a latex screed (flexible levelling compound).

Once the Cablewarm® heating cable is laid, test the circuit using an ohmmeter to check the resistance readings (multimeters are available from Floor Heating Ltd). The correct ohms reading can be found on the information label on the Cablewarm® heating cable cold tail or the box packaging.

Finally, to prevent potential damage to the Cablewarm® heating cable, avoid excess traffic over the area until the final flooring is laid.

Floor Preparation

All floors should be suitably prepared prior to laying the Cablewarm® heating cable:

1. Concrete sub-floors - if the sub-floor is a new concrete floor it should be allowed to cure naturally – as a guideline you should allow 1 week per 25mm but this is dependant upon weather conditions. If the finished concrete floor is not level then a thin layer of levelling compound should be applied to give a smooth and level surface.

2. Wooden sub-floors - timber floors should be clean and level.
Where necessary (especially if laying tiles on top of the Cablewarm® underfloor heating), suitable plywood over-boarding should be laid, in line with the Tiling Federation recommendations.

The use of a suitable Primer/Sealer is recommended by adhesive manufacturers on both concrete and wooden sub-floors to seal the porous sub-floor, prior to applying adhesives or levelling compounds.

Tile Fixing

For more information on the Floor Heating Ltd recommended range of flexible tile adhesives, grouts and flexible levelling compounds click here.

Installation of Floor Heating Thermal Insulation

Where any underfloor heating is installed heat energy will travel in both directions, down as well as up. Cement floors act as a heat sink absorbing this energy, creating a large drag on the performance of the flooring above. A high quality thermal barrier between the heat source and the sub-floor will significantly improve the performance of your floor heating, speeding up the initial warm up times and saving money on electricity costs - the thicker the insulation the better the results.

Floor Heating Ltd recommend the use of Fastwarm® High Performance Thermal Insulation Boards. For more information on Fastwarm® click here.

Thermostats

It is normal practice to site the floor heating thermostat within the room to be heated, however for bathrooms the thermostat is required to be sited outside.

Connection is only required at one end of the twin conductor cable mats. The first 3 metres of black connection cable can be cut as required. The red heating cable must never be cut or shortened.

If connecting your Cablewarm® heating cables via a 13 amp thermostat:

A 13 amp thermostat will control a maximum wattage of 3000 watts.

The maximum equivalent combination Cablewarm® heating cables in the range is the Cablewarm® CWC152700 heating cable.

If connecting your Cablewarm® heating cables via a 15 amp thermostat:

A 15 amp thermostat will control a maximum wattage of 3450 watts.

The maximum equivalent combination Cablewarm® heating cables in the range is the Cablewarm® FHC3400 heating cable.

If connecting your Cablewarm® heating cables via a 16 amp thermostat:

A 16 amp thermostat will control a maximum wattage of 3680 watts.

The maximum equivalent combination Cablewarm® heating cables in the range is the Cablewarm® FHC3400 heating cable.

If two or more Cablewarm® heating cables are connected to the thermostat a simple electrician’s connector block of suitable ampage loading should be used. Any attempt to connect more than a single wire directly into the thermostat terminals may result in damage to the thermostat terminal and invalidate the manufacturer’s guarantee.

Click thermostats for more information.

There are 2 options to control larger installations in excess of 3680 watts:

Option 1 - Divide the heated areas into separate zones, controlled by individual thermostats, up to the maximum – as above.

Option 2 - A contactor is required to control your Cablewarm® heating system with a single thermostat – see below.

Contactor

Used where a single thermostat is required to control a total area of underfloor heating exceeding 3680 watts or a total loading of 16 amps.

The Floor Heating Limited contactor will control up to a maximum of 22,000 watts or 96 amps total loading – maximum Cablewarm® heating cables up to 147m2

 Click contactor for more information.

Positioning The Floor Sensor

Having determined the size of the area to be heated and the correct size Cablewarm® heating cable required; the next step in the installation process is to position the floor sensor correctly.

From the thermostat position, mark the floor immediately below the thermostat and cut a channel in the Fastwarm® insulation board (or sub-floor if no insulation is being installed), approximately 10mm x 10mm deep and 300mm long – this will form the location for the flexible floor probe conduit.  Following the instructions provided with the thermostat, the probe should be fed into the conduit trunking, taped over the end (to protect the sensor from ingestion from tile adhesive or levelling compound) fixed into position with either Fastwarm® floor tape (or similar gaffer type tape) and connected to the thermostat.

It is normal practice to site the thermostat within the room to be heated; however, for wet areas like bathrooms and en-suites, the thermostat is required, under current electrical regulations, to be sited outside the room.

Connection is required at only one end of the twin conductor Cablewarm® heating cables. 

The first 3 metres of black connection cable (referred to as a cold tail) can be cut as required but the red heating cable must never be cut or shortened.

Please note that all electric underfloor heating systems should be installed and connected to conform to current electrical legislation.

If in doubt, Floor Heating Limited recommend that a suitably qualified electrician should be consulted prior to installing your Cablewarm® heating system. A qualified electrician should make the final connection of the thermostat and commission the system: the installation will require a certificate to be issued by the electrician to conform to current electrical legislation and to validate your manufacturer’s guarantee.

Cablewarm® Heating – Power Connection and Testing

It is highly recommended that you connect your Cablewarm® underfloor system via a fused spur (to isolate the system for future maintenance). The power supply should be from a safety contact breaker (RCD) to the thermostat – a qualified electrician would be able to advise you.

The electrician should affix a suitable advisory warning notice to the electricity distribution box and complete the attached guarantee certificate, which must be returned to Floor Heating Limited within 10 days; a copy should also be retained to serve as part of the guarantee requirement.

Switching on Your Cablewarm® Heating System

Before switching on the Cablewarm™ under floor heating system allow a minimum of 3 days for natural drying of the tile adhesive and grout or levelling compound. It is recommended to initially operate the system for 1 hour, gradually increasing daily operation by a further 1 hour per day to full continuous use after 6-7 days.

Tiling Over Cablewarm® Heating Cables

Once the Cablewarm® heating cables are laid suitable protection boards should be used to prevent any possible damage during the tiling phase.

A good quality rapid setting, flexible tile adhesive should be laid evenly and spread in the same direction as the cables are running, in order to fully encapsulate the heating cable, leaving no air spaces.  NOTE: To avoid any potential damage to the Cablewarm® heating cables that may be caused by using a steel notched trowel, Floor Heating Limited strongly recommend using a plastic notched trowel for this operation.

An alternative method of construction would be to lay a thin layer of flexible, self-levelling compound (sometimes referred to as latex) to cover the heating cable before laying the flexible tile adhesive, to give a level surface prior to laying the tile adhesive.

Flexible Tile Adhesives And Grouts

For more information on the Floor Heating Ltd recommended range of flexible tile adhesives and grouts click here.

Wood Or Laminated Engineered Wood Flooring Over Cablewarm® Heating Cables

A flexible, rapid setting, Levelling Compound suitable for underfloor heating systems is required to completely encapsulate the heating cable; it is recommended that at least 6-7mm be applied to give adequate cover to the heating cables.

Follow manufacturer’s instructions for flooring installation: however for best results, it is recommended that a low tog rated insulation/acoustic layer be used in order that heat from the Cablewarm® underfloor heating system is not thermally blocked.

Soft Flooring Like Carpet Or Linoleum Types Over Cablewarm® Heating Cables

A flexible, rapid setting, Levelling Compound suitable for underfloor heating systems is required to completely encapsulate the heating cable; it is recommended that at least 10mm be applied to give adequate cover to the heating cables.

For best results it is recommended that a low tog rated underlay be used in order that heat from the Cablewarm® underfloor heating system is not thermally blocked.

Flexible Levelling Compounds

For more information on the Floor Heating Ltd recommended range of flexible levelling compounds click here.

Typical Cablewarm® Cable Heating Installation Diagrams

Illustration of a typical concrete sub-floor with Cablewarm® heating cables and Fastwarm® thermal floor insulation boards.

Illustration of a typical timber sub-floor with Cablewarm® heating cables