Cablewarm® Electric Underfloor Heating Mats Installation Guide For Tile Floors 

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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 a high temperature PVC (melt point 105°C) outer protective jacket; to form a twin conductor heating cable.

Cablewarm® underfloor heating cables are totally waterproof and incorporate an earth screen, making them perfectly suited for installations in wet areas.

The resulting heating cable is extremely safe, durable and robust, with a thin profile of 3mm.

Cablewarm®150 heating cables are attached to a 500mm open weave mesh mat backing at 75mm preset factory spacing, to produce the Standard Output Cablewarm®150 heating mats (150W/m2) and are ideally suited for the majority of underfloor heating applications.

Cablewarm®200 heating cables are attached to a 500mm open weave mesh mat backing at 75mm preset factory spacing, designed to produce a High Output heating mat (200W/m2). Cablewarm®200 heating mats should be used in primary heating applications for conservatories; areas of high heat loss or where no additional thermal insulation is being installed, where a high heat output is required.

Measuring Up Cablewarm® Under Floor Heating Mats

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

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

Cablewarm® Heating Mats - Sizing Guides and Technical Data

Cablewarm®150 Heating Mat - Power Output 150W/m²

Cablewarm®200 Heating Mat - Power Output 200W/m²

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 Cablewarm® heating mats 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® Floor Heating Mats

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®150 heating mat range, the CWM150-1500 (10m2) 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.

Installation of Large Areas Using a Combination of 2 Cablewarm®200 Heating Mats 

Illustrated below is a 19m² conservatory requiring a primary heating source. High output 200W/m2 Cablewarm®200 conservatory heating mats have been selected for the installation.

After making an adjustment for the conservatory corners of 1m2, a 10% standard perimeter allowance has been deducted to give a total heated area of 17.1m2: from the Cablewarm®200 conservatory heating mat range, the CWM200-3400 (17m²) has been selected - a combination of two Cablewarm®200 heating mats.

Using the larger of the two heating mats, run this out from the termination point to the opposite end of the room: check the remaining floor area will accommodate the additional heating mat. Lay the additional heating mat and where necessary cut the mat backing to allow the floor heating cable to be run around fixed units, odd shapes, corners and previously laid matting. Remember, never overlap the heating mats 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.

Floor Preparation

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

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.

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.

Primer/Sealer

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.

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

Installation of Underfloor 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® or go the Fastwarm® insulation FAQ page.

Cutting and Shaping Cablewarm® Under Floor Heating Mats

NOTE: Never cut the cable, this will invalidate the manufacturer’s guarantee: only the mat backing mesh can be cut.

The Cablewarm® 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 mat contact Floor Heating Ltd. Provided that the mat and cable have not been cut, laid or damaged in anyway, then it can be exchanged.

Once the Cablewarm® heating mat 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 mat cold tail.

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

Laying Cablewarm® Underfloor Heating Mats

Having now planned the layout of the heating mat to obtain the best fit within the floor area, the mat now requires to be stuck down to the Fastwarm® insulation, or wood/cement sub-floor if no insulation has been laid.

To hold the mat firmly to the insulation or sub-floor, sticky strips have been manufactured onto the underside of the mat backing and can be seen with a smooth protective layer. Progressively lay the mat into the planned heated area, peeling the protective strips to expose the tacky surface of the tape, firming the mat down as you go.

Thermostats and Floor Sensor

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 mats via a 13 amp thermostat:

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

The maximum equivalent combination Cablewarm® heating mats in the Cablewarm®150 range is the FHM3000 heating mat (20m2)

The maximum equivalent combination Cablewarm® heating mats in the Cablewarm®200 range is the CWC200-3000 heating mat (15m2)

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

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

The maximum equivalent combination Cablewarm® heating mats in the Cablewarm®150 range is the FHM3400 heating mat (22m2)

The maximum equivalent combination Cablewarm® heating mats in the Cablewarm®200 range is the CWC200-3400 heating mat (17m2)

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

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

The maximum equivalent combination Cablewarm® heating mats in the Cablewarm®150 range is the FHM3600 heating mat (24m2)

The maximum equivalent combination Cablewarm® heating mats in the Cablewarm®200 range is the CWC200-3600 heating mat (18m2)

If two or more Cablewarm® heating mats 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.

Contactors

A Contactor can be used where a single thermostat is required to control a total area of underfloor heating in excess of 3680 watts or a total loading exceeding 16 amps.

The Floor Heating Contactor will control up to a maximum of 22,000 watts or 95 amps total loading:

Maximum Cablewarm®150 heating mats up to 146m2 

Maximum Cablewarm®200 heating mats up to 110m2

Click contactors for more information.

Positioning The Floor Sensor

Having determined the size of the area to be heated and the correct size Cablewarm® heating mat 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.

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

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

To comply with current Part P Electrical Safety Regulations, it is now a requirement to 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® Underfloor Heating

Once the Cablewarm® heating mats/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 installation would be to pour a thin layer of flexible, self-levelling compound (sometimes referred to as latex) to cover the heating cable to give a level surface prior to laying the tile adhesive. Once the levelling compound has dried (12 – 24 hours) tiles can be laid as normal using a good quality flexible tile adhesive.

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

Tiling Tools:

To simplify the installation of your electric underfloor heating system, Floor Heating offer an extensive range of tiling tools available on the website; suitable for both trade and DIY. To view the tiling tools click here.

Wood Or Laminated Engineered Wood Flooring Over Cablewarm® Underfloor Heating Mats or Cables

A flexible, rapid setting, Levelling Compound suitable for under floor heating systems is required to completely encapsulate the heating cable; it is recommended that at least 5-6mm be applied to give adequate cover to the heating cables.

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

Soft Flooring Like Carpet Or Vinyl Types Over Cablewarm® Floor Heating Mats or Cables

A flexible, rapid setting, Levelling Compound suitable for under floor 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 carpets: 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.

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

Finished Under Floor Heating Installation Diargrams

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

Illustration of a typical timber sub-floor with Cablewarm® Under Floor Heating Mat or Cable