The FH undertile heating mat system is suitable for a wide range of floor coverings –

ceramic, stone, limestone, slate, terracotta, porcelain or marble. The FH electrical

underfloor heating system is designed for installation directly below tiles and stone flooring,

and the following instructions should be read carefully before you begin your installation.

FH systems can be applied to insulation construction boards, concrete, WBP plywood

(weather & boil proof plywood) and existing old tile surfaces. Insulation construction board is

already primed, comprising a cement polymer mortar finish on both sides of the board.

Electrical Requirements

It is recommended the installation is carried out in accordance with local electrical regulations

and the wiring of the system to the mains electrical supply is performed by a qualified

electrician.

The heating system is designed for operation at 230V 50Hz.

All installations require a 30mA RCD (residual current device) for safe operation.

Make sure the total current (amps) of your FH system and other appliances connected to

the circuit do not exceed the current capacity of the circuit. Normal ring main circuits are rated

at 13A and the electrical feed can be taken from a 30mA RCD via a 13A fused spur.

The FHSSTAT thermostat has a 13A maximum rating. When the total load of your FHsystem exceeds 2850 watts (19m² system) use a contactor to switch the electrical load, or

alternatively split the heating into more than one heating zone each operated by its own

thermostat – always consult your electrician.

In bathrooms the thermostat control should be mounted outside the bathroom.

The heating cable must never be cut.

To facilitate installation the cold lead wire can be cut to suit.

FLOOR PREPARATION

Wooden Subfloors – timber floorboards and chipboard. Make sure any loose boards are

firmly fixed and reinforce the floor if necessary to prevent any movement in the floor that could

cause tiles to crack. The floor should be level.

Reinforcement can be applied to the floor by covering the complete floor with 18mm WBP

plywood (weather & boilproof plywood).

Alternatively, when you have a firm floor insulation construction board such as Marmox can

be applied overall to the floor. This will add the benefit of improving the insulation properties

and only a 10mm thickness is required to obtain good results.

Concrete Subfloors – Before proceeding repair any imperfections in the floor and level the

floor with approved building materials.

Wooden & Concrete Subfloors - Clean the floor surface so that it is free from dust, dirt,

grease etc.

Prime floors with a water based PVA adhesive primer to improve bonding between the

adhesives and the subfloor.

Most tile or hardware outlets will supply this item and you will be able to purchase the exact

specification and quantity required for the floor area involved.

First Step

Plan the installation.

Draw a general view of the room and mark the area which will be covered with heating

elements. Avoid heating under units and sanitary ware as this can cause heat blockage and it

is unnecessary to heat these areas anyway.

Mark the position of the supply lead(s) – the cold lead wire, at floor level. This will be close to

and below the thermostat position in most cases.

When decided on this position you can cut a groove in the floor to accommodate the

protective floor sensor tube. The sensor must run centrally (in the middle) between two runs

of heating element so it is important to note where the element will be positioned. Make the

sensor tube level with the heating element as shown below.

Make sure the sensor tube has a gradual bend when it enters floor level - this will ensure the

sensor cable can be easily inserted. The tube can be cut to length to suit.

Seal the end of the tube.

The black cable joint between heating element (blue cable) and cold lead wire (white cable)

must be located on the floor. This joint should be level with the heating system – another

small groove may be necessary.

Floor Insulation

On wood or concrete subfloors, a thermal barrier between the heating element and subfloor

increase performance, heat up time and saves electricity costs.

To maximise the efficiency of the installed heat energy, insulation should be installed, either

below the subfloor or as a layer of insulation construction board on top of the subfloor, OR

BOTH.

Testing

IMPORTANT: Before and during installation resistance continuity tests are necessary. Also,

measure the insulation resistance value - the minimum reading should be 10Mohms

regardless of the element length.

• Test before installing, immediately after installing and before putting the heating into

operation.

Consult a qualified electrician.

A digital multimeter is ideal for testing cable continuity and its resistance (ohms), as well as

the resistance of the sensor cable.

A multimeter is not be capable of taking insulation resistance readings. Insulation resistance

readings should also be carried out as required by BS7671.

Mat Layout & Fixing

Planning is important and when calculating the heated floor area leave a gap unheated

around the room perimeter of between 50-100mm. The heated floor area must be free, avoid

heating under kitchen cabinets, sanitary ware and appliances.

Make sure the FH system can fit the floor area to be heated. It is better to have just too little

than too much over. Remember, NEVER cut the heating element. Cut only the element

carrier when needed, and turn / flip the mat to meet your requirements as shown in the small

illustrations below.

PLAIN WALL CUT                                                   

LOOSE CABLE

OPEN CORNER

 OBSTACLE CUT

Check that the cold lead wire for the mat(s) will reach the connection – (this is the connection

with the junction box, depending on the number of mats, or direct to the thermostat). If it does

not, extend by removing some of the heating element from the carrier and fix the heating

element to the floor with fixing tape.

Arrange the mat on the floor, roll out and make the appropriate cuts at walls and to facilitate

loose cable, open corners and obstacle cuts. Do not remove the two sided adhesive tape until

you have planned which way you intend to lay the mat. Once the mat installation has been

planned remove the two sided tape and stick to the subfloor pushing lightly to ensure good

adhesion. It helps to walk on the mat in stocking feet.

The FH undertile heating mat system is installed the professional way with the heating

elements facing downwards. This is especially helpful when laying your tiles directly onto the

mat without first applying a screed. Also, because the elements are on the underside of the

glass fibre mesh they are shielded from sharp trowels and possible damage.

Typical Layout of the FH Undertile Heating Mat System

Tiling

To fix tiles select a single step or two step method. Latex, acrylic or polymer based adhesives

are acceptable.

Single Step: Using a flexible adhesive the tiling can be carried out as a single operation

directly on top of the heating mat. Allow a depth of adhesive sufficient to lay the tile and to

encapsulate the heating element with no air gaps

Two Steps: Apply a thin layer of flexible self levelling compound just sufficient to cover the

mat and encapsulate the heating elements with no air gaps. Allow to cure in accordance with

the manufacturers instructions. This will provide protection to the heating mat prior to tiling.

Next apply the tiles in flexible tile adhesive in the normal manner.

Both steps are approved for under tile heating.

All adhesives must be flexible and suitable for underfloor heating. These are available from

most tile or builders merchant outlets and the outlet will provide full instructions on the

application of the adhesives and screed materials.

Grouting

Use a latex, acrylic or epoxy grout for grouting between the tiles. Latex, acrylic and

polymers add flexibility to grouts to resist cracking. Epoxy grouts provide high strength, good

thermal shock resistance and fast cure. Do not use sharp objects to clean the grout from

between the tiles. Most damage to the heating cable occurs when excess grout is scraped

away and a sharp tool goes deep enough to cut the cable.

Reminders

Do – read the instructions

Do - Use approved adhesives and floor screeds – consult your local tile or builders merchant

outlet

Do - use the right size of mat(s) and only apply the mat to the area to be heated

Do - consult a qualified electrician

Do - make sure the heating is connected to an RCD rated 30mA maximum.

Do - make sure the black joint between the blue heating element and the white cold lead wire

is in the floor beneath the tiles.

Do - keep a record of where the floor probe is positioned and the general layout of the

heating mat for future reference.

Do Not - overload circuits – consult your Electrician

Do Not - cut the heating element

Do Not - cross or touch heating elements

Do Not - cut or prepare tiles on top of the mat

Do Not - cut or prepare tiles on top of the mat

Visit My eBay Shop: FLOORHEATERS