FAQ

Most floor finishes are suitable for use with underfloor heating providing the floor has been prepared correctly and any manufacturer's temperature guidelines have been adhered to. With finishes such as wood laminates and carpets it is essential that the heating mat is completely covered with a latex levelling compound before the specified finish is fitted.

The DEVImat cannot be shortened as this will alter the resistance of the mat and may cause it to overheat. It is important that the area that requires heating is measured accurately (free floor area only) and that you always round down the measurements.

Fuses blow or circuit breakers trip when there is either a short circuit or an overload. A short circuit being the more common of the two causes. This is generally due to mechanical damage, for example the heating cable being cut, squashed or possibly drilled through.

The DEVImat is designed as a retrofit product to be laid directly onto an existing floor surface, so does not require insulation. However, if there is room within the floor to add insulation or a tile-backer board this will enhance performance.

The mat does have an adhesive backing, but if the floor is dusty or greasy it will not stick particularly well. Priming the floor will help the mat to fully adhere to the floor surface.

There are a number of reasons why this could happen;

• Check that you have a supply (voltage) to the thermostat.
• Check the thermostat is operating.
• Check the settings on the thermostat particularly the 'nt' setting.
• Check the continuity and resistance of the mat.
  
  These checks may have to be carried out by a qualified electrician.

The cold tails have to be brought out of the floor and have to be connected in parallel. i.e. Core colours connected together, brown with brown, blue with blue etc.

The 100w/m² mats are for installation on wooden floors. If the wooden floor is ventilated, it is important to have some form of insulation beneath.

150w/m² mats are for installation onto concrete based floors.

200w/m² mats are for installation onto concrete based floors where a more responsive heat is required.

The underlay usually supplied with wood laminate flooring is an acoustic underlay about 2-3mm thick, this is acceptable. If you are installing anything other than this, please call our technical team at DEVI for advice.

DEVI does not recommend that the DEVImat is installed under any such fixtures for a number of reasons;

• It can inhibit the heat being produced from the system.
• If ever a fault was to occur, then it would be extremely difficult to carry out a repair.

DEVI would recommend that each section of floor has its own 'mat' and thermostat. If one size mat and thermostat were to be used then where do you install the sensor? In this scenario the floors would deliver uneven temperatures.

The covering has to be flexible or have a flexible additive.

The adhesive bed has to be thick enough to cover the cables; generally 4-5mm is sufficient.

DEVI would recommend that the adhesive used is allowed to dry/cure naturally and to follow manufacturers recommendations.

This depends on various factors, such as:

• What system has been installed?
• What type of screed has been laid?
• What depth the floor screed is?

This could be anything from 30 minutes for a Devimat under tiles to 5-7 hours for a storage system.

The actual width of the mat is 430mm but it is recommended that it is installed at 500mm intervals to ensure the there is an appropriate space between runs.

The difference between the two mats is the 'cold tail'.

• The twin conductor mat, there is no second connection tail to return to the thermostat.
• The single conductor mat there is a single cold tail at each end of the mat and they have to be brought back together at the connection point.

This is the connection at the end of the twin conductor mat where the heating element is connected to the neutral return. This is manufactured within the cable.

It is recommended that the mirror mats are wired into the lighting circuit, which is switched on and off with the room light. The connection to the lighting circuit can be done using a box set in the wall adjacent to the mirror and sealed with a blank plate or by a joint box within an adjacent void.

There are 3 sizes available:

• 80mm x 60mm
• 50mm x 70mm
• 60mm x 60mm

It is recommended that any screed be allowed to cure naturally and this would again depend upon its thickness. Generally the length of time from the screed being laid and the system being switched on is sufficient for it to dry out.

There is a small retaining clip in the centre slot along the top of the square cover. This should be pressed with a small screwdriver; at the same time ease the cover off. There is a diagram showing how to do this supplied within the thermostat box.

Electrical wiring regulations do not allow thermostats to be fitted within bathrooms. So, as it is placed outside the room it cannot sense the air temperature in the bathroom. Therefore, the thermostat is linked to floor sensor and reads out as a comfort setting between 1-10. This is not air temperature. Each number shown on the face relates to 5°c . For example, No. 6 would relate to 30°c floor temperature.

There could be two reasons for this:

• The times programmed into the thermostat are the times you wish the room to be at the temperature set. The time it takes time to achieve this temperature is added to the start time to ensure the temperature is achieved for the start time set. i.e if it takes 2 hours to achieve temperature and the time set is 7am it will switch itself on at 5am.
• Another reason could be that the set back or 'LO' setting has been incorrectly set during configuring the thermostat. This is the setting that directs the system to switch back on to offer frost protection. This should be set at -25°. This means that if the temperature drops 25 degrees below the temperature shown on the face it will switch back on. So, if this was incorrectly set to read -5° and the face temperature showing 21°, as soon as the temperature dropped to16° the system would switch back on.
  
  This becomes more of an issue when the thermostat is set to operate on floor sensor as the readout is a comfort setting between 1-10, with each number relating to 5°.
  
  If the user were to turn the thermostat to 10 to 'try' and get more heat they would effectively be asking for 50° and even if the Lo setting was set at -25° the system would switch back in when the floor temperature dropped to 25° which would not take long particularly in the winter months.

The thermostat should generally be positioned in the room it is controlling so it can accurately read the air temperature. It should also if possible be out of direct sunlight and away from any draughts or any alien heat source may affect it, i.e. a radiator or TV.

Thermostats for bathrooms & en-suites have to be placed remotely either outside the door or in a cupboard and linked to a floor sensor.

Check that you have a supply (voltage) going to the thermostat as this quite often means that there is no supply to the thermostat.

This symbol indicates that the temperature is ’below set point’ or has not reached the temperature set and is currently heating.

According to electrical wiring regulations, thermostats should not be fitted in rooms with a fixed bath or shower.

This is indicating there is a fault somewhere on the control system. The flashing brings your attention to the fact there is a fault and at the same time it shows an error code number between 2 & 7. Explanations for these codes can be found in the user guide booklet.

The reason for this is that when you set up the thermostat the 'nt' setting is the maximum temperature the floor will reach as this is the 'upper limit'. So even though you turn it up to 10, it will still switch off at whatever temperaure the 'nt' is set at. Incidentally each number relates to 5 degrees therefore 6 would equal 30°c.

The thermostats can be networked, which means that a number of them can be linked together through the wiring with one being the master and the rest being slaves. This allows information to be programmed into the master which is then passed to the slaves.

The 'LO' setting is the 'set back' temperature. This is the temperature below that which you see on the face that the thermostat will switch back on again even in an off period, i.e. if the 'LO' setting is say -10 and the temperature showing on the face is 21, if the temperature drops to 11 degrees it will switch back on.

The 550 is a flush mounted thermostat so requires a 47mm deep box set in the wall.

The code is 0044 and has to be set before any setting changes can be made. This is done by pressing and holding the grey button in for approx 12 seconds until the word ‘CODE’ appears then rotate to 0044 and press, then continuing with the configurations.

The 130 series are surfaced mounted manual thermostats.
The 520 series are flush mounted programmable thermostats.

• On the 130 series the green light indicates that the thermostat is 'on' but not charging the system. This changes to red when actually charging the system.
  
• The 710 is an anticipatory controller and has two lights, the one on the left by the 'limit' button is green when not heating and turns to red when charging. The one in the top right corner is red and will flash indicating that the floor has taken a charge on the 'off peak'.
  
• The 750 is another anticipatory controller that has two lights, one by the E6 button that shows green when not heating and changes to red when charging.
  
• The 754 is the multi-zone slave unit with a light for each zone situated to the left of the E6 control, this will be green when not heating and red when charging. The red light by the moon symbol indicates that an overnight charge has been taken and will remain on for 11 hours after the start of the charge period.

The use of an RCD is recommended particularly in ‘wet’ areas such as bathrooms & en-suites. An RCD offers greater protection in the event of a fault.

Yes. In most cases all mats & cables can be repaired. Gaia offers a full fault finding and warrantied repair service.

The running cost of a cable or mat is dependant upon its rating/output and is based on the units of electricity consumed.

A unit of electricity is 1000watts (1KW) for 1hour at the unit cost of electricity 
i.e 1500w x Ihr x 6.5p/unit = 9.75p/hr. 
Operated on ‘off peak’ this would be 1500w x 1hr x 3p/unit =4.5p/hr

The DEVImat warm floor system costs approximately 0.5p per hour, per m2 to run.

• All DEVImats and DEVIflex cables - 10 years.
• Thermostats – 2 years.

• All mats, cables and controls are covered against manufacturing defect.
• Any failure caused by mechanical damage will be attended to but the cost covered by the customer.

DEVI will send an engineer to attend a fault but the cost of the visit will have to be guaranteed. Any costs involved will be determined once the fault is located.

This will vary from product to product.

• For twin conductor cables/mats there will be a 3 core cable attached with identifiable core colours.
• For single conductor mats there will be a blue & black cold tail blue being neutral and black being live.
• For single conductor cables both cold tails are black and there is no polarity, i.e it doesn’t matter which cable is connected to live and which to the neutral.

Both the cold tails and the sensor cables can be extended by up to 50 meters.

This will depend upon the finish specified.

• For timber, 20mm for soft wood, 30mm for hard wood and most wood laminates are OK but may need to be treated on merit.
• Most vinyls are suitable as long as manufacturers temperature limits are adhered to.
• Carpets and underlays are suitable but the lower the tog rating the better for the system response times.

This will depend upon the area being heated and the density of cable / mat installed. Your electrician should be able to calculate this once he knows the rating of the underfloor heating installed.

Yes, providing the mat / cables are covered with a latex levelling compound first.

Underfloor heating relies on the heat it produces being unrestricted, if it is restricted it may cause that particular area to overheat and at worst discolour the floor. Items such as beanbags, mattresses laid directly on the floor may cause problems. Anything that allows air movement under it is OK.

A floor sensor is a limiting device that governs the upper limit temperature that the floor has been set to on the thermostat.

The floor sensor is supplied in the base of the thermostat box.

The floor sensor is wired back to the appropriate thermostat and connected into the NTC terminal. There is no polarity on the cables therefore it does not matter which cable goes in which terminal.

The DEVIreg 540 /550 thermostats can be programmed to operate as air sensing, floor sensing or air & floor sensing. A floor sensor must be installed when floor or room & floor sensing is chosen. This is particularly necessary when controlling heating in bathrooms and en-suites where thermostats are placed outside the door.