Devimat heating mats

  1. What floor finish is suitable for use with the devimat system?
    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 suitable Floor Leveling Compound before the specified finish is fitted.
  2. The devimat is too big for the room, can I cut it?
    No, the mat Element cannot be shortened as this will alter the resistance of the element which may lead to overheating. It is therefore important that the area to be heated is measured accurately (free floor area only) and that you select the closest smaller area element. Please feel to ask us for help.
  3. The fuse keeps blowing when I use the mat?
    CONTACT YOUR ELECTRICIAN.  Fuses blow or circuit breakers trip on either short circuit or on overload, short circuit being the most common cause.
  4. Do we require insulation with devimat products?
    The devimat is designed 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 we strongly recommend this as it will enhance performance and reduce operating costs. Please contact us for information on Insulation board (FBoard).
  5. Does the floor need to be primed before laying the devimat?
    The mat has an adhesive backing and if the floor is dusty or greasy, it will not stick particularly well. Priming the floor will significantly help the mat to fully adhere to the floor surface.
  6. The system is not heating up!
    There are a number of reasons why this could happen.
    1. Check that you have a supply (voltage) to the thermostat.
    2. Check the thermostat is operating.
    3. Check the settings on the thermostat
    4. Check the continuity and resistance of the mat.
    NB. These checks may have to be carried out by a qualified electrician.
  7. I have a large area that requires two mats, how do I connect them together?
    The cold tails have to be brought out of the floor and have to be connected in parallel. ie. Core colours connected together, brown with brown, blue with blue etc.
  8. I want to use devimat underneath a laminate flooring, what type of underlay do you recommend?
    The underlay usually supplied with wood laminate is an acoustic about 2-3mm thick, this is acceptable. If you are installing anything other than this, please call our technical team at DEVI for advice.
  9. Can I put the devimat underneath a bath / shower tray / kitchen units etc.?
    DEVI does not recommend that the devimat is installed under any such fixtures for a number of reasons. eg. (a) It can inhibit the heat being produced from the system. (b) If ever a fault was to occur it would be extremely difficult to carry out a repair etc.
  10. I have a floor which is made up of both timber and concrete.  Can I use a single heating mat for the floor?
    DEVI strongly recommends that each section of floor has its own ‘mat’ and thermostat as in this instance, each floor surface has a different maximum temperature limit. Contact us to discuss the best options for this floor.
  11. What type of tile adhesive / leveling compound / tiling grout do you recommend?
    The covering has to be flexible or have a flexible additive. Talk to your Tiler for advice.
  12. How thick does the layer of tile adhesive/leveling compound need to be?
    The adhesive bed has to be thick enough to cover the cables, generally 4-5mm is sufficient.
  13. How long do I have to leave the heating system, after tiling, before I can switch on?
    DEVI would recommend that the adhesive used is allowed to dry/cure naturally and to follow manufacturers recommendations.
  14. How long does the heating system take to warm up?

    This depends on various factors, such as

    • what system has been installed (Undertile or Inslab)?
    • the type of screed that has been laid?
    • the depth is the floor screed?
    • etc.

    This Time could be anything from 30 minutes for a Devimat placed under tiles through to 5 – 7 hours for an Inslab storage system.

  15. What is the width of the mat?
    The actual width of the mat is 480mm but it is recommended that it be laid at 500mm intervals to ensure the correct gap between runs is achieved.
  16. What is the difference between Twin & Single Conductor mats?

    The difference between the two mats is the ‘cold tail’.

    With the Twin Conductor mat, there is no second connection tail to return to the thermostat. With 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.

  17. What is the black thing at the far end of the Twin Conductor mat?
    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.

Deviclear Mirror Demisters

  1. How do I wire my mist free mirror mat?
    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 via 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.
  2. What sizes are the mirror mats?
    There are 3 “standard” sizes: 1 – 600mm x 330mm 2 – 600mm x 660mm 3 – 600mm x 990mm However, we can make a Mirror Demister Foil tailored to ANY length required. Two standard “widths” are available – 400mm & 600mm.

Deviflex cables

  1. How long do I have to leave the heating system, after screeding, before I can switch on?
    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 ready to switch on is sufficient for it to dry out.


Devireg 550

  1. How do I remove the front from the devireg 550 thermostat?
    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. The supplied Instruction Booklet with your thermostat shows you how to do this.
  2. Why does my devireg 550 thermostat only show a 1-10 scale?
    Where the thermostat is connected to the Floor Sensor, the Screen reading shows as a Comfort Setting between 1-10. This is not a temperature. Each number relates to 5°C i.e. No. 6 would relate to 30°C floor temperature.
  3. Why is my devireg 550 thermostat coming ON in Timer mode, when it is not programmed to?
    There could be two reasons for this.
    The times programmed into the thermostat are the times you wish the room to be at the Set temperature. The time it takes to achieve this temperature is added to the start time automatically by your devireg550. eg if it takes 45mins to achieve temperature and the time set is 7am, the devireg550 will switch itself on at 6.15am.
    The Set-Back or ‘LO’ setting may be incorrectly set. This is the setting that directs the system to switch back on to offer frost protection or to prevent your floor from falling below a particular temperature . Typically, the LO setting would be set at -25°C. This means that if the temperature drops 25 degrees below the Comfort temperature setting, it will switch back on and maintain a temperature of 25ºC less than your Comfort Temperature. So, if the LO setting was set to -5°C and the Comfort temperature is set to 21°C, as soon as the temperature dropped to16°C, the system would switch back on and maintain a temperature of 16ºC.
    This becomes more of an issue when the thermostat is set to operate on Floor Sensing as the Thermostat 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°C and if the Maximum Floor Temp is set at 50ºC, then even if the LO setting was set to -25°C the system would switch back in when the floor temperature dropped to +25°C which would not take long particularly in the winter months. (The Maximum Floor Temperature Setting would normally be set at 35ºC for Concrete floors & 27ºC Wooden floors).
  4. Where can I put the thermostat?
    The thermostat should generally be positioned in the room it is controlling so that, if required, it can accurately read the air temperature. It should also be out of direct sunlight and away from any draughts or any alien heat source which may affect it, ie a radiator or TV. The Electrical Regulations will also determine Thermostat positioning.
  5. The thermostat display is blank, what is wrong?
    This would normally indicate no power supply – Check
  6. What does the 3 wavy line symbol mean?
    When showing, this indicates that the element is ON and that the temperature is below the Set Point temperature.
  7. Can the thermostat be positioned inside the bathroom?
    Yes. Refer to your Electrician for the Regulations regarding placement position and wiring etc.
  8. The outer ring on my devireg 540 / 550 thermostats is flashing, why?
    The thermostat is indicating a fault condition. The flashing “outer ring” brings your attention to the fact there is a fault and the small number showing indicates the error code (between 2 & 7). Refer to the Thermostat Booklet for a description of the fault or contact DEVI and we will help you identify the problem.
  9. My Floor remains at the same temperature at Setting 6.0 through to 10.0?
    This is caused when setting the Thermostat Activation details and the Floor Sensor is being used. The ‘Mt’ setting, being the Maximum Temperature the floor will reach, will be set at 30ºC. So, even though you turn your Thermostat up to 10, it will still switch off when reaching 30ºC (the Maximum Temperature limit). Remember that each Number relates to 5ºC, therefore 6 equals 30°C.
  10. What are the network terminals used for?
    The Devireg 550 thermostat can be networked which means that a number of Devireg 550’s can be linked together (through wiring) with one Thermostat being the Master and the rest being Slaves (up to 31 in number). This allows information to be programmed into the Master which is then automatically passed to the Slaves – a PC based software Control system is also available – Devi PC Pro.
  11. What is the ‘LO’ setting for?
    The ‘LO’ setting is the ‘set back’ temperature or SAVINGS TEMPERATURE. This is the (lower) Temperature that applies when a heating (COMFORT) temperature period has finished. For example, if the ‘LO’ setting is say -10 and the temperature set & showing on on the thermostat is 25ºC (or # 5), then if the temperature drops to 15ºC (25-10=15), The Thermostat will switch back on and maintain the floor at 15ºC. So, if you wish to effectively have no heating between COMFORT (heating) periods, adjust the ‘LO’ setting to -30 (being the maximum selection available).
  12. How do I mount the devireg 550 thermostat?
    The 550 is a flush box mounted thermostat so requires a 47mm deep box set into the wall.
  13. What is the Devireg 550 setup code?
    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 16 seconds until the word ‘CODE’ appears. Release the button and rotate clockwise to 0044, press the button then continuing with the Configurations.

Other Thermostats

  1. What is the difference between the devireg 130 series and 530 series?
    The 130 series are surfaced mounted manual thermostats. The 530 series are a flush mounted Manual and programmable thermostats.
  2. What do the lights indicate on the devireg 130 series / 530 series / 330 series / 710 / 750 / 754 controllers?
    On the 130 / 530 / 330 series, a green light indicates that the thermostat is powered but not heating. The light changes to red when the heating is ON.
    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 during the ‘off peak’ supply period.
    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.


  1. Do you have to use an RCD?
    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. Check with your Electrician for the Regulations regarding RCD’s and their use.
  2. My mat / cable has been damaged / broken, can I fix it?
    Yes, all mats & cables can be repaired. DEVI offer a comprehensive and accurate fault (location) finding service.
  3. What is the estimated running cost of the system (Mat / Cable)?
    The running cost of a cable or mat is dependent 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 ie 1500w x 1 hr x $0.22c/unit = $0.33/hr. operated on ‘off peak’ this would be 1500w x 1hr x $0.011/unit = $0.165/hr
    The Devimat Undertile floor system costs approximately 3.3c per hour, per m² to run.
  4. How long is the warranty on DEVI products?
    All devimats/deviflex cables – 10 years. Thermostats – 2 years.
  5. What does the DEVI warranty cover?
    All mats, cables and controls are covered against manufacturing defect. Any failure caused my mechanical damage will be attended to but the cost will be covered by the customer.
  6. Can we get a DEVI technician to come out and look at the system?
    Yes, DEVI will send a Qualified Technician to find any fault but the cost of the visit will have to be guaranteed by the Customer should the fault not be a Warranty Claim. If the fault is not a warranty Claim DEVI will advise fault location/repair costs before work is started..
  7. Can I extend the cold tails / sensor cable?
    Both the cold tails and the sensor cables can be extended by up to 50 meters.
  8. What is the maximum floor finish thickness I can have with Devimat / Deviflex heating cables?
    This will depend upon the finish specified. For Timber surfaces: 20mm for soft wood; 30mm for hard wood; most wood laminates are OK but may need to be treated on merit (talk with your floor covering supplier). Most vinyls are suitable as long as manufacturers temperature limits are adhered to and the elements are encased within the floor or a surface screed / FLC. Most carpets and underlays are suitable.
  9. What type of supply do I need?
    This will depend upon the area being heated and the density of cable / mat installed. Typically, we install at approx 140 to 150 w/m² of heated floor area. Contact your Electrician for advice or call us at DEVI.
  10. Is my underfloor heating suitable for use underneath carpets?
    Yes providing the mat / cables are covered with a latex Floor Leveling Compound first.
  11. Are there restrictions on what furniture I can have on top of my underfloor heating system?
    Underfloor heating relies on the heat it produces being unrestricted. If it is restricted it may cause “hot spots” and at worst, discolour the floor. Things such as beanbags, mattresses laid directly on the floor may cause problems. Anything that allows air movement under it is OK.
  12. What is a ‘floor sensor’?
    A Floor Sensor is a device that is connected to the Thermostat and allows the floor temperature to be fully controlled. .
  13. What box is the floor sensor in?
    The floor sensor is supplied in the thermostat box.
  14. Where is the floor sensor wired to?
    The floor sensor is wired back to the Thermostat and connected to the “NTC” terminal. There is no polarity on the cables.
  15. Is the floor sensor necessary? (I haven’t installed one)

    DEVI recommends always installing a Floor Sensor.

    The 550 / 535 / 540 thermostats can be programmed to operate as any 1 of these 3 options –

    • Air Sensing
    • Floor Sensing only
    • Air & Floor Sensing.

    A Floor Sensor must be installed when Floor or Floor/Air Sensing is chosen.

    Without a Floor sensor, the Maximum Floor Temperature cannot be controlled.

    A Floor Sensor is essential with Wood, Vinyl or Carpet floor coverings.