Posting a message to the forum will remove the above advertisement

  1. laugh TilersForums.co.uk Tiling Job Of The Month Competition! laugh

    Vote on June competition by clicking HERE (click the thumbs up on the job you want to win!

    Enter in July competition by clicking HERE (click 'add your JOTM entry' and then 'add media')


     

  2. ismoat Building Products

Discuss Goofed on Underfloor Heating Wattage in the Tiling Forum area at TilersForums.co.uk.

  1. john56897452

    john56897452 Active Member

    Location:
    NOTTINGHAM
    So fitted Quartz starstone floor tiles. Used Mapei super flexible UFH compatible adhesive on screwed and glued 6mm Hardie backer board. Finished with Granfix maxigrout flexible grout.

    Floor area about 1.3msq so smallish. I checked with the supplier (Tile choice ) and tiles ok for 150 watt UFH. Turns out I have fitted 300w warmup loose wire. Not switched on at all yet or commissioned. Has quartz tile technology come on enough yet or is my floor doomed?

    I may add I have no intention of using full heat just maybe 20 degrees or so to take the chill off the tiles in cold weather. Main heating in this small en suite is a radiator. Any expert advice on my options beside the obvious of don't switch on.
     
  2. Uheat - Jake

    Uheat - Jake Tilers Forums Official Sponsor TF Official Sponsor

    Knowing nothing about the tile side, what spacings have you got the cable at? As that's 230w/m2 which is more than likey below the minimum fixing distance for a heating cable to be fixed at which could be very dangerous.
     
  3. mma

    mma Professional Tiler

    Location:
    Leicester
    Are those tiles suitable for ufh?? Heat sources can cause the tiles to warp. Done some Quartz recently and it said on the box, not suitable for conservatories...
     
  4. john56897452

    john56897452 Active Member

    Location:
    NOTTINGHAM
    Fixing wire 50 to 70mm. As stated above supplier said good for 150w UFH.

    Many thanks
     
    • Like Like x 1
  5. Plan Tec Tiling

    Plan Tec Tiling Administrator Staff Member Trusted Advisor Professional Tiler JOTM Winner Top Contributor

    Location:
    Wimborne, Dorset
    As far as I see it you only have one sensible option..... give it a go and see what happens!
     
  6. Plan Tec Tiling

    Plan Tec Tiling Administrator Staff Member Trusted Advisor Professional Tiler JOTM Winner Top Contributor

    Location:
    Wimborne, Dorset
    Just had a brainwave...... I'm no electrician, but is there any way that a sparky could reduce the wattage down that is fed to the cable to 150w????
     
  7. jcrtiling

    jcrtiling Professional Tiler TTA Member Top Contributor

    Location:
    Salisbury
    I thought more wattage just got you to temperature quicker not making floor any hotter so don't know what the problem is if that is the case .
     
    • Informative Informative x 1
  8. Plan Tec Tiling

    Plan Tec Tiling Administrator Staff Member Trusted Advisor Professional Tiler JOTM Winner Top Contributor

    Location:
    Wimborne, Dorset
  9. 3_fall

    3_fall Administrator. Staff Member Trusted Advisor Professional Tiler JOTM Winner Top Contributor

    Location:
    SW London
    Warm up have a 24hr hotline, and it is pretty good to be fair.
    I must admit, I thought the distance for warm up cable was 70-110mm... 90mm being the optimum.

    With the Ditra Heat E I've just installed,
    3 nib separation gives 136w (which they recommend for floors) and 2 nib separation gives approx 200w, which is what they recommend for walls.
    Must admit I've never heard of a 300w installation.
     
  10. john56897452

    john56897452 Active Member

    Location:
    NOTTINGHAM
    Think I've solved it. I can use a 300w+ dimmer switch between the wire and the thermostat. This will give total control to adjust the wattage.....hence the heat, and still be controlled by the floor sensor for temperature. This will give the best possible conditions for warming the tiles limiting shock heat. I can place a meter in series with the heat wire and adjust the wattage current reading to take into account initial warm up and continuous use. Could set it for 100w to give the tiles the best chance, with slow controlled warm up.
     
    Last edited: Jul 18, 2017
  11. Plan Tec Tiling

    Plan Tec Tiling Administrator Staff Member Trusted Advisor Professional Tiler JOTM Winner Top Contributor

    Location:
    Wimborne, Dorset
    Out of interest was this a solution from the electricians forum?
     
  12. john56897452

    john56897452 Active Member

    Location:
    NOTTINGHAM
    No......I clicked from your answer re lowering the wattage. Many thanks for that.

    Might help other people with the quartz tile UHF confliction. Dimmers for 700w plus are available.
     
  13. Uheat - Jake

    Uheat - Jake Tilers Forums Official Sponsor TF Official Sponsor

    A dimmer switch wouldn't be suitable for use with UFH.
    A dimmer takes away voltage therefore dropping the voltage of the heating cable below 230v will not give any power to the cable thus not heating the element at all and most likey buring the dimmer out.
     
  14. john56897452

    john56897452 Active Member

    Location:
    NOTTINGHAM
    Surely dropping the voltage drops the current available drawn by the heating cable hence controlling the heat (current drawn = heat, the max at 240v would be 300w). How can say a 700w rated dimmer be burnt out by a 300w max load? The cable is rated for 240v not dependent on 240v. Applying voltage via a variac would produce the same results.

    Using ohms law 240v at 300w would draw 1.25a. The current would not change by varying the voltage but the wattage would. If the voltage dropped to 120v the wattage rated by the heater wires would be 150w. Conversely to drop the wattage to a low 100w would require a voltage reduction to 80v. I think.
     
    Last edited: Jul 18, 2017
  15. Localtiler

    Localtiler Professional Tiler Top Contributor

    Location:
    Yorkshire
    I don't beleive there is a 300w kit available.
    On the subject of spacing, the warm up dcm pro, which is probably the same cable, have a strange recommendation, can anyone enlighten me on how you run that at 190w per m? Do you alternate the spacing ?
    IMG_4201.jpg
     
  16. Uheat - Jake

    Uheat - Jake Tilers Forums Official Sponsor TF Official Sponsor

    It's down to the spacings of the cables, if you want 200w/m2 for a heating cable you'd do the following,

    5 x 200 = 1000w so you need 1000w cable to heat that area at 200w/m2, you then find a cable around that wattage, so ours would be an Elektra 980w 98m Cable.
    You then have to work the spacings out by doing the area divided by the length of the cable. 5 / 98 = 0.051. You then have your cable spacings of 51mm.

    If you'd want 160w/m2 or 100w/m2 then you'd just change the equation around to suit them wattages and find a cable to suit.

    [​IMG]
    [​IMG]

    ad1b517efdd1eb4b2f36448d05724e38.png
     
    • Like Like x 2
    Last edited: Jul 19, 2017
  17. David Rogers

    David Rogers Active Member

    Location:
    Oxford
    John,

    Ohms Law is that V=iR where V = voltage, i = current and R = resistance (all applied to DC, but works for many sorts of AC too). The resistance of your UFH cable doesn't change with voltage, but is ultimately responsible for the heat output (watts) defined as i.V. If the cable is rated at 300W with a 240V supply (1.25 amps), then the resistance is 192 ohms (R = V/i = 240/1.25).

    If you reduce your voltage to 120V, Ohm's calculation suggests that your new current through that same resistance will be 0.625 amps (i = V/R = 120/192), generating a total heating wattage of only 75W (watts = Vi = 120*0.625) - very much less than you imagine.

    I agree with the comment about how modern dimmers on AC supplies actually work (they might either 'chop off' the peak voltage or else 'chop off' the time for which the full voltage is applied). They do not work in the same way as the good old (wire-wound) variable resistances of yesteryear. Whilst I doubt you will fry the dimmer (whatever they're doing, their output will be limited by the 192 ohm resistance of the UFH cable), you should maybe seek advice from the dimmer manufacturer/UFH cable supplier. Good Luck!
     
  18. john56897452

    john56897452 Active Member

    Location:
    NOTTINGHAM
    Thanks David,

    So the maths were about in the right area. Found a 10amp 1000w rated dimmer switch that should be more than up to the job. The theory stands though by reducing the voltage to say even 120v only 75w will be achieved by the heating wire. Still controlled by the floor sensor even if it takes all day to reach 20 c. This has got to be kind to the tiles and more than meets the tile manufacturers recommended 150w spec.
     
  19. Plan Tec Tiling

    Plan Tec Tiling Administrator Staff Member Trusted Advisor Professional Tiler JOTM Winner Top Contributor

    Location:
    Wimborne, Dorset
    Do keep us updated with how you get on with this. Do you have a infra red thermometer to read the surface temperature?
     
  20. john56897452

    john56897452 Active Member

    Location:
    NOTTINGHAM
    Yes I do have a hand held infrared thermometer. Just waiting for the dimmer to arrive before wiring everything up. Floor been laid about three weeks now so should be ready.
     
    • Like Like x 1
Loading...
Similar Threads - Goofed Underfloor Heating Forum Date
Electric UFH Partial underfloor heating Underfloor Heating Forum Jul 10, 2017
Tiling on underfloor heating The Welcome Forum Jul 5, 2017
Electric UFH Cost of underfloor heating Underfloor Heating Forum Jun 11, 2017
Water UFH WATER OR ELECTRIC UNDERFLOOR HEATING - New Extension Underfloor Heating Forum Jun 11, 2017
Water UFH Tiling on underfloor heating. Underfloor Heating Forum Jun 10, 2017
For Sale Underfloor Heating w/ Touch Screen Thermostat For-sale and Wanted Forum Jun 8, 2017
  • Find a Tiler Post a Job Ask a Question Tile Events Tile Pics Blog Adhesive Poll Handy Downloads