
Underfloor Heating Systems
1. Introduction
Thermolay is an underfloor electric heating system which is installed immediately under the finished 
surface of tiles or stone slabs. It renders the floor surface warm to the touch and supplements other 
heating in the same room.
Thermolay Comes In Three Forms:
Cable  Gives the best flexibility of layout and W/m2 (heating power per unit area), but requires additional work 
when laying. Three kit sizes cover areas from 1.2m
Mat  Requires less work when laying than cable, but gives a fixed W/m
2
1.0m
 to 5.0m2. Comes with self adhesive tape runs pre-attached for initially fixing mat to floor.
Flexi-Fast Mat This can be stretched lengthwise by 50% giving 133 to 200 W/m
with the same flexibility of layout as the Mat. Six kit sizes cover areas from 1.6m
At heat value of 200W/m2 (Flexi-Fast unstretched) can be useful in getting the best level of underfloor heating in a conservatory but 
it is not possible to rely on underfloor heating alone to heat a conservatory because of the large area of glazing, particularly the roof. 
In other rooms (if the building meets the latest Building regulations) it is possible to heat the room with underfloor heating alone 
if 200W/m2 (Flexi-Fast unstretched) is used. 
It is important that the correct size of mat/cable is used since the heating cable must not be cut. You will need to plan the layout carefully 
(see section 4) prior to purchase and get the right size mat/cable for the installation. It is possible to use more than one mat/cable for an 
installation by parallel connection but no cable in the system is allowed to cross over or under any other.
2
 to 6.4m2.
2
 of 160. Six kit sizes cover sizes from 
2
. It requires the least work when laying 
2
 to 15.0m2.
2. What You Will Need
a. Electric Cable/Mat (one or more as required):
Cable Kits – 100 to 200 W/m
Part No  Length  Coverage  W  Ω 
UFHC24  24m  1.2 to 2.4m 
UFHC32  32m  1.6 to 3.2m 
UFHC64  64m  3.2 to 6.4m
Supplied with a reel of securing tape.
Mat Kits (Width 0.5m) – 160W/m
Part No  Length  Coverage  W  Ω 
UFHM2 2m 1.0m 
UFHM3 3m 1.5m 
UFHM4 4m 2.0m 
UFHM6 6m 3.0m 
UFHM8 8m 4.0m 
UFHM10 10m 5.0m
Securing tape built into webbing.
Flexi-Fast Mat Kits (Width 0.4m) – 133 to 200W/m
(Mat Width 0.4m, length can be stretched to 150% of figures 
quoted) – 133 to 200W/m
Part No  Length  Coverage  W  Ω 
FFM25  2.5m  1.0 to 1.5m 
FFM40  4.0m  1.6 to 2.0m 
FFM60  6.0m  2.5 to 3.7m 
FFM100  10.0m  4.0 to 5.0m 
FFM150  15.0m  6.0 to 9.0m 
FFM250  25.0m  10.0 to 15.0m
Supplied with fixing pegs.
2
b. Controller
Installations without temperature control could give a floor 
temperature of around 55°C which is not dangerously hot but is 
wasteful of energy.
There are three controllers (temperature probe included) in the 
Thermolay range, which, as well as regulating floor temperature by 
means of an inclusive remote temperature probe, two of three will 
define the time periods when the system is active. These are:-
2
2
  240W  220 Ω
2
  320W  165 Ω
2
  640W  83 Ω
2
2
  160W  330 Ω
2
  240W  220 Ω
2
  320W  165 Ω
2
  480W  110 Ω
2
  640W  83 Ω
2
,  800W  66 Ω
2
2
  200W  264 Ω
2
  320W  165 Ω
2
  480W  110 Ω
2
  800W  66 Ω
2
  1200W  44 Ω
2
  2000W  26 Ω
TPT1 Electronic ON/OFF Thermostat
An electronic thermostat with ON/OFF control 
and a 10º to 30ºC temperature range.
TPT44 24 Hour Digital Clock Thermostat
Programmable thermostat with a 24 hour clock 
face which controls both underfloor and room 
TPT1
temperature.
TPT88 24 Hour/7 Day Multi-Programmable 
Thermostat
Stylish 7 day programmable thermostat with 
large display screen.
RAMSES 714 A Electronic Thermostat
An electronic thermostat with ON/OFF control 
TPT44
and a 10º to 30ºC probe temperature range.
All controllers come complete with a 4 metre 
flying lead temperature probe.
c. RCD Protection
This is essential to give the highest level of 
electrical safety protection. The 10 year 
guarantee cover of mats and cables as 
components is not effective unless the 
installation is protected by an RCD. 
This could be covering the total house supply but 
a better solution would be to use the RCD10WPV 
or the TPF10WL from the Thermolay range.
d. Screed
This is used to cover cable or mat and provide a 
bedding to locate and restrain tiles/stone slabs. 
The required screed is self levelling or latex and 
it is possible to use standard flooring grade tile 
adhesive. A different grade is usually 
recommended for wood and concrete/screed 
floors respectively. Suitable products are 
manufactured by Ardex, Bal, Evostick and F.W. 
Ball amongst others. Please consult your local tile stockist or DIY 
store, who would also be able to recommend a suitable flexible 
additive which is essential to be mixed with the adhesive and a 
suitable primer for the floor surface.
TPT88
RAMSES 714 A
RCD10WPV
e. Duct Tape
For the Mat and Flexi-Fast Mat systems you will need a reel of duct 
tape (e.g. Duck) to fix the cold cable and probe with flying lead.

3. Preparation of Surface
Wood Floor
This will generally be either floorboards or chipboard panels. With floorboards 
any loose boards will need to be firmly fixed and it will be necessary to cover 
the complete floor with 20mm plywood sheeting fixed at 200mm centres.  
With chipboard panels ensure they are all firmly fixed and cover with plywood 
as above. The use of a primer recommended by your screed/adhesive supplier 
is essential. This must be applied to the complete floor surface to be tiled.
Grooves will need to be made to accommodate the cable/mat flying lead  
(cold cable) and the temperature probe with its flying lead as these are  
thicker than the heating cables (mat or cable).
Concrete/Screed Floor
Repair any fissures or patches with a cement sand mixture with PVA added to 
improve adhesion. The use of a primer recommended by your screed/adhesive 
supplier is essential. This must be applied to the complete floor surface to  
be tiled.
Grooves will need to be made to accommodate the cable/mat flying lead (cold 
cable) and the temperature probe with its flying lead as these are thicker than 
the heating cables (mat or cable).
4. Planning Mat/Cable Layout
Cable Layout
The layout and installation of mat/cable must be carried out in accordance 
with these instructions. If there is any doubt about how to proceed please 
contact the Helpline on 020 8450 0515 or a competent professional person.
For wood floors the gap between the cable runs should be 82mm (see figure 1).  
This gives 120W/m 
should be 62mm, this gives 160W/m 
runs should be 50mm.
Initially decide on a location for the RCD and controller* then plan the run of 
the cold cable to the start of the heating cable and the run of the temperature 
probe flying lead, remembering that no cable should cross over or under any 
other or the temperature probe which should be positioned as in figure 3.  
The cold cable and probe flying lead are 4m long and may be shortened  
if necessary. 
Cables should be run backwards and forwards between walls or obstructions 
(see the example given in figure 2). Cables should not be run under  
permanent fixtures. The cables should not get closer to the tiling edge than 
50mm and should clear permanent fixtures by the same amount.
If the largest cable in the range is not long enough a second cable can be used 
with the two cold cables connected to the controller – black to black to 
controller live output and blue to blue to controller neutral output.
* These should not be located in a bathroom or near a sink or cooking facilities in a kitchen.
Figure 1
Figure 2
Figure 3
2
. For concrete/screed floors the gap between cable runs 
2
. To give 200W/m2 the gap between cable 
Wood 
floors
82mm
120W/m
Conserve energy by 
avoiding areas (such as 
under water cistern) which 
are not a normal area for 
foot contact.
Heating Cable
Temperature Probe
Controller (must not be 
mounted inside bathroom
A groove should be made 
in the floor surface to 
bring the upper surface of 
=
=
the temperature probe and 
cable level with the 
heating cable.
Concrete/ 
screed floors
62mm 50mm
2
160W/m
2
200W/m
Mat Layout
These have a fixed output of 160W/m2 and are suitable for concrete/ 
screed floors.
Initially decide on a location for the RCD and controller* then plan the run of 
the cold cable to the start of the heating mat and the run of the temperature 
probe flying lead remembering that no cable should run under or over any 
other or the temperature probe which should be positioned as in figure 3.  
The cold cable and probe flying lead (both 4m in length) may be shortened  
as necessary.
Mats should run backwards and forwards between walls or obstructions. The 
techniques shown in figures 4 and 5 may prove useful. When cutting the mat 
webbing to give direction changes or bypassing of obstacles take care not to 
cut or damage the heating cable. Mat runs should be separated by at least 
30mm and should not be run under permanent fixtures. The cables within the 
mats should not get closer to the tiling edge than 50mm and should clear 
permanent fixtures by the same amount. If the longest mat in the range is not 
long enough to cover the required area a second mat or cable can be used 
with the two cold cables connected to the controller controller – black to black 
to controller live output and blue to blue to controller neutral output.
* These should not be located in a bathroom or near a sink or cooking facilities in a kitchen.
Figure 4
When cutting the mat 
webbing to give direction 
changes or the bypassing 
of obstacles take care not 
to cut or damage the 
heating cable.
Figure 5
Obstacle cut
Empty square
Filled square
Corner cuts Plain wall cut
Flexi-Fast Mat Layout
These give an output of between 133 and 200W/m2 depending on the degree 
of stretch (maximum stretch gives 133W/m
Initially decide on a location for the RCD and controller* then plan the run of 
the cold cable to the start of the heating mat and the run of the temperature 
probe flying lead remembering that no cable should run under or over any 
other or the temperature probe which should be positioned as in figure 3.  
The cold cable and probe flying lead (both 4m in length) may be shortened 
2
as necessary.
Mats should run backwards and forwards between walls or obstructions. 
Generally it will be sufficient to pin the mat at the start and finish of each  
run if there is a degree of stretch in the mat. The techniques shown in figures  
4 and 5 may prove useful. When cutting the mat webbing to give direction 
changes or bypassing of obstacles take care not to cut or damage the heating 
cable. Mat runs should be separated by at least 30mm and should not be run 
under permanent fixtures. The cables within the mats should not get closer to 
the tiling edge than 50mm and should clear permanent fixtures by the same 
amount. If the longest flexi-fast mat in the range is not long enough to cover 
the required area at the required W/m 
used with the two cold cables connected to the controller – black to black to 
controller live output and blue to blue to controller neutral output.
* These should not be located in a bathroom or near a sink or cooking facilities in a kitchen.
2
).
2
 a second flexi-fast mat or cable can be 
150mm

5. Installation of Cable or Mat 6. Installation of Controller & RCD
Wood Floor
Initially remove any dust and debris from the floor surface and follow the notes on preparing 
the surface in section 3. Then check the flexi-fast mat or cable resistance against the figures 
given in section 2, also check the temperature probe resistance (approx 110kΩ at 20°C for 
RAMSES 714 A and TPT88, 10kΩ at 20°C for TPT1 and TPT44, decreasing with increasing 
temperature). If the readings are okay proceed with laying the flexi-fast mat or cable:-
a. Cable.
During the installation wear soft soled shoes and avoid treading on the probe or any 
of the cables. Working to the planned layout make grooves for the cold cable and the probe 
with flying lead to give the same overall height above floor level as the heating cable then 
remove debris. Tape the temperature probe and flying lead as well as the cold cable into their 
respective grooves using the tape provided. When positioning the heating cable ensure that 
it is well clear of the temperature probe (see figure 3). Tape the cable to the floor according 
to the plan developed in section 4 with an 82mm cable spacing as shown in figure 1. 
The cable should be taped at every bend and also five times along the runs between bends 
as shown in figure 6. 
Check the cable and probe resistance and then coat the cables and adjacent floor with a thin 
layer of adhesive with the essential flexible additive.
The cable and probe resistance should be checked again after the adhesive has set. 
If the cable and probe resistance is okay the adhesive with the essential flexible additive should 
now be spread evenly over a section of the floor until the cable is completely covered, then slab 
laying or tiling is carried out over this section. The process is repeated section by section until 
the floor is completed.
When grouting it is essential to use a flexible additive mixed with the grout. The cable and 
probe resistance should be checked again on completion of the grouting.
NOW ALLOW 10 DAYS FOR THE SCREED TO COMPLETELY SET AT A NORMAL ROOM 
TEMPERATURE BEFORE COMMISSIONING.
Figure 6
b. Flexi-Fast Mat
During the installation wear soft soled shoes and avoid treading on the probe or any 
of the cables. Working to the planned layout make grooves for the cold cable and the probe 
with flying lead to give the same overall height above floor level as the heating cable then 
remove debris. Tape the temperature probe and flying lead as well as the cold cable into their 
respective grooves using duct tape. When positioning the flexi-fast mat ensure that the heating 
cable is well clear of the temperature probe (see figure 3). Drill two holes 6mm dia. at least 
17mm deep close to the ends of each run of flexi-fast mat. These are to locate the push-fit 
plugs supplied. They should engage with each of the two outer runs of webbing within the 
flexi-fast mat (not the cable). The start of each run of flexi-fast mat should be placed in position 
smooth side down and the plugs pushed home hard trapping the webbing under the heads of 
the plugs. The mat should be stretched to close to its maximum length to give 133W/m 
two more plugs pushed home into the pre-drilled holes at the end of the run. Cut the webbing 
(avoiding damage to the heating cable) to reverse direction or avoid obstacles using the 
techniques shown in figures 4 and 5 whilst continuing to fix further runs of the flexi-fast mat. 
When reaching the last two or three runs the stretch can be adjusted to use up the complete 
cable (count the cable loops on one side of the remaining mat length to do this). 
Check the cable and probe resistance and then coat the cables and adjacent floor with a thin 
layer of adhesive with the essential flexible additive.
The cable and probe resistance should be checked again after the adhesive has set. 
If the cable and probe resistance are okay the adhesive with the essential flexible additive 
should now be spread evenly over a section of the floor until the flexi-fast mat is completely 
covered, then slab laying or tiling is carried out over this section. The process is repeated section 
by section until the floor is completed.
When grouting it is essential to use a flexible additive mixed with the grout. The cable and 
probe resistance should be checked again on completion of the grouting.
NOW ALLOW 10 DAYS FOR THE SCREED TO COMPLETELY SET AT A NORMAL ROOM 
TEMPERATURE BEFORE COMMISSIONING.
2
 and 
Concrete or Screed Floor
Initially remove any dust and debris from the floor surface and follow the notes on preparing 
the surface in section 3. Then check the flexi-fast mat or cable resistance against the figures 
given in section 2, also check the temperature probe resistance (approx 110kΩ at 20°C for 
RAMSES 714 A and TPT88, 10kΩ at 20°C for TPT1 and TPT44, decreasing with increasing 
temperature). If the readings are okay proceed with laying the flexi-fast mat or cable:-
a. Cable
Proceed as for wood floor (a) except use a cable spacing of 62mm (see figure 1).
b. Mat
During the installation wear soft soled shoes and avoid treading on the probe or any 
of the cables. Working to the planned layout make grooves for the cold cable and the probe 
with flying lead to give the same overall height above floor level as the heating cable then 
remove debris. Tape the temperature probe and flying lead as well as the cold cable into their 
respective grooves using duct tape. When positioning the mat ensure that the heating cable is 
well clear of the temperature probe (see figure 3). Fix the matting smooth side down using the 
three runs of adhesive tape already fixed to it. This is best achieved by removing the backing on 
this tape over a short length then fixing the mat down before moving to the next section. Cut 
the webbing (avoiding damage to the heating cable) to reverse direction or to avoid obstacles 
using the techniques shown in figures 4 and 5. 
Check the cable and probe resistance and then coat the cables and adjacent floor with a thin 
layer of adhesive with the essential flexible additive.
The cable and probe resistance should be checked again after the adhesive has set. 
If these are both okay the adhesive with the essential flexible additive should now be spread 
evenly over a section of the floor until the mat is completely covered then slab laying or tiling is 
carried out over this section. This process is repeated section by section until the floor is 
completed.
When grouting it is essential to use a flexible additive mixed with the grout. The cable and 
probe resistance should be checked again on completion of the grouting.
NOW ALLOW 10 DAYS FOR THE SCREED TO COMPLETELY SET AT A NORMAL ROOM 
TEMPERATURE BEFORE COMMISSIONING.
c. Flexi-Fast Mat
Proceed as for wood floor (b) except the degree of stretch is low to give 200W/m2.
Note: The 10 year guarantee cover of mats and cables as components is not effective 
unless the installation is protected by an RCD.
The installation of the Controller and RCD must be carried out according to their 
respective instructions and the installation must comply with the current I.E.E. Wiring 
Regulations. If there is any doubt about how to proceed please contact the Helpline 
on 020 8450 0515 or a competent professional person.
Fix the controller and RCD in the required positions. We suggest the controller is mounted 
around head height for ease of programming. Terminate the incoming supply leads to the RCD 
in accordance with its instructions. Connect the RCD output to the incoming supply terminals of 
the controller in accordance with its instructions. After measuring and recording the overall 
cable resistance the cold cable may now be connected to the output terminals of the controller, 
shortening the cold cable as necessary. After measuring and recording the temperature probe 
resistance and the approximate room temperature the probe flying lead may now be connected 
to the probe terminals on the controller, shortening the flying lead as necessary.
7. Commissioning
Referring to the appropriate instructions turn the RCD on and set the controller to the 
maximum temperature in continuous operation. There should be a noticeable change in the 
floor surface temperature after one hour with a wood floor and up to five hours with a 
concrete floor.
The controller should now be adjusted to a temperature giving the required comfort and the 
timing (if incorporated) set as required.
We recommend a temperature setting of 28°C
8. Do’s and Do Not’s
Do not cut the heating cable. 
Do not leave surplus matting or cable rolled up under units or fixtures – use the right size. 
Do not cross any cables. 
Do not switch mat or cable on until 10 days after fitting. 
Do not cut or prepare tiles etc on top of the finished area.
Do consult the Helpline or a competent professional person if you are unsure how to proceed. 
Do use an approved flexible additive mixed with screed/adhesive. 
Do use an approved flexible additive mixed with the grout. 
Do cover the area where mats or cables have been laid for protection. 
Do keep a record of cable and probe resistance for later referral. 
Do keep a drawing of where the mat/cable was laid to enable any future structural work to 
proceed without damage.
Do fit an RCD if the installation is not protected by one already. Timeguard does not 
guarantee cables or mats where the installation is not RCD protected.
9. Guarantees
Heating Cables, Mats, Flexi-Fast Mats, Temperature Probes 
(including flying leads).
It is necessary to retain proof of purchase to validate the guarantee. 
In the unlikely event of any of these products becoming faulty due to defective 
material or manufacture within 10 years of the date of purchase please contact 
Timeguard and it will be replaced free of charge. 
This guarantee is subject to the following conditions:a. The cable/mat/flexi-fast mat has been installed and used in full compliance with 
the installation instructions 1 – 8 above. 
b. The cable/mat/flexi-fast mat has been earthed and protected by an RCD at all times. 
c. The cable/mat/flexi-fast mat has been used with a controller supplied by Timeguard. 
d. Proof of purchase will be required so keep an invoice detailing the cable/mat/
flexi-fast mat(s) and controller purchased. 
e. Accidental damage to the cable/mat/flexi-fast mat during or after installation is not 
covered.
The guarantee covers the above components ONLY but NOT installations and 
associated floor covering products.
There is no other guarantee, express or implied. No claim can be brought 
against the manufacturer or its agents for any consequential damages 
whatsoever.
Controllers and RCD’s.
It is necessary to retain proof of purchase to validate the guarantee. 
In the unlikely event of any of these products becoming faulty due to defective 
material or manufacture within 3 years of the date of purchase please return it to 
your supplier with proof of purchase and it will be replaced free of charge.
There is no other guarantee, express or implied. No claim can be brought 
against the manufacturer or its agents for any consequential damages 
whatsoever.
Helpline & Technical Service Direct Line 
Tel: 020 8450 0515 Fax: 020 8450 0635
Email: csc@timeguard.com 
Website: www.thermolay.co.uk
Victory Park, 400 Edgware Road, London NW2 6ND
Timeguard Limited 
A  Group Company
67.058.472
Zerofour – January 2012