Full Product Manual

Planning the Installation
SECTION 3
5
3.4 Calculation of On-Center Spacing (OC)
In order to fit the TempZone™ Floor Heating Cable properly in the designated space, it is necessary to
determine the spacing between the cables. This is called on-center spacing or OC. Refer to either the
“Product Selection Guide--120V” or “Product Selection Guide--240V” in section 9 to determine appropriate
spacing for the installation.
Combine cable lengths if more than one is needed for the installation. Once the OC spacing has been
calculated and the correct length of cable for the area to be heated is obtained, installation of the floor
heating cable can begin. The formula assumes that 3-inch spacing will be used between the heating cable
and walls or fixed objects, and full OC spacing between cable runs. To make cable placement easier, make
a measuring template out of cardboard in the width of the OC spacing less the thickness of the cable. Place
the template along to the cable run just completed to determine where the next run of cable should be
positioned.
IMPORTANT: To avoid overheating, OC spacing should not be less than 3 inches and area loading
should not exceed 15 watts/square foot.
IMPORTANT: Do not order more cable than necessary as cable cannot be shortened.
3.7W Cable vs 3W Cable Wattage Yields
3 W Cable 3.7 W Cable
Membrane Type
(number of studs)
Watts/linear ft 3 3.7
Watts/ft2 at 2.5” 14.4 17.76* Prodeso (2)
Watts/ft2 at 3” 12 14.8 Cable Fixing Strip (3)
Watts/ft2 at 3.5” 10.3 12.7 DITRA-HEAT (2)
Watts/ft2 at 3.75” 9.6 11.84 Prodeso (3)
Watts/ft2 at 4” 8.7 11.1 Cable Fixing Strip (4)
Watts/ft2 at 4.75” 7.6 9.3 DITRA-HEAT (3)
Watts/ft2 at 5” 7.2 8.9 Cable Fixing Strip (5) & Prodeso (4)
Wire diameter variable 4.37
DITRA-HEAT: 1.75”
Prodeso spacing: 1.25”
Strips: 1”
*Not recommended as it exceeds the 15 watt per square foot limit set by the National Electric Code.