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Under-Carpet Heating Install - FAQ

What method of under-carpet heating does Heatwell use?
Heatwell uses our Pro Series heating element.  The Pro Series cable is attached to the floor, a fibreglass matt is placed over the top, a self-levelling compound or screed is poured over the top.  The result is a heating element that is encased and protected from heavy furniture.
We do not use a matt style system.  We have found that heavy furniture can damage the heating element wire with a matt system.

How long does the self-levelling compound (screed) take to dry?
Please allow 24 hours. In cold conditions, drying could take more than 24 hours. Tiling or waterproofing should not be done if the floor is not fully dry.

When is the under-carpet heating installed?
Underfloor heating under carpet is done just before the carpet is laid.  All painting and other prep work should already be complete.

Can any type of carpet or underlay be used?
Unfortunately not.  You must be very careful of the thermal factor of your carpet and underlay.  With products like thick wool carpet, there is a natural level of insulation that does not work well with under-carpet heating.  Some types of underlay are designed with insulation in mind.
Please ask your carpet specialist if your choice of carpet will suit under-carpet heating.

Can under-carpet heating be installed over the top of any type of floor?
Underfloor heating can be installed directly over concrete as long as there are no cracks, holes, or sharp protrusions.
Installation over the top of particle board or plywood however is not recommended.  Expansion and contraction of particle board or plywood is a certainty in NZ’s conditions, Expansion and contraction risks cutting the electrical element where the flooring butts together.

How should particle board or plywood be prepped?
There are three excellent options.  The most common is laying tile and slate underlay.
Another option is to lay 6mm insulation sheeting. Infinity from Tile Max is an example.  Insulation sheeting has the big advantage of improving the efficiency of the underfloor heating and will save you money in the long run.
The third option is to incorporate an anti-fracture rubber-based system.  Strata Flex from Surtec is an example.  This option is probably the most expensive, however, it adds the least to the floor height.

What condition does the floor need to be prior to the under-carpet heating installation?
All floors need to be clean, free of dust, and free of paint.  They also need to be free of any cracks, holes or sharp protrusions.
A floor that is being renovated needs have all the remains of the previous flooring removed.  Including glue from fixing down carpet or underlay.

Is there any wall prep required?
Yes.  We need to mount the thermostat / controller.  The cold tails that are attached to both ends of the heating element must come up from the floor to the thermostat mounting.
25mm holes need to be drilled through the wall nogs.  A 50mm wide and 25mm deep section must be checked out of the bottom plate of the wall.
A draw wire from the thermostat mount down to the bottom plate is essential.
The mounting box for the thermostat can be installed either vertically or horizontally.  Heatwell has thermostat options for both.

What does the Electrician need to know?
A 900W element draws 3.91amps and is 58.78ohms in total.

Any heating element 1000W or above needs a dedicated RCD circuit breaker back to the board.
All our thermostats have a 15amp maximum capacity.
We allow 100W per m2 for under-carpet heating.

What does the Carpet Layer need to know?
Please don’t drop anything sharp or heavy on the screeded surface.
Be very careful of your carpet gripper!  Where the floor heating goes up the wall to the thermostat is the danger point.  Putting a nail through the cable will ruin everyone’s day!


258 Forrest Hill Rd
Forrest Hill

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Ph: 09 392 8533
Toll free: 0800 392 853

Email: info@heatwell.co.nz

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