Safety

A safety device must be installed on heating systems that, in-

dependently of the control unit, can also operate in the absence

of electric current to cut off the supply of hot water to system

circuits, so that the temperature around the heating elements

does not exceed 55 °C for screeds based on cement or calcium

sulphate. These values can be reduced for other types of cov-

erings, for example to 45 °C for asphalt support layers. In any

case, the manufacturer's specifications must be followed for all

types of coverings.

Cooling systems require a dew point detection device to cut

off the supply of cold water before the formation of condensa-

tion, while the temperature around the cooling elements must

not reach the dew point.

Clearances

The system piping must be positioned more than:

- 50 mm away from adjacent structures;

- 200 mm away from chimneys and open fireplaces, open or

walled-up shafts and lift shafts.

Expansion edge strips

Before pouring the screed, an edge strip should be laid along

the walls and any other component of the building that pen-

etrates into the screed, such as doors, pillars and treads.

The edge strip must extend from the support base to the upper

layer of the floor finish, and allow the screed to move by at least

5 millimetres.

If there are more insulation layers, the edge strip must be laid

before laying the upper layer. When the screed is cast, the edge

strip must be secured in order to avoid any change of posi-

tion. The upper section of the edge strip, above the floor finish

should not be cut before the floor covering is completed, or be-

fore the filling is cured in the case of textile or plastic coverings.

Expansion joint in screeds

Heated screeds on which stone or ceramic coverings are ap-

plied must be divided with joints into surface areas no larger

than 40 m2 and with a maximum length of 8 metres. In the case

of rectangular rooms, the areas may exceed these dimensions

but with a ratio between the two sides of at most two to one.

Each irregular area must have joints so that there are only rec-

tangular areas with the above-specified dimensions.

If contraction joints are made, their depth should not exceed

one third of the thickness of the screed, taking into account the

position of the pipes and sealing such joints after initial heating.

Movement joints and edge strips can only be crossed by supply

pipes (output and return of a circuit), and only at the same level.

In this case, they must be covered by a tube of flexible insulation

about 30 cm long.

As far as possible, expansion joint strips must start from edges,

in points where there are enlargements or narrowings of the

screed surface. Expansion joint strips or "trowel cut" joints must

be made on doors or corridors.

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Underfloor Radiant Systems - Product Guide

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