The direct heating systems from Danfoss – the Deviflex DTIR range – require an installed output of up to 150 W/m2 and the heating cables are placed near the floor surface. Normally, heating cables or mats are placed in the lower part of a concrete layer with a max. thickness of 5 cm.
The direct heating system may be installed either as a total heating system or as a supplementary heating system. As a total heating system the DEVI system is the only heating system in a room. As a supplementary heating system the DEVI system supplements another heating system in a room, e.g. electrical radiators.
The total heating system is designed to cover the total heat loss and provide full heating while the supplementary heating system is designed to provide a warm and comfortable floor.
The Deviflex installed output
The installed output shows how many watts per m2 (W/m2) have to be installed in order to cover the heat loss and provide the necessary heating. The heat loss mainly depends on the climate conditions and the insulation in the building. We will assume that information about the heat loss is available.
When the total heating output for a room is to be determined, the available area (m2) has to be estimated. This means that the area covered by cupboards, bathtubs, lavatories, etc. has to be deducted from the total area of the room. Therefore, the required installed output will be proportionally higher on the usable floor space.
In order to ensure a quickly responding heating system, the total calculated output has to be increased by approx. 30%. The result of this calculation will reveal the required output for the heating element – cable or mat.
Normally, the calculated output for a new and well insulated building would be 40-60 W/m2 and up to 150 W/m2 in the bathrooms. If the calculated installed output is higher than 150 W/m2, we recommend that additional heating systems be considered.
In houses with large glass and door areas we recommend the use of rim zone heating. The installed output in a rim zone area is approx. 200 W/m2. For further information about rim zone heating, please refer to the paragraph “Accumulating heating”.
DEVImat – the product choice for under concrete floors
When DEVI’s underfloor heating system is installed as a direct heating system, the deviflex cables with a maximum output of 18 W/m should be used. Besides, the devifast™ fitting bands will ensure a quick and easy installation. Alternatively, the devimat (a pre-prepared cable mat) with a maximum output of 150 W/m2 may be used. When the total required output has been calculated, the cable with the nearest and higher output should be chosen.
To exploit the optimal comfort and economy of the system thermostats with simple or intelligent timers should be used – the Danfoss devireg 540 or the Danfoss devireg 550. You can browse the full offer of Concrete Floors Underfloor Heating Solutions from Danfoss – the DEVImat Deviflex system.