Devex Systems’ storage heating is designed to be used in concrete slabs in houses, offices, and factories where there is an opportunity to use electricity on an ‘Off-Peak’ or ‘Time of Use’ tariff.

The heating cables are embedded in a thick layer of concrete (generally between 70-150mm in thickness). The concrete slab stores the heat produced during the low tariff period and emits this heat throughout the rest of the day.

Installed output

In order to accurately determine the size of the heating element, a heat loss calculation for each room should be carried out. As this is beyond the scope of this Floor Heating Guide, we will assume that heat loss calculations are available and we will provide typical values.

To ensure that the heating systems respond quickly, a safety factor of 30% should be added in to the heat loss calculation. A low tariff period of, for example, 8 hours means that the cables have 8 hours to generate the required amount of heat to be released over the next 16 hours before the next low tariff period begins.

The following equation is used to calculate the total required output for storage heating systems:
Required Output = Calculated heat loss x 24/t x C, where: t = Period of heat generation (time of low tariff availability), hours. C = Safety factor of 1.3

Typical installed output for a storage heating system is 170W/m. For wet areas the installed output is typically 200W/m. Where the required installed output is greater than 200W/m, the heating system should be supplemented by another heating system.

Product choice

The deviflex DSOT-34 cable has been specifically designed for In Slab heating under Australian conditions and is recommended for this application. The DSIG-17 and DTIP-18 can also be used in this application. However, additional care is required as these cables are not as robust as the DTCE-30. They also require more cable and closer spacing due to their lower output per lineal metre.