Taking into account the DIN VDE 0100-701 standard, electrical underfloor heating systems with an operating voltage of up to 25V alternating voltage (AC) or up to 60V direct voltage (DC) may also be installed in a shower without a tray. The following points from the standard, among others, must be taken into account here:
701.30 Determination of general characteristics
Chapter point 701.30.103 defines that showers without a tray belong to area 1 and not to area 0.
701.5 Selection and installation of electrical equipment
Under chapter point 701.512.2.4.101.3, area 1 is defined in such a way that electrical equipment protected by extra-low voltage by means of SELV or PELV may be installed there. Permissible are 25V alternating voltage (AC) or 60V direct voltage (DC) and the power source must be installed outside areas 0 and 1. Further information can be found in chapter 701.414 - Protective measure: protection by extra-low voltage by means of SELV or PELV.