The most frequently used bath heating systems consist of plastic exchangers, with the accompanying pipes and regulation systems also made from plastics. The exchangers can be set up inside (circulation of centrally heating liquid) or beside (circulation of processing liquid) the bath, depending on customer preferences. When the exchanger is set up inside the bath, special removable protection plates are supplied in order to limit loss and damage to a minimum. It is therefore also possible to remove exchangers from the bath without having to remove processing liquids.