All Herz HIUs incorporate a first Fix rail with isolation ball valves to allow shell and core pipework to be completed without the HIU being fitted, this also aids maintenance once the HIU is installed. First fix rail ball valves are fitted with drain valves to facilitate draining with integral test points fitted on the primary and secondary heating circuits on most units.
Herz offer 2 indirect HIUs incorporating two heat exchangers for domestic hot water and space heating, the Guildford and Dublin models. Herz also offer a direct HIU, the York HIU, with a single heat exchanger for domestic hot water and the space heating supplied direct through the HIU from the primary supply. All three of these HIUs incorporate a Pressure temperature control valve which allows the DHW heat exchanger to operate on demand only and gives the DHW 100% priority over the space heating.
When the hot water demand ceases the pressure temperature control valve will immediately stop the primary flow into the heat exchanger. Therefore there is no drain on the primary heating when there is no demand, so no “extra energy usage” when residents are on holiday for example.
Herz offer a HIU with a single heat exchanger supplying DHW. The Oxford HIU also incorporates the pressure temperature control valve to control the DHW supply and temperature. The Oxford HIU has dual orientation and has been designed with the ball valve connections at the top or at the bottom depending on the requirement.
Herz also offer a HIU with a single heat exchanger supplying heating. The Ecosse model has been specifically deigned for projects with existing water cylinders or alternative hot water storage or supply methods. This HIU can be easily configured into an "S" Plan system.