Types of Heat interface Unit solutions...
Indirect heat interface units facilitate a separation between the primary and secondary systems, using a plate heat exchanger to transfer energy from liquid in the primary system to liquid in the secondary system. Where installations call for separation between the primary and secondary systems indirect heating interface units provide this.
A further distinction can be made between heat interface units which are thermostatically controlled and those which use proportional hydraulic control.
Thermostatic Control & Proportional Hydraulic Control
Most heat interface units on the market utilise thermostatic control systems. These units have the advantage of a lower initial cost, but in many cases the users will notice a fluctuation in hot water temperature. Many brands of heat interface units (HIU) address this problem by using a fast-responding thermostat specifically designed for use in heat interface units (HIU).
Proportional hydraulic control enables a more constant domestic hot water temperature, completely eliminating the use of thermostatic control. There is a slightly higher initial cost, but a better experience for building occupants as water temperature stabilises very quickly.