The HD is installed on the return line from the solar collector(s). When the temperature in the storage tank exceeds the pre-set limit (~80^oC / 176^oF), the controller switches a solenoid which directs the solar return flow through the HD before returning it back into the standard flow line. Alternatively a thermostatic mixing valve/tempering valve set to a suitable temperature can be used, providing mechanic, automatic regulation of flow through the heat dissipator.

As the hot water passes through the HD, heat is dissipated via the aluminium fins to surrounding air, the vertical fin arrangement promoting a passsive air current.

One HD-25 unit can dissipate 100% of the heat produced by an AP-30 collector in full sun, during very high ambient temperatures.

The copper pipe to and from the collector should be heavily insulated, as should the lengths of pipe to and from the HD. The solenoid valve prevents flow of collector return water through the HD during normal temperature operation, thus preventing unnecessary heat loss.