Although fully modulating across all demand conditions the operation can be described in three distinct demand modes.
Demand below output rating
Under this condition all the required DHW passes directly through the integral heat exchanger and is heated to the required outlet temperature in a single operation. The flow through the integral heat exchanger is made up of the point of use demand with the remaining balance being drawn from the buffer storage. It is by this method that the entire buffer storage is maintained at the required set point.
Demand at the output rating
Under this condition all the required DHW passes directly through the integral heat exchanger and is heated to the required outlet temperature in a single operation. The flow through the heat exchanger is made up entirely of the point of use demand. The buffer storage volume is available for use at the required outlet temperature.
Demand above output rating
Under these conditions the required DHW is made up of the integral heat exchanger flow supplemented by the buffer storage. Cold incoming water is restricted to the base of the buffer storage. Internal deceleration plates fitted inside the buffer storage prevent temperature dilution of the stored volume. The period of peak flow is used to determine the required volume of stored water.