Reversible or multipurpose?
Often the market tends to associate the multipurpose units operation with heat pumps, so it is necessary to define the unit trying to be as simple and direct as possible and starting from what a multipurpose unit is NOT.
A multipurpose unit is NOT a reversible heat pump and it is NOT a chiller.
A multipurpose unit, thanks to the complexity of its operating logic and the design of its circuit, is designed to make the most out of the possibility to supply both hot and cold water at the same time.
If a multipurpose unit is conceived in similar terms to a reversible heat pump or a chiller during the system design phase, this could lead, later on, to problems and malfunctions in the field, both to the unit and to the system as a whole.
It is true that a multipurpose unit can supply hot, cold or hot + cold water. Such a unit, however, due to the operation logic and control of refrigerant gas and oil returns, needs to switch, rotate and defrost the refrigerant circuits according to the parameters set in the factory, since such a unit is designed to work predominantly on the HOT + COLD setting (combined load).
This means that in a multipurpose unit, the flow on the hot water and cold water circuits must always be guaranteed (PUMPS in ON mode) since the absence of flow could not only damage the unit, but will generate alarms that will lead to the unit shutting off.
It follows that the correct selection of a multipurpose unit brings with it benefits in terms of energy savings and design-phase savings which will be summarized below.
In the next articles, we will deal with the most common errors in sizing both a heat pump and a multipurpose, and we will give some valuable suggestions.