Principle of operation of the hydraulic clutch

A hydraulic coupling is a device designed to connect the boiler and heating circuits. It allows for the connection of several heating devices with the same or different operating parameters (gas boiler, water-jacketed fireplace, heat pump, etc.) with several heating circuits, even those with different temperature parameters (DHW production, supply to convection radiators, supply to underfloor heating, etc.). Learn more about the essential component connecting boiler and heating circuits: the hydraulic coupling. Diagram, operating principles, and construction—you’ll find all the information about this product in the post below.

The FERRO RSHI model is an insulated vertical water tank featuring hot connections at the top (supply from the heat source and outlet to the loads) and cold connections at the bottom (return of the medium from the loads, return of the medium to the heat source), and it is a type of hydraulic coupling. The operating principle of this equipment is simple in theory—each connected circuit must be equipped with its own flow pump, which ensures proper circulation of the heating medium.

Advantages of using a hydraulic coupling

The greatest advantage of a hydraulic coupling is the virtually complete absence of interference between the operation of heating system circuit pumps and the operation of heat sink circuit pumps; furthermore, heat sink system pumps do not interfere with each other’s operation, nor do heat source circuit pumps.

The hydraulic coupling is used in medium- and high-capacity systems, where it successfully replaces multi-way mixing valve and mixing-pump systems. Four basic operating states of the hydraulic coupling can be distinguished:

system startup. This is performed with the heating medium flow through the heat consumers shut off. The temperature of the coupling rises, and the medium returning to the heat source (boiler) reaches the correct return temperature, which significantly helps protect the boiler against low-temperature corrosion. Next, the fluid circulation in the heat consumer circuits is started;

the heat demand from the heating circuits exceeds the amount of energy generated by the heat source(s), meaning that the fluid flow on the load side draws energy from the heat exchanger, cooling the fluid returning to the boiler. A signal indicating an increase in energy demand is sent to the heat source control system, causing the source to supply more energy to the heat exchanger,

heat production on the source side is equal to the thermal energy demand on the consumption side. In this situation, the flow of the heating medium occurs, so to speak, “across the coupling,” directly from the supply connections fed by the boiler to the supply connections of the heat consumption circuits. Similarly, the return from the heat consumers goes directly to the heat sources through the hydraulic coupling,

the heat demand on the consumer side is lower than its production at the source. The flow of the heat transfer fluid is reduced by the heat receiver controls; excess thermal energy accumulated in the hydraulic coupling returns to the boiler; the boiler controls respond by reducing the output of the heat source(s) or shutting down one of them, etc., thereby lowering the volume and/or temperature of the fluid supplied to the coupling. As a result, the system moves toward thermal equilibrium on both the source and load sides.

In addition to easily connecting various heat sources to different heat receivers without the need for manual adjustment, the hydraulic coupling also has other advantages:

it allows for the venting of the heating medium in the coupling and the removal of air accumulated in the upper part of the coupling via an automatic air vent with a foot valve,

it also allows for the removal of sludge from the heating medium and the safe accumulation of sediment at the bottom of the coupling,

the coupling is cheaper than multi-way valves and less prone to failure due to its exceptionally simple design.

Another type of heat exchanger is the FERRO RSHI hydraulic heat exchanger integrated with a manifold. The design of the hydraulic heat exchanger is based on a rectangular tank with connections on one side for connecting the heat source and on the other side for connecting heat consumers. The tank contains the heat exchanger and the distributor. They are separated by a partition that allows the fluid to flow from the heat exchanger to the distributor on the hot and cold connection sides. The entire unit is thermally insulated.