classNomenclatureSymbols

Information

Nomenclature

Active network

An active network is defined as a network where the pressure differential at the boundaries of each connected consumer circuit is primarily driven by the primary circuit circulating pump.

The primary circuit is necessarily equipped with a circulating pump. The connected consumer circuits may be equipped with a circulating pump or not.

Passive network

A passive network is defined as a network where the pressure differential at the boundaries of each connected consumer circuit is primarily driven by the consumer circuit circulating pump.

The connected consumer circuits are necessarily equipped with a circulating pump. However, the primary circuit may be equipped with a circulating pump or not. In the former case, a decoupling device (such as a fixed bypass, a hydraulic separator, or a supply-through loop) is used to cancel out the pressure differential created by the primary pump.

Primary circuit

The word "primary" is used to refer to the source-side circuit which distributes heat or cold and connects with the central plant.

Note that if the central plant already uses a primary-secondary arrangement, then what is called the "primary" circuit is this package is actually the "secondary circuit".

Secondary (consumer) circuit

The word "secondary" or "consumer" is used to refer to the load-side circuit that integrates the terminal units.

Note that if the central plant already uses a primary-secondary arrangement, then what is called the "secondary" circuit is this package is actually the "tertiary circuit".

Symbols

Symbol	Description
	Balancing valve
	Check valve (the arrow indicating the flow direction is not part of the symbol)
	Circulating pump
	Consumer circuit (typically a heating or cooling circuit or a terminal unit)
	Controller (the dotted lines represent the wiring to the sensor and actuator)
	Self-acting Δp control valve (the dotted lines represent the capillary pipes for pressure measurement)
	Three-way valve with modulating actuator (the arrow indicating the flow direction is not part of the symbol)
	Two-way valve with modulating actuator