Glossary

Overview

This glossary explains the central technical terms from VICUS Districts and maps them to the English terms of the user interface and the data model. The tables are structured by subject area: network topology, heat demand and sizing, calculation and results, as well as plants and control.

Network Topology

Term	UI/data-model term (EN)	Short definition
Consumer	Consumer	Heat consumer in the network, e.g. a building. Each consumer is assigned a connection load or a demand profile.
Transfer station	SubStation	Node type for consumers: the point at which heat is transferred from the network to the building.
Energy plant	Source / Energy center	Feed-in node of the network; this is where heat generation and usually the network pump are located.
Mixer	Mixer	Branching or intermediate node without a consumer function. Pipe fittings (e.g. T-pieces, bends) are assigned at mixer nodes.
Node	Node	Collective term for all network points: transfer stations, energy plants and mixers.
Route / edge	Edge	Connection between two nodes; represents the line section with length and assigned pipe.
Supply	Supply pipe	Line that carries the warm fluid from the energy plant to the consumers.
Return	Return pipe	Line that carries the cooled fluid from the consumers back to the energy plant.
Active network	Active network	The network currently selected for editing and calculation, when a project contains several networks.
Coordinate origin	World coordinate origin	Reference point of the project in UTM coordinates. All geometry and network coordinates are stored relative to this origin; its Z coordinate sets the absolute elevation level of the project.
UTM zone	UTM zone	Zone of the UTM coordinate system in which the project coordinates lie. It is detected when georeferenced data is imported (e.g. OSM or GIS) and is stored together with the coordinate origin.
Terrain elevation / node elevation	Node elevation	Elevation of a network node as a Z coordinate relative to the coordinate origin; the absolute elevation only follows from adding the Z coordinate of the origin. No terrain model is kept. Without an elevation query, all nodes sit at 0 m.

Heat Demand and Sizing

Term	UI/data-model term (EN)	Short definition
Connection load	Connection power	Nominal heat output of a consumer in kW; the basis of pipe sizing. A distinction is made between connection load (nominal) and connection load (installed capacity).
Simultaneity	Diversity	Temporal overlap of the peak loads of several consumers. The simultaneity optimization shifts demand profiles in time to obtain realistic aggregate loads.
Part load ratio	Part load ratio	Share of the connection load applied as the load of a consumer in the steady-state calculation.
Pipe fitting	Pipe fitting	Shaped parts such as bends and T-pieces; they cause additional pressure losses and are counted in the bill of materials.
Bill of materials	Bill of materials	Tabular listing of the installed pipe lengths and fittings of the network, e.g. for cost estimation and tendering.

Calculation and Results

Term	UI/data-model term (EN)	Short definition
Operating point	Operating point	Load case of the steady-state calculation (e.g. full load or a part-load case); results are stored and displayed per operating point.
Index point	Index point	Hydraulically most unfavorable point of the network, at which the differential pressure is hardest to maintain.
Setpoint of pressure maintenance	Setpoint of pressure maintenance	Gauge pressure applied at a freely selectable reference node; it sets the pressure level of the whole network. Every other node pressure follows from it through the pressure losses and the elevation difference against that node. In engineering terms the resting pressure, see Pressure Calculation in the Network.
Geodetic height	Geodetic height	Elevation along the route under consideration, shown in the network report as the third diagram of the pressure profile over the route length. It comes from the node elevations and is therefore likewise referenced to the coordinate origin.
Static or geodetic pressure component	Geodetic pressure component	Pressure contribution from the elevation of a node; roughly 1 bar per 10 m of elevation difference, that is about 0.1 bar per meter. It does not enter the solution of the hydraulic system of equations but is added to the pressure quantities of the result presentation.
Operating pressure	Operating pressure	Pressure that actually acts inside the pipes: the gauge pressure including the geodetic component. The pressure limits are checked against this quantity, in the status line of the route profile and in the network report. Being a gauge pressure, it compares directly with PN, MOP and the values of a technical connection specification.
Pressure without the geodetic component	Pressure without the geodetic component	Pressure curve without the geodetic component, that is the pressure lost to friction along the route. How steeply the curves fall shows in which sections a lot of pressure is lost; in the network report the diagram is called Pressure loss line.
Gauge pressure	Gauge pressure	Pressure above atmospheric pressure, the way a manometer reads it. Nominal pressure ratings and the figures in the technical connection requirements are gauge pressures — and so is every network pressure computed by VICUS Districts.
Nominal pressure PN	Nominal pressure (PN)	Pressure rating of a pipe as a gauge pressure in bar, e.g. PN 16. In the pressure check, the lowest rating along the checked route determines the permissible operating pressure. Gauge is checked against gauge, so the comparison is exact. A pipe with no nominal pressure rating assigned gets no upper limit.
Minimum operating pressure	min. operating pressure	Lower pressure limit of the pressure check: the vapor pressure at the hottest point of the checked route plus the minimum pressure margin, less the ambient pressure — the vapor pressure is an absolute pressure while the checked profile is a gauge pressure. The default value of 1.5 bar is made up of 0.5 bar protection against evaporation (broad professional consensus) and around 1.0 bar as a planning recommendation for the control tolerance and transients, see Meeting operating pressure limits in heat networks.
Pressure exceedance	Pressure exceedance	Amount by which the operating pressure exceeds the permissible pressure of the pipe; 0 as long as the limit holds. It replaces the former result quantity Over pressure and reports exceedances only — there is no negative branch.
Ambient pressure	Ambient pressure	Air pressure at the altitude of the project, computed from the z coordinate of the coordinate origin according to the standard atmosphere and not enterable. 1.013 bar at sea level, 0.899 bar at 1000 m. It is needed in exactly one place: converting the vapor pressure onto the gauge-pressure scale.
Temperature difference (spread)	Temperature difference	Difference between supply and return temperature; together with the power, it determines the mass flux.
False color	False colors	Coloring of the network elements in the 3D scene according to a result quantity, e.g. pressure loss or temperature.

Plants and Control

Term	UI/data-model term (EN)	Short definition
Plant	Sub network	Reusable hydraulic circuit made of components (e.g. pump, heat exchanger, heat pump) that is assigned to a network node.
Simplified energy plant	Simplified energy center (pump + heater)	Predefined plant for the energy plant, consisting of a pump and an ideal heat generator.
Simplified consumer	Simplified consumer (pressure loss only)	Predefined consumer plant that only represents the pressure loss.
Heating curve	Heating curve	Supply temperature as a function of the outdoor temperature; controls the outlet temperature of the energy plant.
Index-point controller	Index point controller	Controller that monitors the pressure difference at the index point of the network and controls the pump accordingly.

Related Topics

• The network model
• Pipe sizing: method
• Plants: concept