Line diagrams describing the interconnection of components in a system showing the engineering principles. The main features of a Developed Design schematic drawing should be as follows:

• The drawings should include all the engineering components that make the system work, such as main plant, distribution, inline equipment supporting engineering performance, terminal plant providing HVAC performance. Quantities of performance specified components would only be indicative at this stage, with accurate quantities on schedules or similar.
• Symbols and line conventions should be in accordance either with a recognised standard, such as ISO or BS, or a supplied legend.
• The drawings should be labelled with appropriate pipe, duct, busbar and cable sizes, pressures and flow rates. These details may be subject to adjustment during technical design and construction stages.
• The drawings should indicate components which have a sensing, control or measurement function.
• The major components indicated on the schematic drawing should be identified for cross-referencing purposes.

Where appropriate these drawings should indicate typical room/area details to show key principles of the systems within/serving them.